BMI Calculator
Calculate your Body Mass Index and see your healthy weight range
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Body Mass Index (BMI) is weight in kilograms divided by height in metres squared. It is a quick screening tool: a BMI of 18.5–24.9 is considered normal. BMI does not distinguish muscle from fat, so athletes should also check body-fat percentage.
How to use this BMI calculator
Enter your height and weight and your BMI is calculated instantly — no sign-up needed. You can switch between metric (cm·kg) and imperial (in·lbs) units, and choose between the WHO international standard and the Asia-Pacific standard, which uses lower cut-offs because health risks in Asian populations rise at lower BMI values.
How to read your result
The color bar shows where you fall: underweight, normal, overweight or obese. A result in the normal range is linked with the lowest risk of weight-related disease, while values above it are associated with higher risk of type 2 diabetes, high blood pressure and cardiovascular disease. Rather than a one-off number, track the direction your BMI moves over months — that trend is far more informative.
The formula and where it comes from
BMI = weight (kg) ÷ height (m)². The index was devised by the Belgian statistician Adolphe Quetelet in the 1830s and adopted by the WHO as the standard population-level screening measure for underweight and obesity. Height is squared because body weight scales roughly with the square of height, which lets one number compare people of different sizes fairly.
Limits and practical tips
BMI cannot tell muscle from fat: muscular athletes may read 'overweight' while people with little muscle can hide excess fat inside a 'normal' BMI. It is also less reliable for adults over 65, during pregnancy, and for children. For a fuller picture, combine it with our body-fat percentage, waist-to-height ratio and FFMI calculators — and log your meals in the CaloNote app to act on what you find.
Frequently Asked Questions
- What is a healthy BMI?
- A BMI of 18.5–24.9 is classified as normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.
- Is BMI accurate for athletes?
- Not always. BMI does not separate muscle from fat, so muscular people can read as overweight. Athletes should also check body-fat percentage.
- How do I lower my BMI?
- Lower BMI by losing fat through a moderate calorie deficit and regular activity. The CaloNote BMI calculator shows the weight needed to reach a normal BMI.