This calculator accepts centimetres and kilograms or feet, inches and pounds, converts everything to metric internally, and updates the moment you type. It marks your BMI on a colour-coded category scale and shows the weight range that would put you in the healthy band for your height. Nothing is uploaded - the maths runs entirely in your browser.
BMI Calculator
Runs entirely in your browser - no upload, no sign-up.
Your measurements
Your BMI22.9Normal weight
Healthy weight for your height
57 - 77 kg
BMI is a screening tool, not a diagnosis. It does not tell muscle from fat, so athletes and older adults should read it with care.
What is a BMI calculator?
A BMI calculator works out your Body Mass Index from your height and weight using the formula BMI = kg / m squared. Enter your measurements in metric or imperial units and it returns your BMI number plus the WHO weight category - underweight, normal, overweight or obese - along with the healthy weight range for your height.
How to use
- 1Pick your units. Choose Metric for centimetres and kilograms, or Imperial for feet, inches and pounds.
- 2Enter height and weight. Type your height and weight. The result updates instantly - there is no button to press.
- 3Read your BMI and category. See your BMI number, its WHO category on the colour scale, and the healthy weight range for your height. Copy the result if you need it.
Who it's for
- Anyone tracking their weight checking where they sit on the standard BMI scale before setting a goal.
- People starting a fitness or diet plan finding the healthy weight range for their height.
- Nurses and health teachers demonstrating how the BMI formula and WHO categories work.
- Travellers and readers of foreign health sites converting between metric and imperial units in one step.
FAQ
Is the BMI calculator free?
Yes. It is completely free, needs no sign-up, and runs in your browser. Your height and weight are never uploaded or stored.
What is the BMI formula?
BMI equals your weight in kilograms divided by the square of your height in metres (kg / m squared). For imperial units the tool converts pounds to kilograms and feet and inches to metres first, then applies the same formula.
What are the BMI categories?
The World Health Organization uses these adult ranges: below 18.5 is underweight, 18.5 to 24.9 is normal or healthy weight, 25 to 29.9 is overweight, and 30 or above is obese. The exact boundary value always falls into the higher band.
Is BMI accurate for everyone?
No. BMI is a screening tool, not a diagnosis. It cannot tell muscle from fat, so athletes may read as overweight and some older adults with low muscle may read as normal despite excess fat. Use it as a starting point and talk to a clinician about your individual health.
Can I use it for children?
This calculator uses the adult WHO categories. Children and teenagers are assessed with age- and sex-specific BMI-for-age percentiles instead, so use a dedicated child BMI chart for anyone under 20.
What is a healthy BMI weight range?
For any height, the healthy range is the weight that gives a BMI between 18.5 and 25. The calculator computes it for you from your height, so you can see how much weight change would move you into or out of the normal band.