About BMI Calculator
BMI Calculator computes your body mass index from your height and weight, in either metric (cm/kg) or imperial (ft-in/lb) units. Alongside the number it shows which WHO category you fall into — underweight, healthy, overweight, obese — and the healthy weight range for your height. It's a quick, browser-only screening tool with no sign-up, useful for tracking trends over time or filling out a health form.
- No uploads
- Browser-only
- Works offline
- 100% free
How it works
- 1
Pick your units
Toggle between metric (centimetres, kilograms) and imperial (feet/inches, pounds).
- 2
Enter height and weight
Type the values or use the steppers. The BMI updates live with every change.
- 3
Read your result
See your BMI, the WHO category, and the weight range you'd need to be in to land in the 'healthy' band for your height.
Related tools
Browse allEquated monthly instalment, total interest, full amortization schedule. Multi-currency.
Scientific calculator with parentheses, sin/cos/log and a history.
Split a bill, calculate tip, round up the per-person total.
Years, months, days lived — plus days until your next birthday.
Frequently asked questions
Are my files uploaded to a server?
No. Every tool on SnapToolz runs entirely inside your browser using JavaScript and WebAssembly. Your file is read locally, processed in memory, and the result is offered as a download. Nothing is sent to a server — there isn't one to send to.
Is this medical advice?
No. BMI is a rough screening metric, not a diagnosis. It doesn't distinguish muscle from fat, doesn't account for age, sex, ethnicity, frame size, or body composition, and can mis-categorise athletes and the elderly. This tool is for educational purposes only — for medical guidance speak to a qualified healthcare professional. See our /disclaimer page for full terms.
What BMI range is considered 'healthy'?
The WHO standard for adults is: under 18.5 underweight, 18.5–24.9 healthy, 25.0–29.9 overweight, 30+ obese. Some regional bodies (e.g. for South-Asian populations) use slightly lower cut-offs for the overweight and obese bands due to differing health-risk profiles at lower BMI values.
Does this work for children?
Adult BMI categories don't apply to children and teenagers — paediatric BMI is interpreted on age-and-sex percentile charts (BMI-for-age), not against fixed bands. Use a paediatric BMI tool or speak to your child's doctor.
Does it work offline?
Yes. SnapToolz is a Progressive Web App. After your first visit, the app is cached on your device and every tool keeps working without an internet connection.
Is SnapToolz free?
Yes — every tool is 100% free with no sign-up, no watermark, no hidden tier. The whole platform is open source and we have no plan to gate features.