Lean Body Mass Calculator
Enter your gender, weight, and height. Add your body fat percentage if you know it for a second calculation method.
Enter weight in kg for metric, or lb for imperial.
Enter height in cm for metric, or inches for imperial.
Leave blank to use the Boer formula. If filled in, lean body mass is calculated from your body fat percentage instead.
What Is Your Lean Body Mass?
A lean body mass calculator estimates your weight minus body fat, giving your muscle, bone, water, and organ weight in one number. Enter your gender, weight, and height, and it returns lean body mass, fat mass, and implied body fat percentage using the Boer formula or your own body fat measurement.
Lean body mass is everything in your body except fat: muscle, bone, water, skin, and organs. If you weigh 80 kg with 61 kg of lean mass, the other 19 kg is fat. Two people can weigh the same yet differ greatly in muscle and fat, which is why this split matters more than total weight.
Use the calculator above to get your lean body mass in seconds. Enter your gender, weight, and height, and add your body fat percentage if you know it.
How to Use the Lean Body Mass Calculator
- Select your gender, since the Boer formula differs for men and women.
- Choose metric or imperial units, then enter your weight in kilograms or pounds.
- Enter your height in centimeters or inches.
- Optional: enter your body fat percentage from calipers, a smart scale, or a DEXA scan.
- Click Calculate, then read your lean body mass, fat mass, and body fat percentage.
The Boer Formula Explained
When you leave body fat blank, the calculator uses the Boer formula. For men, lean body mass equals 0.407 times weight in kilograms plus 0.267 times height in centimeters minus 19.2. For women, it equals 0.252 times weight plus 0.473 times height minus 48.3.
The Boer formula is an estimate, not a diagnosis. It works best for adults of average build, and less well for very muscular athletes or very tall or short people. Measured the same way each month, it still tracks trends reliably.
The Body Fat Method
If you enter a body fat percentage, the calculator switches methods: lean body mass equals weight multiplied by one minus body fat divided by 100. A person weighing 75 kg at 20 percent body fat has 60 kg of lean mass and 15 kg of fat. This method is only as accurate as your measurement, so a recent estimate from a body fat percentage calculator is a good starting point.
Why Lean Body Mass Matters More Than Weight
Total weight hides the detail that matters. Losing 3 kg of fat while gaining 3 kg of muscle leaves weight unchanged, yet health and appearance improve. Lean mass also guides nutrition: protein and calorie targets are often set per kilogram of lean mass, not total weight.
Lean mass also puts other numbers in context. A BMI calculator can label a muscular person overweight even when body fat is low, because BMI uses only height and weight. A calorie deficit calculator also gives better targets when you know how much of your weight is lean tissue.
Lean Body Mass Calculator: Verified Examples
The table below shows checked results from both methods. Use them to check your own result.
| Profile | Method | Lean body mass | Fat mass | Body fat |
|---|---|---|---|---|
| Male, 80 kg, 180 cm | Boer | 61.4 kg | 18.6 kg | 23.2% |
| Female, 60 kg, 165 cm | Boer | 44.9 kg | 15.1 kg | 25.2% |
| Male, 90 kg, 185 cm | Boer | 66.8 kg | 23.2 kg | 25.7% |
| Female, 70 kg, 170 cm | Boer | 49.8 kg | 20.3 kg | 28.9% |
| 75 kg, 20% body fat | Body fat | 60.0 kg | 15.0 kg | 20.0% |
How to Improve Your Lean Body Mass
Build lean mass with three habits: resistance training two to four times per week, focusing on squats, presses, and rows; protein at roughly 1.6 to 2.2 grams per kilogram of body weight per day; and seven to nine hours of sleep per night, when most muscle repair happens.
Re-test every four weeks, not daily. Daily weight swings from water and food can move the result by a kilogram or more and hide the real trend. Weigh first thing in the morning, use the same units each time, and compare months, not days.
Frequently Asked Questions
What is a good lean body mass?
There is no single good number, since healthy lean mass depends on height, sex, and build. Compare your result with your own past results and with healthy body fat ranges, roughly 10 to 20 percent for men and 18 to 28 percent for women.
Is lean body mass the same as muscle mass?
No. Muscle mass counts only skeletal muscle, while lean body mass counts everything that is not fat, including muscle, bone, water, and organs. Lean body mass is therefore always higher than muscle mass alone.
How accurate is the Boer formula?
The Boer formula is a validated population estimate, accurate enough for general fitness tracking in most adults. Individual error can reach a few kilograms, especially for very muscular or very lean people. A DEXA scan gives a direct measurement if you need clinical precision.
Can I calculate lean body mass without body fat percentage?
Yes. That is exactly what the Boer formula is for. Enter your gender, weight, and height, leave the body fat field blank, and the calculator estimates lean body mass from those three inputs.
Should lean body mass go up when I lose weight?
Ideally, lean body mass stays steady or rises slightly while fat mass falls. If lean mass drops sharply during weight loss, you may be losing muscle, which usually means your calorie deficit is too large or your protein intake and training are too low.
How often should I check my lean body mass?
Once every four weeks is enough for most people. Monthly checks smooth out daily water swings and show genuine trends from training and nutrition, while daily checks mostly add noise.
