BMI Calculator

Enter your height in centimetres and your weight in kilograms. The tool divides weight by height in metres squared and shows the result to one decimal place, with a category label underneath:

BMI = weight (kg) ÷ height (m)²

With the defaults, 70 kg at 175 cm gives 70 ÷ 1.75² = 22.9, labelled Healthy weight. BMI is a screening number. It is an estimate based on two measurements, not a diagnosis, and it says nothing about where your weight is carried or what it is made of.

The boxes take metric units only, so convert before you type:

• Height: turn feet into inches, add the inches, then multiply by 2.54. 5 ft 4 in is 64 in, which is 162.56 cm.
• Weight: multiply pounds by 0.4536. 130 lb is 58.97 kg.

Those two values give a BMI of 22.3. You can type decimals, so there is no need to round the converted height to a whole centimetre. Rounding 162.56 down to 162 would nudge the BMI up slightly, which matters only if you sit near a category edge.

The labels follow the adult bands used by the WHO and the CDC. The tool shows four labels; the CDC splits the top band into three classes, which the tool does not show separately:

If your result is 30 or more, read the number against the table to see which class it falls in.

The label is decided from the unrounded BMI, while the big number is rounded to one decimal. Right at a boundary this can look odd. At 175 cm:

• 76.5 kg gives a BMI of 24.98. The tool displays 25 but labels it Healthy weight, because 24.98 is still under 25.
• 76.6 kg gives 25.01, which also displays as 25 and is labelled Overweight.

To find the weight at which you cross a line, rearrange the formula: weight = BMI × height (m)². At 175 cm, the 18.5, 25 and 30 lines fall at 56.7 kg, 76.6 kg and 91.9 kg. At 160 cm they fall at 47.4 kg, 64.0 kg and 76.8 kg. The Ideal Weight Calculator on this site shows the 18.5 to 24.9 range for your height directly.