BMI Calculator
Calculate your Body Mass Index in metric or US units, see which weight category you fall into, and find the healthy weight range for your height.
BMI is a screening number for adults 20+. It does not measure body fat directly — talk to a doctor for health advice.
How to calculate BMI
- Choose metric (cm and kg) or US units (feet, inches and pounds).
- Enter your height and weight.
- Your BMI, category and healthy weight range update instantly.
Formula: BMI = weight in kg ÷ (height in metres)². For US units the calculator converts pounds and inches to metric first, so both give the same result.
Adult BMI categories (WHO): under 18.5 underweight · 18.5–24.9 healthy · 25–29.9 overweight · 30 and above obese.
Frequently asked questions
Is BMI accurate?
BMI is a quick screening tool, not a diagnosis. Muscular people can have a high BMI without extra fat, and older adults can have a normal BMI with low muscle mass.
Can I use this BMI calculator for children?
No. Children and teens are assessed with age- and sex-specific percentile charts. Ask a paediatrician.
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. Some Asian health bodies use lower cut-offs (23 for overweight).
What is a BMI calculator?
A BMI calculator turns your height and weight into a single number, the body mass index, and places it in a weight category. It is the same quick screening measure doctors, insurers and public health surveys use to flag whether a weight may be too low or too high for a person’s height.
BMI does not measure body fat, muscle or where fat is stored. It is a starting point for a conversation, not a diagnosis, and the result here is an estimate for adults only. If you have concerns about your weight or health, speak to a doctor.
Worked examples
Metric: 165 cm and 72 kg
- Convert height to metres: 165 cm = 1.65 m.
- Square it: 1.65 × 1.65 = 2.7225.
- Divide weight by that figure: 72 ÷ 2.7225 = 26.4.
- On the WHO scale, 26.4 falls in the overweight range (25 to 29.9). The healthy range at this height is about 50.4 to 67.8 kg, so the calculator shows roughly 4.2 kg above the upper limit.
US units: 5 ft 4 in and 140 lb
Height is 64 inches. The US shortcut formula is BMI = 703 × weight in pounds ÷ (height in inches)², so 703 × 140 ÷ 4,096 = 24.0, which is inside the healthy range. The calculator converts to metric first and gives the same 24.0.
Healthy weight range by height
The middle column uses the standard adult range of BMI 18.5 to 24.9. The last column shows the weight at a BMI of 23, the lower cut-off often used for Asian populations (see below). Values are rounded.
| Height | Healthy range (BMI 18.5–24.9) | Weight at BMI 23 |
|---|---|---|
| 150 cm | 41.6 – 56.0 kg | 51.8 kg |
| 155 cm | 44.4 – 59.8 kg | 55.3 kg |
| 160 cm | 47.4 – 63.7 kg | 58.9 kg |
| 165 cm | 50.4 – 67.8 kg | 62.6 kg |
| 170 cm | 53.5 – 72.0 kg | 66.5 kg |
| 175 cm | 56.7 – 76.3 kg | 70.4 kg |
| 180 cm | 59.9 – 80.7 kg | 74.5 kg |
| 185 cm | 63.3 – 85.2 kg | 78.7 kg |
BMI for Asian and Indian adults
People of South Asian origin tend to have more body fat and a higher risk of type 2 diabetes and heart disease at the same BMI. For this reason, a 2004 WHO expert consultation suggested extra “action points” for Asian populations at a BMI of 23 (increased risk) and 27.5 (high risk). Indian clinical guidelines commonly treat 23 as the start of overweight. The calculator above uses the standard WHO categories, so if you are of Asian descent, read a result of 23 to 24.9 as a sign to take a closer look rather than as fully in the clear.
Tips for an accurate reading
- Weigh yourself at the same time of day, ideally in the morning, in light clothing.
- Measure height without shoes, standing straight against a wall.
- Look at the trend over months, not a single day; normal day-to-day weight changes can move BMI by a few tenths.
- Pair BMI with waist size. A large waist can signal health risk even when BMI is in the healthy range.
- Do not use adult BMI during pregnancy, for children and teens, or for very muscular athletes.
More questions
Is the BMI calculation different for women?
No. Adult women and men use the same formula and the same categories. Women usually carry more body fat than men at the same BMI, which is one reason BMI is best read alongside other measures like waist size.
What BMI is considered obese?
On the WHO scale, a BMI of 30 or more is classed as obese. It is further split into class 1 (30 to 34.9), class 2 (35 to 39.9) and class 3 (40 and above).
Does BMI change with age?
The formula is the same for all adults, but body composition changes with age. Older adults tend to lose muscle, so the same BMI can mean more body fat later in life.
How can I work out BMI without a calculator?
Divide your weight in kilograms by your height in metres, then divide by your height in metres again. For example, 60 kg at 1.60 m is 60 ÷ 1.6 ÷ 1.6 = 23.4.
To convert between kilograms and pounds or centimetres and feet, use the unit converter. You can also check your exact age with the age calculator or work out a percentage change in weight with the percentage calculator.
Further reading: Body mass index (Wikipedia).