1. Your setup
2. This week's numbers
Sunday morning, after the bathroom and before eating or drinking. * = needed for body fat.
3. Your results
Save your first week to see results.
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4. Progress
Your chart appears after two weeks of entries.
Your entries are saved only in this browser on this device. Nothing is sent anywhere unless you choose to email it. Free review: send me your summary and I'll reply in writing with what I see in your numbers and what I'd change first.
How to measure for the body fat calculator
Neck — needed for body fat
Just below the larynx (Adam's apple), with the tape angled slightly downward toward the front. Head facing straight ahead, shoulders relaxed.
Waist — needed for body fat
Men: at the navel. Women: at the narrowest point between the bottom of the ribs and the top of the hips. Stand upright, abdomen relaxed, and measure after a normal (not forced) exhale.
Hip — needed for body fat (women)
Around the glutes at the widest point.
Shoulders
Around the widest point of the shoulders, after a normal exhale.
Chest
At the nipple line, passing under the armpits and over the shoulder blades, after a normal exhale.
Bicep (left)
Halfway between the elbow and the bony point on top of the shoulder, arm hanging relaxed.
Forearm (left)
Halfway between the wrist and the elbow.
Wrist (left)
At the thinnest point.
Thigh (left)
Halfway between the center of the kneecap and the crease where the leg meets the hip.
Calf (left)
At the widest point of the calf muscle.
Ankle (left)
At the narrowest point, just above the ankle bone.
Measure on bare skin, left side for limbs, snug but not tight. Take each one twice; if they differ by more than ¼ inch, take a third and average the two closest.
Free body composition spreadsheet
Prefer Excel? Download the same tracker as a 52-week spreadsheet with the formulas built in.
Questions
How accurate is the Navy body fat method?
It is an estimate from tape measurements, typically within about 3–4 percentage points of lab methods. Measured the same way each week, it is very good at showing whether body fat is trending up or down.
Why track lean mass and fat mass instead of just weight?
Weight alone can't tell you whether you lost fat or muscle. Lean mass and fat mass show what the change on the scale is actually made of.
Is my data private?
Yes. Your entries are saved only in your own browser on your device. Nothing is sent anywhere unless you choose to email it to me.
Do I need an account?
No. There is no sign-up. Open the page, enter your numbers, and it remembers them on that device.
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Get in touchBody fat % is estimated with the U.S. Navy circumference method and is typically within about 3–4% of lab methods. Use it to track trends, not as a diagnosis. This tool is not medical advice.