BMI calculator
Enter your height and weight to see your body mass index and the healthy weight range for your height. For adults aged 20 and over.
Runs in your browser. Your height and weight are not sent or saved.
Your BMI
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A screening number, not a diagnosis or medical advice.
How BMI is worked out
Body mass index is weight in kilograms divided by height in meters squared. For someone 1.75 m tall weighing 70 kg: 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.9. In US units the same sum is 703 × pounds ÷ inches squared: 5 ft 9 in is 69 inches, so 703 × 160 ÷ (69 × 69) = 23.6.
| Height and weight | BMI | Adult category |
|---|---|---|
| 1.65 m, 50 kg | 18.4 | Underweight |
| 1.60 m, 55 kg | 21.5 | Healthy weight |
| 1.75 m, 70 kg | 22.9 | Healthy weight |
| 5 ft 9 in, 160 lb | 23.6 | Healthy weight |
| 6 ft 0 in, 200 lb | 27.1 | Overweight |
| 1.80 m, 95 kg | 29.3 | Overweight |
| 1.70 m, 105 kg | 36.3 | Obesity class 2 |
Adult BMI categories
For adults aged 20 and over, the US Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) use the same cut-offs:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity class 1 |
| 35.0 to 39.9 | Obesity class 2 |
| 40 and above | Obesity class 3 (severe) |
Source: CDC, Adult BMI Categories. The healthy weight range shown with your result is the weight that would give a BMI from 18.5 to 24.9 at your height: for 1.75 m that is 56.7 to 76.3 kg.
BMI chart: healthy weight by height
The weight range that gives an adult BMI from 18.5 to 24.9, worked out with the same formula as the calculator. Weights are rounded to 0.1 kg or to the nearest pound.
| Height | Healthy weight |
|---|---|
| 150 cm | 41.6 to 56.0 kg |
| 155 cm | 44.4 to 59.8 kg |
| 160 cm | 47.4 to 63.7 kg |
| 165 cm | 50.4 to 67.8 kg |
| 170 cm | 53.5 to 72.0 kg |
| 175 cm | 56.7 to 76.3 kg |
| 180 cm | 59.9 to 80.7 kg |
| 185 cm | 63.3 to 85.2 kg |
| 190 cm | 66.8 to 89.9 kg |
| Height | Healthy weight |
|---|---|
| 5 ft 0 in | 95 to 127 lb |
| 5 ft 3 in | 104 to 141 lb |
| 5 ft 6 in | 115 to 154 lb |
| 5 ft 9 in | 125 to 169 lb |
| 6 ft 0 in | 136 to 184 lb |
| 6 ft 3 in | 148 to 199 lb |
What BMI doesn't tell you
BMI is a quick screening number based only on height and weight. It doesn't measure body fat directly, so it can overstate fat in very muscular people and understate it in older adults who have lost muscle. It doesn't apply during pregnancy. Some health bodies use lower cut-offs for people of South Asian, Chinese and some other Asian backgrounds, because health risks rise at a lower BMI. The CDC advises looking at BMI together with other measures, such as waist size, blood pressure and cholesterol, and talking to a doctor about what your number means for you.
For children and teens aged 2 to 19, BMI is compared with others of the same age and sex using growth charts, so the adult categories here don't apply. Use the CDC Child and Teen BMI Calculator instead, which compares a child with others of the same age and sex.
Questions
How do I calculate BMI?
Divide your weight in kilograms by your height in meters squared. In pounds and inches, multiply the weight by 703 and divide by the height in inches squared. The worked example above shows both, or type your numbers into the calculator to skip the sums.
What is a healthy BMI?
For adults, 18.5 to 24.9 is the healthy weight range used by the CDC and WHO. The chart above turns that into a weight range for each height. A number inside the range doesn't prove good health, and one outside it doesn't prove poor health; it is a starting point for a talk with a doctor.
Is there a BMI calculator for women?
This one. For adults the formula and the categories are the same for women and men, so no separate version is needed. During pregnancy the adult categories don't apply, so ask your midwife or doctor.
Can I use it for children?
Not for the category. The number itself is worked out the same way, but for ages 2 to 19 the CDC compares it with growth charts for the same age and sex, so use the CDC Child and Teen BMI Calculator linked above.
Is BMI accurate?
As a measurement it is exact, since it only uses height and weight. As a measure of body fat it is rough: it can't tell muscle from fat, which is why the section above lists the people it fits least well.
Is a BMI of 25 bad?
25 is where the overweight range starts for adults, but it is a screening threshold, not a diagnosis. Two people with the same BMI can have very different health. A doctor can tell you what it means together with your other measures.
Is BMI different for men and women?
For adults, no: the same formula and the same categories apply to men and women. For children and teens, sex is part of the growth charts.
Does it matter if I use kg or pounds?
No. Both give the same BMI, apart from rounding. Switch units above and the calculator converts for you.