Health & Fitness Calculators
Free, science-based calculators for BMI, calories, body composition, and sleep
Track wellness with 18+ calculators that use the same formulas doctors and dietitians rely on - Mifflin-St Jeor for BMR, WHO categories for BMI, and 90-minute sleep cycles for rest.
Quick Answer · Featured snippet
Quick reference: BMI 25 = overweight (WHO); a 30-year-old 175 cm adult weighing 77 kg has BMI 25.1; average adult needs 2,000-2,500 kcal/day (Mifflin-St Jeor); 7-9 hours of sleep per night is recommended for adults.
Verified formulas, no signup · Updated for 2026
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Most popular health calculators
BMI Calculator
Body mass index with WHO weight categories
Calorie Calculator
BMR + TDEE for your activity level
Body Fat Calculator
Body fat % using the US Navy method
Pregnancy Due Date
Estimate due date via Naegele's Rule
Macro Calculator
Protein, carbs & fat for your goal
Ideal Weight
Healthy weight range using 4 formulas
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See all 30+ calculatorsAll health & fitness calculators
30+ free tools · sorted by topic100% freeNo signup
BMI Calculator
Calculate body mass index and assess weight status
Calorie Calculator
Estimate BMR, TDEE and daily calorie needs
Calorie Deficit Calculator
Calorie target and macros for weight loss or gain
Body Fat Calculator
Estimate body fat percentage
BMR Calculator
Calculate basal metabolic rate
TDEE Calculator
Total daily energy expenditure for calorie planning
Macro Calculator
Protein, carb, and fat targets for your goals
Pregnancy Calculator
Due date, current week, and milestone tracker
Pregnancy Due Date Calculator
Estimate your due date using Naegele Rule
Ovulation & Fertility Calculator
Estimate your fertile window and ovulation date
Ideal Weight Calculator
Estimate ideal weight range
Water Intake Calculator
Daily water needs based on weight and activity
Sleep Calculator
Optimal sleep times based on cycles
Pace Calculator
Running and exercise pace
One Rep Max (1RM) Calculator
Estimate your one rep max for any lift
BAC Calculator
Estimate blood alcohol content
MAP Calculator
Calculate mean arterial pressure from blood pressure
Snow Day Calculator
School closure probability
What makes our health & fitness calculators different
Updated for 2026Clinically-Validated Formulas
Mifflin-St Jeor for BMR, WHO BMI categories, Deurenberg for body fat, Naegele Rule for due dates.
Instant, Clear Results
See BMI category, calorie target, sleep window, and more in seconds - no medical jargon.
Private - Nothing Stored
Weight, age, and cycle data live in your browser. We never see or save them.
Learn While You Calculate
Each tool explains the formula, what the numbers mean, and how to act on them.
Frequently asked questions about our health calculators
Are these health calculators medically accurate?
We use the same formulas clinicians use: Mifflin-St Jeor for BMR, Deurenberg for body fat, the WHO BMI cutoffs, and Naegele Rule for due dates. They are screening tools, not medical diagnoses - always consult a clinician for medical decisions.
Should I rely on BMI to assess my health?
BMI is a useful population-level screening tool but does not distinguish muscle from fat. For a fuller picture, use our body fat calculator alongside BMI.
Is my health data private?
Yes. All calculations happen in your browser. We do not log, store, or transmit any of the values you enter.
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is what you burn at complete rest. TDEE (Total Daily Energy Expenditure) = BMR multiplied by an activity factor - it estimates what you actually burn each day including movement and exercise.
Do I need the first day of my last period to use the pregnancy calculator?
For the most accurate estimate, yes - that date anchors the standard 280-day (40-week) calculation. If you do not know it, you can enter an ultrasound-based gestational age instead.