Health & Fitness
Body Fat Calculator
Estimate body fat percentage from a tape measure — no callipers or scales needed.
Body Fat Calculator
About the Body Fat Calculator
This estimates body fat percentage from a tape measure using the US Navy circumference method. Men need height, neck and waist; women need height, neck, waist and hips. No callipers, no scales, no gym equipment.
It also runs the Deurenberg BMI-based estimate as a cross-check and shows both. When the two agree you can have reasonable confidence; when they diverge, that gap is itself informative, and the page explains what it usually means.
Enter your weight as well and you get fat mass and lean mass in kilograms — more useful than a percentage when you are tracking change, because you can see whether you are losing fat or losing lean tissue.
How to use the Body Fat Calculator
- Choose your sex — women also need a hip measurement.
- Enter your height.
- Measure your neck just below the larynx and enter it.
- Measure your waist — at the navel for men, narrowest point for women.
- Optionally add weight and age for fat mass, lean mass and a BMI cross-check, then select Calculate body fat.
The Navy formula
Men : %BF = 495 ÷ (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450
Women: %BF = 495 ÷ (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.22100×log₁₀(height)) − 450
All measurements in centimetres.
Worked example
A man 180 cm tall, neck 38 cm, waist 88 cm.
Waist minus neck: 88 − 38 = 50 cm.
Feeding those into the formula gives 18.4% body fat.
18.4% — just inside the "average" band for men
At 80 kg, that is 14.7 kg of fat and 65.3 kg of lean mass. Losing 4 cm from the waist with everything else unchanged would take him to 15.3%, into the fitness band.
Healthy body fat ranges
| Category | Men | Women |
|---|---|---|
| Essential fat | 2 – 5% | 10 – 13% |
| Athletic | 6 – 13% | 14 – 20% |
| Fitness | 14 – 17% | 21 – 24% |
| Average | 18 – 24% | 25 – 31% |
| Above average | 25% and over | 32% and over |
Women carry more essential fat than men — this is normal physiology, not a difference in fitness. Dropping toward the essential floor is not a goal for either sex; it carries real health consequences, including hormonal and menstrual disruption in women.
How accurate is the tape method?
The Navy method typically lands within about 3–4 percentage points of a DEXA scan for people of average build. That is respectable for a tape measure and free, but it is an estimate, not a measurement.
Where it drifts:
- Very lean or very heavy people — accuracy falls at both extremes.
- Unusual fat distribution — the formula assumes a typical pattern for your sex.
- Muscular builds — a thick neck lowers the estimate, sometimes flatteringly.
- Measurement error — a 1 cm mistake at the waist moves the result by roughly a percentage point.
Consistency beats precision here. Measure the same way, at the same time of day, with the same tape, and the trend will be reliable even if the absolute number is a little off.
Measuring properly
- Neck — just below the larynx, tape sloping slightly down at the front. Do not flex.
- Waist (men) — at the navel, horizontal all the way round.
- Waist (women) — at the narrowest point, usually above the navel.
- Hips (women) — at the widest point of the buttocks.
- Measure on bare skin, standing relaxed, at the end of a normal breath out. Do not pull the tape tight or hold your stomach in.
- Take each measurement three times and use the middle value.
Measure first thing in the morning before eating. Waist circumference varies by a centimetre or more across a day, which is enough to change the result.
Navy, Army and other tape standards
Several organisations use circumference methods, and they are not interchangeable. This calculator implements the US Navy formula above. The US Army's body composition programme uses its own procedure and its own pass standards, which have been revised in recent years, so an Army result will not match what you see here.
If you need a figure for an official assessment, use the standard your own organisation publishes and have it taped by whoever is authorised to do it. A web calculator is for personal tracking.
FFMI calculator: fat mass, lean mass and FFMI
Percentages hide what is actually happening. Enter your weight and the tool gives fat mass and lean mass in kilograms, which is what you want when tracking progress — a stable percentage with rising lean mass is a very different outcome from a stable percentage with both falling.
From lean mass you can also work out fat-free mass index, a way of judging muscularity independent of fat:
FFMI = lean mass (kg) ÷ height (m)²
Roughly: 18–20 is average for men, 20–22 well-trained, above 25 is unusual without pharmaceutical help.
For weight against height instead of composition, see the BMI calculator. To turn lean mass into a calorie figure, the BMR calculator accepts a body fat percentage for the Katch-McArdle equation.
This is a screening tool, not a diagnosis. It cannot see your muscle mass, bone density, medical history or family background, and it does not replace an examination. If you are concerned about your weight or health, speak to a doctor who can assess you properly.
