Health Calculators
BMI Calculator
Body Mass Index (kg/m²) with WHO classification.
How it works
Three steps, no friction.
- Step 1
Enter your measurements
Switch between metric and imperial — the form adapts to your unit choice.
- Step 2
Run the calculation
Formulas from WHO, NIH, Mifflin-St Jeor, Mosteller, and the US Navy — all client-side.
- Step 3
Review your report
Get the result, category band, healthy range, and a downloadable Markdown/CSV/JSON report.
Benefits
Why teams choose WebRul.
- 100% client-side — no health data ever leaves your browser
- Reference formulas cite peer-reviewed sources (WHO, NIH, Mifflin, Mosteller, US Navy)
- Metric & imperial units with real-time validation
- Copy, download, and print-friendly reports (Markdown, CSV, JSON, TXT)
- Accessible, keyboard-first UI with reduced-motion support
FAQ
Questions, answered.
What is a healthy BMI range?
The WHO defines 18.5–24.9 kg/m² as the healthy weight band for most adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese.
Is BMI accurate for athletes or older adults?
BMI does not distinguish muscle from fat, so athletes can register as overweight without excess fat. For older adults and children, use age- and sex-specific references.
Which formula does this tool use?
BMI = weight (kg) ÷ height² (m²). Imperial inputs are converted to metric first.
Is my data stored anywhere?
No. All calculations run entirely in your browser — nothing is uploaded or logged.
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Need something custom?
Talk to the WebRul team about custom integrations, private tooling, or enterprise access.