BMI Calculator
Calculate your Body Mass Index (BMI) from height and weight in metric or imperial units, with category, healthy weight range, and ideal body weight.
About this tool
Body Mass Index (BMI) is a number derived from your height and weight that screens for weight categories (underweight, healthy, overweight, obese). It is widely used by doctors, fitness apps, and insurance forms because it takes two seconds to compute and needs no equipment. This calculator works in metric (centimetres and kilograms) or imperial (inches and pounds) — toggle the unit and your values convert automatically.
Alongside your BMI it shows the category with a colour-coded scale, your BMI Prime (the ratio of your BMI to the upper healthy limit of 25, useful for tracking progress toward a target), the healthy weight range for your exact height (BMI 18.5–24.9), and the ideal body weight estimated by the Devine formula when you pick a sex. If you are outside the healthy range, it tells you roughly how many kilos or pounds separate you from it.
Example: a 175 cm, 70 kg person has a BMI of 22.9 (Normal weight), a healthy range of roughly 56.7 – 76.3 kg, and an ideal body weight (Devine, male) of about 70.9 kg. The same person switching to imperial sees 68.8 in / 154.3 lb with identical results.
FAQ
Is BMI accurate for everyone? ›
BMI is a quick screening tool, not a diagnostic. It does not distinguish muscle from fat, so very muscular athletes can register as "overweight" without being unhealthy. It also underestimates body fat in older adults who have lost muscle mass. