Health & Fitness Calculators
Evidence-based health and fitness estimates using the same equations clinicians and coaches use, such as Mifflin-St Jeor, the U.S. Navy body-fat method and Naegele's rule. Results are estimates, not medical advice.
16 free calculators · no sign-up · results stay in your browser
- BMI Calculator Popular Body mass index with WHO or Asian-Indian categories and your healthy weight range.
- Calorie Calculator Popular Maintenance calories and daily targets to lose or gain weight, in kg or lb.
- TDEE Calculator Popular Calories you burn per day at every activity level, with Mifflin-St Jeor and Katch-McArdle.
- BMR Calculator Calories burned at rest with Mifflin-St Jeor, Harris-Benedict and Katch-McArdle side by side.
- Body Fat Calculator Popular Body fat % from tape measurements (U.S. Navy method), with fat mass, lean mass and ACE category.
- Ideal Weight Calculator Ideal body weight from 4 formulas plus the healthy BMI weight range for your height.
- Macro Calculator Daily and per-meal grams of protein, carbs and fat for your calorie target and goal.
- Protein Calculator Daily and per-meal protein in grams by body weight and goal, with protein in common foods.
- Water Intake Calculator Daily water goal by body weight, exercise and climate, in litres, cups and fl oz.
- Due Date Calculator Popular Due date, weeks pregnant today and trimester dates from your last period, conception, IVF or a scan.
- Ovulation Calculator Ovulation date, fertile window and next period for the coming cycles, with due dates if you conceive.
- Sleep Calculator Popular Best bedtimes or wake-up times in whole sleep cycles, plus recommended sleep hours by age.
- Pace Calculator Pace per km or mile, finish time or distance, with splits and 5K to marathon predictions.
- One Rep Max Calculator Estimate your 1RM from any set of 1 to 12 reps with six formulas and a training load chart.
- Target Heart Rate Calculator Max heart rate, target exercise range and five training zones by age, with optional Karvonen method.
- Calories Burned Calculator Calories burned for 40 activities by body weight and time, using 2024 Compendium MET values.
About these calculators
These health and fitness calculators use the formulas found in clinical and sports-science research. The BMI calculator supports both the WHO categories and the lower cut-offs used for Asian and Indian adults. The calorie, BMR and TDEE calculators use the Mifflin-St Jeor equation, which research has found to be the most accurate for most adults.
For body composition, try the body fat calculator (U.S. Navy tape-measure method) and the ideal weight calculator, which compares four published formulas. Planning nutrition? The macro and protein calculators turn a calorie target into grams of protein, carbs and fat.
For pregnancy and fertility, the due date and ovulation calculators apply Naegele's rule and cycle-length adjustments. Runners and lifters can use the pace, one-rep max and heart-rate zone tools to plan training.
Every result here is an estimate based on population averages. Your body, medical history and medications matter, so use these numbers to start a conversation with your doctor, dietitian or midwife, not to replace one.
Many of these tools build on each other. BMR is the energy your body uses at rest. Multiplying it by an activity factor gives TDEE, your daily maintenance calories. Subtracting about 500 kcal a day from TDEE gives a steady weight loss of roughly 0.5 kg (1 lb) a week, and the macro and protein calculators split that target into grams of protein, carbohydrate and fat.