Lean Body Mass Calculator for Women
Last reviewed: October 2026 by the Get Tips For Better Life Editorial Team
Lean body mass (LBM) is everything in your body except fat: muscle, bones, organs, skin and water. Knowing it helps you see whether weight changes come from fat or muscle, and it’s used to set protein targets and some calorie formulas.
This free lean body mass calculator for women uses three trusted formulas, or your body fat percentage if you know it. No sign-up, and nothing you enter is saved.
Lean Body Mass Calculator for Women
Estimate your lean body mass (everything that isn’t fat: muscle, bone, organs and water) with 3 formulas, or from your body fat %.
Formulas for women: Boer (1984), James (1976) and Hume (1966). BMR uses the Katch-McArdle equation. These estimate lean mass from height and weight only, so they can be off for very muscular or very heavy women. A DEXA scan measures it directly. Not medical advice.
Lean Body Mass Formulas for Women
| Formula | For women (weight in kg, height in cm) |
|---|---|
| Boer (1984) | 0.252 x weight + 0.473 x height – 48.3 |
| James (1976) | 1.07 x weight – 148 x (weight / height)² |
| Hume (1966) | 0.29569 x weight + 0.41813 x height – 43.2933 |
| From body fat % | weight x (1 – body fat % / 100) |
The calculator shows the average of the three formulas. If you enter your body fat %, it uses that instead, which is usually more accurate. The James formula becomes unreliable at higher body weights, so the average helps smooth that out.
Lean Body Mass Chart for Women
Average of the three formulas, in pounds. Use the lean body mass calculator above for your exact number:
| Height | 140 lb | 160 lb | 180 lb | 200 lb |
|---|---|---|---|---|
| 5’0″ | 89 | 94 | 98 | 102 |
| 5’2″ | 94 | 99 | 104 | 108 |
| 5’4″ | 98 | 104 | 109 | 113 |
| 5’6″ | 102 | 108 | 114 | 118 |
| 5’8″ | 107 | 113 | 119 | 124 |
How Much Lean Mass Should a Woman Have?
There’s no single target, because lean mass depends on your height, frame and activity. A simpler way to judge it is through body fat. Using the American Council on Exercise body fat ranges for women:
| Body fat (women) | Category | Lean mass as % of body weight |
|---|---|---|
| 14% to 20% | Athletes | about 80% to 86% |
| 21% to 24% | Fitness | about 76% to 79% |
| 25% to 31% | Average | about 69% to 75% |
| 32% or more | Above average body fat | under about 68% |
Women naturally carry more essential fat than men, so a lean mass of about 65% to 75% of body weight is common for healthy women. Check your body fat with our body fat calculator for women. What matters most is the trend: keeping or building lean mass as you age. Compare your result with the body fat percentage chart for women.
BMR Based on Lean Body Mass
If you know your lean body mass, you can estimate your basal metabolic rate (BMR, the calories you burn at rest) with the Katch-McArdle equation:
BMR = 370 + 21.6 x lean body mass (kg)
The calculator shows this for you. It’s often more accurate than height-and-weight formulas for women who are very muscular or carry more fat than average. Compare it with our BMR calculator for women.
Worked Example
A woman who is 5’4″ (163 cm) and 165 lb (74.8 kg):
- Boer: 0.252 x 74.8 + 0.473 x 163 – 48.3 = about 47.6 kg (105 lb)
- James: about 48.7 kg (107 lb)
- Hume: about 46.8 kg (103 lb)
- Average: about 105 lb of lean mass, so roughly 64% lean and 36% fat
- BMR from lean mass: 370 + 21.6 x 47.6 = about 1,400 calories a day
Why Lean Body Mass Matters After 40
- Muscle loss speeds up with age, and the menopause transition can add to it. Less muscle means a lower metabolism and more risk of falls.
- Lean mass burns more calories than fat, even at rest.
- Strong muscles protect bones and joints.
How to protect it:
- Strength training 2 or more days a week. Weights, bands or bodyweight moves all count.
- Enough protein, spread across meals. Find your target with the protein calculator.
- Lose weight slowly. Fast weight loss takes more muscle with it. Plan a sensible pace with the calorie deficit calculator.
How Accurate Is a Lean Body Mass Calculator?
Formula-based estimates use only height and weight, so they can be off by several pounds, especially for very muscular or very heavy women. More accurate ways to measure:
- DEXA scan: the most accurate common method
- Bioelectrical impedance (smart scales): convenient, but affected by hydration
- Skinfold calipers: accurate in trained hands
For tracking progress at home, use the same method each time and watch the trend.
Frequently Asked Questions
What is the difference between lean body mass and muscle mass?
Lean body mass includes muscle plus bones, organs, skin and water. Muscle is only part of it, roughly half.
Is lean body weight the same as lean body mass?
Yes, the terms are usually used to mean the same thing.
How can I increase lean body mass after 40?
Strength training, enough protein, and enough sleep. Many women can gain muscle at any age with regular resistance exercise.
Which lean body mass formula is most accurate?
For most women, the Boer formula gives the closest estimate of the three, which is why many calculators use it as the main result. Our lean body mass calculator shows all three side by side, plus the average. If you know your body fat % from a DEXA scan or calipers, that’s more accurate than any formula.
Does lean body mass decrease with age?
Yes. Adults slowly lose muscle with age, and research from the SWAN study found women tend to lose lean mass faster during the menopause transition. Strength training and enough protein can slow or even reverse this.
Can I calculate lean body mass without knowing my body fat %?
Yes. The Boer, James and Hume formulas only need your height and weight. They’re estimates, but good enough to track changes over time.
Is lean body mass the same as fat-free mass?
Almost. Fat-free mass excludes all fat. Lean body mass is usually defined as including a small amount of essential fat (in nerves and organs). In everyday use, the two terms are treated as the same.
Why does my lean body mass seem low?
Formulas are estimates. If you have more muscle than average, they may underestimate it. Entering a measured body fat % gives a better number.
Related Tools
- Body Fat Calculator for Women
- Protein Calculator for Women Over 40
- BMR Calculator for Women
- Body Shape Calculator
- All free tools
This calculator is for general information only and is not medical advice. Read our Medical Disclaimer and Editorial Policy.
Sources
- Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol. 1984
- Hume R. Prediction of lean body mass from height and weight. J Clin Pathol. 1966
- James WPT. Research on obesity. London: Her Majesty’s Stationery Office; 1976
- American Council on Exercise: Percent Body Fat Calculator and norms
- McArdle WD, Katch FI, Katch VL. Exercise Physiology (Katch-McArdle BMR equation)
- Greendale GA, et al. Changes in body composition and weight during the menopause transition (SWAN). JCI Insight. 2019