Skinfold Body Fat Calculator (7-Site)

Seven caliper pinches, your age and sex. More sites means the estimate depends less on any one measurement.

How the Skinfold, 7-site method works

Sum the seven readings (S). Men BD = 1.112 − 0.00043499·S + 0.00000055·S² − 0.00028826·age; women BD = 1.097 − 0.00046971·S + 0.00000056·S² − 0.00012828·age. Then body fat % = 495 ÷ BD − 450.

Worked example

A 30-year-old man whose seven sites sum to 100 mm: BD ≈ 1.0654, so body fat ≈ 14.6%.

Body-fat ranges (adults)

Category	Men	Women
Essential fat	2–5%	10–13%
Athletes	6–13%	14–20%
Fitness	14–17%	21–24%
Average	18–24%	25–31%
Above average	25%+	32%+

Other ways to estimate body fat

U.S. Navy method — tape measure only, the quickest.
Skinfold, 3-site — Three caliper pinches. The Jackson-Pollock generalised equation.
RFM — Relative Fat Mass — one ratio of height to waist, no caliper.
From BMI — Roughest estimate — from BMI, age and sex, nothing to measure but weight and height.

Whichever you pick, stick with it: the direction over weeks matters more than the exact figure. To lower body fat, run a modest deficit with the calorie calculator, keep protein high via the macro calculator, and lift.

Source: Jackson & Pollock 1978 / 1980, 7-site generalised equation. Siri body-density conversion: Siri 1961.

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Frequently asked questions

What are the seven sites?

Chest, midaxillary (side of the torso), triceps, subscapular (below the shoulder blade), abdomen, suprailiac (above the hip bone) and thigh. Unlike the 3-site version, the same seven sites are used for both men and women — only the equation coefficients differ.

Is 7-site better than 3-site?

Slightly. Adding sites reduces the effect of a single mis-measurement, so the 7-site result is a little more stable and is the standard for careful field testing. For casual tracking the 3-site version is quicker and close enough.

Do I need a partner?

For the back sites (subscapular, midaxillary) yes — you cannot pinch and read them accurately on yourself. The front sites you can do alone. A consistent partner also removes some measurement drift.

What caliper should I buy?

A spring-loaded caliper with a constant jaw pressure (around 10 g/mm²) and a dial or digital readout. Cheap plastic calipers without constant pressure add several millimetres of error. Whatever you buy, use the same one every time.

How does this compare with a DEXA scan or a smart scale?

DEXA is more accurate and also shows regional fat and bone density, but costs money. Bioimpedance scales are convenient but swing with hydration. A careful 7-site skinfold sits between them and is free after the caliper.

Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.