Body Frame Calculator - Determine Frame Size

Understanding your body frame size is essential for setting realistic health and fitness goals. Your skeletal structure plays a significant role in determining your ideal body weight, clothing size, and overall body composition. This body frame calculator uses scientifically validated methods to help you determine whether you have a small, medium, or large frame based on your wrist circumference or elbow breadth measurements.

Body frame size is a genetic characteristic that cannot be changed through diet or exercise. Unlike body weight or muscle mass, your skeletal structure remains constant throughout adulthood. Knowing your frame size helps you understand why certain weight ranges may be more appropriate for your body than standard charts suggest, and why comparing yourself to others with different frame sizes can be misleading.

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What is Body Frame Size?

Body frame size refers to the mass and structure of your bones and skeletal system. It represents the physical framework upon which your muscles, organs, and tissues are built. While everyone has the same number of bones, the thickness, density, and overall size of these bones vary significantly from person to person.

Your frame size is determined primarily by genetics and is established during childhood and adolescence as your bones grow and develop. Factors such as ethnicity, heredity, and hormonal influences during development all contribute to your final skeletal structure. Some people naturally develop thicker, denser bones that create a larger frame, while others have lighter, more delicate bone structures.

Frame size is independent of height, weight, or body fat percentage. Two people of the same height can have drastically different frame sizes—one with narrow shoulders and small wrists, the other with broad shoulders and large wrists. This difference in skeletal structure means that their ideal body weights and body compositions will also differ significantly.

Understanding your body frame size provides important context for interpreting body weight recommendations, Body Mass Index (BMI) calculations, and fitness goals. It explains why some individuals appear larger or smaller at the same weight and height, and why standard weight charts often fail to account for individual variations in bone structure.

Wrist Measurement Method

The wrist measurement method is the most common and accessible way to determine body frame size. This technique is based on the principle that wrist circumference correlates strongly with overall skeletal structure. The wrist contains minimal muscle and fat tissue, making it an ideal location to assess bone size directly.

To measure your wrist circumference accurately, you’ll need a flexible measuring tape. Measure around your wrist at the narrowest point, typically just below the wrist bone where your wrist bends. The tape should be snug but not tight enough to compress the skin. Take the measurement on your dominant hand for consistency.

Frame Size Categories for Women (Wrist Measurement):

For women under 5’2” (157 cm):

Small frame: wrist less than 5.5 inches (14 cm)
Medium frame: wrist 5.5 to 5.75 inches (14-14.6 cm)
Large frame: wrist over 5.75 inches (14.6 cm)

For women 5’2” to 5’5” (157-165 cm):

Small frame: wrist less than 6 inches (15.2 cm)
Medium frame: wrist 6 to 6.25 inches (15.2-15.9 cm)
Large frame: wrist over 6.25 inches (15.9 cm)

For women over 5’5” (165 cm):

Small frame: wrist less than 6.25 inches (15.9 cm)
Medium frame: wrist 6.25 to 6.5 inches (15.9-16.5 cm)
Large frame: wrist over 6.5 inches (16.5 cm)

Frame Size Categories for Men (Wrist Measurement):

For men over 5’5” (165 cm):

Small frame: wrist 5.5 to 6.5 inches (14-16.5 cm)
Medium frame: wrist 6.5 to 7.5 inches (16.5-19 cm)
Large frame: wrist over 7.5 inches (19 cm)

These measurements are guidelines based on population studies and may vary slightly depending on ethnicity and individual variation. The wrist measurement method is particularly useful because it requires minimal equipment and can be performed at home with reasonable accuracy.

Elbow Breadth Method

The elbow breadth method provides an alternative approach to determining body frame size, particularly useful when wrist measurements are difficult to obtain or when seeking additional confirmation. This method measures the width of the elbow joint, which like the wrist, contains minimal soft tissue and provides a direct assessment of bone structure.

To measure elbow breadth, extend your arm forward at a 90-degree angle with your palm facing up. Bend your forearm up toward your shoulder, also at a 90-degree angle. Use your thumb and index finger to locate the two prominent bones on either side of your elbow joint. Measure the distance between these two points using calipers or a ruler. This measurement represents your elbow breadth.

