Clavicle Length Calculator
For classifying biacromial breadth and frame size. Based on official CDC NHANES anthropometric data
Proper Measurement Technique
Position
Subject sits upright with arms hanging naturally at sides
Landmark Identification
Locate the most lateral borders of the acromial processes (bony protrusions on each shoulder)
Measurement
Using a sliding caliper, measure the straight-line distance between these landmarks from behind
Verification
Take multiple measurements and calculate the average
Analysis Results
Frame Classification
Population Percentile
Shoulder-to-Height Ratio
Structural Analysis
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Training Implications
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CDC NHANES Reference Data
| Classification | Measurement Range | Population Percentile |
|---|
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Calculate Hand Size →Clavicles Can Continue Growing Until Age 30
Unlike most bones that stop growing after puberty, clavicles (collarbones) have growth plates that can remain open until age 25-30 in men. This means your shoulder width can still increase well into adulthood.
The clavicle bone is the last bone in the body to fuse, for many men, it fuses at age 25 – 27, however it is not uncommon for it to fuse up until 30, here’s how you can check if your clavicle has fused:
Check for tenderness at the inner end of your collarbone (near the center of your chest) – sensitivity here can indicate an active growth plate.
Support growth with adequate nutrition (calcium, vitamin D, protein), resistance training, and quality sleep.
Track measurements every 3-6 months using the biacromial width method in our calculator to monitor changes.
While genetics primarily determine shoulder width, optimizing these factors during your 20s may help maximize your natural potential if your growth plates remain open.
Checking If Your Clavicles Are Fused
- Prominence test: Stand in front of a mirror with good lighting and look at where your collarbone meets your breastbone (the medial end of the clavicle). Compare the left and right sides. If you notice a bump or slight protrusion at this junction, it might indicate the growth plate is still open. In fully fused clavicles, this area typically appears smoother.
- Palpation comparison: With your fingers, gently feel the medial end of your clavicle (inner end near the center of your chest). If you can feel a slight ridge or bump that’s more prominent than other areas of your collarbone, the growth plate might still be open. Try comparing with someone over 30 if possible.
- Subtle movement test: Place your fingers on the inner end of your clavicle while slowly moving your shoulder in different directions. An unfused growth plate might allow slightly more movement or even a subtle clicking sensation at this junction compared to a fully fused one.
- Photo documentation: Take close-up photos of your clavicle area every few months under the same lighting conditions. Compare them to look for subtle changes in appearance at the medial end, which might indicate ongoing development before complete fusion.
These methods aren’t definitive, but they’re practical approaches you can try at home for the clavicle specifically.
Biacromial Width and Frame Size
Biacromial width (shoulder width) is a key skeletal measurement used in anthropometry to assess frame size. Unlike muscle mass or body fat, which can change with training and nutrition, biacromial width is primarily determined by genetics and represents the distance between the most lateral points of the acromial processes on each shoulder.
The measurement is particularly valuable because it’s one of the few external measurements that directly corresponds to skeletal structure rather than soft tissue. When combined with height, it provides insight into proportional development and can be used to establish frame size classifications.
Measurement Standards
Standardized measurement protocols are essential for obtaining accurate and comparable results. The National Health and Nutrition Examination Survey (NHANES) methodology used by the CDC requires measurements to be taken:
With the subject seated upright
Using sliding calipers from behind the subject
Measuring from the most lateral points of each acromial process
Taking multiple measurements to ensure accuracy
Home measurements can be taken with a tape measure but tend to be less accurate than caliper measurements. The most common error is measuring across the deltoid muscles rather than the bony landmarks, which results in inflated values.
