BMI (Body Mass Index) is a simple calculation using your height and weight. The formula is: BMI = weight(kg) / height(m)². It's used as a screening tool to identify potential weight problems in adults.

What is a healthy BMI range?

For adults: Underweight (<18.5), Normal weight (18.5-24.9), Overweight (25-29.9), Obese (≥30). However, BMI doesn't measure body fat directly and may not reflect health accurately for everyone.

Is BMI 100% accurate?

No! BMI is a screening tool, not a diagnostic. It doesn't account for muscle mass, bone density, body composition, or age. Athletes, pregnant women, children, and elderly may get misleading results. It's best used with other health assessments.

Can children use this calculator?

This calculator uses adult standards. For children and teens under 18, BMI must be compared to age and gender-specific growth charts using percentiles. Please consult a pediatrician for accurate child BMI assessment.

Yes! The Toolzilla BMI Calculator is 100% free and private. All calculations happen in your browser.

BMI Calculator

Calculate your Body Mass Index and weight category

Free BMI Calculator with Age & Height - 2025

Calculate your Body Mass Index (BMI) instantly and discover your ideal weight range with our advanced calculator

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