BMI is a terrible metric. It was invented in the 1830s by a Belgian mathematician studying population averages, not individual health. It does not distinguish between muscle and fat and labels most athletes as "overweight."
So I built BodyCalc Tool — calculators that actually tell you something useful.
Body Fat Calculator
Uses the US Navy method (neck + waist + height for men, + hips for women). Validated against DEXA in multiple studies. Measurable at home with a $2 tape measure — no fancy equipment needed.
TDEE Calculator
Total Daily Energy Expenditure using Mifflin-St Jeor, with activity multipliers from sedentary to athlete. The activity multiplier is where most calculators get sloppy — I added concrete examples: "Moderate = you break a sweat, can talk. Example: 30 min jog at 6mph."
Waist-to-Hip Ratio
A better cardiovascular risk predictor than BMI. Ratio above 0.90 (men) or 0.85 (women) correlates with higher heart disease risk even at "normal" BMI. Most people have never measured this.
Ideal Weight + Protein Calculators
Ideal weight uses four formulas (Robinson, Miller, Devine, Hamwi) to show a realistic range instead of one magic number. Protein calculator uses the research-backed 0.8-2.2g/kg range based on activity level and goal.
What I learned
- People want context, not numbers. A raw body fat percentage means nothing without knowing what is healthy for your age and gender.
- Imperial + metric is non-negotiable. Half my users are American (lbs/inches), half international (kg/cm).
- Privacy matters for health data. All calculations happen in the browser. Nothing stored server-side.
→ bodycalctool.com — all calculators free, no signup
