What is my lean body mass?
Enter your sex, height and weight. The lean body mass calculator gives your lean mass by three published formulas and the body fat percentage it implies.
- Lean body mass (Boer)
- 135.6
At 5 ft 10 in and 180 lb, your lean body mass is about 135.6 lb by the Boer formula.
- Lean body mass, Boer (kg)kg
- 61.5
- Body fat (Boer)
- 24.7%
- Lean body mass (James)lb
- 138.5
- Lean body mass, James (kg)kg
- 62.8
- Lean body mass (Hume)lb
- 126.9
- Lean body mass, Hume (kg)kg
- 57.6
Lean body mass (Boer): 135.6. At 5 ft 10 in and 180 lb, your lean body mass is about 135.6 lb by the Boer formula.
This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use
How to calculate
Estimates lean body mass (everything but fat) from sex, height and weight by the Boer, James and Hume formulas, with the body fat percentage it implies.
Example with the default inputs (Sex Male, Height 5 ft 10 in, Weight 180 lb): At 5 ft 10 in and 180 lb, your lean body mass is about 135.6 lb by the Boer formula.
Method: Boer: men 0.407W + 0.267H − 19.2, women 0.252W + 0.473H − 48.3; James: men 1.1W − 128(W/H)², women 1.07W − 148(W/H)²; Hume: men 0.32810W + 0.33929H − 29.5336, women 0.29569W + 0.41813H − 43.2933 (W in kg, H in cm).
- The formulas are for adults. They estimate lean mass from height and weight only, not from a body scan.
- Body fat is the weight minus the Boer lean mass, as a percent of the weight.
- Height from 1 to 2.5 m (3 ft 3 in to 8 ft 2 in) and weight from 25 to 350 kg (55 to 772 lb).
Worked examples
Each example is checked against the calculator on every build.
- Sex Male, Height 5 ft 10 in, Weight 180 lb gives Lean body mass, Boer (kg) 61.5, Lean body mass (Boer) 135.6, Body fat (Boer) 24.7%, Lean body mass, Hume (kg) 57.6, Lean body mass (Hume) 126.9, Lean body mass, James (kg) 62.8, Lean body mass (James) 138.5.Source: De Cassai A et al., Regional anesthesia in obese patients, Saudi J Anaesth 2025, lean body mass table: Boer, James and Hume formulas, height in cm, weight in kg (https://europepmc.org/article/PMC/PMC12007849, retrieved 2026-10-02)
- Sex Female, Height 5 ft 5 in, Weight 132.3 lb gives Lean body mass, Boer (kg) 44.9, Lean body mass (Boer) 98.9, Body fat (Boer) 25.2%, Lean body mass, James (kg) 44.6, Lean body mass, Hume (kg) 43.4.Source: De Cassai A et al., Regional anesthesia in obese patients, Saudi J Anaesth 2025, lean body mass table: Boer, James and Hume formulas, height in cm, weight in kg (https://europepmc.org/article/PMC/PMC12007849, retrieved 2026-10-02); Caruso D et al., Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula, BioMed Res Int 2018 (https://europepmc.org/article/PMC/PMC6110034, retrieved 2026-10-02)
- Sex Male, Height 5 ft 6.9 in, Weight 286.6 lb gives Lean body mass, Boer (kg) 79.1, Lean body mass, Hume (kg) 70.8, About the James formula The James formula is left out: above 124.2 kg at your height and sex it gives less lean mass for more weight, which is not realistic..Source: Caruso D et al., Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula, BioMed Res Int 2018 (https://europepmc.org/article/PMC/PMC6110034, retrieved 2026-10-02)
How it works
With W your weight in kilograms and H your height in centimetres:
| Formula | Men | Women |
|---|---|---|
| Boer (1984) | 0.407W + 0.267H − 19.2 | 0.252W + 0.473H − 48.3 |
| James (1976) | 1.1W − 128 (W ÷ H)² | 1.07W − 148 (W ÷ H)² |
| Hume (1966) | 0.32810W + 0.33929H − 29.5336 | 0.29569W + 0.41813H − 43.2933 |
- Lean body mass by each formula, in pounds and in kilograms (1 lb = 0.45359237 kg exactly). The Boer result is the headline: in pounds for US units, in kilograms for Metric.
