BMI calculator: formula, chart and what your result means
Body mass index is the quickest way to see whether your weight is in a healthy range for your height. Here is a calculator, the formula step by step, the WHO chart and what BMI can’t tell you.
Key takeaways
- BMI = weight (kg) ÷ height (m)².
- 18.5 to 24.9 is a healthy weight; from 25, overweight; from 30, obesity.
- It doesn’t tell muscle from fat: add your waist measurement.
- It is a starting point, not a diagnosis.
Article contents
BMI calculator
Enter your weight and height. The calculator gives you your BMI, its category and the healthy weight range for your height.
25.7your BMI
- CategoryOverweight
- Healthy weight for your height51–67 kg
What is BMI?
Body mass index (BMI) relates your weight to your height. It is the measure the World Health Organization uses to classify adult weight, because it is quick, free and easy to compare.
How it is calculated
BMI = weight (kg) ÷ height (m)²
Example: a person who weighs 70 kg and is 1.65 m tall. First square the height: 1.65 × 1.65 = 2.72. Then divide the weight: 70 ÷ 2.72 ≈ 25.7.
BMI chart
| Category | BMI |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 to 24.9 |
| Overweight | 25 to 29.9 |
| Obesity class I | 30 to 34.9 |
| Obesity class II | 35 to 39.9 |
| Obesity class III | 40 or more |
In the example, a BMI of 25.7 falls in the overweight range. For 1.65 m, a healthy weight is roughly 51 to 67 kg.
What BMI doesn’t tell you
BMI is a useful starting point, but it has limits:
- It doesn’t tell muscle from fat. A very muscular person can come out as overweight without carrying extra fat.
- It doesn’t say where the fat is. Fat around the belly matters more for health risk. Measuring your waist completes the picture.
- It doesn’t apply to everyone the same way. Children and teenagers use age-based charts, and it isn’t used during pregnancy.
What to do with your result
If you want to lose or gain weight, the next step is to find out how many calories you need and, if you want to lose, how to set a calorie deficit you can keep up.
Frequently asked questions
How do you calculate BMI?
Divide your weight in kilograms by your height in metres squared. For example, 70 kg ÷ (1.65 × 1.65) ≈ 25.7.
What is a normal BMI?
For adults, a BMI of 18.5 to 24.9 is considered a healthy weight by the World Health Organization.
Is BMI the same for men and women?
Yes. Adults use the same formula and the same chart for men and women.
Is BMI accurate if I lift weights?
With a lot of muscle, BMI can come out high without extra fat. In that case your waist or body fat percentage is more useful.
Sources
- World Health Organization. Obesity and overweight — Fact sheet. www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
- World Health Organization. Healthy diet — Fact sheet. www.who.int/news-room/fact-sheets/detail/healthy-diet
We write nutrition guides with the same calculations and sources the app uses, cited at the end of each article.
This content is for information only and does not replace advice from a doctor or dietitian. If you have a health condition, are pregnant or take medication, check with a professional before changing how you eat.