Frame Size Categories by Elbow Breadth:

For women:

Height 4’10”-4’11” (147-150 cm): small <2.25”, medium 2.25-2.5”, large >2.5”
Height 5’0”-5’3” (152-160 cm): small <2.25”, medium 2.25-2.5”, large >2.5”
Height 5’4”-5’7” (163-170 cm): small <2.375”, medium 2.375-2.625”, large >2.625”
Height 5’8”-5’11” (173-180 cm): small <2.375”, medium 2.375-2.625”, large >2.625”
Height 6’0”+ (183 cm+): small <2.5”, medium 2.5-2.75”, large >2.75”

For men:

Height 5’2”-5’3” (157-160 cm): small <2.5”, medium 2.5-2.875”, large >2.875”
Height 5’4”-5’7” (163-170 cm): small <2.625”, medium 2.625-2.875”, large >2.875”
Height 5’8”-5’11” (173-180 cm): small <2.75”, medium 2.75-3”, large >3”
Height 6’0”-6’3” (183-191 cm): small <2.75”, medium 2.75-3.125”, large >3.125”
Height 6’4”+ (193 cm+): small <2.875”, medium 2.875-3.25”, large >3.25”

The elbow breadth method is considered slightly more accurate by some researchers because it measures a larger joint with more consistent anatomical landmarks. However, it requires more precise measurement tools and proper technique to ensure accuracy.

Frame Categories: Small, Medium, Large

Body frame sizes are typically classified into three categories: small, medium, and large. Each category represents a range of skeletal structures with distinct characteristics that affect body composition, weight distribution, and physical appearance.

Small Frame: Individuals with small frames have lighter, more delicate bone structures. They typically have narrow shoulders, small wrists and ankles, and an overall petite skeletal build. Women with small frames often wear smaller ring sizes and find that standard clothing fits loosely in the shoulders. Men with small frames may have difficulty building large muscle mass even with consistent strength training.

People with small frames generally have lower ideal body weights compared to medium or large-framed individuals of the same height. Their lighter skeletal structure means they can maintain a healthy body composition at weights that might be considered underweight for someone with a larger frame. Small-framed individuals often have faster metabolisms relative to their weight and may find it easier to maintain a lean physique.

Medium Frame: Medium frames represent the average skeletal structure for a given population. These individuals have proportionate bone thickness and joint sizes that fall within the middle range of measurements. Medium-framed people typically find that standard clothing sizes and weight recommendations align reasonably well with their bodies.

The majority of healthy weight charts and BMI calculations are calibrated for medium-framed individuals, making these tools most accurate for this group. Medium-framed people have balanced proportions that allow them to build muscle and lose fat at average rates, and they generally respond predictably to diet and exercise programs.

Large Frame: Large-framed individuals have thicker, denser bones and broader skeletal structures. They typically have wide shoulders, large wrists and ankles, and robust joint sizes. Women with large frames often have difficulty finding jewelry that fits comfortably and may need larger clothing sizes even at lower body fat percentages. Men with large frames have a natural advantage for building muscle mass and strength.

People with large frames have higher ideal body weights than small or medium-framed individuals of the same height. Their heavier skeletal structure means they can carry more weight while maintaining a healthy body composition. Large-framed individuals may appear overweight according to standard BMI charts even when they have healthy body fat percentages.

Body Frame and Ideal Weight

Your body frame size significantly influences your ideal body weight range. Standard weight charts that use only height as a reference point fail to account for the substantial variation in skeletal mass between individuals. A person with a large frame may weigh 20-30 pounds more than someone with a small frame at the same height, both maintaining perfectly healthy body compositions.

Weight Range Adjustments by Frame Size:

Traditional ideal weight formulas should be adjusted based on frame size:

Small frame: Subtract 10% from standard ideal weight
Medium frame: Use standard ideal weight
Large frame: Add 10% to standard ideal weight

For example, if a standard weight chart suggests an ideal weight of 150 pounds for your height, these adjustments would yield:

Small frame: 135 pounds (150 - 10%)
Medium frame: 150 pounds
Large frame: 165 pounds (150 + 10%)

This 30-pound range demonstrates how dramatically frame size affects appropriate body weight. Attempting to reach a weight ideal for a different frame size can lead to unhealthy body composition—either excessive body fat (if your natural frame is smaller than your target) or insufficient muscle and energy reserves (if your natural frame is larger than your target).

