BMI Calculator
Body Mass Index (BMI) is a quick screening measure that relates your weight to your height. It doesn't distinguish muscle from fat, so use it as a general indicator, not a diagnosis.
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What is the BMI Calculator?
Body Mass Index (BMI) is a simple number that estimates whether your weight is in a healthy range for your height. It's widely used by doctors and health organisations as a quick first-pass screening tool because it needs only two easily-measured values.
BMI has limits: it doesn't distinguish muscle from fat, or account for age, sex, or body-fat distribution — so a muscular athlete may register as ‘overweight’ without excess fat. Treat it as one signal among several, not a diagnosis.
How to Calculate
BMI is calculated in three steps:
- Convert your height to metres (centimetres ÷ 100).
- Square that height.
- Divide your weight in kilograms by the squared height:
BMI = weight ÷ height².
The result is then matched to a category: below 18.5 (underweight), 18.5–24.9 (normal), 25–29.9 (overweight), or 30 and above (obese).
Formula
BMI = weight (kg) / height (m)2
- Below 18.5 — Underweight
- 18.5 to 24.9 — Normal
- 25 to 29.9 — Overweight
- 30 and above — Obese
Worked Examples
Example 1 u2014 Normal range
70 kg at 175 cm: BMI = 70 ÷ 1.75² ≈ 22.9 (Normal).
Example 2 u2014 Overweight range
85 kg at 170 cm: BMI = 85 ÷ 1.70² ≈ 29.4 (Overweight).
Example 3 u2014 Underweight range
50 kg at 175 cm: BMI = 50 ÷ 1.75² ≈ 16.3 (Underweight).
Definitions
- Weight
- Your body weight in kilograms.
- Height
- Your height in centimetres (converted to metres in the formula).
- BMI
- Body Mass Index — weight divided by height squared. A screening indicator, not a diagnosis.
- Category
- Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), or Obese (≥30).
How to Use
- Enter your weight in kilograms.
- Enter your height in centimetres.
- Read your BMI value and category instantly.