Body Fat Percentage Calculator
The U.S. Navy tape method. A cloth tape measure and two minutes gets you closer to the truth than any bathroom scale.
Where you sit
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The Navy tape method is accurate to roughly 3 percentage points against a DEXA scan, which is close enough to track a direction over months. Measure first thing in the morning, before food, with the tape snug but not compressing the skin. Men: waist at the navel. Women: waist at the narrowest point and hips at the widest. Always compare like with like — the trend across eight weeks tells you far more than any single reading. General fitness information, not medical advice.
How to measure body fat percentage without a lab
Your scale weight tells you almost nothing on its own. Two men at 190 pounds can look like completely different species, and the difference is body fat percentage — how much of that weight is fat and how much of it is muscle, bone and water. It is the number that decides whether you look heavy or look strong, and it is the only honest way to tell whether a diet is working.
The Navy tape method
This calculator uses the U.S. Navy circumference method, the same one the military uses for body composition standards. It needs a cloth tape measure and nothing else. For men it compares your waist to your neck against your height. For women it adds the hips. It is not perfect, but it lands within about three percentage points of a DEXA scan, and it costs nothing and can be repeated every Sunday morning for the rest of your life.
How to take the measurements properly
Measure first thing in the morning, before eating or drinking, after using the bathroom. Stand relaxed, do not suck in. Keep the tape level and snug against the skin without compressing it. Men measure the waist across the navel; women measure the waist at its narrowest point and the hips at the widest. Take each measurement twice and use the average. Most of what people call measurement error is actually measuring a different spot each time.
What the number should be
For men, 14 to 17 percent is lean, healthy and maintainable while still training hard and eating enough to grow. Six to 13 percent is stage and photoshoot territory, and it is a short-term condition, not a way to live. For women those bands sit roughly ten points higher. Chasing a contest number year round is how people end up tired, weak and injured.
Why lean mass is the number to actually watch
When you cut, the goal is not to lose weight. It is to lose fat while holding on to every pound of lean mass you have built. Run this calculator every four weeks and watch two numbers: fat mass should fall, lean mass should hold. If lean mass is dropping, you are cutting too hard, not eating enough protein, or not lifting heavy enough. Fix that before you cut another calorie.
Common questions
Is the tape method accurate enough? For tracking change over time, yes. For a single number you would stake money on, no — nothing short of a DEXA is. The direction over eight weeks is what matters.
Why did my body fat go up after one good week? Water, sodium, food volume and stress all move waist measurements day to day. Measure weekly, judge monthly.
Do smart scales work? They use bioelectrical impedance, which is heavily affected by hydration. They are consistent enough to show a trend but frequently wrong on the absolute number.
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