Health & Fitness Calculators

Health & Fitness Calculators

20+ free health calculators based on WHO and CDC guidelines. BMI, BMR, calories, pregnancy, body fat and more. Updated 2026.

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Body Metrics
6 calculators
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BMI Calculator
Body Mass Index with WHO classification
800K+ searches/month
Body Fat Calculator
Estimate your body fat percentage
400K+ searches/month
Ideal Weight Calculator
Your ideal weight range by height
500K+ searches/month
Popular
BMR Calculator
Basal Metabolic Rate using Harris-Benedict
900K+ searches/month
Lean Body Mass Calculator
Your fat-free body mass estimate
200K+ searches/month
Waist-to-Hip Ratio
Assess cardiovascular health risk
150K+ searches/month
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Why Use Our Health Calculators

24 free health calculators that show the formula they use and where the numbers come from: CDC, NIH, WHO, ACOG, the National Academies and the 2024 Compendium of Physical Activities. Results are estimates to help you plan, not a diagnosis.

Every health calculator on this page follows official guidelines. The BMI calculator uses WHO classifications. The calorie and TDEE calculator uses the Mifflin-St Jeor equation, the most validated formula for estimating metabolic rate. The pregnancy due date calculator uses standard 40-week gestational calculations confirmed by ACOG.

Use these tools together for a complete picture. Start with the BMI calculator for body composition context, then the calorie calculator for your daily energy needs, and the ideal weight calculator to set realistic goals.

All calculations run in your browser. No health data is ever stored or transmitted. Always consult a healthcare professional before making significant changes to diet or exercise.

Which Calculator Answers Your Question

Your questionUse this
Is my weight in a healthy range?BMI Calculator, Ideal Weight Calculator
How many calories should I eat?Calorie Calculator, Calorie Deficit Calculator
How much protein, carbs and fat?Macro Calculator
When is my baby due?Pregnancy Due Date Calculator
When am I most fertile?Ovulation Calculator
When should I go to bed?Sleep Cycle Calculator
How many calories did my workout burn?Calories Burned Calculator
What pace do I need for my race goal?Running Pace Calculator

Reference Values Worth Knowing

MeasureReference value
Healthy adult BMI18.5 to 24.9 (25 to 29.9 overweight, 30 and above obesity)
Physical activity for adults150 to 300 minutes of moderate activity a week, plus muscle strengthening on 2 days
Sleep for adults 18 to 607 hours or more a night
Total water intake (food and drinks)About 3.7 L a day for men and 2.7 L for women
Waist-to-hip ratio linked to higher risk0.90 or more for men, 0.85 or more for women
US standard drink14 g of pure alcohol (12 oz beer at 5%, 5 oz wine at 12%, 1.5 oz spirits at 40%)
Legal driving limit0.08% BAC in every state except Utah (0.05%)
Pregnancy length280 days (40 weeks) from the first day of the last period

These values describe populations, not individuals. For decisions about your health, talk to a doctor, midwife or registered dietitian.

Sources. CDC adult BMI categories and sleep recommendations; Physical Activity Guidelines for Americans, 2nd edition (HHS); National Academies Dietary Reference Intakes for water; WHO waist circumference and waist-hip ratio report; NIAAA standard drink definition; NHTSA and Utah Code on BAC limits; ACOG Committee Opinion 700.

Health & Fitness Questions

Common questions about BMI, calories, body fat, pregnancy and fitness in 2026.

For adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. BMI is weight in kg divided by height in meters squared. Use the BMI Calculator for an instant result in metric or imperial.

To lose 1 lb per week, create a 500-calorie daily deficit from your TDEE. Most adults need 1,600 to 2,400 calories/day depending on age, sex, weight, and activity. Never go below 1,200 cal (women) or 1,500 cal (men) without medical guidance. Use the Calorie / TDEE Calculator for your exact number.

Average BMR is roughly 1,400 to 1,800 cal/day for women and 1,600 to 2,200 for men, declining about 2% per decade after 30. The Mifflin-St Jeor equation: (10 x kg) + (6.25 x cm) - (5 x age) + 5 (men) or -161 (women). Use the BMR Calculator for your exact baseline.

The US Navy method uses circumference measurements: neck + abdomen (men), neck + waist + hips (women). Healthy ranges: men 10 to 20%, women 18 to 28%. Athletes: 6 to 13% (men), 14 to 20% (women). Use the Body Fat Calculator for the Navy method or BMI-based estimate.

Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period. If you know conception date, add 266 days instead. Only about 5% of babies are born exactly on their due date. Use the Pregnancy Due Date Calculator for LMP, conception, or IVF transfer date methods.

A 155 lb person burns roughly 280 calories/hour at 3.5 mph, 350 at 4 mph, and 420 at 4.5 mph. Formula: METs x weight (kg) x hours. Walking METs range from 3.5 (moderate) to 5 (brisk). Use the Calories Burned Calculator for your exact weight and pace.

Devine formula: men: 50 kg + 2.3 kg per inch over 5 ft; women: 45.5 kg + 2.3 kg per inch over 5 ft. A 5’10” man has ideal weight of ~166 lbs. BMI 18.5 to 24.9 is the broader healthy range. Use the Ideal Weight Calculator to compare multiple formulas side by side.

Ovulation occurs 14 days before your next period, not 14 days after. For a 28-day cycle that is day 14; for a 32-day cycle, day 18. The fertile window is 5 days before ovulation plus ovulation day. Use the Ovulation Calculator with your last period date and average cycle length.

Keep waist circumference less than half your height (waist-to-height ratio below 0.5). Health risks rise above 35 inches for women and 40 inches for men. These thresholds are linked to cardiovascular and metabolic disease. Use the Waist-to-Hip Ratio Calculator for a fuller assessment.

General guidelines: 3.7 liters (125 oz) for men and 2.7 liters (91 oz) for women daily from all sources. Simpler estimate: body weight in lbs divided by 2 = daily oz needed. Add 12 oz per 30 minutes of exercise. Use the Water Intake Calculator for a personalized recommendation.
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