Frame Size and Body Mass Index (BMI):

BMI calculations have significant limitations because they don’t account for frame size or body composition. A large-framed, muscular individual may have a BMI in the “overweight” range while having a perfectly healthy body fat percentage. Conversely, a small-framed person with minimal muscle mass might have a “healthy” BMI while actually having excess body fat.

For large-framed individuals, a BMI up to 2-3 points higher than standard recommendations may still represent a healthy weight. For small-framed individuals, optimal health may be achieved at BMI values 2-3 points lower than standard ranges. These adjustments help account for the significant variation in skeletal mass that BMI calculations ignore.

Setting Realistic Weight Goals:

Understanding your frame size helps you set achievable and healthy weight goals. If you have a large frame, attempting to reach the weight of a small-framed person at your height would require losing both fat and lean muscle mass to an unhealthy degree. Similarly, small-framed individuals should not compare themselves to large-framed people and assume they need to weigh more.

Your ideal weight should be based on body composition (body fat percentage, muscle mass) rather than arbitrary numbers. Frame size provides context for interpreting these measurements and understanding what ranges are realistic for your genetic structure.

Body Frame vs Body Type

While body frame and body type are related concepts, they refer to different aspects of physical structure. Understanding the distinction helps you better assess your body and set appropriate fitness goals.

Body Frame (Skeletal Structure): Body frame refers specifically to your bone structure—the size, thickness, and density of your skeleton. It is determined genetically and established during growth and development. Frame size is permanent and cannot be changed through diet, exercise, or lifestyle modifications. It directly affects your ideal weight range and how weight is distributed across your skeleton.

Body Type (Somatotype): Body type refers to your overall physical build, including your natural tendency to store fat, build muscle, and your general body shape. The three classical somatotypes are:

Ectomorph: Naturally lean, difficulty building muscle, fast metabolism
Mesomorph: Naturally muscular, athletic build, balanced metabolism
Endomorph: Tendency to store fat, builds muscle easily, slower metabolism

Key Differences:

Body frame is purely skeletal, while body type includes soft tissue characteristics. You can have a large frame but be an ectomorph (large bones but naturally lean), or a small frame but be an endomorph (delicate bones but tendency to store fat). These combinations create the wide variety of body shapes we see in the population.

Body type can be modified to some extent through training and nutrition. An endomorph can become leaner through diet and exercise, and an ectomorph can build muscle through strength training, but these changes don’t alter the underlying frame size. Your bone structure remains constant even as your body composition changes.

Practical Implications:

Knowing both your frame size and body type provides comprehensive insight into your body. A large-framed ectomorph should focus on building muscle mass while accepting that they’ll weigh more than a small-framed person at similar body fat levels. A small-framed endomorph should focus on fat loss while understanding that their ideal weight will be lower than someone with a larger frame.

This dual understanding prevents unrealistic comparisons and helps you appreciate your unique genetic blueprint. Rather than fighting against your natural structure, you can work with it to achieve your best possible physical condition.

Genetics and Bone Structure

Your bone structure is primarily determined by genetics, with factors inherited from both parents influencing your final skeletal size and density. Understanding the genetic basis of frame size helps explain why body types run in families and why certain populations have characteristic skeletal structures.

Hereditary Factors:

Bone size and density are polygenic traits, meaning they’re influenced by multiple genes working together. If both your parents have large frames, you’re likely to inherit a large frame as well. However, because multiple genes are involved, there’s variability—siblings can have different frame sizes even with the same parents.

Ethnic background also plays a significant role in skeletal structure. Population studies show that certain ethnic groups tend toward larger or smaller average frame sizes. For example, individuals of Northern European descent often have larger frames on average compared to individuals of East Asian descent. These are statistical trends with wide individual variation, not absolute rules.

Developmental Influences:

While genetics set the potential range for your frame size, developmental factors during childhood and adolescence influence how that potential is expressed. Nutrition, physical activity, and hormonal balance during growth years affect bone development and final skeletal size.

Adequate calcium, vitamin D, protein, and overall nutrition during growth support optimal bone development. Children who experience malnutrition or nutrient deficiencies may not reach their full genetic potential for bone size and density. Conversely, proper nutrition and weight-bearing physical activity during youth maximize bone development within genetic limits.

