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 35+ calculatorsWhat 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.