BMI Calculator
Calculate your Body Mass Index based on height and weight
BMI Calculator computes Body Mass Index — weight relative to height squared — and maps it onto the WHO's standard weight-status bands used in routine health screenings.
Content reviewed: August 24, 2026
Encrypted with HTTPSProcessed in your browser
All processing runs locally in your browser. Your files and text are not sent to Tool-web's server.
Actions:
How to Use
- Enter your weight (kg or lbs)
- Enter your height (cm or ft/in)
- Click "Calculate" to get your BMI
- Review the BMI category and health range
Features
- Metric and imperial units
- BMI category classification
- Healthy weight range display
- Visual BMI chart
- Quick reset
Tips for getting BMI Calculator right
- Measure height without shoes and weigh at a consistent time of day for repeatable numbers
- Track the trend across weeks, not day-to-day jumps — water and food weight swing results by a kilo or more
- BMI screens populations well but individuals poorly; athletes routinely land in 'overweight' on muscle alone
Formula and worked example
BMI = weight(kg) ÷ height(m)². For 70 kg at 1.75 m: 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 — comfortably inside the normal band.
WHO weight-status bands
| BMI (kg/m²) | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obesity |
Known limitations
- Doesn't distinguish muscle from fat — body composition needs other measurements
- Not valid during pregnancy or for children (age-specific charts exist)
- The same BMI can carry different health risk across ethnic groups; some guidelines use adjusted thresholds
- It measures size, not fitness — blood pressure, lipids, and activity tell the rest of the story
Frequently Asked Questions
What are the BMI categories?
Underweight (below 18.5), Normal (18.5-24.9), Overweight (25-29.9), and Obese (30 and above).
Is BMI accurate for everyone?
BMI is a general indicator. Athletes and muscular individuals may have higher BMI without being overweight.
Can I switch between metric and imperial?
Yes. The tool supports both metric (kg/cm) and imperial (lbs/ft) unit systems.
Privacy & Security
Calculation runs locally in your browser. Height and weight inputs are never transmitted or stored.
Tips & Best Practices
- Measure height without shoes and weigh at a consistent time of day for repeatable numbers
- Track the trend across weeks, not day-to-day jumps — water and food weight swing results by a kilo or more
- BMI screens populations well but individuals poorly; athletes routinely land in 'overweight' on muscle alone
Comments
0/1000
Explore more Calculators
Browse all tools in the Calculators collection.