How to use the BMI calculator
- Choose Metric (cm, kg) or US (feet, inches, pounds) units.
- Enter your height and weight.
- Press Calculate to see your BMI on a gauge, your weight category, the healthy weight range for your height and how far you are from it.
BMI formula
\text{BMI} = \dfrac{\text{weight (kg)}}{\text{height (m)}^2}In US units, multiply by 703 to convert pounds and inches:
\text{BMI} = 703 \times \dfrac{\text{weight (lb)}}{\text{height (in)}^2}\text{BMI} = \frac{70}{1.75^2} = \frac{70}{3.0625} = 22.922.9 is in the normal weight range.
\text{BMI} = 703 \times \frac{160}{69^2} = \frac{112{,}480}{4{,}761} = 23.623.6 is in the normal weight range.
BMI categories for adults
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy (normal) weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obesity, class 1 |
| 35 – 39.9 | Obesity, class 2 |
| 40 and above | Obesity, class 3 (severe) |
These cut-offs, used by the World Health Organization and the US CDC, apply to adults aged 20 and over regardless of sex. Some Asian health guidelines use lower cut-offs because risks rise at a lower BMI – India's guidelines, for example, treat 23–24.9 as overweight and 25 or more as obese.
Healthy weight for your height
The healthy range is a BMI of 18.5 to 24.9. In weight terms:
| Height | Healthy weight (kg) | Height | Healthy weight (lb) |
|---|---|---|---|
| 150 cm | 41.6 – 56.0 | 5 ft 0 in | 95 – 127 |
| 155 cm | 44.4 – 59.8 | 5 ft 2 in | 101 – 136 |
| 160 cm | 47.4 – 63.7 | 5 ft 4 in | 108 – 145 |
| 165 cm | 50.4 – 67.8 | 5 ft 6 in | 115 – 154 |
| 170 cm | 53.5 – 72.0 | 5 ft 8 in | 122 – 164 |
| 175 cm | 56.7 – 76.3 | 5 ft 10 in | 129 – 174 |
| 180 cm | 59.9 – 80.7 | 6 ft 0 in | 136 – 184 |
| 185 cm | 63.3 – 85.2 | 6 ft 2 in | 144 – 194 |
| 190 cm | 66.8 – 89.9 | 6 ft 4 in | 152 – 205 |
Other numbers in the result
- BMI Prime –
\text{BMI Prime} = \frac{\text{BMI}}{25}, where 25 is the top of the healthy range. Below 1.00 is under the limit; 1.20 means 20% over it. - Ponderal index –
\text{PI} = \frac{\text{weight (kg)}}{\text{height (m)}^3}. It changes less with height than BMI, so it can suit very tall or very short people better. - Weight to gain or lose – the difference between your weight and the nearest edge of the healthy range.
Limits of BMI
- Muscle vs fat: muscular people can have a high BMI without excess fat.
- Fat location: BMI doesn't show belly fat; waist size (or waist ÷ height) adds useful information.
- Age and body type: older adults lose muscle, so the same BMI can mean more body fat.
- Not for everyone: children and teenagers use age- and sex-specific percentiles, and BMI isn't used during pregnancy.
BMI is a screening number, not a diagnosis. Talk to a healthcare professional about your own health.
Frequently asked questions
What is a healthy BMI?
For adults, 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 overweight and 30 or more obese.
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. For 160 lb and 69 in: 703 × 160 ÷ 4,761 = 23.6.
Is BMI different for men and women?
No. Adults use the same categories regardless of sex, although women typically carry more body fat at the same BMI.
Is BMI accurate for athletes?
Not always. Muscle is dense, so a very muscular person can have a high BMI without excess body fat.
Can children use this calculator?
No. Children and teenagers are assessed with age- and sex-specific BMI percentiles. This calculator is for adults.