How accurate is BMI as a health metric?

BMI is a population-level screening tool, not an individual diagnostic. It does not account for muscle mass, bone density, or fat distribution. The calculator includes body fat % and waist-to-height ratio for a fuller picture.

What is a healthy BMI for my age?

BMI ranges shift slightly by age. For adults 18-24, 18.5-24.9 is standard. For adults 55+, up to 27 may be healthy to avoid frailty. This calculator shows age-adjusted ranges.

Is this BMI calculator free?

Yes, completely free. No signup required. Results are computed in your browser and no health data is transmitted to any server.

Why does BMI fail for athletes?

Athletes often have higher muscle mass, which increases body weight without increasing health risk. BMI cannot distinguish muscle from fat, so the calculator adds body fat % estimation for context.

BMI Calculator

Calculate your Body Mass Index in seconds.

Unit System

Weight (kg)

Height (cm)

What is BMI?

Body Mass Index (BMI) is a simple screening method for weight categories: underweight, normal weight, overweight, and obesity. It is not a diagnostic of body fatness or health.

Last updated: June 07, 2026

What is BMI?

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