Body composition

BAI + BMI Calculator

Two complementary metrics side by side: BMI for weight-based screening, BAI for fat-based estimation. Disagreements between them are informative.

BMI and BAI use different inputs. BMI weight + height, BAI hip + height. When they agree, body fat is likely close to BMI's implied category. When BAI is high but BMI normal, abdominal fat may be elevated. When BMI is high but BAI normal, muscle mass is likely high.

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Body
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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

Interpreting disagreement

  • Both normal: straightforward, composition aligns with screening thresholds
  • BMI overweight, BAI normal: elevated muscle mass, common in lifters
  • BMI normal, BAI overweight: "skinny fat", normal weight but elevated body fat
  • Both elevated: high body fat with no offsetting muscle, diet/training focus

Frequently asked questions

Why use both BMI and BAI?
They measure different things. BMI flags weight relative to height; BAI estimates body fat. When they disagree, the disagreement itself is the data, it reveals whether weight excess is muscle or fat.
Which is more accurate?
Neither is "more accurate", they measure different constructs. For body fat percentage, neither beats a direct measurement (DEXA, calipers). Both are screening tools.