Lean Muscle Mass Calculator

Lean muscle mass, often called fat‑free mass, includes your muscles, bones, organs, and water — everything except stored fat. Tracking this number helps you understand if you’re gaining muscle or losing fat. Our Lean Muscle Mass Calculator uses the simple and proven formula: Lean Mass = Total Weight × (1 − (body fat % / 100)). It gives an instant snapshot of your body composition.

Athletes and fitness enthusiasts rely on lean mass to tailor nutrition and training. For example, if you weigh 80 kg at 15% body fat, your lean mass is 68 kg. Bulking or cutting cycles become measurable when you monitor this figure. Remember, the calculator is an estimate; methods like DEXA or hydrostatic weighing are more precise but this tool is perfect for daily tracking.

Why use it? Setting goals: you might aim to increase lean mass while keeping fat stable. It’s also valuable for calculating protein needs (1.6–2.2 g per kg lean mass). Whether you’re a bodybuilder, weekend warrior, or on a weight loss journey, knowing your muscle mass empowers smarter decisions. Always combine with how you feel and perform. The tool works for all adults, but if you have extreme leanness or obesity, consult a professional. Update your stats every few weeks to see trends.

All calculations are done locally in your browser — no data leaves your device. Use it as often as you like, completely free. The values are in kilograms, but you can easily convert: 1 kg = 2.2 lbs. Stay strong and lean!