BMI Calculator
Body mass index from height and weight, with the healthy range for your height.
Your figures
Result
How to use this tool
- Enter your figures in the fields on the left.
- Results update instantly as you type — there is no button to press.
- Change any input to see how sensitive the answer is to it.
BMI was designed to describe populations, not individuals. It takes no account of muscle mass, bone density, body composition or fat distribution, so a muscular person can register as overweight while carrying very little fat.
How it works
The calculation runs in your browser as you type — there is no submit button and nothing is sent anywhere. Change any figure and the results update immediately, which makes it easy to see how sensitive the answer is to each input.
Every formula used here is standard and documented in the questions below. Where a result depends on an assumption, the assumption is stated rather than buried.
Frequently asked questions
What is a healthy BMI?
Conventionally 18.5 to 24.9. Below 18.5 is classed as underweight, 25 to 29.9 as overweight, and 30 and above as obese.
Is BMI accurate for athletes?
No. Muscle is denser than fat, so athletes routinely register as overweight or obese by BMI while having very low body fat.
Does BMI differ by ethnicity?
Health risk thresholds do. Several health bodies use lower cut-offs for people of South Asian descent, where metabolic risk rises at a lower BMI.
Is this calculator free?
Yes, with no account, no limits and no data collection. It runs entirely in your browser.
Should I rely on this for a financial or medical decision?
No. It is a planning estimate built on standard formulas and stated assumptions. For decisions that matter, speak to a qualified professional who can account for your full circumstances.
Is this calculator accurate?
The arithmetic is exact — it uses the standard formula, shown in the questions above. What limits accuracy is the assumptions: the figures you enter, and factors the formula does not model such as fees, taxes and rule changes. Treat the result as a well-founded estimate rather than a quotation.
Do I need to sign up or download anything?
No. It runs in your browser, updates as you type, and stores nothing. There is no account, no download, and no limit on how many times you use it.
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Your files stay on your device. This tool runs entirely in your browser. No file is uploaded, transmitted, or stored. You can verify this by opening your browser's Network tab while using the tool.
Disclaimer. This calculator provides estimates based on standard formulas and the assumptions stated above. It is not financial, medical, tax or legal advice. For decisions that matter, consult a qualified professional. See our full disclaimer.