Is it safe to use the Body Fat Calculator online?

Yes — and ours is safer than most. Many free online tools quietly upload your files to their servers to do the work. We don't. Everything happens inside your browser on your own device, so your files never reach the internet. There's no upload step, no server copy, and no way for us (or anyone else) to see what you're working on.

Are my files uploaded to a server?

No. There's no server-side processing here. The whole tool is a tiny app that runs in your browser — we don't even have a server that could receive your files. You can confirm this by opening your browser's network tab while you use the tool: nothing leaves your device.

Do I need to sign up or pay?

No. There's no account, no email collection, no credit card. The tool is free to use as much as you want, on as many files as you want. We're supported by a few unobtrusive ads on the page — not by your data.

How accurate is it really?

±3-4% vs DXA in validation studies. Skinfold callipers (~±3%) and DXA (~±1%) are more accurate but need equipment. BIA scales (~±5%) are noisier than this.

Men: BF% = 86.010·log₁₀(waist−neck) − 70.041·log₁₀(height) + 36.76. Women: BF% = 163.205·log₁₀(waist+hip−neck) − 97.684·log₁₀(height) − 78.387. All in cm.

What are healthy ranges?

Men: essential 2-5%, athletes 6-13%, fitness 14-17%, average 18-24%, obese ≥25%. Women: essential 10-13%, athletes 14-20%, fitness 21-24%, average 25-31%, obese ≥32%.

Body Fat Calculator (US Navy Method)

Body fat percentage from tape-measure circumferences using the US Navy method — accurate to ±3-4% versus DXA scans, with no equipment beyond a tape measure. Different formulas for men (neck + waist) and women (neck + waist + hip).

Features

US Navy circumference method (validated against DXA)
Separate male / female formulas
Metric (cm/kg) or imperial (in/lb) input
Body-fat category: essential, athletic, fitness, average, obese
Lean body mass and fat mass (kg/lb) breakdown
Visual fat-distribution badge

How to body fat calculator (us navy method)

Pick sex + units — Men: neck + waist. Women: neck + waist + hip.
Measure circumferences — Neck below larynx; waist at navel (men) or narrowest (women); hip at widest.
Enter height + weight — Optional but unlocks lean/fat mass.

Frequently asked questions

Is it safe to use the Body Fat Calculator online?: Yes — and ours is safer than most. Many free online tools quietly upload your files to their servers to do the work. We don't. Everything happens inside your browser on your own device, so your files never reach the internet. There's no upload step, no server copy, and no way for us (or anyone else) to see what you're working on.
Are my files uploaded to a server?: No. There's no server-side processing here. The whole tool is a tiny app that runs in your browser — we don't even have a server that could receive your files. You can confirm this by opening your browser's network tab while you use the tool: nothing leaves your device.
Do I need to sign up or pay?: No. There's no account, no email collection, no credit card. The tool is free to use as much as you want, on as many files as you want. We're supported by a few unobtrusive ads on the page — not by your data.
How accurate is it really?: ±3-4% vs DXA in validation studies. Skinfold callipers (~±3%) and DXA (~±1%) are more accurate but need equipment. BIA scales (~±5%) are noisier than this.
What's the formula?: Men: BF% = 86.010·log₁₀(waist−neck) − 70.041·log₁₀(height) + 36.76. Women: BF% = 163.205·log₁₀(waist+hip−neck) − 97.684·log₁₀(height) − 78.387. All in cm.
What are healthy ranges?: Men: essential 2-5%, athletes 6-13%, fitness 14-17%, average 18-24%, obese ≥25%. Women: essential 10-13%, athletes 14-20%, fitness 21-24%, average 25-31%, obese ≥32%.