- Body fat (Boer) = (W − Boer lean mass) ÷ W × 100%.
- James is left out when your weight is above its peak, W = 1.1H² ÷ 256 for men or 1.07H² ÷ 296 for women (the weight where the formula stops rising), and the page says so. It is also left out when it is not more than 0 or not less than your weight.
The height and weight are read as the exact values you typed (5 ft 10 in is exactly 177.8 cm; 180 lb is exactly 81.6466266 kg), and every result is worked out exactly and rounded once, half up, to 0.1 (lb, kg or %). The peak weight in the note is rounded the same way.
Rules
- Height from 1 to 2.5 m (3 ft 3.4 in to 8 ft 2.4 in), weight from 25 to 350 kg (55.1 to 771.6 lb).
- There is no answer when Boer or Hume gives a lean mass that does not round to more than 0 kg and less than your weight. This happens only at heights and weights far from an adult’s.
Worked examples by hand
A man, 5 ft 10 in and 180 lb. H = 177.8 cm, W = 180 × 0.45359237 = 81.6466266 kg. Boer = 0.407 × 81.6466266 + 0.267 × 177.8 − 19.2 = 33.2302 + 47.4726 − 19.2 = 61.5028 = 61.5 kg, or 61.5028 ÷ 0.45359237 = 135.6 lb. Body fat = (81.6466 − 61.5028) ÷ 81.6466 = 24.7%. James: W ÷ H = 0.459205, squared × 128 = 26.9912, so 1.1 × 81.6466 − 26.9912 = 62.8 kg (138.5 lb). The peak is 1.1 × 177.8² ÷ 256 = 135.8 kg, above his weight. Hume = 0.32810 × 81.6466 + 0.33929 × 177.8 − 29.5336 = 57.6 kg (126.9 lb).
A woman, 165 cm and 60 kg. Boer = 0.252 × 60 + 0.473 × 165 − 48.3 = 15.12 + 78.045 − 48.3 = 44.865 = 44.9 kg (98.9 lb); body fat = (60 − 44.865) ÷ 60 = 25.225% = 25.2%. James = 1.07 × 60 − 148 × (60 ÷ 165)² = 64.2 − 19.5702 = 44.6 kg. Hume = 0.29569 × 60 + 0.41813 × 165 − 43.2933 = 43.4 kg.
A man, 170 cm and 130 kg. Boer = 0.407 × 130 + 0.267 × 170 − 19.2 = 52.91 + 45.39 − 19.2 = 79.1 kg. Hume = 70.8 kg. The James peak is 1.1 × 170² ÷ 256 = 124.18 kg, below 130 kg, so James is left out.
Other questions people ask
What is lean body mass?
Everything in your body that is not fat: muscle, bone, organs, skin and water. It is your weight minus your fat mass. Doctors use it to dose some drugs and contrast media, because fat takes up some drugs much less than lean tissue.
Which lean body mass formula is best?
None is best for everyone. Boer (1984) is the most widely used and is the headline here. James (1976) breaks down at high weights, and Hume (1966) usually gives a little less. A body scan such as DEXA measures lean mass directly.
Why is the James result missing for me?
The James formula has a (weight ÷ height)² term, so above a certain weight it gives less lean mass the more you weigh, which cannot be right. For a man of 170 cm that peak is 1.1 × 170² ÷ 256 = 124.2 kg. Past the peak the calculator leaves James out.
How is body fat worked out here?
Body fat % = (weight − lean body mass) ÷ weight × 100, with the Boer lean mass. For a 180 lb man of 5 ft 10 in it is about 24.7%. It is an estimate from height and weight only.
Can lean body mass change?
Yes. Strength training and enough protein can add muscle, while dieting without exercise can lose some. These formulas cannot see that: they only use height and weight, so two people with the same numbers get the same answer.
Do the formulas work for children?
No. They were built from adult data. For children, ask a doctor; this page is for adults.