Health & Fitness Calculators

7 free calculators in this subject.

BMI, body fat, calorie needs, heart rate zones. Health calculators that show the ranges, cite the WHO or CDC source, and include the limitations every medical professional will remind you of.

Body Metrics

BMI Calculator

Check your Body Mass Index

Metabolism

BMR Calculator

Estimate your basal metabolic rate using the Mifflin-St Jeor formula

Body Composition

Body Fat Percentage Calculator

U.S. Navy circumference method — works with a tape measure

Nutrition

Daily Calorie Needs (TDEE) Calculator

Total Daily Energy Expenditure via the Mifflin-St Jeor equation

Macros Calculator

Compute your daily protein, carb, and fat targets

Fitness

Heart Rate Zones Calculator

Find your max HR and 5 training zones for cardio workouts

Running

Running Pace Calculator

Convert between distance, time, and pace for any run

About health & fitness calculators

Health calculators are a paradox: the arithmetic is trivial, but misreading the output causes real harm. A BMI of 27 doesn't mean "you're unhealthy" — it means "in population studies, this range correlates with higher risk, but the correlation breaks down for athletes, elderly adults, and specific ethnic groups." Our health calculators show the number and the nuance in the same view, with a band interpretation reviewed by a medical editor.

Frequently asked questions

Should I make health decisions based on these?

No — and we say so on every calculator. These are screening tools for context, not a substitute for a clinical consultation. We link to authoritative sources (WHO, CDC, NIH) on each calculator.

Why do some calculators show multiple formulas?

Health math often has competing standards — Mifflin-St Jeor vs. Harris-Benedict for BMR, for example. Where the field hasn't converged, we show both and explain when each is preferred.