Health & Fitness Calculators
BMI, BMR, calorie, body-fat, macro and pace calculators with clear, science-based formulas.
free tools · no sign-up · works in your browser
BMI Calculator
Calculate your Body Mass Index from height and weight, and see which BMI category you fall into. Enter height in centimetres and weight in kilograms.
Calorie (TDEE) Calculator
Estimate your daily calorie needs (TDEE) based on your BMR and activity level, plus targets for losing or gaining weight.
Ovulation Calculator
Estimate your ovulation date, fertile window and next period from your last period and average cycle length.
One Rep Max (1RM) Calculator
Estimate your one-rep max for any lift from the weight and reps you completed, using the Epley and Brzycki formulas.
Macro Calculator
Calculate your daily protein, carb and fat targets (macros) based on your calorie goal and chosen split.
Body Surface Area (BSA) Calculator
Calculate body surface area using the Du Bois and Mosteller formulas — the standard for medical dosing.
Body Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy method from a few simple tape measurements.
Running Pace Calculator
Work out your running pace per kilometre and per mile from a distance and a finish time — useful for planning a 5K, 10K, half or full marathon.
BMR Calculator
Calculate your Basal Metabolic Rate — the calories your body burns at rest — using the Mifflin-St Jeor equation.
Pregnancy Due Date Calculator
Estimate your baby's due date from your last menstrual period (LMP) using Naegele's rule.
Calories Burned Calculator
Estimate calories burned for walking, running, cycling, lifting and more — based on MET values, your weight and duration.
Daily Water Intake Calculator
Estimate how much water you should drink each day based on your body weight and activity.
Ideal Weight Calculator
Find your ideal body weight range based on height and gender using established medical formulas.
Lean Body Mass Calculator
Estimate your lean body mass (everything except fat) using the Boer formula from height, weight and gender.
Protein Intake Calculator
Find your daily protein target in grams, based on your body weight and goal — maintenance, muscle gain or fat loss.
A1C to Average Glucose Calculator
Convert an HbA1c percentage into estimated average glucose (eAG) in mg/dL and mmol/L.
Waist-to-Hip Ratio Calculator
Calculate your waist-to-hip ratio and see whether it is at or above the WHO risk threshold (0.90 for men, 0.85 for women).
Heart Rate Zone Calculator
Calculate your five training heart-rate zones from your age — recovery to max effort — for smarter cardio.
Choosing a health calculator, and reading the result
Every result here is an estimate from a published formula, not a diagnosis. Use it to understand a number or to prepare questions for a doctor, dietitian or coach.
Body size and composition
BMI Calculator compares weight with height and places the result in the standard adult categories. It cannot tell muscle from fat, so a muscular person can read as overweight. Body Fat Percentage Calculator uses tape measurements (the US Navy method) and says more about composition, which makes it the better check if you lift weights.
Energy and diet
BMR Calculator estimates the calories your body uses at rest. Calorie (TDEE) Calculator starts from the same Mifflin-St Jeor equation and multiplies it by your activity level, which makes it the right starting point for a weight goal. Macro Calculator then splits a daily calorie target into protein, carbohydrate and fat, so run the calorie calculator first and carry its number across.
Training and pregnancy
One Rep Max (1RM) Calculator estimates your heaviest single lift from a set of several reps, so you can plan training loads without testing a true maximum. Ovulation Calculator estimates the fertile window from the date of your last period and your cycle length, and Pregnancy Due Date Calculator counts forward from the first day of the last period. Cycles vary, so both give likely dates, not certain ones; an early ultrasound is the more accurate way to date a pregnancy.
Calculations run in your browser and nothing you enter is saved or sent anywhere.