Free online health calculators — BMI, daily calories, body fat percentage, and pregnancy due date. All calculations run instantly in your browser.
Body Mass Index (BMI) is a measure of body weight relative to height. Enter your details below to find your BMI and weight category.
Estimate your Total Daily Energy Expenditure (TDEE) — the number of calories you need each day based on your age, sex, height, weight, and activity level. Uses the Mifflin-St Jeor formula.
Estimates body fat percentage using the U.S. Navy circumference method — no calipers needed. Measure your waist, neck (and hips for women) with a soft tape measure.
Estimate your due date (EDD — Estimated Date of Delivery) using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP).
The World Health Organization (WHO) defines a healthy BMI as between 18.5 and 24.9. Below 18.5 is considered underweight; 25–29.9 is overweight; 30 and above is obese. BMI is a useful screening tool but does not directly measure body fat or account for muscle mass, age, or ethnicity.
TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, including exercise. It is calculated by first finding your BMR (Basal Metabolic Rate) using the Mifflin-St Jeor equation — the most accurate formula for most adults — then multiplying by an activity factor. To lose weight, eat below your TDEE; to gain, eat above it.
The U.S. Navy circumference method has an accuracy of roughly ±3–4% compared to DEXA scans (the gold standard). It is less accurate than hydrostatic weighing or DEXA but requires no equipment beyond a tape measure, making it the most practical free estimation method available.
The standard method is Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period, adjusted for your cycle length. A full-term pregnancy is 37–42 weeks. Only about 5% of babies are born exactly on the due date, so the EDD is an estimate within a 5-week window.
Healthy body fat ranges differ by sex: for men, 6–24% is considered acceptable, with 14–17% being fit; for women, 16–30% is acceptable, with 21–24% being fit. Athletes typically fall in the 6–13% (men) or 14–20% (women) range. Essential fat (the minimum needed for survival) is around 3–5% for men and 10–13% for women.
Yes, completely free. All calculations run in your browser — no account required, no personal data stored or transmitted. Results are for informational purposes only and do not constitute medical advice. Consult your healthcare provider for personalized guidance.