Body Fat Calculator

A tape measure and two minutes gives an estimate of your body fat — and this page prints it the honest way, as a band, because the method’s own validation is three to four percentage points wide. You also get it in pounds of fat and pounds of lean mass, which is the half that tells you whether a diet is working.

You are

The equations are sex-specific, and the women’s one needs a hip measurement as well.

ft in
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Weight and age add the pounds of fat and lean mass, and the second estimate. Type units if it is easier — 86 cm, 72 kg.

Where to put the tape

    Your body fat is somewhere in

    25.2–33.2%

    What each range means
    CategoryBody fatWhat it is

    A tape estimate is not a measurement, and a category is a published classification rather than a statement about your health. Nothing here diagnoses anything. If a number on this page worries you, the useful next step is a conversation with a doctor, not a tighter tape.

    Equations and categories checked 2026-09-23.

    Quick answer: a tape measure will tell you your body fat to within about three or four percentage points — no better, and no worse. For men the equation needs height, neck and waist; for women, hips as well. The typical non-athlete sits around 18–24% (men) or 25–31% (women), and the useful number is not today’s reading but which way it moves over a month.

    How to use it

    Measure with a cloth tape, standing relaxed, at the end of a normal breath out — not sucked in, not pushed out. Men measure the waist across the navel; women at the narrowest point, usually just above it. Take each measurement three times and use the middle one: a quarter of an inch at the waist moves the answer by about half a percentage point.

    Add your weight and age and you also get the answer in pounds of fat and pounds of lean mass, plus a second estimate that uses no tape at all.

    Why the answer is a range

    The equations on this page came out of the Naval Health Research Center in 1984, where they were fitted against hydrostatic weighing — dunking people in a tank, the laboratory standard of the day. They correlate with it at about 0.90, and their typical error is three to four percentage points.

    Three points does not sound like much until you look at what it crosses. A woman reading 29% is somewhere between 25% and 33%, which spans two of the five published categories. Printing “29.2%” and stopping would suggest a precision that no tape measure has ever had, so this page prints the range first and the single figure underneath it.

    The same honesty applies to the second method. Estimating body fat from BMI, age and sex — Deurenberg’s 1991 equation — needs no tape and has a standard error of about four points, and it fundamentally cannot tell muscle from fat: a rower and a sedentary person of the same height, weight and age get the same answer. It is here because it is what the BMI-based calculators are doing, and because seeing the two disagree is more informative than either one alone. They are not averaged.

    The military moved on, which is worth knowing

    This is still called “the Navy method”, but the US Army stopped using a multi-site tape test: Army Directive 2023-11 phased in a single abdominal measurement, and since June 2024 the one-site method is the only circumference test it authorises. The Navy equations remain what the fitness world means by a tape test, and they remain an estimate — which is the whole point of the band above.

    What the categories mean, and what they do not

    The five bands come from the American Council on Exercise and they are a classification, not a diagnosis. Two things are worth saying plainly. First, “essential fat” is a floor, not a target: below roughly 5% for men and 13% for women the body stops doing things it needs to do, and for women that shows up as periods stopping and bone density falling. Second, where the fat sits matters as much as how much of it there is — which is what a waist measurement tells you, and why it is worth writing down alongside this number.

    The number that actually tells you a diet is working

    Scale weight moves with water, salt, carbohydrate and the time of the month, and it can hide a real change for weeks. Lean mass is the number that says whether a deficit is costing you muscle: if it is falling fast, the deficit is too big or the protein is too low. Measure the same way, at the same time of day, once a fortnight, and watch the trend rather than any single reading.

    FAQ

    How accurate is the Navy body fat calculator?
    Its own validation against hydrostatic weighing reports a correlation of about 0.90 and a typical error of three to four percentage points. That makes it good enough to place you in a broad band and to track change over time, and not good enough to argue about a decimal point. DEXA scans are tighter but not perfect either, and they cost money.
    What is a healthy body fat percentage?
    The American Council on Exercise puts the typical non-athlete at 18-24% for men and 25-31% for women, with “fitness” ranges of 14-17% and 21-24%. Those are descriptions of populations rather than targets for you, and a doctor looking at your health would also want your waist, your blood pressure and your blood work, none of which a tape can see.
    Why is my BMI-based estimate so different from the tape one?
    Because they are measuring different things. The tape equations use where your body is wide; the BMI equation only knows your height, weight, age and sex. If you carry more muscle than average, the BMI estimate reads high; if you carry very little, it reads low. When the two disagree by several points, the tape number is the better of the two — and the disagreement itself is information.
    Can I lose fat from just my stomach?
    No — spot reduction is not a thing anybody has been able to demonstrate. You lose fat roughly in the pattern your genetics dictate, and for many people the waist is the last place it goes. What a deficit does control is the total, and this page is a reasonable way to watch it fall.
    How often should I measure?
    Once every two weeks is plenty, measured the same way at the same time of day — ideally in the morning, before eating. Measuring daily produces noise you will read as progress or failure, and neither reading will be real.
    Is a body fat scale more accurate than this?
    Not necessarily. Bathroom scales that estimate body fat pass a small current through you and infer fat from resistance, which is strongly affected by how hydrated you are — the same person can read several points apart morning and evening. Both methods are estimates; the tape at least gives the same answer for the same body whatever it has drunk.
    What is lean body mass?
    Everything that is not fat: muscle, bone, organs, blood, water. It is the number worth protecting during a diet, because losing it is what makes a person “skinny fat” at the end of a long cut, and it is why the protein target and some resistance training matter more than the size of the deficit.