Is it safe to use the BMI Calculator online?

Yes — and ours is safer than most. Many free online tools quietly upload your files to their servers to do the work. We don't. Everything happens inside your browser on your own device, so your files never reach the internet. There's no upload step, no server copy, and no way for us (or anyone else) to see what you're working on.

Are my files uploaded to a server?

No. There's no server-side processing here. The whole tool is a tiny app that runs in your browser — we don't even have a server that could receive your files. You can confirm this by opening your browser's network tab while you use the tool: nothing leaves your device.

Do I need to sign up or pay?

No. There's no account, no email collection, no credit card. The tool is free to use as much as you want, on as many files as you want. We're supported by a few unobtrusive ads on the page — not by your data.

Is BMI accurate for athletes?

No. BMI doesn't distinguish muscle from fat. Athletes often score 'overweight' despite low body fat. Use the body-fat tool for a better estimate.

What are the BMI categories?

WHO: <18.5 underweight, 18.5-24.9 healthy, 25-29.9 overweight, ≥30 obese. Asian thresholds slightly lower (overweight ≥23, obese ≥27.5).

Does it work for children?

BMI for children is interpreted as a percentile against age/sex norms — use a paediatric chart, not adult thresholds.

BMI Calculator

Body Mass Index from your height and weight. WHO classification (underweight / healthy / overweight / obese). Includes the healthy weight range for your height so you know where you'd land.

Features

Metric (cm/kg) or imperial (ft·in/lb) input
WHO BMI categories with colour-coded indicator
Healthy weight range for your height
Difference from nearest healthy weight
Asian-population threshold option (lower obesity cutoff)
Children/teen BMI percentile note (consult specific charts)

How to bmi calculator

Pick units — Metric or imperial.
Enter height + weight — Result is instant.
Read the category — Plus your healthy weight range.

Frequently asked questions

Is it safe to use the BMI Calculator online?: Yes — and ours is safer than most. Many free online tools quietly upload your files to their servers to do the work. We don't. Everything happens inside your browser on your own device, so your files never reach the internet. There's no upload step, no server copy, and no way for us (or anyone else) to see what you're working on.
Are my files uploaded to a server?: No. There's no server-side processing here. The whole tool is a tiny app that runs in your browser — we don't even have a server that could receive your files. You can confirm this by opening your browser's network tab while you use the tool: nothing leaves your device.
Do I need to sign up or pay?: No. There's no account, no email collection, no credit card. The tool is free to use as much as you want, on as many files as you want. We're supported by a few unobtrusive ads on the page — not by your data.
Is BMI accurate for athletes?: No. BMI doesn't distinguish muscle from fat. Athletes often score 'overweight' despite low body fat. Use the body-fat tool for a better estimate.
What are the BMI categories?: WHO: <18.5 underweight, 18.5-24.9 healthy, 25-29.9 overweight, ≥30 obese. Asian thresholds slightly lower (overweight ≥23, obese ≥27.5).
Does it work for children?: BMI for children is interpreted as a percentile against age/sex norms — use a paediatric chart, not adult thresholds.