What is BMI? How to Calculate Body Mass Index

Body Mass Index (BMI) estimates whether your weight is healthy for your height, using only weight and height.

BMI Formula

BMI = weight (kg) ÷ height (m)²

Example: 70 kg, 170 cm (1.7 m)

• 1.7 × 1.7 = 2.89
• 70 ÷ 2.89 = 24.2

Healthy Ranges (Asian/Thai standard)

BMI	Category
Below 18.5	Underweight
18.5 - 22.9	Normal
23 - 24.9	Overweight
25 - 29.9	Obese class I
30+	Obese class II

BMI Limitations

BMI doesn’t distinguish muscle from fat. Athletes can have high BMI yet be very fit. Use BMI alongside waist measurement.

Calculate Instantly

Use our BMI Calculator — enter weight and height, get your result and category instantly. Free.