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BMI calculator

Calculate body mass index from height and weight and see its WHO weight category.

Input
Output

BMI calculator

Paste a height and weight as "height;weight" — one entry per line — and this tool calculates the body mass index (BMI) and classifies it into a WHO weight category: underweight, normal weight, overweight, or obesity class I, II or III. Multiple lines are processed as a table, one BMI and category per row, which makes it handy for checking several people, or several dates on a weight-tracking log, at once.

Switch between metric (centimetres and kilograms) and imperial (feet-inches and pounds) with the units option; imperial height accepts a plain number of inches or a feet'inches notation like 5'10. Turn on "Show healthy weight range" to see the weight span that keeps that height inside the normal BMI band, and "Show BMI Prime and WHtR" to add BMI Prime — your BMI divided by the upper limit of normal — and, when a line supplies a third field for waist size, the waist-to-height ratio. Decimal places set the rounding, and the output format switches between a plain sentence, a labeled table block, or CSV per entry.

The tool handles Windows (CRLF) and Unix (LF) line endings alike, skips blank lines, and names the line number if an entry isn't valid. The tally above the output shows how many entries were calculated and the resulting BMI, or the average across several entries. BMI is a screening measure only — it ignores muscle mass, bone density, age and sex — and every result carries a reminder that it doesn't replace a medical exam.

Everything runs locally in your browser; no height, weight or waist measurement is ever uploaded. Copy the result, download it as a .txt file, or send it to another tool's input to continue working with it.

FAQ

How is BMI calculated?
Metric: weight in kilograms divided by height in metres squared. Imperial: 703 × weight in pounds, divided by height in inches squared. Both formulas give the same BMI for the same body.
What are the WHO weight categories?
Underweight is below 18.5, normal weight is 18.5–24.9, overweight is 25–29.9, and obesity is split into class I (30–34.9), class II (35–39.9) and class III (40 and above).
What is BMI Prime?
BMI Prime is your BMI divided by 25, the upper edge of the normal range. A BMI Prime of 1.0 sits exactly at that boundary, so values above 1 indicate a BMI in the overweight or obese range.
How do I get the waist-to-height ratio?
Add a waist measurement as a third field, e.g. 170;65;80, and turn on "Show BMI Prime and WHtR". WHtR is waist size divided by height, using the same unit for both.
Is my height or weight uploaded anywhere?
No. Every calculation runs locally in your browser — nothing you type is sent to a server.