BMI Calculator – Calculate BMI Online (Free Tool)
Free online BMI Calculator tool to calculate your Body Mass Index. Enter height and weight to determine BMI category and health indicators. All calculation happens locally.
Example Output
BMI = weight / height² (in metres) — 70 / 1.75² ≈ 22.86, comfortably in the Normal range.
BMI 22.86 — Normal weight
What is BMI Calculator?
BMI Calculator computes Body Mass Index from your height and weight and tells you which WHO category it lands in. Supports metric (cm/kg) and imperial (ft-in/lb) inputs so you don't need to convert first. BMI is a screening number — it doesn't measure body composition — but it remains a quick, widely-used reference for general weight ranges.
Why use this tool?
- Works on desktop, tablet, and mobile in any modern browser
- Stable behavior across visits — no surprise version drift
- Your data stays private — all processing happens locally in the browser
- No upsell to a paid plan: every feature is free forever
- Designed for everyday quick tasks — open the page, get the answer, move on
How to use
- Choose metric (cm/kg) or imperial (ft-in/lb) units
- Enter your height and weight
- Read the BMI value and category (Underweight / Normal / Overweight / Obese)
- Compare against the WHO ranges shown below the result
Examples
Metric input
180 cm, 75 kg → BMI 23.15 (Normal). The formula is kg / m²: 75 / (1.8 × 1.8) = 23.15.
Imperial input
5'10" (70 in), 165 lb → BMI 23.67 (Normal). Formula: 703 × lb / in² = 703 × 165 / 4900 ≈ 23.67.
Common use cases
- Quick health screening for adults
- Tracking your trend over time as part of a health journal
- School/PE class demonstrations
- Pre-doctor-visit reference before discussing weight management
Troubleshooting
- BMI seems high but I'm very muscular.
- BMI doesn't distinguish muscle from fat. Athletes and bodybuilders routinely score "Overweight" or "Obese" while being lean. Use body-fat percentage or waist-to-hip ratio instead for that case.
- Different result than my doctor's scale.
- Different scales use slightly different formulas (some use waist circumference, age, etc.). Our calculator uses the standard WHO BMI formula. If they differ, ask your doctor what scale they use.
Frequently Asked Questions
BMI (Body Mass Index) = weight (kg) ÷ height² (m²). For imperial: 703 × weight (lb) ÷ height² (in²). The tool accepts both metric and imperial input.
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