Health & Fitness Calculators — Free Online Tools
BMI, calorie, pregnancy due date, ovulation, body fat, and fitness tools. From BMI and calorie needs to pregnancy timing and body composition, our health calculators give you clear, private answers about your body and fitness.
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BMI Calculator
Free BMI calculator. Enter your height and weight to instantly compute your Body Mass Index and see where you fall on the WHO weight classification scale.
OpenBMR Calculator
Free BMR calculator using the Mifflin-St Jeor equation. Enter age, weight, height and gender to estimate calories you burn at complete rest each day.
OpenCalorie Calculator
Free daily calorie calculator. Enter your age, weight, height, gender, and activity level to estimate the calories you need each day to maintain, lose, or gain weight.
OpenBody Fat Calculator
Free body fat percentage calculator using U.S. Navy method. Enter neck, waist, and hip measurements to estimate your body composition without calipers.
OpenIdeal Weight Calculator
Free ideal weight calculator using multiple formulas (Robinson, Miller, Devine, Hamwi). Enter height and gender to find your healthy weight range.
OpenWater Intake Calculator
Free water intake calculator. Enter your weight, exercise duration, and climate to estimate how many ounces or liters of water you should drink each day.
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Pregnancy Due Date Calculator
Free pregnancy due date calculator. Enter the first day of your last period or your conception date to estimate your baby due date and see your trimesters.
OpenOvulation Calculator
Free ovulation calculator. Enter your last period date and cycle length to estimate your fertile window, ovulation day, and the best days for conception.
OpenSleep Calculator
Free sleep calculator to help you sync your bedtime or wake time with natural 90-minute sleep cycles for better rest and easier waking.
OpenHeart Rate Calculator
Free heart rate calculator to find your maximum, resting, and training heart rate zones. Useful for optimizing cardio and tracking cardiovascular fitness.
OpenTDEE Calculator
Free TDEE calculator. Enter your details and activity to find Total Daily Energy Expenditure — the calories you actually burn in a full day.
OpenMacro Calculator
Free macronutrient calculator. Enter your calorie goal and dietary preference to split those calories into optimal grams of protein, carbohydrates, and fat.
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Waist-to-Hip Ratio Calculator
Free waist-to-hip ratio calculator. Enter your waist and hip measurements to estimate your body shape and cardiovascular risk outlook.
OpenLean Body Mass Calculator
Free lean body mass calculator. Enter total weight and body fat percentage to find how many pounds or kilos of muscle, bone, and organ tissue you carry.
OpenCalories Burned Calculator
Free calories burned calculator for 50+ activities. Enter your weight and duration to estimate how many calories running, walking, biking and more burn.
OpenAbout Health Calculators
Knowing your numbers is the foundation of good health decisions. Our 15 free health and fitness calculators translate standard formulas into instant, easy-to-read results: body mass index, basal metabolic rate, daily calorie targets, macronutrient splits, body fat percentage, hydration needs, heart-rate training zones, and more.
We also cover life-stage planning with pregnancy due-date and ovulation calculators, plus fitness-tracking tools like TDEE, calories burned, waist-to-hip ratio, and lean body mass. Every calculation happens privately in your browser — no account, no data upload. Your health information stays on your device.
These tools use widely accepted clinical formulas (such as the WHO BMI categories and Mifflin-St Jeor equation). They are educational, not a substitute for professional medical advice. Use them to set informed goals, track progress, and prepare better questions for your doctor.