Body Fat Calculator: US Navy Tape Method
Body fat percentage is the share of your weight that is fat. With a tape measure, the US Navy method estimates it from your height, neck and waist, plus hips for women: a 28-year-old man at 178 cm with a 38 cm neck and 84 cm waist comes out at 15.7%. Expect an estimate within a few points, not a scan. The guide below shows the same maths step by step.
Body Fat Calculator
US Navy Circumference Equations
Classification aligned with American Council on Exercise (ACE) standards.
American Council on Exercise (ACE) Categorization
Body fat categories for men and women.
| Category | Men Range | Women Range | What It Means |
|---|---|---|---|
| Essential Fat | 2% – 5% | 10% – 13% | The minimum fat the body needs to function. Not a target. |
| Athletes | 6% – 13% | 14% – 20% | Typical of many trained athletes. |
| Fitness / Fit | 14% – 17% | 21% – 24% | Lean, above the athletic band. |
| Average / Acceptable | 18% – 24% | 25% – 31% | A common range for adults. |
| Elevated / Obese | 25%+ | 32%+ | Above the ACE average band. Waist size and other health markers add context. |
How the US Navy Method Works
Developed by Hodgdon and Beckett at the Naval Health Research Center in 1984, the US Navy Circumference Method utilizes logarithmic anthropometric equations to estimate whole-body density (Db) and subsequent body fat percentage without expensive specialized radiological hardware.
1. The Mathematical Equations
Male Body Density: Db = 1.0324 - 0.19077 × log10(Waist - Neck) + 0.15456 × log10(Height)
Female Body Density: Db = 1.29579 - 0.35004 × log10(Waist + Hips - Neck) + 0.22100 × log10(Height)
Siri Equation for Body Fat %: BF% = (495 / Db) - 450
Body Composition Measurement Modalities Compared
| Method | Precision for One Person | Accessibility | Primary Limitation |
|---|---|---|---|
| DEXA Scan (Dual X-Ray) | The closest of these to a lab reference, though results still vary by machine | Low (clinic or lab) | Cost, small radiation dose |
| US Navy Tape Method | Can miss by several percentage points | Very High (Any Standard Tape) | Requires precise anatomical tape placement |
| Skinfold Calipers (7-Site) | Depends heavily on who takes the measurement | Moderate (Skilled Technician) | High inter-tester variability |
| Bioelectrical Impedance (BIA) | Shifts with hydration, meals and time of day | High (Smart Bathroom Scales) | Heavily distorted by water, food, and sweat |
2. Visceral Fat vs. Subcutaneous Fat
Body fat distribution is a more critical biomarker for cardiometabolic disease than total fat mass alone. Subcutaneous adipose tissue (under the skin) functions primarily as a protective energy reserve, whereas deep Visceral Adipose Tissue (VAT) surrounding the liver and mesenteric organs secretes inflammatory adipokines (TNF-alpha, IL-6), promoting insulin resistance, hepatic steatosis, and atherosclerosis.
How to Take Tape Measurements Accurately
Neck Circumference
Wrap the tape horizontally around the neck, starting directly below the larynx (Adam's apple). Keep the tape snug but without compressing soft tissue.
Waist Circumference
Men: measure across the navel (belly button). Women: measure the natural waist, the narrowest point of the abdomen, usually about halfway between the navel and the bottom of the breastbone. Keep the tape level, arms at your sides, and read it at the end of a normal breath out.
Hips (Females Only)
Measure around the hips where the buttocks stick out most when viewed from the side. Keep the tape parallel to the floor all the way round.
How to Calculate Body Fat Percentage
Body fat percentage is the share of your weight that is fat. This calculator estimates it with the US Navy circumference method: height, neck and waist on a tape, plus hips for women. The equations use centimetres. Inches are converted before the math. The result is an estimate you can repeat at home, not a clinic scan.
The opening inputs print 15.7%
The form opens on male, age 28, 75 kg, 178 cm, neck 38 cm and waist 84 cm. Age is stored and not used. Waist minus neck is 84 − 38 = 46 cm.
Body density = 1.0324 − 0.19077 × log10(46) + 0.15456 × log10(178). log10(46) is 1.66276 and log10(178) is 2.25042, so density is 1.06302.
Body fat uses the Siri equation, (495 ÷ density) − 450. That is 495 ÷ 1.06302 − 450 = 15.654, which the card prints as 15.7%. 15.7 is under 18 and at least 14, so the label is Fitness (14–17%).