Army body fat calculator: the one-site tape test (ABCP)
Soldiers who go over the Army height and weight table are taped under the Army Body Composition Program (ABCP). This section works as an army tape test calculator and an army body fat percentage calculator. In 2023 the US Army replaced its old neck-and-waist tape test with a simpler one-site method. It uses only your body weight and your waist at the navel.
Men: Body fat % = −26.97 − (0.12 × weight in lb) + (1.99 × waist in inches)
Women: Body fat % = −9.15 − (0.015 × weight in lb) + (1.27 × waist in inches)
Worked example
A male soldier weighs 180 lb with a 36-inch waist.
−26.97 − (0.12 × 180) + (1.99 × 36) = −26.97 − 21.6 + 71.64.
Army body fat ≈ 23.1%
A female soldier at 140 lb with a 32-inch waist: −9.15 − 2.1 + 40.64 = 29.4%.
| Age | Men — max body fat | Women — max body fat |
|---|---|---|
| 17–20 | 20% | 30% |
| 21–27 | 22% | 32% |
| 28–39 | 24% | 34% |
| 40 and over | 26% | 36% |
Army rules change. Check the current AR 600-9 and your unit's guidance before an official weigh-in. This page is for self-checks only.
Navy body fat calculator: why use it?
The calculator above uses the full US Navy method — neck, waist, and hips for women. Because it uses more measurements than the Army's one-site test, many people use it to track progress at home. Measure at the same time of day, with the tape snug but not tight, and take the average of three tries.
Body fat calculator caliper method (3-site)
Skinfold calipers pinch a fold of skin and fat. The Jackson-Pollock 3-site method is the most common home version.
- Men: chest, abdomen and thigh.
- Women: triceps, just above the hip bone (suprailiac) and thigh.
Men: density = 1.10938 − 0.0008267×S + 0.0000016×S² − 0.0002574×age
Women: density = 1.0994921 − 0.0009929×S + 0.0000023×S² − 0.0001392×age
Body fat % = 495 ÷ density − 450
S is the sum of the three skinfolds in millimetres. A 30-year-old man with a sum of 50 mm gets a density of 1.0643 and about 15.1% body fat. Calipers need practice; results from a trained tester are more reliable.
Other ways to use this calculator
One tape measure, several standards.
- US Navy body fat calculator — this calculator uses the full Navy method: neck, waist and, for women, hips.
- Navy method body fat percentage calculator — measure three times and use the average for each site.
- Army body fat calculator — the Army's one-site formula is shown above with a worked example.
- Body fat caliper calculator — use the Jackson-Pollock 3-site formula above with your skinfold readings.
- Tape measure body fat — all you need is a soft tape measure and a few minutes.
- Lean body mass calculator — add your weight and the result shows your lean mass and fat mass.
Frequently asked questions
Usually within about 3 to 4 percentage points of a DEXA scan for people of average build — good for a tape measure, but an estimate rather than a measurement. It drifts at the extremes, for unusual fat distribution, and for very muscular builds where a thick neck lowers the result. Measure consistently and the trend will be reliable even if the absolute figure is slightly off.
For men, roughly 14–17% is the fitness range and 18–24% is average. For women it is 21–24% and 25–31%. Women naturally carry more essential fat — that is physiology, not fitness. Going toward the essential minimum is not a goal for either sex; it carries genuine health risks, including hormonal and menstrual disruption.
Neck just below the larynx with the tape sloping slightly down at the front. Waist at the navel for men, at the narrowest point for women. Hips at the widest point of the buttocks for women. Measure on bare skin, standing relaxed, at the end of a normal breath out, without pulling the tape tight. Take three readings and use the middle one.
They are different methods measuring different things. The tape result uses your actual body shape; the Deurenberg estimate works only from BMI, age and sex, so it assumes an average build. When they diverge noticeably it usually means your build is not average — more muscle than typical, or fat distributed differently. Trust the tape result, since it reflects your real measurements.
Since 2023 the US Army uses a one-site tape test. Men: −26.97 − 0.12 × weight (lb) + 1.99 × waist (in). Women: −9.15 − 0.015 × weight + 1.27 × waist. A 180 lb man with a 36-inch waist comes out at about 23.1%.
Both are estimates, typically within a few percentage points of lab methods. The Navy method uses more measurements. For an official result, always use the method your own service requires.
Sources and further reading
- NHLBI — Assessing your weight and health risk — waist circumference and health risk thresholds
- American Council on Exercise — Body fat percentage norms — the category ranges shown above
- US Army — Army Body Composition Program (AR 600-9) — the separate Army standard, which this tool does not implement
- NIH — Body composition measurement methods — how circumference methods compare with DEXA
- Army Publishing Directorate — AR 600-9 — official Army body composition standards