Free tools for adults 20+

Health and fitness calculators

Every calculator shows its formula, a worked example and its sources. Your numbers stay in your browser. These tools estimate and screen. They do not diagnose, prescribe or replace a clinician.

Energy and body mass

Daily calorie calculator (TDEE)

Maintenance calories, resting energy and adult BMI in one step.

BMR calculator

Resting energy with the Mifflin–St Jeor equation and worked arithmetic.

Adult BMI calculator

CDC adult BMI categories for ages 20 and older.

Body shape

Waist-to-height ratio calculator

NICE bands: keep your waist under half your height.

Waist-to-hip ratio calculator

WHO thresholds for waist-to-hip ratio and waist size.

Body fat calculator

U.S. Navy tape-measure estimate with ACE descriptive ranges.

Ideal body weight calculator

Devine, Robinson and Miller formulas next to the CDC healthy BMI range.

Food and fluid

Protein intake calculator

The 0.8 g per kg RDA and the range studied in people who train.

Water intake calculator

National Academies adequate intake for adult men and women.

Training

Calories burned calculator

MET-based energy estimate for twelve common activities.

Heart rate zone calculator

Tanaka maximum heart rate with moderate and vigorous zones.

One-rep max calculator

Epley and Brzycki estimates from a set of up to 10 reps.

Guides

Read how we choose and check sources in the editorial methodology.