Fat mass uses the unrounded percentage: 75 kg × 15.654% = 11.7 kg. Lean mass is the rest of the weight, 63.3 kg. Katch-McArdle BMR is 370 + 21.6 × lean mass in kg, which rounds to 1,736 kcal.
Women use hips, and a different equation
Women do not use waist minus neck alone. The form adds hips: waist + hips − neck. Select Female or the hip row stays hidden and the male equation runs. A woman at 65 kg and 165 cm, with neck 31 cm, waist 68 cm and hips 94 cm, has a sum of 131 cm.
Density = 1.29579 − 0.35004 × log10(131) + 0.22100 × log10(165) = 1.04472. Body fat is 495 ÷ 1.04472 − 450 = 23.809, which prints as 23.8%. That is under 25, so the label is Fitness (21–24%). Fat mass is 15.5 kg, lean mass is 49.5 kg, and Katch-McArdle BMR is 1,440 kcal.
The chart bands sit higher for women. Essential fat on this page is 10–13% for women and 2–5% for men. That is why the same tape numbers are not a fair comparison across the sex switch.
What the category labels mean
The chart follows American Council on Exercise bands. The card prints the cut that contains the result. Men: under 6% is Essential Fat (2–5%), under 14% is Athletic (6–13%), under 18% is Fitness (14–17%), under 25% is Average (18–24%), and 25% or above is High Body Fat (25%+). Women: under 14% is Essential Fat (10–13%), under 21% is Athletic (14–20%), under 25% is Fitness (21–24%), under 32% is Average (25–31%), and 32% or above is High Body Fat (32%+).
Fitness or Average is a common range for many adults, not a score you must hit. Essential fat is the low end of the chart, not a long-term target. The label is not a diagnosis. See the medical disclaimer.
Lean mass and the Katch-McArdle number
Lean body mass here is weight minus fat mass: muscle, bone, organs and water together. The tape does not measure muscle on its own. Katch-McArdle then estimates calories at rest from that lean mass: 370 + (21.6 × lean mass in kg), the general equation Cunningham proposed in 1991. On the opening man that is 1,736 kcal. It can suit someone whose tape result is far from average, and it is still an estimate, not a measured metabolic rate.
Daily calories are a separate step. The same 75 kg, 178 cm, 28-year-old man at the homepage activity of ×1.55 has a TDEE of 2,678 kcal on the TDEE calculator. A fat-loss target comes off that TDEE, not off the 1,736 kcal resting figure. The calorie calculator and the macro calculator set that intake. The BMR calculator uses Mifflin-St Jeor and Harris-Benedict, which do not need a tape.
Body fat percentage and BMI
BMI only compares height and weight. The same opening man is a BMI of 23.7 on the BMI calculator and 15.7% body fat here. A muscular adult can print a high BMI with a lower body-fat percentage than weight alone suggests. This tape method can also read high when muscle adds to the neck or the waist. Neither number is a scan.
What this page does not calculate
Calipers, a smart scale and a DEXA scan are different methods. This form only runs the Navy tape equations. It does not apply an Army, Navy or other service pass-or-fail table. Age starts at 14 and is ignored, so the same tapes print 15.7% at 28 and at 60. Do not turn that adult estimate into a diet for a teenager. If the percentage would fall under 2% or rise over 60%, the card stays inside that range. If a man's waist is not larger than his neck, or a woman's waist plus hips is not larger than her neck, the form shows an error instead of a percentage.
Keeping Tape Measurements Consistent
Use a soft tape that does not stretch. Measure in the morning, before you eat, with the tape snug and level. The neck box is the circumference just below the larynx. Men measure the waist at the navel; women measure the narrowest point of the waist, as the Navy method specifies. Use the same landmark every time. Hips, for women only, are the widest point, with the tape parallel to the floor. Do not suck the stomach in. Repeat every 2 to 4 weeks. One reading moving by a point is often water, not fat.
Body fat from BMI: a second estimate
If you have no tape measure, BMI gives a rougher estimate. A study of 1,229 people aged 7 to 83 produced this adult formula: body fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, with sex as 1 for men and 0 for women. Its typical error was about 4 percentage points, and it slightly overestimated body fat in people with obesity (Deurenberg et al., 1991).
For the opening man, BMI 23.7 at age 28 gives 18.6%, against 15.7% from the tape. For the opening woman, BMI 23.9 at age 30 gives 30.2%, against 23.8%. Two methods, two answers: the tape sees waist size, while BMI only knows weight and height. Use one method consistently and watch the trend.
