Calculate your BMI

Body mass index (BMI) assesses your body size from your height and weight. Free, instant calculation with no sign-up: no data is collected.

Your measurements

Sex (optional)

The BMI calculation is the same for both. This information is only used to personalise the comment.

Enter your height in centimetres (e.g. 170) and your weight in kilograms.

Your result

23.5
Healthy weight
1618.525303540
Healthy weight for your height53-72 kg
Difference from healthy weightwithin the normal range

BMI is a general indicator. It does not distinguish between fat mass and muscle mass.

My calorie needs Weight loss guides

BMI categories according to the WHO

Category BMI (kg/m²)
Underweight Under 18.5
Healthy weight 18.5 to 24.9
Overweight 25 to 29.9
Obesity class I 30 to 34.9
Severe to morbid obesity 35 and over

How is BMI calculated?

Body mass index is calculated by dividing your weight in kilograms by your height in metres squared. The formula is: BMI = weight ÷ (height × height).

For example, for a person weighing 70 kg and measuring 1.75 m: 70 ÷ (1.75 × 1.75) = 22.9, which corresponds to a healthy weight. Our calculator does this automatically and places your result on the WHO scale.

Is BMI different for a woman and a man?

The BMI calculation is the same for women and men: the formula does not change with sex. The WHO reference thresholds (18.5 and 25) are also the same. In practice, at the same BMI, women have on average a slightly higher percentage of body fat than men, but the index does not make this distinction. This is one of its limitations.

What is the ideal BMI?

A BMI between 18.5 and 24.9 is considered normal and is associated with the lowest health risk. Below 18.5 is classed as underweight; above 25, overweight; above 30, obesity. These thresholds are statistical reference points, not absolute targets: your comfortable healthy weight also depends on your build and body composition.

What should you do after calculating your BMI?

If your BMI falls outside the normal range, the next step is to understand your real needs. You can calculate your daily calorie needs to adjust your diet, explore our balanced recipes with calculated calories, or read our guides on balanced eating and weight loss. For personalised support, a doctor or a dietitian remains the best option.

Frequently asked questions about BMI

How is body mass index calculated?
BMI = weight (kg) ÷ height² (m). For 68 kg and 1.70 m: 68 ÷ (1.70 × 1.70) = 23.5. It is a simple measure that places your body size on a reference scale.
Is BMI reliable for everyone?
No. It is not suitable for very muscular athletes (muscle is denser than fat), pregnant women, children or older people. It is a population-level indicator, to be completed with waist circumference and body fat percentage.
What does a BMI that is too low mean?
A BMI below 18.5 indicates underweight, which can signal undernutrition, deficiencies or frailty. If that is you, ask a doctor or dietitian for advice.
What does a BMI that is too high mean?
Above 25 is classed as overweight; above 30, obesity. This increases cardiovascular and metabolic risks. A moderate calorie deficit and physical activity help you return gradually to the normal range.
Does BMI take muscle mass into account?
No, this is its main limitation: it does not distinguish muscle from fat. Two people with the same BMI can have very different body compositions. Body fat percentage is a useful complement to BMI.
Where can I find help to improve my BMI?
Start by calculating your calorie needs and read our weight loss guides. For personalised follow-up, a doctor or dietitian remains the best option.
This calculator provides an estimate for information only and does not replace the advice of a health professional. No data entered on this page is collected or stored.