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Body Fat Calculator

Body Fat Calculator is part of Toolspire and is ready as soon as this page loads. Men use height, neck and waist. Women also use the hip. A published check is a man at 70 in, 15 in neck and 33 in waist, about 9.1%. The page converts centimetres to inches before the formula.

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What you can do here

Centimetres in, inches inside

The tape most readers have is metric. The formula is not rewritten; the conversion is explicit.

Two equations

The select swaps the male and female Navy formulas. Hip is used only for the female one.

Impossible tapes refused

A waist that is not larger than the neck makes log of a non-positive number. The page returns nothing.

The sequence

How to use the Body Fat Calculator

  1. 1

    Measure in centimetres

    Height without shoes. Neck under the larynx. Waist at the navel for the male equation, and the hip at the widest point for the female equation.

  2. 2

    Pick the matching formula

    The constants are different. Leaving the select on male while typing a hip does not use the hip.

  3. 3

    Treat the percent as a band

    A tape pulled tight can move the result by more than a point. This is not a scan.

Worth knowing

  • Body Fat Calculator on Toolspire: the male equation is 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450, in inches.
  • The female equation adds the hip: log10(waist + hip − neck), with the constants 1.29579, 0.35004 and 0.22100.
  • You type centimetres. The page divides by 2.54 before those equations, because the published constants expect inches.
  • A man at 70 in, neck 15 in, waist 33 in (177.8 cm, 38.1 cm, 83.82 cm) lands near 9.1%.

What the Navy method actually measures

The equations estimate body fat from circumferences and height. They do not see muscle, and they punish a larger waist relative to the neck. The constants were published for inches, so a centimetre entry is converted with 2.54 and only then logged. A result outside a plausible range usually means the tape was on the wrong landmark or the wrong formula was selected. It is not a diagnosis and not a substitute for a clinical measurement.

FAQ

Questions about Body Fat Calculator

Where does Body Fat Calculator run?

Body Fat Calculator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

Do I type centimetres or inches?

Centimetres. The page converts to inches because the US Navy constants were fitted in inches.

Which waist measurement does the male formula use?

The abdominal circumference at the navel, with the neck measured below the larynx. A chest measurement will not do.

Why does the female formula need the hip?

The published equation adds hip to waist and subtracts neck before the logarithm. Without a positive hip the log is refused.

Is this the same as BMI?

No. BMI is weight over height squared. This page never asks for weight. A muscular person can have a moderate Navy estimate and a high BMI, or the reverse.

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