BMI & Health Calculator
Calculate your BMI, healthy weight range and daily calorie needs from height, weight, age and activity level. Free, and nothing is stored.
Body mass index, with its limits stated
Enter your height and weight in metric or imperial units to get your BMI — weight in kilograms divided by height in metres squared — along with the standard WHO categories: under 18.5 is classed as underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30+ obese.
BMI is a population screening measure, not a diagnosis. It cannot distinguish muscle from fat, so athletes often read as overweight while carrying little body fat, and it misses fat distribution, which matters more for health risk than the total. Treat the number as a starting point for a conversation with a doctor, not a verdict.
Like every tool on this site, the calculation runs in your browser — your height and weight are never uploaded, logged or shared.
Frequently asked questions
How is BMI calculated?
Weight in kilograms divided by height in metres squared. Imperial entries are converted first, so 154 lb at 5 ft 9 in is 69.9 kg at 1.75 m, giving a BMI of 22.8.
What is the difference between BMR and TDEE?
BMR is the energy your body uses at complete rest. TDEE multiplies it by an activity factor, from 1.2 for a sedentary day to 1.9 for hard daily exercise, to estimate the calories that would maintain your current weight.
Which formula is used for the calorie figures?
The revised Harris-Benedict equation, which takes weight, height, age and sex. It is an estimate for the average adult; individual metabolism varies by a few hundred calories a day.
How is the ideal weight range worked out?
It is the weight span that puts your height between a BMI of 18.5 and 24.9. At 1.75 m that is 56.7 to 76.3 kg, and the range is shown in pounds when imperial units are selected.
Is BMI valid for children or athletes?
The adult categories do not apply to children and teenagers, who are assessed on age-and-sex percentiles. For muscular people BMI overstates fatness, so a reading of 26 in a weight-trained adult is not necessarily a concern.