Body Fat
Body Fat — runs in your browser. Inputs are not stored.
Body fat % (estimate)
Enter values, then press Calculate.
Not a medical diagnosis. An estimate for reference; follow a professional or device for accurate measurement.
How to use
- In Method, choose the US Navy formula or a BMI-based estimate.
- Select sex (male or female). Navy + female also opens a hip-circumference field.
- For Navy, enter height (cm), neck, and waist (plus hips for women). For BMI, enter height, weight (kg), and age.
- Press Calculate for body-fat % and a note (US Navy / BMI estimate).
- Measure the tape level on the skin; circumference can change after meals or with posture. Results are for reference.
Key concepts
This body-fat calculator is for estimating body-fat % without InBody or calipers. The US Navy formula uses logs of height and neck/waist (and hips for women). The BMI method is a regression from BMI, age, and sex. Units are cm for height and circumferences, kg for weight. If you can measure circumferences, Navy is commonly used. A 1 cm tape error can swing the result.
Numbers can differ from DEXA, hydrostatic weighing, or a clinician. BMI often overestimates fat in muscular people. This is not a medical diagnosis. Inputs are not sent to a server. Athletes are especially prone to BMI overestimating fat; Navy is sensitive to waist. Use it as a trend, not a prescription.
Example
Male, Navy, height 170 cm, neck 38 cm, waist 80 cm often lands around 14% body fat. Switch to BMI (weight 70 kg, age 30) at the same height and the formula differs, so the value can diverge. Female Navy includes a waist + hips − neck term, so hip input is required. Female Navy example: height 160, neck 32, waist 70, hips 95 uses a different formula than the male example. Measuring before meals is relatively stable.
Notes
This result is not medical diagnosis or treatment advice. Discuss health, pregnancy, and nutrition decisions with a clinician.
Related: calorie calculator (BMR·TDEE) · water-intake calculator · protein-intake calculator
Frequently asked questions
Which is right for body fat, US Navy or BMI?
If you can measure circumferences, Navy is commonly used. BMI is a quick estimate from fewer inputs. Both are estimates—keep measurement conditions consistent rather than picking a “winner.”
Why do women need hip circumference for body fat?
The female Navy formula includes a waist + hips − neck term. The BMI method does not. The hip field is needed only for Navy + female.
Can I use the body-fat calculator for diagnosis?
No. It is for reference and does not replace medical judgment. Do not substitute this number for DEXA or clinic results.
Are body-fat units cm and kg?
Height and circumferences are cm; weight is kg. Convert inches first (×2.54).
Are body-fat numbers sent to a server?
No. Calculation runs only in the browser. Circumferences and weight are multiplied only here.
Where should I measure neck and waist?
Neck is often below the larynx; waist near the navel. Repeat the same points. It may differ from official protocol. Use the same posture and breath each time for comparison.
Last reviewed: 2026-09-04