BMI Calculator

Body Mass Index (BMI) is a widely used screening metric that estimates body fat based on a person's height and weight. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and has been endorsed by the World Health Organization (WHO) and healthcare systems worldwide as a quick, cost-free way to flag potential weight-related health risks.

The formula is straightforward: BMI = weight (kg) ÷ height² (m²). For a person who weighs 70 kg and stands 1.75 m tall, the BMI is 70 ÷ (1.75 × 1.75) = 22.86. The WHO classifies this as "Normal weight" (BMI 18.5–24.9). Values below 18.5 indicate underweight; 25.0–29.9 is overweight; 30.0 and above is obese.

Why does this matter? Research consistently shows that BMI outside the healthy range correlates with elevated risk for type 2 diabetes, hypertension, cardiovascular disease, sleep apnoea, and certain cancers. A routine BMI check takes under 30 seconds and can prompt an early conversation with a doctor — potentially years before a condition becomes symptomatic.

Metric and Imperial support

The UtilsGo BMI Calculator accepts both metric (kilograms and centimetres) and imperial (pounds, feet, and inches) inputs. Imperial inputs are automatically converted to metric before the BMI formula is applied, so the result is identical regardless of which unit system you prefer. A separate "Ideal Weight" panel shows the minimum and maximum healthy weight for your entered height, in your chosen units.

Important limitations of BMI

BMI is a population-level screening tool, not a diagnostic one. It cannot distinguish between fat mass and muscle mass — a professional athlete or bodybuilder with very high muscle density may have an "overweight" BMI despite having extremely low body fat. Conversely, elderly individuals can fall in the "normal" range while having too little muscle (a condition called sarcopenia). Pregnant women, children under 18, and people of certain Asian ethnicities may require adjusted thresholds. Always discuss your BMI result with a qualified healthcare professional for a full health assessment.

All calculations are performed locally in your browser. No height, weight, or health data is transmitted to any server.