BMI Calculator | Free Body Mass Index Tool

Formula

This calculator uses the standard bmi calculator formula:

BMI Formula (metric)

BMI = weight (kg) / height² (m²)

What is a normal BMI? ⌄

A normal BMI is between 18.5 and 24.9. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.

How is BMI calculated? ⌄

BMI = weight (kg) ÷ height² (m²). For example, 70 kg at 1.75 m gives 70 ÷ 3.0625 = 22.9.

Is BMI accurate for athletes? ⌄

BMI can overestimate body fat in muscular individuals like athletes because it does not distinguish between fat and muscle mass.

What BMI is considered overweight? ⌄

A BMI of 25.0 to 29.9 is classified as overweight. A BMI of 30 or higher is classified as obese.

Can I use this calculator for children? ⌄

This calculator uses the adult BMI formula. For children and teens, BMI-for-age percentile charts from CDC are more appropriate.

How often should I check my BMI? ⌄

Checking BMI every 3–6 months is sufficient for tracking trends. More frequent monitoring is rarely necessary for healthy adults.