BMI Calculator

What this tool does

The BMI Calculator divides your weight by the square of your height to give your body mass index, then classifies it with the WHO adult categories or the lower cut-offs recommended for Asian populations. It also shows the weight range that would put you between BMI 18.5 and the top of the healthy band, plus BMI Prime.

Body mass index is a quick screening number that relates weight to height. Doctors and public-health bodies use it because it needs only two measurements and correlates reasonably well with body fat across large groups. A single number, though, is easy to misread: it says nothing about where fat sits, how much muscle you carry, or whether your weight is changing. Knowing the healthy weight band for your exact height is often more useful than the BMI value itself.

This calculator applies the standard definition BMI = weight (kg) ÷ height (m)², converting pounds and feet-and-inches first if you use imperial units. You can classify the result with the World Health Organization adult bands (healthy 18.5 to 24.9) or with the WHO expert consultation cut-offs for Asian populations (healthy 18.5 to 22.9), which reflect higher cardiometabolic risk at lower BMI. Everything is computed in your browser.

How to use BMI Calculator

1. Choose Metric (kg, cm) or Imperial (lb, ft + in) under Units.
2. Enter your weight and height; for imperial, put feet and inches in their separate boxes.
3. Pick the classification: WHO international or Asian populations.
4. Read Your BMI and its category in the highlighted card.
5. Check the healthy weight range for your height and the gain or loss needed to reach it.
6. Use the category table to see the weight that corresponds to each BMI band at your height, and download it as CSV if needed.

Tips for better results

• Weigh yourself in the morning, after the toilet and before eating, so repeated checks are comparable.
• Pair BMI with a waist measurement: a waist above half your height signals central fat even at a "healthy" BMI.
• BMI Prime expresses your BMI as a fraction of the healthy upper limit, so 1.10 means 10% above it.
• Track the trend over months rather than reacting to one reading.

Common use cases

• Checking whether a recent weight change has moved you into a different WHO category.
• Setting a realistic target weight band before starting a nutrition plan.
• Screening family members of South Asian, East Asian or Southeast Asian heritage with the lower Asian cut-offs.
• Filling in health forms or insurance questionnaires that ask for your BMI.

Common mistakes to avoid

• Applying adult categories to children and teenagers, who need age- and sex-specific BMI percentiles.
• Treating a high BMI as proof of excess fat in very muscular people such as rugby players or bodybuilders.
• Entering height in metres into the centimetres box (1.75 instead of 175).
• Using BMI during pregnancy, when weight gain is expected and assessed differently.