BMI Calculator
Free online BMI calculator. Metric or imperial. Enter height and weight to get your Body Mass Index, category (underweight/normal/overweight/obese), and healthy weight range. 100% browser-based, no signup.
Metric & Imperial
Toggle between metric (cm + kg) and imperial (ft + in + lb). The formula switches automatically: BMI = kg/m² or 703 × lb/in².
Color-Coded Category
Your BMI is mapped to a WHO category — underweight, normal, overweight, or obese — with color coding and a visual scale bar showing where you sit.
Live Results
BMI and category update instantly as you type. No buttons to press, no waiting. Switch units without losing your numbers.
Healthy Weight Range
For your exact height, the calculator shows the weight range that falls in the healthy BMI 18.5–24.9 band — your target zone for normal weight.
What is BMI?
Body Mass Index (BMI) is a number derived from your height and weight. It gives a rough indication of whether you are underweight, normal weight, overweight, or obese. The WHO defines categories: underweight < 18.5, normal 18.5–24.9, overweight 25–29.9, obese ≥ 30.
How is BMI calculated?
In metric: BMI = weight(kg) ÷ height(m)². In imperial: BMI = 703 × weight(lb) ÷ height(in)². The 703 constant converts imperial units to match the metric scale. Both formulas produce the same BMI value.
Is BMI accurate?
BMI is a population-level screening tool, not a body-composition measurement. It does not distinguish muscle from fat, so very muscular athletes may classify as overweight or obese despite low body fat. Always consult a clinician for individual assessment.
What is the healthy weight range for my height?
The calculator displays the weight range corresponding to BMI 18.5–24.9 for the exact height you entered. Falling inside this range puts you in the normal-weight category — but body composition, age, and muscle mass also matter.
Does the calculator store my data?
No. All math runs in your browser. Your height and weight are never uploaded, logged, or sent to any server. No signup, no cookies, no tracking.
Ready to use the BMI Calculator?
Free, no signup, no watermark. 100% browser-based. Your data never leaves your device.
Open the tool