Free BMI Calculator
Work out your body mass index in seconds. Enter your height and weight in metric or imperial units, and see your BMI, which WHO category it falls in, and the healthy weight range for your height.
BMI is a quick screening number for adults. It does not tell muscle from fat, so read it as a starting point, not a diagnosis.
- Category
- Normal
- Height
- 170.0 cm
- Weight
- 70.0 kg
- Healthy weight range
- 53.5 to 72.0 kg
A quick screening number for adults. For anything that matters to your health, talk to a doctor or a qualified professional.
Work out your BMI in four steps.
Pick your units, type your height and weight, and read your BMI, your category and your healthy weight range. Everything updates as you type.
Pick your units
Switch between metric (centimetres and kilograms) and imperial (feet, inches and pounds). The maths adjusts for you.
Enter height and weight
Type your height and weight. Everything updates as you type, so there is nothing to submit.
Read your BMI
See your body mass index and which WHO category it falls in, with a marker on the scale so you can see how close you are to the next band.
See your healthy range
The tool shows the weight range that would put you in the normal band for your height, in the units you chose.
The four BMI bands.
The World Health Organization groups adult BMI into four ranges. The calculator shows which one you are in and how close you are to the next.
Underweight
Below 18.5
Below the healthy range. It can be worth checking in with a doctor about diet and any underlying causes.
Normal
18.5 to 24.9
A healthy weight for your height for most adults. The goal is usually to stay in this band.
Overweight
25 to 29.9
Above the healthy range. Small, steady changes to food and activity move the number in the right direction.
Obese
30 and above
Well above the healthy range, and linked to higher health risk. A doctor can help you plan a safe approach.
How the BMI maths works.
The same formula in both unit systems, with a worked example. The calculator converts imperial to metric for you.
The BMI formula
BMI = weight in kilograms / (height in metres x height in metres)
Imperial: BMI = 703 x weight in pounds / (height in inches x height in inches)
Example: Someone 1.70 m tall weighing 70 kg has a BMI of 70 / (1.70 x 1.70), which is 24.2, in the normal range.
A note on the number
BMI is a fast way to screen a whole population, but it cannot tell muscle from fat and it does not account for age, sex or body shape. Very muscular people can read as overweight, and health risk can rise at a lower BMI for many people of South Asian background, so the WHO suggests lower action points of around 23 and 27.5.
Use it as a starting point, then look at the fuller picture with a professional.
Health scoring, built into your product.
A single BMI check is easy. Building it into a patient portal, a clinic system or a wellness app, with records, history, alerts and reporting behind it, is a different job. That is the kind of custom software and health-tech we build at Techliphant, shaped around how your organisation actually works.
Working out ages too? Try the age calculator.
Common BMI questions.
BMI is your weight in kilograms divided by your height in metres squared. So BMI = weight (kg) / (height (m) x height (m)). If someone is 1.70 m tall and weighs 70 kg, that is 70 / (1.70 x 1.70), which works out to a BMI of 24.2.
For most adults, a BMI from 18.5 to 24.9 is considered a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or more is in the obese range. These are general screening bands, not a diagnosis.
The World Health Organization uses four adult bands: underweight is below 18.5, normal is 18.5 to 24.9, overweight is 25 to 29.9, and obese is 30 and above. The calculator shows which band you are in and how close you are to the next one.
Use the imperial formula: BMI = 703 x weight in pounds / (height in inches x height in inches). First convert your height to inches (feet times 12, plus the extra inches). Set the tool to imperial and it does all of this for you.
BMI is a quick screening number, not a full picture of health. It does not tell muscle from fat, so very muscular people can read as overweight when they are not. It is also less reliable for older adults, and it is not used the same way for children, pregnant people or athletes. Treat it as a starting point and talk to a professional for anything that matters.
Yes. Research shows health risk can rise at a lower BMI for many people of South Asian and other Asian backgrounds, so the WHO suggests lower action points: around 23 and above as overweight and 27.5 and above as obese. If that applies to you, read your result against those lower numbers.
A healthy weight is the range that keeps your BMI between 18.5 and 24.9 for your height. The calculator works this out and shows it in kilograms or pounds, so you can see the low and high end of the range for you.
Yes on both. It is free, there is no sign-up, and it runs entirely in your browser. Nothing you type is sent anywhere or stored, so your height and weight stay on your own device.
This one is great for a quick personal check. If you need BMI, health scoring or eligibility built into a patient portal, a clinic system or an insurance app, with records, history and reporting behind it, that is custom software. That is the kind of product we build at Techliphant.
Private by design: this calculator runs entirely in your browser, so nothing you type is uploaded or stored. BMI is a general screening indicator, not medical advice or a diagnosis. For decisions about your health, please speak to a doctor or a qualified health professional.
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