Adult BMI
Calculate body mass index from height and weight in metric or UK units.
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For adults aged 18 and over only. BMI is a screening measure, not a diagnosis. It is unsuitable during pregnancy and may be misleading for very muscular people. Risk thresholds can be lower for some ethnic backgrounds; this tool does not assess personal risk.
How it works
BMI = weight in kilograms ÷ height in metres squared. Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 inch = 2.54 cm.
A quick example
75 kg at 175 cm gives a BMI of 24.5, within the standard adult reference range of 18.5 to below 25.
Reference: Adult weight and BMI guidance — NHS. Checked 5 October 2026.
Good to know
What ranges are shown?
The general adult reference bands are below 18.5, 18.5 to below 25, 25 to below 30, and 30 or above. A number alone does not determine your health.
Where can I get personal guidance?
Use the NHS adult BMI tool, which includes additional context, or speak to a qualified health professional. Do not use this tool for children.