BMI Calculator
Body mass index.
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What BMI measures — and what it does not
Body Mass Index is weight in kilograms divided by height in metres squared. It was devised in the 1830s by the Belgian statistician Adolphe Quetelet as a way of describing populations, not individuals, and it was only adopted as a clinical shorthand much later. The standard adult categories are under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, and 30 or above obese.
Its limitations are well documented and worth stating plainly. BMI cannot distinguish muscle from fat, so athletes are routinely classified as overweight. It says nothing about where fat is distributed, though abdominal fat carries far more metabolic risk than fat elsewhere. It performs differently across ethnic groups — several health authorities apply lower thresholds for people of South Asian descent — and it is not valid for children, pregnant women, or the elderly. It is a screening indicator, not a diagnosis.
Why we built this tool
People check BMI out of general health curiosity, because a form or an insurer asks for it, or as one rough input among others when tracking a change over time.
Height and weight are health data, which almost every privacy regime treats as a special category deserving extra protection. Sending them to a website that logs them is a poor trade for a two-operation calculation. Ours computes in your browser with nothing transmitted and nothing stored — your figures do not exist anywhere after you close the tab. Discuss any result that concerns you with a clinician; a number from a web page is not medical advice.
Tips and common mistakes
- BMI cannot distinguish muscle from fat, so athletes are routinely misclassified.
- Several health authorities apply lower thresholds for people of South Asian descent.
- It is not valid for children, pregnant women, or the elderly.
- Treat it as one rough screening number and discuss anything concerning with a clinician.
Open BMI Calculator with a link
BMI Calculator can be handed its input by the link that opens it, so the page arrives with the work already done. This is meant for assistants and scripts: if a chatbot, an editor extension, or a command-line agent already holds your content, it can build a link instead of asking you to copy and paste into a box.
The payload rides in the fragment — the part of a URL after the #. Browsers never send the fragment to a server, so anything handed over this way stays on your device exactly as a dropped file would. A link that uses the query string instead is rewritten into the fragment by the page before any analytics or ad script can read the address.
#height=— height#weight=— weight#age=— age in years#gender=— male or female
Example: https://mygadgets.ink/tools/bmi-calculator/#height=...&weight=...&age=...&gender=...
Quick start: using BMI Calculator
- Enter your height and weight in whichever units you prefer.
- Read the calculated BMI and its category.
- Treat the category as a broad screening signal, not a verdict.
- Consider the caveats — muscle mass, body composition, and ethnicity-specific thresholds.
- Speak to a healthcare professional about anything that concerns you.
For unit conversions in other contexts, see Unit Converter.