BodyFatCalcLog in

Know your number.
Trust the range.

Four validated ways to estimate body fat — photos, tape, calipers, or all of them reconciled by AI. Every result is an honest range with the math shown.

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Free · 3 photo scans a week · no credit card

Sample resultBest accuracy
18.4%−0.6% vs last

body fat estimate

Likely range 17.1–19.8%

14%24%
AverageACE ranges · men
High confidencePhotos + tape, reconciled by AI
How this was calculated

How it works

  1. 1.

    Pick a method

    Photos, tape, calipers — or best accuracy, which reconciles everything you give it.

  2. 2.

    Enter your inputs

    Guided measurements with diagrams and live feedback. About two minutes.

  3. 3.

    Get your range

    A point estimate inside an honest range, with the formula and its limits shown.

Four ways to measure

Different tools, different trade-offs. All of them are shown with their real error margins — no method pretends to be a lab.

  • Best accuracy

    1 photo scan · recommended

    Photos plus your measurements, reconciled into one range.

  • Photos

    1 photo scan · ~1 min

    1–4 photos analyzed by AI vision. No equipment needed.

  • Tape

    Free · works offline

    Neck and waist with any tape measure. US Navy formula.

  • Calipers

    Free · works offline

    3–7 skinfold sites for practiced hands. Jackson-Pollock.

Typical estimation error by method
MethodTypical error
Tape (US Navy)±3.5% BF
Calipers (JP3/JP7, DW4)±3.3–3.8% BF
Photos (AI vision)varies with photo quality
Best accuracycombines all signals

Typical error vs lab reference methods (standard error of estimate). It’s why every result is a range — a single number would be false precision.

Every result shows its work

No black box. Each estimate ships with the method used, your inputs echoed back, the formula itself, and an honest note on where it can be wrong.

The card on the right is the actual one from the app, shown expanded — not an illustration.

How this was calculated
Method
Tape — US Navy formula
Your inputs
Height 178 cm · neck 38.0 cm · waist 84.5 cm
Formula
BF% = 495 ÷ (1.0324 − 0.19077 · log10(waist − neck) + 0.15456 · log10(height)) − 450= 16.0% here
Limitations
Navy tends to overestimate on very muscular builds — typical error ±3.5%, and the range reflects it.

Photos are never stored

Photos are sent securely for analysis only. They’re never stored — not written to disk, not saved in the database. Analyzed, answered, discarded.

Common questions

Two minutes to your first range

Tape and caliper estimates are always free and unlimited. Photo analysis gives everyone 3 scans a week.

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