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Category
Body Fat Percentage Calculator
Scales only show total weight. Body fat percentage estimates how much of that weight is fat versus lean tissue. This calculator uses the US Navy circumference method: tape measurements of neck, waist and (for women) hips plus height. It is a practical field estimate used by many fitness programmes, not a clinical gold standard, but it gives a useful number without specialised equipment.
Please enter valid positive measurements. For women, hip is required.
Estimated body fat
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How to Use the Body Fat Calculator
- Select sex and preferred units (centimetres or inches).
- Measure height, neck just below the larynx, and waist at navel level.
- Women: also measure hips at the widest point.
- Enter the values and calculate to see estimated body fat % and a general category.
Choose your sex and units first. Metric uses centimetres and imperial uses inches, and the labels change with your choice. Enter height, neck and waist, and hip as well if you chose Female (the hip box is hidden for men). Measure each place the same way every time. The result shows your estimated body fat and a category.
Body Fat Calculator Formula Explained
US Navy Circumference Equations
For men: body fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450. All lengths must be in the same unit. The logarithms capture the non-linear relationship between girth and estimated fat. Results are sensitive to measurement technique; consistent tape placement improves repeatability.
Imperial measurements are converted to centimetres (× 2.54) before the equation runs. The calculator then labels the result. For men: below 6% is Essential fat, 6 to 13.9% Athletic, 14 to 17.9% Fitness, 18 to 24.9% Average and 25% or more Obese. For women: below 14% is Essential fat, 14 to 20.9% Athletic, 21 to 24.9% Fitness, 25 to 31.9% Average and 32% or more Obese. These are broad labels, not a medical assessment.
Body Fat Calculator Example Calculation
A man 180 cm tall with a 38 cm neck and 90 cm waist gets an estimated 19.8% with the Navy method, which the calculator labels Average. A woman of similar height with neck, waist and hip measurements entered correctly will use the female equation, which includes hip circumference. Consistent morning measurements give more comparable trends over weeks.
Worked example: choose Male and Metric, then enter 180 cm height, 38 cm neck and 90 cm waist. The result is 19.8%, category Average. Choose Female and Metric with 165 cm height, 32 cm neck, 78 cm waist and 98 cm hip, and the result is 30.4%, category Average. Choose Male and Imperial with 70 in height, 15 in neck and 35 in waist, and the result is 19.3%.
When to use this tool
Use this when you want a practical body-composition estimate without clinic equipment—useful for gym tracking. It is not a substitute for DXA or professional assessment when medical decisions are involved.
Key Features & Benefits of This Body Fat Calculator
- US Navy circumference method — needs only your height and tape measurements of neck and waist (plus hips for women), with no special equipment.
- Separate equations for men and women — the hip box appears only when you choose Female.
- Centimetres or inches — the labels switch with your choice of units.
- Category label — Essential fat, Athletic, Fitness, Average or Obese, with separate ranges for men and women.
- Instant, free and private — runs entirely in your browser, no sign-up, nothing stored.
Good to know
Tape placement matters: neck just below the larynx, waist at navel level, and for women hips at the widest point. Repeat measurements at the same time of day for trends that are meaningful in fitness tracking.
Body Fat Calculator — FAQs
How accurate is the Navy method?
It is an estimate with typical error of a few percentage points. Hydrostatic weighing, DXA or professional calipers are more precise when available.
When should I measure?
Morning, before eating, with the same tape tension each time produces more comparable results across sessions.
Why is hip required only for women?
The original Navy equations include hip circumference for women because it improved the statistical fit in the validation samples.
How accurate is the US Navy method compared to DEXA scans?
It typically comes within a few percentage points of clinical methods for most body types, though accuracy can drop for very lean or very heavy individuals.
Sources and review
Sources last checked: . These sources give the background for this calculator. They are general information and do not replace advice from a doctor, midwife or registered dietitian.
- Hodgdon and Beckett (1984): Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and Height: Naval Health Research Center report 84-11, the basis of the male equation.
- Hodgdon and Beckett (1984): Prediction of Percent Body Fat for U.S. Navy Women from Body Circumferences and Height: Naval Health Research Center report 84-29, the basis of the female equation.