Health Calculators

BMI — weight in kilograms divided by height in metres squared — remains the most widely used screening number in clinical and public-health settings, with 18.5–24.9 defined as the standard healthy range. It is a starting point, not a diagnosis: a rugby player and a sedentary adult can share the same BMI for entirely different reasons, which is why the BMI calculator here pairs the raw score with BMI Prime so you can see both the absolute value and how far it sits from the midpoint of the healthy band.

Calorie tools make up the second major cluster. BMR is what your body burns at rest; multiply it by an activity factor — roughly 1.2 for a sedentary lifestyle up to about 1.9 for hard daily training — and you get TDEE, your true daily energy expenditure. The 21 tools here cover that full chain: TDEE and BMR, plus body-fat percentage, ideal weight, body surface area, running pace, and kidney-function screening via GFR. Each returns the formula and the substituted values, not just a number.

All results are estimates based on population averages and validated equations — useful for tracking trends and setting baselines, but not a substitute for clinical assessment. Use them to ask better questions of a doctor or dietitian, not to replace that conversation. Pick a tool below — the most-used ones appear first.

Most popular

8 tools

BMI Calculator — Asian Thresholds, Prime, Trefethen Calculate BMI, BMI Prime, Ponderal Index, and Trefethen BMI. Visual gauge, weight targets, and Asian-adjusted thresholds. Running Pace Calculator — Race Predictor + Splits Calculate running pace (time divided by distance) with race time prediction, training pace zones, per-mile and per-km splits, and a pace-to-finish-time chart for 5K, 10K, half, and marathon. Body Fat Calculator — U.S. Navy Tape Method Estimate your body fat percentage using the U.S. Navy method. Enter your measurements for an accurate body composition assessment. TDEE Calculator — Maintenance Calories + Macros Find maintenance calories with 3 BMR formulas plus macros for cutting or bulking. Most adults: 1,800–2,800 cal/day. Includes goal timeline.

Body Surface Area Calculator — 8 Clinical Formulas Calculate body surface area using 8 formulas: Du Bois, Mosteller, Haycock, and more. Used for drug dosing and clinical assessments. Ideal Weight Calculator — 4 Formulas + Healthy BMI Calculate ideal body weight using Robinson, Miller, Devine, and Hamwi formulas. Compare results with healthy BMI range. BMR Calculator — Basal Metabolic Rate (Mifflin-St Jeor) Calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation. See daily calorie needs for 6 activity levels. GFR Calculator — CKD-EPI 2021, MDRD, Cockcroft-Gault Estimate glomerular filtration rate using CKD-EPI 2021, MDRD, and Cockcroft-Gault. Includes pediatric Schwartz formula.

All health calculators

21 tools

Weight Loss Percentage Calculator — Track Loss kg/lb Calculate your weight loss percentage from initial and current weight. Shows total loss in pounds and kilograms. BMI Calculator — Asian Thresholds, Prime, Trefethen Calculate BMI, BMI Prime, Ponderal Index, and Trefethen BMI. Visual gauge, weight targets, and Asian-adjusted thresholds. Body Fat Calculator — U.S. Navy Tape Method Estimate your body fat percentage using the U.S. Navy method. Enter your measurements for an accurate body composition assessment. TDEE Calculator — Maintenance Calories + Macros Find maintenance calories with 3 BMR formulas plus macros for cutting or bulking. Most adults: 1,800–2,800 cal/day. Includes goal timeline. Calorie Calculator — Mifflin-St Jeor Daily Needs Calculate daily calorie needs using the Mifflin-St Jeor equation. Find calories for weight loss, maintenance, and gain. Sleep Calculator — Bedtime, Wake Time, Nap Cycles Calculate optimal bedtimes, wake times, and nap durations based on sleep cycles. Includes age-based sleep recommendations. Running Pace Calculator — Race Predictor + Splits Calculate running pace (time divided by distance) with race time prediction, training pace zones, per-mile and per-km splits, and a pace-to-finish-time chart for 5K, 10K, half, and marathon. Macro Calculator — Protein, Carbs, Fat from TDEE Calculate daily macros with built-in TDEE. Enter body stats or calories directly to get protein, carbs, and fat targets. BAC Calculator — Blood Alcohol from Drinks & Weight Estimate blood alcohol content based on drinks, weight, gender, and time elapsed. Educational use only. Period Calculator — Cycle, Ovulation, Fertile Window Track menstrual cycle and predict next period. Calculate fertile window and ovulation dates for the next 6 months. Pregnancy Calculator — Due Date from LMP or Conception Calculate pregnancy due date from LMP or conception. Track gestational age, trimesters, and milestones.

Conception Calculator — Estimate from Due Date or LMP Estimate conception date from due date, last period, or ultrasound. Includes the fertile window and full timeline. Bra Size Calculator — US, UK, EU, Australian Sizing Calculate bra size from bust and band measurements. Convert between US, UK, EU, and Australian sizing standards. Lean Body Mass Calculator — Boer, James, Hume Calculate lean body mass using Boer, James, and Hume formulas. Estimate fat-free mass from height, weight, and body fat. Body Surface Area Calculator — 8 Clinical Formulas Calculate body surface area using 8 formulas: Du Bois, Mosteller, Haycock, and more. Used for drug dosing and clinical assessments. Ideal Weight Calculator — 4 Formulas + Healthy BMI Calculate ideal body weight using Robinson, Miller, Devine, and Hamwi formulas. Compare results with healthy BMI range. BMR Calculator — Basal Metabolic Rate (Mifflin-St Jeor) Calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation. See daily calorie needs for 6 activity levels. Army Body Fat Calculator — AR 600-9 Tape Test Calculate body fat using the Army tape test method (AR 600-9). Check compliance with military body composition standards. 1RM Calculator — One Rep Max + Training % Table Calculate one rep max from weight and reps. Get percentage-based training recommendations across 5 formulas. GFR Calculator — CKD-EPI 2021, MDRD, Cockcroft-Gault Estimate glomerular filtration rate using CKD-EPI 2021, MDRD, and Cockcroft-Gault. Includes pediatric Schwartz formula. Calories Burned Walking — Pace, Weight, MET-Based Calculate calories burned walking based on pace, body weight, and duration. Uses MET values from the Compendium of Physical Activities.