Body mass index calculator
BMI is a one-line number that gets used constantly and understood rarely. Here it comes with the weight range for your height, and with the part the formula misses.
Your figures
Result
- WHO category
- Normal weight
- Lowest healthy weight (kg)
- 56.7
- Highest healthy weight (kg)
- 76.3
- Above the range (kg)
- 0.0
- Below the range (kg)
- 0.0
The weight that puts you in each category, at your height
| Category | BMI from | Weight from |
|---|---|---|
| Underweight | 0.0 | 0.0 |
| Normal weight | 18.5 | 56.7 |
| Overweight | 25.0 | 76.6 |
| Obesity class I | 30.0 | 91.9 |
| Obesity class II | 35.0 | 107.2 |
| Obesity class III | 40.0 | 122.5 |
What we assume
- Uses the World Health Organization cut-offs for adults.
- The healthy range is BMI 18.5 to 24.9 applied to your height.
- BMI cannot tell muscle from fat, or where the fat sits.
- It does not apply to children, pregnancy, or older people who have lost muscle mass.
How it is calculated
Body mass index is one division:
BMI = weight (kg) / height (m)²
At 72 kg and 1.75 m: 72 / (1.75 × 1.75) = 72 / 3.0625 = 23.5.
The WHO cut-offs
Under 18.5 is underweight; 18.5 to 24.9 is normal; 25 to 29.9 is overweight; and from 30 onwards it is classed as obesity, split into three grades at 30, 35 and 40.
Why we run the formula backwards
Knowing your BMI is 23.5 says very little on its own. What does say something is the weight range that matches your height, so we solve for weight at BMI 18.5 and at 24.9. At 1.75 m that range runs from 56.7 to 76.3 kg.
What the formula cannot see
BMI was designed in the nineteenth century to describe populations, not people. It divides a weight by a height and stops there: it does not know whether that weight is muscle or fat, or whether the fat sits on the hips or around the organs, which is the part that actually carries risk. A rugby player and someone entirely sedentary can share a number.
It is still a useful first glance, and it costs nothing. But if the answer surprises you, waist measurement and body fat percentage tell you considerably more.
An example
At 72 kg and 1.75 m, BMI is 23.5: normal weight. The healthy range for that height runs from 56.7 to 76.3 kg, leaving about 4 kg of room before the overweight cut-off.
Frequently asked questions
Does BMI work the same for men and women?
The WHO cut-offs are the same for both, although at the same BMI women typically carry a higher fat percentage. It is one of the reasons BMI falls short as an individual measure.
I lift weights and it says overweight. Is that right?
The number is calculated correctly and read incorrectly. Muscle is denser than fat, so a very muscular person can pass 25 with no excess fat at all. In that case body fat percentage is a far more honest measure.
Does it apply to children?
Not with these cut-offs. In children BMI is read against age-and-sex percentiles, because a growing body changes proportions. This calculator is for adults.
Which predicts risk better, BMI or waist size?
Waist circumference generally predicts cardiovascular risk better, because it points at abdominal fat, which is the metabolically active kind. Most guidelines suggest looking at both.
Keep calculating
All tools →- Ideal weight for your height There is no ideal weight, there are four formulas that give four different numbers. Here they are together, with the BMI range alongside, so the real spread is visible.
- Body fat percentage A tape measure and three measurements give a body fat estimate that says considerably more than BMI, because this one does know what your weight is made of.
- Daily calories you need How many calories you burn a day given your body and your activity, and the figure that matches each goal. Using the real 7,700 kcal per kilo, not the rounded "500 a day".
Updated on 2026-09-10. Calculations run in your browser; nothing you type is sent to a server.