What is normal BMI range?

18.5 to 24.9 is normal. Below 18.5 is underweight. 25-29.9 is overweight. 30+ is obese.

Is BMI accurate for athletes?

No — BMI can overestimate body fat in muscular individuals. Use body fat percentage or waist circumference as supplementary measures.

BMI Formula — How to Calculate Body Mass Index

BMI is a simple screening tool that uses your height and weight to estimate body fat. While not perfect, it's widely used by healthcare professionals.

BMI Formula (Metric)

BMI = Weight (kg) / Height² (m²)

Where:

BMI = Body Mass Index
Weight = Body weight in kilograms
Height = Height in meters

Step-by-Step:

1
Convert height to meters
If in cm, divide by 100. If in feet/inches, multiply feet by 0.3048 + inches by 0.0254.
2
Square the height
Height × Height.
3
Divide weight by height²
BMI = kg / m².

Worked Examples:

Adult BMI

Weight: 70 kgHeight: 1.75 m

Result: BMI = 22.9 (Normal)

BMI = 70 / (1.75 × 1.75) = 70/3.0625 = 22.86