BMI Calculator

About this BMI calculator

This tool gives a quick, accurate BMI using either U.S. units (lb, ft/in) or metric (kg, cm). You’ll see your BMI value, the adult category it falls into, BMI Prime (your BMI relative to 25), and a healthy weight range for your height. Everything runs locally in your browser for speed and privacy.

BMI is a screening metric, not a diagnosis. It doesn’t separate fat from muscle or account for body composition, age-related changes, or where weight is carried. Still, it’s useful for trend tracking, setting goals with your coach or clinician, and comparing against public health guidance. If you’re highly muscular, pregnant, or looking at kids or teens, BMI by itself is less informative. Pair it with measures like waist circumference, body fat estimates, and how you feel day to day.

If you need a deeper dive, check our Body Fat Calculator and BMR & Calorie Calculator.

How to use this BMI calculator

1. Choose Units (U.S. or Metric).
2. Enter your height and weight. Age is optional.
3. Click Calculate to see BMI, category, BMI Prime, and a healthy weight range.
4. Use Download CSV to save a snapshot of your results.

You might also like Body Fat and Water Intake.

What your results mean

• BMI: weight (kg) ÷ height² (m²). A quick screening metric, not a body fat measurement.
• Category: Underweight <18.5; Healthy 18.5–24.9; Overweight 25–29.9; Obesity I 30–34.9; II 35–39.9; III ≥40.
• BMI Prime: BMI ÷ 25 (upper limit of “Healthy”). Below 1 is under the cutoff; above 1 is over.
• Healthy weight range: The weights that place BMI between 18.5 and 24.9 for your height.

For kids and teens, use BMI-for-age percentiles. For decisions about health, speak with a clinician.