Free Online Body Fat Percentage Calculator, US Navy Tape Method and BMI
Estimate your body fat without a caliper. The US Navy method uses a tape measure at the neck, waist and hip, and the BMI method needs only your height, weight and age. Enter your figures to get the percentage, the category it falls in, and your fat and lean mass in weight, with a plain note on how rough each estimate is.
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Body Fat Percentage CalculatorThe US Navy tape method, or a quick estimate from BMI.
Everything is worked out in your browser. No number you type is sent anywhere, and there is no account.
Your measurements
Nothing is uploaded; every number stays in your browser.
The Navy method is more accurate; the BMI one needs no tape.
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Result
The save button in the top bar keeps the numbers you have filled in, on this device only.
Units and numbers
Display
Size
Theme
Full screen hides the page around the tool. Press Escape, or the button in the bar, to come back.
History
Your data
Settings, history and saved setups live in this browser and nowhere else. There is no account and no server, which also means clearing them here is final.
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The US Navy method measures the girth of your neck and waist, and your hip too for women, then uses
your height to estimate the fat under it all. Because it reads your actual shape, it is noticeably
better than working body fat out from BMI, which knows only your height, weight and age and so
cannot tell a heavy, lean build from a soft one.
Measure carefully; the tape is where the error creeps in. Keep it snug but not tight, level
all the way round, and measure the waist at the navel and the neck just below the larynx. A
couple of centimetres out on the waist can move the result by a whole percent, so measure twice.
Even done well, these are estimates. A DEXA scan or skinfold calipers in trained hands are
more accurate. What a tape method is genuinely good at is tracking change: measured the same way
each time, it shows the direction and rough size of a shift, which is usually what you actually
want to know.
Where Your Input Goes
Nowhere. And you can check that yourself.
Your measurements are worked out in your browser and never sent anywhere.
It is all done by your own browser. Press F12, open the Network tab, and use the tool:
the page fetches its own code and nothing else. Or load the page, turn off your wifi, and
carry on. It still runs, because there was never a server in the middle.
How to Estimate Body Fat
A few steps, and nothing is uploaded.
1
Choose a methodThe US Navy tape method, or a quick estimate from your BMI and age.
2
Enter your height and sexIn metric or imperial. Women also enter a hip measurement for the Navy method.
3
Add your measurementsNeck and waist for the Navy method, or weight and age for the BMI one.
4
Read the percentageYour body fat, the category, and your fat and lean mass if you gave a weight.
What to Know About Body Fat Estimates
Including the things this tool cannot do.
The Navy method reads your shape; the BMI one does not. Girth at the neck, waist and hip captures far more than height and weight alone, so the tape method is the more accurate of the two. The BMI method is there for when you have no tape, and it is honestly rougher.
How you measure decides the result. Keep the tape snug and level, waist at the navel and neck just below the larynx. A two centimetre error on the waist can shift the answer by a full percent, so measure each spot twice and take the steady figure.
Both are estimates, not a scan. A DEXA scan or skinfold calipers in trained hands are more accurate than any tape formula. What these are good at is tracking change: measured the same way each time, they show the direction and rough size of a shift reliably.
Categories are broad guides. The bands from essential fat through athletic to average are rules of thumb that differ by source, and they differ between men and women. Do not read too much into being a point either side of a line; the trend over months matters more than one reading.
Key Features & Capabilities
What this tool does, and what it deliberately does not.
US Navy tape methodFrom neck, waist and hip girth plus your height.
Or from BMIA quicker estimate when you have no tape measure.
Fat and lean massYour body fat split into weight, if you enter a weight.
As you typeThe result updates while you edit, with no run button.
History and savedRecent results and named setups, on this device only.
Nothing uploadedYour measurements stay in the browser.
About the Body Fat Percentage Calculator
Body fat percentage tells you something BMI cannot: how much of your weight is actually fat. This calculator estimates it two ways. The US Navy method uses a tape measure at the neck, waist and hip and reads your real shape, which makes it the more accurate. The BMI method needs no tape at all, working from your height, weight and age, and is the rougher of the two by some way.
Whichever you use, the result comes with the category it falls in, from essential fat through athletic and fitness to average, and, if you enter your weight, your fat and lean mass in kilograms or pounds. Everything is worked out in your browser, in metric or imperial, and none of your measurements are uploaded.
It is worth being clear that these are estimates. A DEXA scan or calipers in trained hands measure body fat more precisely than any formula from a tape. The real value of a tape method is consistency: measured the same way each time, it tracks change well, and the direction of travel over months is usually far more useful than a single exact-looking number.
Frequently Asked Questions
Which method to trust, how to measure, and how accurate it is.
The US Navy tape method. It measures the girth of your neck and waist, and hip for women, so it reads your actual shape. The BMI method only knows height, weight and age, so it cannot tell a lean heavy build from a soft one. Use the Navy method if you have a tape.
With a soft tape, snug but not tight, and level all the way round. Measure the waist at the navel, the neck just below the larynx, and, for women, the hip at its widest. Measure each twice and use the steady figure, since small errors move the result.
It is an estimate, usually within a few percent of a proper measurement for most people. A DEXA scan or skinfold calipers are more precise. The tape method is best used to track change over time, measured the same way each session, rather than as an exact number.
It differs by sex and source. Broadly, fitness ranges are around 14 to 21 percent for men and 21 to 25 for women, with athletes lower and essential fat lower still. The tool shows the category your figure falls in, but treat the bands as guides, not hard lines.
No. Everything is worked out in your browser, with history and saved setups on this device only. You can confirm it in the Network tab or by working offline.
