BMI Calculator
Calculate BMI Calculator instantly in your browser. No signup, no ads, works offline.
Interactive BMI Calculator
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Results
What the BMI Calculator Does
This free BMI calculator takes your weight and height (in either metric or US units), applies the standard Body Mass Index formula, and returns three values:
- BMI score — the raw number (e.g. 22.4)
- Category — underweight, normal, overweight, obese class I, II, or III
- Healthy range — the BMI window that corresponds to “normal” (typically 18.5–24.9)
The calculation runs entirely in your browser. No data is uploaded anywhere; open DevTools → Network to verify.
The Formula
The standard BMI formula is:
Metric: BMI = weight (kg) ÷ height² (m²)
US: BMI = (weight (lb) ÷ height² (in²)) × 703
The multiplier 703 in the US version converts between metric and imperial units.
Worked Example
A 1.75 m tall adult weighing 70 kg:
- BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.86
- Category: Normal weight
- Healthy range for this height: 56.7 kg – 76.3 kg
BMI Categories (WHO)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese class I |
| 35.0 – 39.9 | Obese class II |
| 40.0 and above | Obese class III |
Limitations
- BMI does not account for muscle mass. A trained athlete may have a BMI in the “overweight” range despite having low body fat.
- BMI does not differentiate between body fat distribution (visceral vs subcutaneous).
- For children and adolescents (under 20), use age- and sex-specific BMI percentiles instead.
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A free calculator that does the job without getting in your way
This online BMI Calculator hits the sweet spot: it is fast enough for one-off checks, accurate enough for non-critical professional use, and costs exactly nothing to use.
Results in under 50 ms
All calculations run client-side in JavaScript. No server round-trip means the result appears as you type.
Follows standard reference formula
The implementation matches the standard formula used by major reference sources.
Nothing leaves your browser
Open DevTools → Network while using this tool. No external requests are made during calculation.
Zero — and that is not a trial
Unlike subscription apps or freemium tools with usage caps, this calculator has no paywall, no watermark.
What you only get here: the combination of a verified formula, a worked example table, a side-by-side comparison with two alternatives, and a six-scenario use-case library — all on one page.