Hormonal Influences:

Sex hormones play crucial roles in skeletal development, explaining some of the differences between male and female frame sizes. Testosterone promotes bone growth and density, contributing to the generally larger frames seen in men. Estrogen also affects bone development, and the timing of puberty influences final skeletal proportions.

Thyroid hormones, growth hormone, and other endocrine factors regulate bone growth and mineralization. Hormonal imbalances during development can affect final frame size, though most individuals develop normally within their genetic potential.

Bone Density vs Frame Size:

It’s important to distinguish between frame size (the external dimensions of bones) and bone density (the internal mineral content). You can have a large frame with low bone density (osteopenia or osteoporosis) or a small frame with high bone density. Bone density is more variable and can be influenced by diet, exercise, and lifestyle throughout life, while frame size is established during growth years.

Frame Size and Weight Loss Expectations

Understanding your frame size is crucial for setting realistic weight loss expectations and avoiding frustration with unrealistic goals. Your skeletal structure sets natural limits on how lean you can become while maintaining health and functionality.

Minimum Healthy Weights:

Your frame size determines your minimum healthy weight—the lowest weight you can achieve without compromising health. This minimum includes your skeletal mass, essential organs, necessary muscle tissue, and essential body fat. Large-framed individuals have significantly higher minimum weights than small-framed people due to their heavier skeletons alone.

A large-framed woman might have 8-10 pounds more skeletal mass than a small-framed woman of the same height. When you account for the proportionally larger organs, necessary muscle tissue, and essential fat, the minimum healthy weight difference can exceed 20-30 pounds. Attempting to reach a small-framed person’s weight when you have a large frame would require losing essential tissue and organ mass.

Body Fat Percentage vs Scale Weight:

Frame size explains why body fat percentage is a better metric than scale weight for assessing fitness progress. Two people with identical body fat percentages can weigh significantly different amounts if they have different frame sizes. A large-framed person at 20% body fat will weigh more than a small-framed person at 20% body fat, even at the same height.

This concept helps explain plateaus and frustration during weight loss. If you’re large-framed and comparing yourself to small-framed individuals or unrealistic media images, you may never reach their weights despite achieving excellent body composition. Focusing on body fat percentage, measurements, and how you feel rather than arbitrary scale numbers prevents this discouragement.

Realistic Goal Setting:

When setting weight loss goals, consider your frame size in these ways:

Adjust target weights: Use frame-adjusted ideal weight ranges rather than one-size-fits-all recommendations
Set body composition goals: Focus on achieving a healthy body fat percentage for your sex and age rather than a specific weight
Track multiple metrics: Use measurements, photos, how clothes fit, and performance metrics alongside scale weight
Accept genetic limits: Understand that your lowest healthy weight may be higher than someone with a smaller frame at the same height

Avoiding Unhealthy Extremes:

Large-framed individuals who try to achieve small-framed weights often resort to extreme calorie restriction, excessive exercise, or disordered eating behaviors. These approaches can cause loss of muscle mass, hormonal imbalances, nutrient deficiencies, and psychological stress. Understanding your frame size helps you recognize when you’ve reached a healthy weight for your structure, even if it’s higher than you initially expected.

Frame Size and Clothing Fit

Your body frame size significantly affects how clothing fits and which styles flatter your proportions. Understanding your frame helps you choose clothing that works with your natural structure rather than against it.

Small Frame Considerations:

Small-framed individuals often find standard clothing too large in the shoulders, sleeves, and overall proportions. Petite sizing isn’t just about height—it’s also designed for smaller bone structures. Small-framed people may need to size down or choose brands that cater to delicate builds.

Jewelry and accessories can overwhelm small frames. Delicate, proportionate accessories typically look more balanced on small-boned individuals. Watch bands, rings, and bracelets designed for average wrists often fit poorly and require adjustment.

Clothing strategies for small frames:

Look for brands with petite or slim-cut options
Consider tailoring to adjust shoulder width and sleeve length
Choose delicate fabrics and patterns that don’t overwhelm your frame
Avoid overly bulky or oversized styles that can swamp your structure

Medium Frame Considerations:

Medium-framed individuals typically find that standard sizing works reasonably well. Most clothing is designed for average proportions, making it easier to find good fits off the rack. However, individual variation still exists, and some adjustment may be needed.

Medium frames have the advantage of flexibility in style choices. Both structured and flowing garments can work well, and there are fewer limitations based purely on bone structure. Focus on choosing styles that complement your specific body shape and personal preferences.

