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TCalculator.

Ffmi Calculator

This free ffmi calculator gives you an answer in a couple of seconds, and shows the full working underneath so you can check it rather than take it on trust. Change any value and the result updates immediately. Nothing is stored, nothing is sent anywhere, and there is no sign-up.

Enter your values

Normalised FFMI

21.0

Lean body mass
68 kg
Unadjusted FFMI
21

How this is calculated

  1. 1

    Work out lean mass

    lean = weight × (1 − body fat %)

    lean = 80 × (1 − 0.15)

    = 68 kg

  2. 2

    Divide by height squared

    FFMI = lean ÷ height²

    FFMI = 68 ÷ 1.8²

    = 21

  3. 3

    Normalise to 1.8 m

    FFMI + 6.1 × (1.8 − height)

    21 + 6.1 × (1.8 − 1.8)

    = 21

  • Accuracy depends entirely on the body fat figure, which is hard to measure precisely outside a DEXA scan.

How to use this ffmi calculator

  1. Fill in your values. Every field starts with a sensible default, so you can change one number at a time and watch what it does to the result.
  2. Read the result. The headline figure sits in the pink box, with supporting numbers listed below it.
  3. Check the working. The breakdown shows each formula and the same formula with your numbers substituted in, so you can follow the method or reproduce it by hand.