Muscle to fat ratio

See your weight split into lean mass and fat. The ratio between them is more useful to track than your weight alone.

Your details

Sex
Age (optional)
Weight
Body fat
Height (optional, for the indexes)
Earlier weight (optional)
Earlier body fat (optional)

No body fat number? Try the body fat calculator first.

Lean to fat

3.5 to 1

kilos of lean for every kilo of fat

  • Lean mass9 st 5 lb
  • Fat mass2 st 9 lb
  • Healthy body fat range for women aged 18 to 39 (Gallagher 2000)21 to 33%, a ratio between 2.0 and 3.8 to 1
  • Your body fat against that rangewithin
  • Add your heightfor fat free and fat mass indexes, which compare people of different heights

Your ratio sits in the usual healthy range for women aged 18 to 39. Lean mass is not all muscle: it includes bone, organs and water too.

Losing muscle without trying, or getting weaker, is worth raising with your GP.

The working

Two piles

Fat mass = weight × body fat %. Lean mass is the rest. At 12 st 0 lb (76.2 kg) and 22% body fat, that is 16.8 kg of fat and 59.4 kg of lean, a ratio of 3.5 to 1.

Tracking

Why the ratio is useful to track

Start strength training and the scales may barely move while the ratio climbs, because you gain a little lean and lose a little fat. That is real progress the scales miss. Check every month or two rather than every week.

Add an earlier weight and body fat and the page shows what changed in each pile. From 12 st 7 lb (79.4 kg) at 25% to 12 st 0 lb (76.2 kg) at 22%, fat fell from 19.8 to 16.8 kg (down 3.1 kg) and lean went from 59.5 to 59.4 kg, so nearly all of the 3.2 kg lost was fat. Use the same scales or the same tester each time, because body fat readings can wobble by a few points.

Ballpark

Typical ratios

Body fatLean to fat
15%5.7 to 1
20%4 to 1
25%3 to 1
30%2.3 to 1
35%1.9 to 1

Healthy range

Your ratio against a healthy body fat range

Gallagher and colleagues (2000) linked body fat to the BMI range of 18.5 to 25 by age and sex. For women aged 18 to 39 that is 21 to 33% body fat, which works out at a lean to fat ratio between 2.0 and 3.8 to 1. For men of the same age it is 8 to 20%, a ratio between 4.0 and 11.5 to 1. The ranges rise a little at 40 and again at 60, so the page uses your age if you give it.

Height matters

Fat free mass index and fat mass index

Taller people carry more of everything, so a ratio alone can hide a low muscle mass. Dividing each pile by height squared (kg/m²) gives the fat free mass index and fat mass index. Schutz and colleagues (2002) measured over 5,600 healthy adults: the middle figures for 18 to 34 year olds were a fat free mass index of 18.9 for men and 15.4 for women, and a fat mass index of 4.0 and 5.5. The height adjusted version (Kouri 1995) adds 6.1 × (1.8 − height in metres), so people of different heights compare fairly. At 1.70 m, 59.4 kg of lean is 20.6 kg/m², or 21.2 height adjusted.

Questions

Common questions

What is a good muscle to fat ratio?

There is no official target. For most adults in the healthy body fat range, it sits between about 2 to 1 and 5 to 1, with men usually higher.

Is lean mass the same as muscle?

Not quite. Lean mass includes bone, organs and water too. Skeletal muscle is around half of it.

Do smart scales measure this?

Many estimate it with a small electrical current. They are handy for trends but can swing with how much water you have drunk.

Sources

Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.

If your weight is on your mind

Talk to your GP if your weight has changed a lot without trying, or if it is worrying you. If food or your body feels hard to think about, Beat has a free helpline on 0808 801 0677 (England, weekdays 3pm to 8pm).

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