BMI Calculator

This BMI (body mass index) calculator takes your height in centimeters and your weight in kilograms, works out your BMI, sorts it into one of four categories (Underweight, Normal, Overweight, Obese), and estimates a healthy weight range for your height. BMI is only a rough screening number. It cannot diagnose anything, and it does not measure body fat. It cannot tell muscle from fat, and it ignores age, sex and pregnancy. All calculations happen in your browser.

How to use it

1. Enter your height in the Height (cm) field. The default is 170.
2. Enter your weight in the Weight (kg) field. The default is 60.
3. The Result area immediately shows something like 'BMI 20.8 · Normal'. There is no button to press.
4. Below it, a line reading 'Based on your height, a healthy weight range is roughly' shows a range such as 53.5 kg – 72.2 kg. A note at the bottom lists the reference ranges.
5. If a field is empty, zero or not a valid number, the result area asks you to enter a valid height and weight.

How it is calculated, with examples (run through the tool's own formula)

BMI = weight in kg divided by the square of height in meters; the page divides your centimeters by 100 first. At 170 cm and 60 kg the BMI is 20.8, which is Normal, with a healthy range of 53.5 to 72.2 kg. At 160 cm and 45 kg the BMI is 17.6, Underweight, and the healthy range is 47.4 to 63.9 kg. At 175 cm and 85 kg the BMI is 27.8, Overweight. At 160 cm and 95 kg the BMI is 37.1, Obese. The healthy range is found by multiplying 18.5 and 25 by the square of your height in meters (the lower bound is rounded up and the upper bound down to 0.1 kg, so any weight inside the range is shown as Normal).

Limits and known quirks

• The categories follow the common international reference: under 18.5 is Underweight, 18.5 to 24.9 Normal, 25 to 29.9 Overweight, 30 and above Obese. The stricter Chinese adult cut-offs (24 for overweight, 28 for obese) are not used, so the same person may get a different label here than under Chinese guidelines.
• Underweight, Overweight and Obese results are all shown in red styling. That is just the interface color, not a medical severity rating.
• BMI does not separate muscle from fat. Athletes and people who lift weights may read as overweight, while someone with little muscle can have a normal BMI and still carry a high percentage of body fat.
• It is not suitable for children and teenagers under 18 (who need age- and sex-based growth charts), or for pregnant and breastfeeding women. The tool has no age or sex input.
• Only metric units (centimeters and kilograms) are accepted; there is no feet, inches or pounds input. BMI is displayed to one decimal place.

Does a normal BMI mean I am healthy?

Not necessarily. BMI uses only two numbers and says nothing about where fat is stored, or about blood pressure, blood sugar or cholesterol. It is a quick reference, and a real health assessment should come from a doctor or dietitian using proper check-up results.

Why is the healthy weight range so wide?

The range is simply worked backward from the Normal BMI band of 18.5 up to (not including) 25, and for a 170 cm person that spans about 18.7 kg. Frame size and muscle mass vary a lot between people, so treat the range as a rough estimate and not as a target weight.

I train with weights. Is the result reliable for me?

It may read high. Muscle is denser than fat, so a muscular person weighs more at the same size, and BMI counts that extra weight as excess. Look at waist measurement or body fat percentage alongside BMI instead of relying on a single number.

Can I use this to plan weight loss or gain?

It only tells you which range you are in now. A real plan has to account for metabolism, activity level and health conditions. If you want a rough daily calorie estimate, the Calorie Calculator on this site can help, but it too is only an estimate.

Privacy and processing

Your height and weight are used only inside your browser to do the arithmetic. They are not uploaded or stored. Reloading the page returns the fields to the defaults of 170 cm and 60 kg.