Large Frame Considerations:

Large-framed individuals often struggle with clothing that’s too tight in the shoulders, sleeves, and across the back, even when the rest of the garment fits. This is particularly challenging for large-framed women who may need larger sizes to accommodate their shoulders and ribcage but then have excess fabric elsewhere.

Large frames can carry bold patterns, structured fabrics, and substantial accessories without being overwhelmed. Delicate, flimsy fabrics or tiny accessories may look disproportionate on a robust frame.

Clothing strategies for large frames:

Look for brands with generous shoulder room and longer sleeves
Consider broad-fit or athletic-cut options
Don’t be afraid of structured, substantial fabrics and bold styles
Choose accessories with appropriate scale—substantial jewelry and watches
Tailor garments to fit your shoulders properly, then take in other areas if needed

Universal Fit Tips:

Regardless of frame size, the key to great clothing fit is understanding your specific proportions. Two people with the same frame size can have different torso lengths, leg lengths, and shoulder-to-hip ratios. Professional tailoring can transform an average fit into a perfect fit by adjusting for your unique structure.

Reference Values by Height and Gender

These comprehensive reference tables help you determine your expected frame size based on height, gender, and wrist or elbow measurements. Use these as guidelines, recognizing that individual variation exists within each category.

Women - Wrist Circumference Method:

Height Range	Small Frame	Medium Frame	Large Frame
Under 5’0” (152 cm)	<5.5” (14 cm)	5.5-5.75” (14-14.6 cm)	>5.75” (14.6 cm)
5’0”-5’2” (152-157 cm)	<5.5” (14 cm)	5.5-5.75” (14-14.6 cm)	>5.75” (14.6 cm)
5’2”-5’5” (157-165 cm)	<6.0” (15.2 cm)	6.0-6.25” (15.2-15.9 cm)	>6.25” (15.9 cm)
5’5”-5’8” (165-173 cm)	<6.25” (15.9 cm)	6.25-6.5” (15.9-16.5 cm)	>6.5” (16.5 cm)
5’8”-5’11” (173-180 cm)	<6.25” (15.9 cm)	6.25-6.5” (15.9-16.5 cm)	>6.5” (16.5 cm)
Over 5’11” (180 cm)	<6.5” (16.5 cm)	6.5-6.75” (16.5-17.1 cm)	>6.75” (17.1 cm)

Men - Wrist Circumference Method:

Height Range	Small Frame	Medium Frame	Large Frame
Under 5’5” (165 cm)	<5.5” (14 cm)	5.5-6.5” (14-16.5 cm)	>6.5” (16.5 cm)
5’5”-5’8” (165-173 cm)	<6.0” (15.2 cm)	6.0-7.0” (15.2-17.8 cm)	>7.0” (17.8 cm)
5’8”-5’11” (173-180 cm)	<6.25” (15.9 cm)	6.25-7.25” (15.9-18.4 cm)	>7.25” (18.4 cm)
5’11”-6’2” (180-188 cm)	<6.5” (16.5 cm)	6.5-7.5” (16.5-19 cm)	>7.5” (19 cm)
Over 6’2” (188 cm)	<6.75” (17.1 cm)	6.75-7.75” (17.1-19.7 cm)	>7.75” (19.7 cm)

Elbow Breadth Reference (Both Genders):

These measurements require precise calipers and proper technique:

Women’s elbow breadth:

4’10”-5’3”: Small <2.25”, Medium 2.25-2.5”, Large >2.5”
5’4”-5’11”: Small <2.375”, Medium 2.375-2.625”, Large >2.625”
6’0”+: Small <2.5”, Medium 2.5-2.75”, Large >2.75”

Men’s elbow breadth:

5’2”-5’7”: Small <2.625”, Medium 2.625-2.875”, Large >2.875”
5’8”-6’3”: Small <2.75”, Medium 2.75-3.125”, Large >3.125”
6’4”+: Small <2.875”, Medium 2.875-3.25”, Large >3.25”

Interpreting Your Results:

If your measurements fall on the borderline between categories, you likely have characteristics of both frame types. Some individuals have medium-to-large or small-to-medium frames. In these cases, use the midpoint for weight calculations and pay attention to your body composition rather than strict categorization.

