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Neck Size Calculator

Enter your neck circumference to find your shirt collar size, compare to average male/female neck sizes, and understand how it relates to body fat estimation. Supports cm and inches.

Neck Circumference Calculator

Collar size · Health risk · Body fat context

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Neck Circumference

Neck circumference is a useful health screening measure. A thick neck is associated with excess visceral fat and elevated sleep apnoea risk. Neck size is also one of the inputs in the US Navy body fat percentage formula — a larger neck relative to waist indicates lower body fat.

Shirt Collar Size Guide

Neck (cm)Neck (in)UK/EU SizeUS Size
35–361435/3614
37–3814.5–1537/3814.5–15
39–4015.539/4015.5
41–4216–16.541/4216–16.5
43–441743/4417
45–4617.5–1845/4617.5–18

Neck Size and Health: What the Research Says

Neck circumference is increasingly used as a clinical screening tool alongside waist circumference. Studies show it independently predicts insulin resistance, sleep apnoea, and cardiovascular risk. Excess neck fat is part of upper body fat distribution (android pattern), which is metabolically more harmful than lower body fat. Unlike waist circumference, neck measurement is not affected by digestive system fullness and may be more consistent across times of day.

Frequently Asked Questions

Stand upright, look straight ahead. For men: measure the neck just below the Adam's apple. For women: measure at the narrowest part of the neck. Hold the tape horizontal and snug — not compressing tissue. Round to the nearest 0.5 cm or 0.25 inch. Take 2 measurements and average them for accuracy.
Not necessarily. Trained athletes (especially powerlifters, wrestlers, and rugby players) develop significant neck muscle mass that increases circumference without excess fat. Context matters — neck size should be interpreted alongside waist circumference, body fat percentage, and overall body composition. The health risk thresholds (>37 cm men, >34 cm women) apply more to sedentary populations.
Measure your neck circumference in cm or inches using the method above. Then refer to the collar size table on this page: EU/UK collar sizes equal the neck measurement in cm (e.g., 39 cm neck = size 39). US collar sizes are in inches (e.g., 15.5" = 39 cm neck). When in doubt, round up to the next half-size for comfort.
The US Navy body fat formula uses neck as a proxy for upper-body leanness. A larger neck relative to waist indicates more muscle mass and less relative fat. Combined with waist (and hip for women), neck circumference feeds into a logarithmic formula that estimates body fat percentage without calipers. It's particularly useful for field environments where DEXA or bodpod testing isn't available.

Related Calculators

Body Fat Navy MethodUS Navy formula uses neck + waist/hip for body fat %.Calculate → Wrist Size CalculatorWrist circumference and frame size.Calculate → Waist to Height RatioWaist-to-height cardiovascular risk index.Calculate → Shoulder to Waist RatioV-taper proportion and aesthetic ratio.Calculate →