Browser-based health and fitness calculators for athletes, patients, and the health-curious. Calculate BMI, TDEE, macro splits, heart rate zones, pregnancy timelines, and more. Every tool shows its formula.
Body Mass Index calculator using the WHO standard formula: weight (kg) / height (m)². Classifies results into underweight, normal, overweight, and obese categories with CDC cutoffs. Supports both metric and imperial units with automatic conversion. Shows the exact formula, interpretation, and healthy weight range for your height.
CalculateBasal Metabolic Rate using Mifflin-St Jeor and Harris-Benedict equations. Shows calories burned at complete rest.
CalculateTotal Daily Energy Expenditure from BMR × activity multiplier. Cutting and bulking calorie targets included.
CalculateU.S. Navy method body fat percentage from neck, waist, and hip measurements. Includes category classification.
CalculateCalculate lean body mass using the Boer, Hume, and James formulas. Shows fat-free mass index alongside.
CalculateWHR calculator with WHO health risk classification. Low, moderate, and high risk thresholds for men and women.
CalculateWHtR calculator — the "keep your waist circumference to less than half your height" metric. Strong cardiometabolic predictor.
CalculateIdeal body weight using Devine, Robinson, Miller, and Hamwi formulas. Shows range across all four formulas.
CalculateDaily calorie needs calculator combining BMR with activity level. Shows maintenance calories, 500-calorie deficit for 1 lb/week loss, and 500-calorie surplus for 1 lb/week gain. Uses the Mifflin-St Jeor equation — the formula recommended by the Academy of Nutrition and Dietetics since 2005.
CalculateProtein, carb, and fat split from daily calories. Presets for cut, maintain, and bulk. Grams per macro displayed.
CalculateDaily water requirement from body weight and activity level. Shows ounces, cups, and liters. Includes exercise adjustment.
CalculateDaily protein needs based on body weight and activity. RDA, athletic, and bodybuilding ranges from 0.8 to 2.2 g/kg.
CalculateDaily fiber recommendation from calorie intake. 14g per 1,000 calories per Institute of Medicine guidelines.
CalculateDaily added sugar limits per AHA guidelines. Men: 36g, Women: 25g. Shows teaspoons and calories from sugar.
CalculateDaily sodium needs and upper limits. FDA recommends < 2,300mg. Shows salt equivalent in teaspoons.
CalculateDaily carbohydrate targets for standard, low-carb, and keto diets. Shows grams and calories from carbs.
CalculateDaily fat intake from calorie target. Shows saturated, monounsaturated, and polyunsaturated fat recommendations.
CalculateTraining heart rate zones using the Karvonen formula (heart rate reserve method). Calculates 5 zones from Zone 1 (50-60% HRR, recovery) through Zone 5 (90-100% HRR, max effort). Shows max heart rate via both the 220-age formula and the more accurate Tanaka formula (208 - 0.7 × age). Includes recommended time-in-zone for endurance, fat burn, VO2 max, and anaerobic training protocols.
CalculatePace from distance and time. Supports km and miles. Shows split times for 5K, 10K, half, and full marathon.
CalculatePredict race times from a recent result using the Riegel formula: T2 = T1 × (D2/D1)^1.06. Accurate within 5% for most runners.
PredictEstimate VO2 max using the Cooper 1.5-mile run test or Rockport 1-mile walk test. Shows percentile ranking by age and gender.
Calculate1RM from weight and reps using Epley, Brzycki, Lombardi, and Mayhew formulas. Shows percentage-based training loads.
CalculateCalories burned per exercise using MET values. 200+ activities from walking to CrossFit. Duration-based calculation.
CalculateOptimal bedtime and wake time based on 90-minute sleep cycles. 5-6 cycles recommended for full recovery.
CalculatePregnancy due date using Naegele's rule from LMP. Shows current week, trimester, and countdown to due date.
CalculateFertility window from cycle length. Shows ovulation date, fertile days, and next period estimate.
CalculateRecommended weight gain per IOM guidelines. Adjusts for pre-pregnancy BMI, singleton vs twin pregnancy.
CalculateEstimate conception date from due date or LMP. Shows likely conception window and fertile period.
CalculateBasal body temperature charting tool. Track daily BBT to detect ovulation through temperature shift pattern.
TrackBlood alcohol content using the Widmark formula. Factors in weight, gender, drinks, and time elapsed.
CalculateDaily caffeine intake and half-life decay. Shows remaining caffeine at bedtime. FDA limit: 400mg/day.
CalculateHealthy weight range from height using BMI 18.5-24.9. Shows in both kg and lbs with visual range indicator.
CalculateExercise hydration needs from body weight, duration, and temperature. Includes pre- and post-workout targets.
CalculateSun exposure time for vitamin D synthesis. Factors in skin type (Fitzpatrick scale), latitude, and UV index.
CalculateInteractive BMI reference with formula explanation, category breakdown, limitations, and history of the index.
ReadMHTC offers 35 free health and fitness calculators that run entirely in your browser. Every calculation happens locally — no health data is sent to servers, no accounts are required, no tracking scripts monitor your inputs. Whether you're calculating BMI for a fitness assessment, determining TDEE for a meal plan, or estimating your pregnancy due date, these tools provide instant results with transparent formulas.
Health calculators apply validated medical and fitness formulas to user-provided inputs like height, weight,
age, and activity level. The BMI calculator uses the WHO standard formula:
weight (kg) / height (m)². The BMR calculator implements the Mifflin-St Jeor
equation, recommended by the Academy of Nutrition and Dietetics since 2005:
BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + s (where s is +5 for males, -161 for
females). The heart rate zone calculator uses the Karvonen formula:
target HR = ((max HR - resting HR) × %intensity) + resting HR.
Each tool follows the same architecture: input fields capture values, a JavaScript function executes the medical formula, and results render with full step-by-step explanation. The TDEE calculator first computes BMR via Mifflin-St Jeor, then multiplies by the appropriate activity factor (1.2 for sedentary through 1.9 for very active). The body fat calculator implements the U.S. Navy circumference method, which uses neck, waist, and hip measurements in gender-specific logarithmic formulas validated against hydrostatic weighing with an R² of 0.86.
The pregnancy due date calculator applies Naegele's rule, established in 1830:
due date = LMP + 280 days. The one rep max calculator implements four
validated formulas — Epley, Brzycki, Lombardi, and Mayhew — and displays all four estimates so users can
choose the most appropriate for their training style.
Every calculator on this site runs client-side. Your browser downloads the HTML, CSS, and JavaScript once, then all health calculations happen locally. The BMI calculator never transmits your weight. The pregnancy calculator never uploads your LMP date. The BAC calculator never sends your drinking history to a server. Open DevTools (F12), switch to the Network tab, and use any calculator — zero outgoing requests fire during computation.
These calculators provide informational estimates based on validated formulas and population averages. They are not diagnostic tools and should not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health, fitness, or nutrition. Individual results may vary based on factors not captured by these formulas, including muscle mass, bone density, medical conditions, and genetic factors.
Use the search bar above to find a specific calculator, or scroll through the categories: Body Composition, Calorie & Nutrition, Fitness & Training, Pregnancy & Women's Health, and General Health.