Body Mass Index (BMI) Calculator
Calculate your Body Mass Index from height and weight in metric or imperial units, see the WHO weight category, and understand what the number does and does not mean.
Body Mass Index divides your weight by the square of your height (kg/m², or 703 × lb/in²) to place you on a scale the World Health Organization uses for population screening: under 18.5, 18.5–24.9, 25–29.9, and 30+. It takes two inputs and five seconds — no equipment, no signup, nothing leaves your device.
The result comes with its category and context. BMI is a screening tool, not a diagnosis: it cannot distinguish muscle from fat, and athletes and older adults often land in surprising categories. Use it as a quick reference point, and read the FAQ below for where it genuinely misleads.
100% in-browser · no upload · no signup · nothing you paste or drop here leaves your device
BMI Calculator
Body Mass Index with WHO classification, healthy weight range, and an interactive scale — 100% private.
BMI is a screening measure, not a diagnosis. It does not account for muscle mass, bone density, age, sex, or body-fat distribution. Talk to a healthcare professional before making any weight-management decisions.
How to read your BMI — and its limits
Your BMI sits on this scale. The green zone (18.5–24.9) is the reference 'normal' range; the inset rounded marks show common BMI points for reference.
In metric units: divide weight in kilograms by the square of height in meters. The category thresholds are fixed by the WHO regardless of age or sex.
| BMI range | Category | Health risk |
|---|---|---|
| < 18.5 | Underweight | Increased (nutritional deficiency) |
| 18.5 – 24.9 | Normal weight | Lowest |
| 25.0 – 29.9 | Overweight | Moderate |
| 30.0 – 34.9 | Obesity (Class I) | High |
| 35.0 – 39.9 | Obesity (Class II) | Very high |
| ≥ 40.0 | Obesity (Class III) | Extremely high |
Ranges per WHO. Asian-Pacific guidelines use lower cut-offs (23 / 27.5) for elevated risk — check what applies to you.
Mia is 175 cm and weighs 74 kg. Let's compute her BMI and healthy range.
- Height²:1.75 m × 1.75 m = 3.0625 m²
- BMI:74 ÷ 3.0625 = 24.2 → Normal weight
- Healthy range:18.5 × 3.0625 to 24.9 × 3.0625 = 56.7 to 76.3 kg
- Verdict:At 74 kg she is inside the normal range.
About this body mass index calculator
This page covers bmi formula, calculate bmi from height and weight, bmi chart adults, is my bmi healthy — all the same underlying task as body mass index calculator. The tool above is FreeToolHub's bmi calculator embedded in full: every feature works right here, and nothing you process is uploaded to any server.
Frequently asked questions
What is the BMI formula?
Metric: weight in kilograms divided by height in meters squared. Imperial: 703 × weight in pounds divided by height in inches squared. A person who is 170 cm and 68 kg lands at 68 ÷ 1.70² ≈ 23.5 — squarely in the normal range.
How accurate is BMI?
For populations, quite useful; for individuals, rough. It misclassifies muscular people as overweight (muscle is denser than fat) and can flag older adults with low muscle mass as healthy. Waist measurement and body composition give a fuller picture — treat BMI as a first checkpoint, not a verdict.