What the BMI Calculator does
This tool turns two numbers, your weight and your height, into a single Body Mass Index score plus the weight category it falls into. BMI is a quick way to see roughly where your weight sits relative to your height, and it is the same figure doctors, gyms and insurers use as a starting point. It is handy if you want a fast self check before a fitness goal, a health review, or just out of curiosity.
The whole calculation happens on your device. Your weight and height are never sent anywhere.
How to use it
- Type your weight into the Weight field (in kilograms, for example 70).
- Type your height into the Height field (in centimetres, for example 175).
- Press Calculate BMI.
- Read your BMI value and the Category below it. Change either number and calculate again to compare scenarios, like a target weight.
The result shows your BMI rounded to one decimal place, then labels it Underweight, Normal, Overweight or Obese using standard adult ranges (below 18.5, 18.5 to 24.9, 25 to 29.9, and 30 and up).
Why use it here
It is instant and free, with no account and no app to install. Because the maths runs in your browser, nothing about your body is uploaded or stored, which matters for personal health data. The formula follows the recognised WHO bands, so the number matches what you would get from a clinic chart.
Tip: BMI is a screening figure, not a full health verdict. It does not know the difference between muscle and fat, so very athletic builds often read higher than expected. Treat it as a rough guide and get a professional opinion for anything important.
Frequently asked questions
- How is BMI calculated in this tool?
- It uses the standard formula: weight in kilograms divided by height in metres squared. You enter weight in kg and height in cm, and the tool converts the height to metres before dividing, then rounds the result to one decimal place.
- What do the BMI categories mean?
- The result is sorted into four bands based on common World Health Organization cutoffs: under 18.5 is Underweight, 18.5 to 24.9 is Normal, 25 to 29.9 is Overweight, and 30 or above is Obese. These ranges are for adults.
- Does this BMI calculator use kg and cm or pounds and inches?
- The fields take metric units: weight in kilograms and height in centimetres. If you only know pounds and inches, convert them first (1 lb is about 0.45 kg, 1 inch is 2.54 cm) and enter the metric values.
- Is BMI an accurate measure of health?
- BMI is a quick screening number, not a diagnosis. It does not separate muscle from fat, so athletes and very muscular people can read high. Use it as general guidance and talk to a doctor for a real assessment.
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Last updated: June 15, 2026