BMI Calculator
Enter your height and weight — in metric or imperial units — to get your body mass index, weight category and healthy weight range.
Your BMI
—
What is BMI?
Body Mass Index is a simple screening number that relates your weight to your height. It was devised in the 1830s by the Belgian statistician Adolphe Quetelet and remains the most widely used first-pass check for weight categories because it needs only two measurements and no equipment. The World Health Organization classifies adult BMI as: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30 or above obese.
How to use this calculator
Choose metric (kilograms and centimetres) or imperial (pounds, feet and inches) with the toggle, then enter your weight and height. Your BMI, its WHO category and the weight range that would put you in the "normal" band for your height all update instantly. Nothing you type leaves your device.
The formula
For imperial units the tool first converts pounds to kilograms (× 0.4536) and feet/inches to metres (× 0.0254 per inch), then applies the same formula. The healthy range shown is the weight that yields BMI 18.5 at the low end and 24.9 at the high end for your height.
Worked example
A person weighing 70 kg at 175 cm (1.75 m): BMI = 70 ÷ (1.75)² = 70 ÷ 3.0625 = 22.9, squarely in the normal band. Their healthy weight range is 18.5 × 3.0625 ≈ 56.7 kg up to 24.9 × 3.0625 ≈ 76.3 kg. If the same person weighed 85 kg, their BMI of 27.8 would fall in the overweight band, and the tool would show they are about 8.7 kg above the top of the healthy range.
What BMI can and cannot tell you
BMI is genuinely useful as a population-level screen and a personal early-warning signal — large studies link high BMI with increased risk of type 2 diabetes, heart disease and joint problems. But it has real limits: it cannot distinguish muscle from fat (fit athletes often read "overweight"), it says nothing about where fat is stored (belly fat matters most), and standard cut-offs understate risk for many South Asians, for whom some guidelines suggest action from BMI 23. Use it as a starting point, alongside waist measurement and medical advice — never as a diagnosis. Our article what BMI tells you — and what it doesn't covers this in depth.
Frequently asked questions
What is a good BMI for South Asians?
Several health bodies recommend lower cut-offs for South Asian populations because health risks rise at lower BMI: overweight from about 23 and obese from about 27.5. If your BMI is 23–25, it is worth discussing with your doctor even though the standard chart says 'normal'.
Is BMI valid for children and teenagers?
Not with adult cut-offs. Children's BMI is assessed against age-and-sex percentile charts. This calculator is intended for adults 18+.
I do a lot of gym — my BMI says overweight. Should I worry?
Possibly not. Muscle is denser than fat, so muscular people often have a high BMI with low body fat. Waist circumference and body-fat percentage are better indicators in that case.
Is BMI useful during pregnancy?
No — weight gain in pregnancy is expected and healthy. Pre-pregnancy BMI is sometimes used by doctors to guide recommended gain, but the calculator should not be applied to a current pregnant weight.
How fast can I safely move toward the healthy range?
Gradual change wins: 0.25–0.5 kg per week through diet adjustments and activity is a widely recommended, sustainable pace. Crash diets usually rebound.