Free Health & Fitness Calculators

Calculate your Body Mass Index (BMI) in metric or imperial units and see which World Health Organization weight category it falls into.

Estimate your Basal Metabolic Rate — the calories your body burns at rest — using the widely used Mifflin-St Jeor equation.

Estimate your body fat percentage using the U.S. Navy circumference method from simple tape-measure inputs (height, neck, waist, and hip for women), all in centimeters.

This calculator estimates your body surface area (BSA) — the total external area of the body — in square metres (m²) from your height and weight. It uses the Mosteller formula, a simple square-root method that is widely cited for its accuracy and ease of calculation, and it also references the older Du Bois and Du Bois equation as an alternative. BSA is often regarded as a more representative measure of metabolic mass than body weight alone, because it is less affected by abnormal fat mass. The result here is a general-information estimate only and is not medical advice; if BSA matters for a clinical decision, your height and weight should be confirmed and the figure interpreted by a qualified healthcare professional.

Estimate the calories you burn in a day (your TDEE) by combining your Basal Metabolic Rate with an activity level.

Estimate how many calories you burn during a workout using the standard MET (Metabolic Equivalent of Task) method — choose an activity, enter your body weight, and set the duration.

This calculator estimates how much water you should drink each day based on your body weight and physical activity level, giving results in liters, milliliters, and fluid ounces.

Find your personalized heart rate training zones using the science-backed Karvonen formula, which accounts for both your age and resting heart rate for more accurate targets.

This calculator estimates ideal body weight (IBW) from your height and sex using the Devine formula, a simple equation introduced by Dr B. J. Devine in 1974. It is widely used in clinical settings as a quick reference, originally to help with weight-based medication dosing rather than to set a personal weight goal. The result is a rough population-level estimate: it depends only on height and sex and ignores everything that makes real bodies differ, such as muscle, bone structure, frame size, age and body composition. Treat the number as background information, not a target to aim for, and speak with a clinician or registered dietitian for guidance tailored to you.

Estimate your lean body mass (LBM) and body-fat mass from your sex, weight, and height using the validated Boer formula. Results update live in kilograms or pounds, with no sign-up and nothing sent to a server.

Find your ideal daily protein, carbohydrate, and fat targets in grams based on your weight, height, age, sex, activity level, and whether you want to lose, maintain, or gain weight.

Estimate your one-rep maximum (1RM) — the heaviest single lift you can perform — by entering the weight you lifted and how many reps you completed.

Estimate your likely ovulation day and most fertile window from the first day of your last period and your average cycle length.

Estimate your baby's due date from the first day of your last menstrual period (LMP) using Naegele's rule, with an optional adjustment for your average cycle length plus first, second, and third trimester date ranges.

Estimate how many grams of protein to eat per day based on your body weight and your goal — from the basic dietary minimum up to a hard-training athlete's intake.

Find your running pace per kilometer and per mile from any distance and finish time, and see your average speed in km/h and mph. Useful for planning 5K, 10K, half-marathon and marathon efforts.

Find the best time to go to sleep or wake up based on 90-minute sleep cycles, so you wake at the end of a cycle rather than in the middle of deep sleep.

Estimate your Total Daily Energy Expenditure (TDEE) — the total calories you burn per day — from your sex, weight, height, age, and activity level using the Mifflin-St Jeor equation.

Calculate your waist-to-hip ratio (WHR) by dividing your waist measurement by your hip measurement, and see which World Health Organization health-risk category it falls into for your sex.

Estimate how many calories you burn walking by entering your weight, walking speed, and duration. Results use validated MET (Metabolic Equivalent of Task) values from exercise science research.