Health

BMI, calorie, heart rate, and hydration.

Health and fitness calculators cover body composition, daily energy needs, training intensity, and pregnancy milestones. Every formula is from a peer-reviewed source — Mifflin–St Jeor for BMR, Karvonen for heart rate zones, the WHO standard for BMI, and the Cooper test protocol for VO2 max estimation. The numbers are useful starting points, not medical advice.

For the concepts behind the calculators, see the in-depth guides below — particularly the calorie/TDEE explainer and the BMI breakdown. For anything that materially affects your health, talk to a clinician who knows your situation.

In-depth guides

Calorie Needs and TDEE

BMR, activity multipliers, the Mifflin–St Jeor formula, and why most online calorie targets are off by a few hundred a day.

BMI Explained

Where BMI is useful, where it falls apart, and what to look at instead.

All calculators

BMI Calculator

Body Mass Index in metric or imperial.

Body Fat (Navy)

US Navy tape-measure method.

Lean Body Mass

Boer, James, and Hume LBM estimates.

Calorie Calculator

BMR, TDEE, and macronutrient split.

Macro + TDEE

BMR, TDEE, and protein/carb/fat targets.

Target Heart Rate Calculator

Training zones and max heart rate.

VO₂ Max

Cooper test, resting HR, or Rockport walk.

One-Rep Max

Six formulas + %-of-1RM programming table.

Running Pace

Solve for pace, time, or distance; splits included.

Hydration Calculator

Daily water based on weight and activity.

Pregnancy Due Date

Due date, gestational age, and trimester.