What is this BMI calculator?
Body Mass Index (BMI) is a quick screening number that relates your weight to your height: kg ÷ m² in metric, or 703 × lb ÷ in² in imperial. This calculator gives you your BMI, your WHO weight category, and the healthy weight range for your exact height — so you know not just the number, but what range to aim for.
Why use this tool?
Doctors, insurers, fitness apps, and military fitness standards all use BMI as a first-pass screening metric. This version supports both metric and imperial units, updates as you type, and runs entirely in your browser — your height and weight are never sent anywhere.
Tips & Best Practices
- BMI is a screening tool, not a body-fat measurement — muscular people often score "overweight" while lean
- Track the trend over months rather than fixating on a single reading
- For children and teens, use age-adjusted BMI percentiles instead (this calculator is for adults)
- Waist circumference and waist-to-height ratio are useful companion metrics
Frequently Asked Questions
What is a healthy BMI?
For most adults: 18.5–24.9 is the healthy range. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is classified as obese (WHO categories).
Is BMI accurate for athletes?
Not always. BMI can't distinguish muscle from fat, so strength athletes frequently land in "overweight" despite low body fat. Use it alongside other measurements.
Is my data private?
Yes. The calculation runs entirely in your browser — nothing is stored or transmitted.
Looking for more tools? Try our Unit Converter, Percentage Calculator, or the complete tools collection.