Body composition

Body Fat Calculator

Enter your body-fat percentage and we switch the BMR formula to Katch–McArdle for higher accuracy. Returns fat mass, lean mass, and full TDEE.

Body fat percentage is the share of your weight made up of fat tissue. Add it as an input below, the calculator switches from Mifflin–St Jeor to Katch–McArdle, which uses lean body mass directly and is more accurate when composition is known.

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Your daily target

· cal/day

Enter your details and click Calculate

  • BMR · cal/day at rest
  • BMI ·  
  • Lean body mass · kg

Pick your goal

Macros at maintenance

30% protein · 40% carbs · 30% fat

Advanced metrics

Numbers are estimates. Eat at your target for 2 to 3 weeks, track weight, and adjust by ±100 cal/day if it does not match your real maintenance. See how accurate is TDEE?

Show advanced metrics 12 metrics · 7 formulas · 2D macro selector · life-stage

All metrics

Calculate above to populate the full metric table.

All 7 BMR formulas (side-by-side)

Mifflin–St Jeor · Harris–Benedict (revised) · Katch–McArdle · Cunningham · Average · Simple multiplier · Custom

TDEE across activity levels

See how much your TDEE changes between sedentary and athlete. Highlighted bar is your current selection.

Macros: 2D selector

Goal × carb-split matrix: Cut / Maintain / Bulk × Low / Moderate / High carb.

Life-stage adjustments

Luteal phase · Pregnancy (T1/T2/T3) · Breastfeeding · Perimenopause · PCOS

If you have a body-fat measurement (DEXA, BIA scale, or caliper estimate), enter it in the Power Mode section to upgrade your estimate. Without one, we use the Boer formula to estimate lean body mass from height and weight.

What counts as a healthy body-fat range?

  • Men: athletes 6–13%, fitness 14–17%, average 18–24%, obese 25%+
  • Women: athletes 14–20%, fitness 21–24%, average 25–31%, obese 32%+

These ranges come from the American Council on Exercise. They're guidance, not diagnosis.

Frequently asked questions

How is body fat percentage calculated?
There are several methods: skinfold calipers, bioelectrical impedance (BIA), DEXA scan, hydrostatic weighing, and US Navy circumference. Each has different accuracy. The most accurate consumer methods are DEXA and hydrostatic weighing.
Why does body fat % change my TDEE estimate?
Knowing your body fat lets us calculate Lean Body Mass directly. Katch–McArdle and Cunningham equations use LBM, which is metabolically more active than fat tissue, giving a more accurate BMR estimate than weight-only formulas.
Is body fat a better metric than BMI?
For body composition, yes. BMI cannot distinguish muscle from fat, a lean, muscular athlete and an overweight sedentary person can have the same BMI. Body fat percentage tells you what your weight is made of.