These health calculators use the same formulas clinicians and dietitians use. The BMI calculator follows the WHO classification, the calorie calculator uses the Mifflin-St Jeor equation to estimate BMR and daily energy needs, and the body-fat calculator applies the US Navy circumference method. Each one is a screening-level estimate, not a diagnosis.
Health & Fitness
Health & Fitness Calculators
8 free health & fitness calculators — each with its own page, the formula explained, a worked example and FAQs.
All Health Calculators
BMI Calculator
Body Mass Index and healthy weight range
Calorie Calculator
Daily calorie needs based on age, height and activity
Ideal Weight Calculator
Ideal body weight by height and gender
Body Fat Calculator
Estimate body fat percentage with Navy method
Pregnancy Due Date Calculator
Calculate pregnancy due date from LMP
Water Intake Calculator
Daily water intake recommendation by weight
Sleep Calculator
Best wake-up times based on sleep cycles
Target Heart Rate Calculator
Max and target heart rate zones for workouts
How to choose the right calculator
For day-to-day targets, the water intake calculator and target heart-rate calculator translate your body weight and age into practical numbers for hydration and training zones, while the ideal weight calculator shows the healthy range for your height across several established formulas. Results depend heavily on accurate inputs — measure carefully, and discuss anything concerning with a healthcare professional who can see the full picture.
Frequently Asked Questions
No. They give screening-level estimates using standard formulas. A number outside the typical range is a prompt to speak with a doctor or dietitian, not a diagnosis in itself.
The Mifflin-St Jeor equation, used here, is currently the most accurate for the general population and is the one most registered dietitians recommend over older Harris-Benedict figures.
BMI only uses height and weight, so it cannot tell muscle from fat. A muscular person can have a high BMI with low body fat. Read the two results together.