Body Fat Calculator
Estimate your body fat percentage, lean mass, and fat mass using the U.S. Navy circumference method. Free, fast, and as accurate as a tape measure can get.
Your Stats
Enter your weight, height, waist, and neck measurements to estimate your body fat.
What Is Body Fat Percentage?
Your body fat percentage is the share of your total body weight that comes from fat. The rest is lean mass: muscle, bone, organs, and water. Two people at the same weight can carry very different amounts of fat, which is why body fat is a much better measure of fitness than weight alone.
A small amount of fat is essential. Your body needs it for hormone production, brain function, joint cushioning, and storing fat soluble vitamins. Too little is just as harmful as too much.
- • Essential: men 2 to 5 percent, women 10 to 13 percent
- • Athlete: men 6 to 13 percent, women 14 to 20 percent
- • Fitness: men 14 to 17 percent, women 21 to 24 percent
- • Average: men 18 to 24 percent, women 25 to 31 percent
How We Calculate Your Body Fat
We use the U.S. Navy circumference method, developed and validated against hydrostatic weighing. It uses a few tape measurements and a logarithmic formula to estimate body fat percentage.
Take Measurements
Waist and neck for men. Waist, neck, and hip for women. Add height and weight to anchor the calculation.
Apply the Navy Formula
The formula uses logarithms of those measurements to estimate body density, which converts to body fat percentage.
Split Fat and Lean Mass
We multiply your weight by the percentage to get fat mass. The rest is lean mass, the engine that drives your metabolism.
Factors That Affect Body Fat
Body fat is shaped by far more than just calories in. These are the big levers.
Calorie Balance
Eating more than your TDEE adds fat. Eating less burns it off. This is the biggest single driver, and nothing else matters as much.
Strength Training
Lifting builds the muscle that defines a low body fat look and protects lean mass when you diet down.
Age and Sex
Women carry more essential fat than men. Both sexes tend to gain fat with age unless training and protein intake stay up.
Genetics
Where you store fat first and lose it last is largely genetic. The total amount you carry is on you.
Sleep and Stress
Chronic poor sleep and high stress raise cortisol and make it easier to add belly fat at the same calorie intake.
Hormones
Thyroid, insulin sensitivity, and life stage all influence how easily your body holds or sheds fat.
Tips To Lower Your Body Fat
- 1
Build the Deficit Through Food
300 to 500 calories under your TDEE per day. Steady, sustainable, and easy to maintain for months.
- 2
Hit a Real Protein Target
1.6 to 2.2 grams per kilogram of body weight protects every gram of muscle when calories drop.
- 3
Lift Heavy, 2 to 4 Times a Week
Strength training is the single biggest signal that tells your body to keep muscle and burn fat instead.
- 4
Walk Every Single Day
10,000 steps adds 200 to 400 calories of burn without the recovery cost of intense cardio.
- 5
Measure the Same Way Each Time
Same tape, same time of day, same body position. The trend over weeks is what matters, not any single reading.
- 6
Be Patient with the Last Few Percent
Going from 25 to 20 percent is straightforward. Going from 12 to 9 is brutal. Set realistic targets and respect the trade offs.
Body Fat Calculator FAQ
Quick answers to the questions people ask most.