Tool
BMI Calculator
Height and weight in, BMI and category out. Metric or imperial, no sign-up, no nonsense.
Calculate your BMI in three steps
No software needed. Works in any browser, on any device.
Enter height and weight
Input in metric (kg/cm) or imperial (lbs/ft). Switch anytime.
Get your BMI instantly
Your BMI value and category — Underweight, Normal, Overweight, or Obese — appear immediately.
See where you stand
View your BMI on the scale with context for each range.
BMI Calculator
BMI
22.9
Category
Normal weight
Metric and imperial
Switch between kg/cm and lbs/ft without re-entering data.
Instant result
Calculates as you type. No submit button needed.
Category context
See which range your BMI falls in and what each category means.
About the BMI Calculator
Body Mass Index (BMI) is a simple measurement that uses your height and weight to estimate whether you are in a healthy weight range. Our free BMI calculator gives you an instant result along with your BMI category and a visual gauge showing where you sit on the scale.
BMI is calculated by dividing your weight in kilograms by your height in metres squared (kg/m²). For imperial units, the formula adjusts using pounds and inches. Our calculator handles both automatically — simply switch between Metric and Imperial using the toggle at the top.
The four standard BMI categories are: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). These ranges are defined by the World Health Organization and are used globally by healthcare professionals.
BMI is a useful screening tool but it does have limitations. It does not account for muscle mass, bone density, age, or sex, which means athletes or highly muscular individuals may have a high BMI without excess body fat. Always consult a healthcare professional for a full health assessment.
All calculations happen instantly in your browser. No data is stored or sent anywhere.
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Use itFrequently Asked Questions
Is BMI an accurate measure of health?
BMI is a screening tool, not a diagnostic measure. It doesn't account for muscle mass, bone density, age, or fat distribution. Athletes often show 'overweight' BMI despite low body fat. It's a starting point — not a health verdict.
What is a healthy BMI range?
For adults: 18.5–24.9 is normal. Under 18.5 is underweight, 25–29.9 overweight, 30+ obese. These thresholds were set from Western European populations and may not apply equally to all ethnicities.
Does BMI work the same for children?
No. Children need age and sex-specific growth charts. Adult BMI categories don't apply to under-18s.
Why does my BMI differ from a doctor's?
BMI = weight(kg) ÷ height(m)². Differences usually come from unit rounding or slightly different measurements.