BMI Calculator
Calculate your Body Mass Index instantly. Get your BMI category, healthy weight range, and health insights. Free and private, it runs in your browser.
⚠️ Note
BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, or fat distribution. Consult a healthcare professional for medical advice.
How to calculate your BMI
Enter your height and weight in metric or imperial units, and the result updates as you type.
- 01
Choose metric or imperial
Metric takes kilograms and centimetres. Imperial takes pounds plus feet and inches. If you know your weight in stone, multiply by 14 for pounds first.
- 02
Enter weight and height
The BMI appears as you type, with its category and the healthy weight range for your height, from a BMI of 18.5 to 24.9.
- 03
Read the number in context
BMI is a quick screening figure. Use it alongside your waist size and how you feel, not instead of a check-up.
Worked example: how BMI is calculated
BMI is weight in kilograms divided by height in metres, squared. For someone who weighs 70 kg and is 1.75 m tall: 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.9. That falls in the 18.5 to 24.9 range the WHO calls normal weight.
In imperial units the formula needs a conversion factor: BMI = 703 × pounds ÷ inches². Someone who weighs 154 lb and is 5 ft 9 in (69 inches) gets 703 × 154 ÷ 4,761 = 22.7, a fraction lower than the metric figure only because 154 lb is a touch under 70 kg.
Healthy weight range by height
These ranges are BMI 18.5 to 24.9 for each height, the same calculation the tool shows under your result. The middle column of the range, BMI 22.9, is shown as a reference point, not a target everyone should aim for.
| Height | Weight range (BMI 18.5–24.9) | Weight at BMI 22.9 |
|---|---|---|
| 150 cm (4 ft 11 in) | 41.6–56.0 kg | 51.5 kg |
| 155 cm (5 ft 1 in) | 44.4–59.8 kg | 55.0 kg |
| 160 cm (5 ft 3 in) | 47.4–63.7 kg | 58.6 kg |
| 165 cm (5 ft 5 in) | 50.4–67.8 kg | 62.3 kg |
| 170 cm (5 ft 7 in) | 53.5–72.0 kg | 66.2 kg |
| 175 cm (5 ft 9 in) | 56.7–76.3 kg | 70.1 kg |
| 180 cm (5 ft 11 in) | 59.9–80.7 kg | 74.2 kg |
| 185 cm (6 ft 1 in) | 63.3–85.2 kg | 78.4 kg |
| 190 cm (6 ft 3 in) | 66.8–89.9 kg | 82.7 kg |
Different cut-offs for South Asian adults
The categories in this tool are the standard WHO ones: under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, 30 and above obese. Research has found that people of South Asian, Chinese and some other Asian backgrounds tend to develop diabetes and heart disease at lower BMIs. A WHO expert consultation in 2004 pointed to 23 and 27.5 as action points for Asian populations, and India's 2009 consensus guidelines treat 23 to 24.9 as overweight and 25 and above as obese.
In practice, for a 165 cm Indian adult, that moves the start of "overweight" from 68.1 kg down to 62.6 kg. The tool doesn't apply these lower cut-offs automatically, so read your number against them if they apply to you.
What BMI can't tell you
- It can't tell muscle from fat. A 90 kg, 180 cm athlete has a BMI of 27.8 and is classed as overweight despite low body fat.
- It ignores where fat sits. Fat around the waist carries more health risk; NICE in the UK suggests keeping your waist to less than half your height.
- It isn't meant for children, teenagers or pregnancy. Children are assessed on age- and sex-specific percentile charts.
- It's less reliable in older adults, who often lose muscle while weight stays the same.