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Everyday & School Calculators

BMI Calculator

Choose your units, enter weight and height, and get your BMI with the standard WHO adult ranges. BMI is a quick screening number, not a diagnosis.

Updated October 3, 2026Written and reviewed by Mateuss M.Method: how we calculate

Try an example:

AnswerBMI 22.9

Healthy weight range (18.5–24.9)
For adults 20+. Not for children or pregnancy.

Step-by-step working 3 steps

1
Convert height to metres
```
175 cm ÷ 100 = 1.75 m
```
2
BMI = weight ÷ height²
```
70 ÷ 1.75² = 70 ÷ 3.0625 = 22.8571
```
3
Compare with the standard adult ranges
```
Healthy weight range (18.5–24.9)
```
These are the WHO adult ranges. BMI is a quick screening number, not a diagnosis: it ignores muscle mass, age, sex and body shape.

How to use the bmi calculator

Pick metric or imperial.
Enter weight and height in those units.
Read your BMI and range.
Talk to a health professional about what the number means for you.

BMI formula

Metric: BMI = kg ÷ m²
Imperial: BMI = 703 × lb ÷ in²
Adult ranges: <18.5 · 18.5–24.9 · 25–29.9 · 30+

For adults aged 20 and over. Children use age- and sex-specific percentiles.

Worked examples

Each example below is generated by the same calculator you used above, so the working always matches the answer.

70 kg, 175 cm

AnswerBMI 22.9

Healthy weight range (18.5–24.9)
For adults 20+. Not for children or pregnancy.

Step-by-step working 3 steps

1
Convert height to metres
```
175 cm ÷ 100 = 1.75 m
```
2
BMI = weight ÷ height²
```
70 ÷ 1.75² = 70 ÷ 3.0625 = 22.8571
```
3
Compare with the standard adult ranges
```
Healthy weight range (18.5–24.9)
```
These are the WHO adult ranges. BMI is a quick screening number, not a diagnosis: it ignores muscle mass, age, sex and body shape.

150 lb, 65 in

AnswerBMI 25.0

Healthy weight range (18.5–24.9)
For adults 20+. Not for children or pregnancy.

Step-by-step working 2 steps

1
BMI = 703 × weight ÷ height²
```
703 × 150 ÷ 65² = 105450 ÷ 4225 = 24.9586
```
Weight in pounds and height in inches.
2
Compare with the standard adult ranges
```
Healthy weight range (18.5–24.9)
```
These are the WHO adult ranges. BMI is a quick screening number, not a diagnosis: it ignores muscle mass, age, sex and body shape.

95 kg, 180 cm

AnswerBMI 29.3

Overweight range (25–29.9)
For adults 20+. Not for children or pregnancy.

Step-by-step working 3 steps

1
Convert height to metres
```
180 cm ÷ 100 = 1.8 m
```
2
BMI = weight ÷ height²
```
95 ÷ 1.8² = 95 ÷ 3.24 = 29.321
```
3
Compare with the standard adult ranges
```
Overweight range (25–29.9)
```
These are the WHO adult ranges. BMI is a quick screening number, not a diagnosis: it ignores muscle mass, age, sex and body shape.

Common mistakes to avoid

Using centimetres as metres

In the metric formula height must be in metres; the calculator converts centimetres for you.

Treating BMI as a diagnosis

It does not measure body fat, muscle, age, sex or fitness.

Applying adult ranges to children

Children and teenagers need growth-chart percentiles.

Frequently asked questions

Is BMI accurate for athletes?

Often not: muscle weighs more than fat, so muscular people can have a high BMI at a healthy body-fat level.

Is this medical advice?

No. It is an educational calculation; see a clinician for health decisions.