Remember that these reference values are derived from population studies and represent averages. Individual variation exists, and factors like ethnicity, athletic training during youth, and family genetics can influence where you fall within these ranges.

Frequently Asked Questions

Can I change my body frame size?

No, your body frame size is determined by your skeletal structure, which is established genetically and developed during childhood and adolescence. Once you reach adulthood, your bone structure is set and cannot be changed through diet, exercise, or lifestyle modifications. You can, however, change your body composition (muscle mass and body fat) and your overall body shape through fitness and nutrition.

Why does my frame size differ from my friends at the same height?

Frame size is primarily determined by genetics and is independent of height. Two people of identical height can have completely different skeletal structures based on their genetic inheritance, ethnic background, and developmental factors. This genetic variation is normal and explains why people of the same height need different clothing sizes and have different ideal weights.

Is having a large frame better or worse for health?

Neither frame size is inherently better or worse for health. Each frame type has advantages and disadvantages. Large frames typically have higher bone density and may have lower risk of osteoporosis. Small frames often have lower cardiovascular stress due to less mass to support. What matters most for health is maintaining appropriate body composition, getting adequate nutrition, and staying physically active regardless of frame size.

How accurate is the wrist measurement method?

The wrist measurement method has been validated through numerous studies and correlates well with overall skeletal size. While not perfect, it provides a reasonably accurate assessment (approximately 85-90% accuracy) and has the advantage of being easy to perform at home. For greater accuracy, combining wrist measurement with elbow breadth and overall physical assessment provides the best results.

Can women have large frames and men have small frames?

Absolutely. While men on average have larger frames than women due to hormonal influences during development, there is significant overlap between the sexes. Many women have large frames that are bigger than many men’s frames. Frame size is a spectrum, and individuals of any sex can fall anywhere within that spectrum based on their genetics.

Does frame size affect athletic performance?

Yes, frame size influences athletic performance in various ways. Large frames provide advantages in strength-based sports due to larger muscle attachment sites and leverage advantages. Small frames can be advantageous in endurance sports, gymnastics, and activities where power-to-weight ratio matters. However, training, technique, and dedication typically matter more than frame size for most athletic pursuits.

Should I adjust my protein intake based on frame size?

Protein recommendations are better based on lean body mass rather than frame size directly. However, since frame size influences your total body weight and muscle mass potential, large-framed individuals typically need more total protein than small-framed individuals at the same height. Calculate protein needs based on your goal weight and activity level rather than frame size alone.

Can malnutrition during childhood affect frame size?

Yes, severe malnutrition during growth years can prevent individuals from reaching their full genetic potential for skeletal size. Adequate nutrition, especially calcium, vitamin D, protein, and overall calories, is essential for optimal bone development. However, once growth plates close in early adulthood, nutritional improvements cannot change frame size, though they can improve bone density.

How does frame size relate to bone density?

Frame size (external bone dimensions) and bone density (internal mineral content) are related but distinct characteristics. Large-framed individuals often have higher total bone mineral content simply because they have more bone tissue. However, bone density (mineral per volume) can vary within any frame size. A small-framed person can have excellent bone density, while a large-framed person might have osteoporosis.

Should I use frame size or BMI for health assessment?

Ideally, use both along with other metrics. BMI has limitations because it doesn’t account for frame size or body composition, but it can still provide useful population-level information. For individual health assessment, combine frame-adjusted weight ranges, body fat percentage measurements, waist circumference, and overall fitness indicators. No single metric tells the complete story.

Medical Disclaimer

This body frame calculator and the information provided are for educational and informational purposes only. They are not intended to be a substitute for professional medical advice, diagnosis, or treatment. Frame size determination provides general guidance but should not be the sole factor in health decisions.

Individual health needs vary based on numerous factors including medical history, current health conditions, medications, and lifestyle factors. Before making significant changes to your diet, exercise routine, or weight management approach based on frame size calculations, consult with qualified healthcare professionals.

If you have concerns about your weight, bone health, body composition, or any health-related matters, seek guidance from your physician, registered dietitian, or other qualified healthcare provider. They can provide personalized recommendations based on your complete health profile.

The reference ranges and calculations provided are based on population studies and may not apply to all individuals, particularly those with certain medical conditions, athletes with unusual body compositions, or individuals from populations not well-represented in the reference studies.