Body Fat Calculator
Estimate body fat percentage using the US Navy method.
How this calculator works
Formula
US Navy tape method using height, neck, waist (and hip for women)
Method
Empirical formula validated against hydrostatic weighing.
Example
Man 178 cm, waist 85 cm, neck 40 cm ≈ 15% body fat.
The complete guide to the Body Fat Calculator
Body Fat Calculator is a free tool from Morecalcs designed to make a common calculation fast, transparent, and accurate. Estimate body fat percentage using the US Navy method. Below is a complete guide to what the tool computes, the formula it uses, when to reach for it, and the pitfalls to avoid.
What Body Fat Calculator does
Estimate body fat percentage using the US Navy method. You enter your values, the tool computes the result instantly, and shows a breakdown of the numbers that went into it. There's no signup, no data leaves your browser, and the calculator is optimized for both mobile and desktop.
How it works under the hood
Empirical formula validated against hydrostatic weighing. The math runs entirely client-side, so results update the moment you type. This makes it fast to explore 'what if' scenarios without waiting for a server round-trip.
The formula
The core equation is US Navy tape method using height, neck, waist (and hip for women). If you're doing this by hand, plug your numbers in directly — the calculator saves you the arithmetic and, more importantly, the errors that come with it.
A worked example
Man 178 cm, waist 85 cm, neck 40 cm ≈ 15% body fat. Enter these values above and confirm the result matches. Then change one input at a time to build intuition for how each variable affects the outcome.
When to use this calculator
Reach for Body Fat Calculator whenever you need a quick, reliable number for planning, comparison, or verification. It's especially useful when the calculation would be tedious or error-prone by hand, or when you want to compare several scenarios side by side. Because it's free and requires no account, you can bookmark it and use it repeatedly.
Common mistakes to avoid
The most common error is entering the wrong unit — for example, using annual instead of monthly figures, or millimeters when the calculator expects centimeters. Read the label above each field carefully. The second most common issue is trusting a single result: whenever the outcome will guide a real decision, run the calculation two or three times with slightly different assumptions to see how sensitive the answer is.
Related tools on Morecalcs
Morecalcs organizes calculators by category so related tools are one click away. From the Body Fat Calculator page you'll find companion tools in the sidebar — they use the same design and share input conventions, so switching between them is seamless.
Why we built it this way
Morecalcs is designed to be the calculator you keep bookmarked because it never gets in your way. No modal ads, no signup wall, no dark patterns. Every tool has a consistent layout: inputs on the left, results on the right, with an explainer below for when you want to understand the math instead of just get an answer.
Sharing your result
Every calculator page has a stable URL and a share-friendly preview, so you can send the tool to a friend and they'll see the same layout. Bookmark this page if you'll use it often — it loads in under a second on any modern connection.
Frequently asked questions
Is Body Fat Calculator free to use?
Yes. Every Morecalcs tool is free with no signup required.
Does the tool store my data?
No. Calculations happen in your browser. Nothing you enter is sent to a server or stored.
How accurate is the result?
The calculator uses the standard textbook formula for this problem. Results are as accurate as your inputs.
Can I use this on mobile?
Yes. Every Morecalcs page is fully responsive and works on any device.