Estimate body fat from neck, waist and height measurements, in cm or inches. Runs on your device.
The US Navy method estimates body fat from tape measurements and height, using logarithms. For men: body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450, with every length in cm. For women the waist term becomes waist + hip − neck, with constants 1.29579, 0.35004 and 0.221. A man of 180 cm with a 38 cm neck and 90 cm waist has waist − neck = 52, so the denominator is 1.0324 − 0.19077 × log10(52) + 0.15456 × log10(180) = 1.0495 and the result is 19.812, shown as 19.8%. Inches are converted to cm first (1 in = 2.54 cm), so 5 ft 11 in, a 15 in neck and a 35.5 in waist give the same 19.8%.
If you enter weight, fat mass is weight × body fat ÷ 100 and lean mass is the rest. At 80 kg and 19.8% that is 15.8 kg of fat and 64.2 kg of lean mass. If you also enter age, the page shows a second figure from the Deurenberg equation: body fat % = 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4, with sex as 1 for men and 0 for women. For the same man, with a BMI of 24.69 at age 35, that is 21.5%. A woman of 165 cm with a 32 cm neck, 75 cm waist and 100 cm hip at 62 kg and age 30 gets 29.9% from the Navy method and 28.8% from Deurenberg. The two methods use different inputs, so a gap of a point or two is normal.
The category comes from the American Council on Exercise table. For men the bands are essential fat 2 to 5%, athletes 6 to 13%, fitness 14 to 17%, average 18 to 24% and obese 25% or more. For women they are 10 to 13%, 14 to 20%, 21 to 24%, 25 to 31% and 32% or more. The table lists whole numbers, so this page reads the category from the body fat as shown, rounded to 1 decimal, and a value runs up to the start of the next band: 5.9% still counts as essential fat for a man and 17.9% as fitness. A figure below the first band is labelled below essential fat. The table under the answer marks your row.
Measure the neck just below the larynx, the waist at the navel for men or the narrowest point for women, and the hip at its widest, with the tape snug but not pressing. For the 180 cm example, a waist of 91 cm instead of 90 cm moves the result from 19.8% to 20.5%, so measure twice. For the male formula the waist must be larger than the neck, otherwise the logarithm is undefined and the page shows a message under the waist box. Measurements that give a figure outside the range the formula can describe show a message too. The page is for adults: age is optional from 18 to 80. It is an estimate, not medical advice, and it does not replace a body scan.
For men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450, with lengths in cm. For women, waist becomes waist + hip − neck and the constants are 1.29579, 0.35004 and 0.221. A man of 180 cm, neck 38 cm and waist 90 cm gets 19.8%.
Neck: just below the larynx, tape level. Waist: at the navel for men, at the narrowest point for women. Hip (women only): at the widest point. Keep the tape snug without pressing the skin. In the 180 cm example, 91 cm instead of 90 cm at the waist moves 19.8% to 20.5%, so measure twice.
The male formula takes the logarithm of waist minus neck, which cannot be worked out when the difference is 0 or negative. Check both measurements. A waist of 45 cm with a neck of 45 cm is refused. A waist of 45.5 cm is accepted but gives a figure outside the formula's range, so the page asks you to check the tape.
The page uses the American Council on Exercise table. A man at 19.8% is in the average band (18 to 24%). A woman at 29.9% is in the average band (25 to 31%). The table under the result marks your row and shows all five bands for your sex.
They use different inputs. The Navy method uses tape measurements and height. The Deurenberg estimate uses BMI, age and sex only, so it cannot see where weight sits. For a 180 cm, 80 kg, 35-year-old man they give 19.8% and 21.5%.
No. The numbers stay in this tab and are not stored on your device or sent anywhere. Reloading the page puts the example back. The page only counts that a result was shown, without any of your numbers.