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BMI Calculator

Calculate your body mass index using metric or imperial measurements.

Your measurements

This calculator uses the standard adult BMI formula.

Height

Weight

For adults aged 18 and over. BMI cannot distinguish between muscle and body fat, and standard thresholds may not suit everyone.

Your BMI result

A screening measure based on your height and weight.

Body mass index

24.2

Healthy weight

UnderweightHealthyOverweightObesity

Healthy weight range for your height

53.5–72.0 kg

Based on the standard adult BMI range of 18.5 to 24.9.

This is general guidance, not a diagnosis or substitute for medical advice.

How to calculate your BMI

Choose metric or imperial measurements, then enter your height and weight. The calculator converts the values when you switch units and shows your body mass index to one decimal place, its standard adult category and an indicative healthy-weight range for the entered height.

BMI is calculated by dividing weight in kilograms by height in metres squared. It is a screening measure rather than a diagnosis, but it can provide a quick starting point for thinking about weight and health.

Worked example

Height: 1.70 m. Weight: 70 kg.

BMI = 70 ÷ (1.70 × 1.70) = 24.2.

Understanding the displayed categories

The calculator uses the standard adult bands shown in the tool: under 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 or above is obesity. Health risk can begin at lower BMI values for some ethnic backgrounds, so a general band may not reflect every person equally.

The healthy-weight range is obtained by applying the lower and upper standard BMI values to your height. It should be treated as context, not as a personal target set by a clinician.

Important limits of BMI

BMI cannot distinguish body fat from muscle or bone. It may be misleading for very muscular people and is not intended here for children, pregnancy, eating disorders or conditions that affect height. If you are worried about your weight or health, speak to a pharmacist, GP or another qualified healthcare professional.

For personalised eligibility and interpretation, use the official NHS adult BMI guidance.

FAQs

Questions about the bmi calculator

What formula does this BMI calculator use?

It uses weight in kilograms divided by height in metres squared. Imperial values are converted to metric before the same formula is applied.

Can children use this result?

No. Children and teenagers need age- and sex-specific centile calculations rather than the adult BMI categories used here.

Why can an athletic person have a high BMI?

BMI measures weight relative to height and cannot separate muscle from fat, so greater muscle mass can raise the result.

Is BMI a medical diagnosis?

No. It is one general screening measure and should be considered alongside other information and professional advice where appropriate.