Body fat percentage by age
The ACE chart above does not change with age, and neither does the Navy formula. At the same BMI, though, older adults tend to carry more fat: in the Deurenberg formula, each 10 years adds about 2.3 percentage points. So a reading that sits in the Average band at 60 is less unusual than the same reading at 25. Treat any chart as a guide rather than a pass or fail.
How to lower your body fat percentage
Body fat falls when you eat below your maintenance calories for long enough, and the percentage falls faster when you keep or build muscle at the same time. In practice that means a moderate calorie deficit from the calorie calculator, a high protein intake from the macro calculator, and regular resistance training. Re-measure every two to four weeks with the same tape landmarks.
Frequently Asked Questions
How do you calculate body fat percentage?
This page uses the US Navy circumference equations in centimetres. The form opens on a man at 75 kg, 178 cm, neck 38 cm and waist 84 cm. Waist minus neck is 46. Body density is 1.0324 − 0.19077 × log10(46) + 0.15456 × log10(178), which is 1.06302. Body fat is 495 ÷ 1.06302 − 450, and the card prints 15.7%. Age is collected and not used.
What is a good body fat percentage?
The card uses these cuts. Men: under 6% Essential Fat, under 14% Athletic, under 18% Fitness, under 25% Average, and 25% or above High Body Fat. Women: under 14% Essential Fat, under 21% Athletic, under 25% Fitness, under 32% Average, and 32% or above High Body Fat. The opening result, 15.7%, prints as Fitness (14-17%). The chart is a guide, not a diagnosis.
Is the body fat calculator different for women and men?
Yes. Men use waist minus neck. Women use waist plus hips minus neck, and the category bands are higher. A woman at 65 kg, 165 cm, neck 31 cm, waist 68 cm and hips 94 cm prints 23.8%, Fitness (21-24%), with 15.5 kg of fat mass and 49.5 kg of lean mass.
How accurate is the US Navy body fat calculator?
It is a tape estimate, not a DEXA scan, hydrostatic weighing, calipers, or a smart scale. An individual result can be several points off, especially if you are very lean, very muscular, or the tape sits in a different place each time. Repeat the same landmarks and read the trend.
What is the Katch-McArdle number on this page?
Katch-McArdle estimates resting calories from lean mass: 370 + 21.6 × lean mass in kg. On the opening inputs, lean mass is 63.3 kg and the card prints 1,736 kcal. It is an estimate from the tape result, not a measured metabolic rate.
Does this page apply Army body-fat standards?
No. The equations are the US Navy circumference formulas. This page does not apply an Army, Navy, or other service pass-or-fail table.
Does age change the body fat result?
No. The age box starts at 14 and the formula ignores it. The same tapes print 15.7% at age 28 and at age 60. Do not turn that adult estimate into a diet for a teenager.
How do I measure my body fat at home?
Use a soft tape measure. Men measure the neck just below the Adam's apple and the waist at the navel. Women measure the neck, the narrowest point of the waist and the widest point of the hips. Enter those with your height and the calculator applies the US Navy equations. Measure at the same time of day each time.
Is body fat from BMI as good as the tape method?
It is rougher. A BMI-based formula had a typical error of about 4 percentage points in its original study, and it cannot see waist size. For the opening man it gives 18.6% against 15.7% from the tape. Either can track change if you stick to one.
Does body fat percentage go up with age?
At the same BMI, it tends to. In one widely used formula, each 10 years adds about 2.3 percentage points of body fat at the same BMI. The tape method here ignores age, so it measures your current shape rather than adjusting for it.
Sources
- Hodgdon JA, Beckett MB. Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and Height. Report No. 84-11. San Diego, CA: Naval Health Research Center; 1984.
- Hodgdon JA, Beckett MB. Prediction of Percent Body Fat for U.S. Navy Women from Body Circumferences and Height. Report No. 84-29. San Diego, CA: Naval Health Research Center; 1984.
- Siri WE. Body composition from fluid spaces and density: analysis of methods. In: Brozek J, Henschel A, eds. Techniques for Measuring Body Composition. Washington, DC: National Academy of Sciences; 1961:223–244.
- American Council on Exercise. Body fat percentage categories (Essential, Athletes, Fitness, Average, Obese).
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. Lippincott Williams & Wilkins (Katch-McArdle equation).
- U.S. Navy. Guide 4: The Body Composition Assessment (BCA). January 2016.
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. British Journal of Nutrition. 1991;65(2):105–114.
- Cunningham JJ. Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. American Journal of Clinical Nutrition. 1991;54(6):963–969.
Results are estimates for healthy adults, not medical advice. See the medical disclaimer and how these calculators work.