Age and Development Factors
Biacromial width follows a predictable growth pattern through childhood and adolescence. According to CDC NHANES data, there are clear developmental milestones:
| Age Range | Males (avg.) | Females (avg.) | Key Development |
|---|---|---|---|
| 3-6 years | 22-26 cm | 22-26 cm | Similar between sexes |
| 7-10 years | 27-31 cm | 27-31 cm | Steady growth |
| 11-14 years | 33-38 cm | 33-36 cm | Sexual dimorphism begins |
| 15-19 years | 39-41 cm | 36-37 cm | Growth plateau |
| 20+ years | 41.1 cm | 36.7 cm | Adult reference values |
Growth in biacromial width typically ceases by late adolescence, with minimal changes after age 20. Unlike height, which can continue to increase until the early twenties, shoulder width stabilizes earlier.
Athletic and Performance Implications
While biacromial width is just one of many factors affecting athletic performance, certain structural tendencies have been observed across sports:
Wider Shoulders (>75th percentile)
Athletes with proportionally wider shoulders often excel in:
- Olympic weightlifting
- Throwing events (discus, shot put)
- Swimming (particularly butterfly and freestyle)
- Rowing and paddling sports
- Powerlifting and strength events
The mechanical advantage comes from improved leverage for overhead and pushing movements, plus increased surface area for muscle attachment.
Narrower Shoulders (<25th percentile)
Athletes with proportionally narrower shoulders often excel in:
- Gymnastics and bodyweight disciplines
- Distance running
- Rock climbing
- Horse racing (jockeys)
- Weight-class combat sports
The advantage stems from favorable strength-to-weight ratio and biomechanical efficiency in certain movement patterns.
It’s important to note that these tendencies represent statistical patterns rather than limitations. Examples of exceptional athletes with atypical dimensions exist in virtually every sport.
Measurement Accuracy Tips
For those taking measurements at home, these tips can help improve accuracy:
Use the Right Tools
A rigid measuring device like a sliding caliper is ideal. If using a tape measure, ensure it doesn’t compress soft tissue or bend around contours.
Find the Landmarks
The acromial process is the bony point at the top outer edge of each shoulder. It can be located by moving your finger along the collarbone toward the shoulder until you feel a distinct bony prominence.
Position Correctly
Measurements should be taken with the subject seated upright, shoulders relaxed but not slumped, arms hanging naturally at the sides.
Multiple Measurements
Take at least three separate measurements and calculate the average. This helps reduce random measurement error.
Avoid Common Errors
Don’t measure across muscle tissue, don’t include clothing bulk, and ensure the measuring device is level and not angled.
Frequently Asked Questions
Can I change my biacromial width through exercise?
No. Biacromial width is a skeletal measurement determined by genetics. While muscle development can increase the visual width of the shoulders, the bony structure itself doesn’t change with exercise.
How does biacromial width relate to shoulder circumference?
Shoulder circumference includes both skeletal width and muscle/fat tissue. Two people with identical biacromial widths can have significantly different shoulder circumferences depending on muscle development and body composition.
Why does the calculator ask for height?
Height is used to calculate the shoulder-to-height ratio, which provides context for the measurement. A 40cm width has different proportional implications on a 160cm person versus a 190cm person.
Are there health implications to different frame sizes?
Frame size is one factor considered in some health assessments, particularly in determining ideal weight ranges. However, it’s just one of many physical parameters and isn’t strongly correlated with overall health outcomes.
How often should measurements be taken for growing children?
Annual measurements are sufficient to track developmental progress. More frequent measurements might not show significant changes and can introduce unnecessary variability.
References
The data and measurement protocols referenced on this page come from the following sources:
- Centers for Disease Control and Prevention. (2009). National Health and Nutrition Examination Survey (NHANES): Anthropometry Procedures Manual.
- Fryar CD, Gu Q, Ogden CL, Flegal KM. (2016). Anthropometric Reference Data for Children and Adults: United States, 2011–2014. National Center for Health Statistics. Vital Health Stat 3(39).
- Norton K, Olds T. (eds.) (2004). Anthropometrica: A Textbook of Body Measurement for Sports and Health Courses. UNSW Press.