Health & Fitness calculators
Health and fitness tools estimate body measures (BMI, body fat, lean mass, ideal weight, waist-to-hip ratio), energy needs and nutrition, training measures such as heart rate zones, VO2 max, one-rep max and race pace, and screening values such as blood pressure category, GFR and blood alcohol. Pregnancy, cycle and baby growth tools are included too.
38 tools · Updated October 21, 2026
Which one do I need?
What body measurements can and cannot tell you
BMI divides weight by height squared and sorts adults into WHO categories (18.5 to 24.9 is the normal range). It is quick and useful for populations, but it cannot tell muscle from fat, so muscular people can be classed as overweight. Body fat estimates such as the US Navy tape method and waist-based measures add information about where weight is carried, which relates more closely to health risk.
No single number is a diagnosis. Use the BMI, Body Fat and Waist-to-Hip Ratio calculators together for a fuller picture, and treat any result as a starting point for a conversation with a clinician rather than a verdict.
Energy balance: BMR, TDEE and calorie targets
Basal metabolic rate is the energy your body uses at rest, commonly estimated with the Mifflin-St Jeor equation. Total daily energy expenditure multiplies BMR by an activity factor to account for movement and exercise. The BMR and TDEE calculators give these figures, and they are estimates that can be off by a few hundred calories for an individual.
A moderate deficit below TDEE leads to gradual weight loss, but the old rule of 3,500 calories per pound overstates long-term results because the body adapts as weight drops. Use the Caloric Deficit Calculator to set a starting target, then adjust it based on your actual weekly trend. The Macro Calculator turns the target into protein, carbohydrate and fat amounts.
Training zones and performance estimates
Heart rate zones divide effort into bands from easy to maximal, usually as percentages of maximum or heart rate reserve. The common 220 minus age formula for maximum heart rate is a rough average and can be off by 10 beats per minute or more for an individual, so a measured maximum or the heart rate reserve method gives better zones.
Performance predictors such as the Race Time Predictor, One-Rep Max Calculator and VO2 Max Calculator extrapolate from a known effort. They are most accurate for distances or loads close to the one you tested and less so for big jumps, such as predicting a marathon from a mile.