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.
BMI Calculator
Calculate body mass index and assess weight status
Calorie Calculator
Estimate BMR, TDEE and daily calorie needs
Body Fat Calculator
Estimate body fat percentage
BMR Calculator
Calculate basal metabolic rate
Ideal Weight Calculator
Estimate ideal weight range
Pace Calculator
Running and exercise pace
Sleep Calculator
Optimal sleep times based on cycles
Snow Day Calculator
School closure probability
BAC Calculator
Estimate blood alcohol content
MAP Calculator
Calculate mean arterial pressure from blood pressure
TDEE Calculator
Total daily energy expenditure for calorie planning
Macro Calculator
Protein, carb, and fat targets for your goals
Ovulation & Fertility Calculator
Estimate your fertile window and ovulation date
Pregnancy Due Date Calculator
Estimate your due date using Naegele Rule
One Rep Max (1RM) Calculator
Estimate your one rep max for any lift
Water Intake Calculator
Daily water needs based on weight and activity
Calorie Deficit Calculator
Calorie target and macros for weight loss or gain
Pregnancy Calculator
Due date, current week, and milestone tracker
What makes our health & fitness calculators different
Clinically-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.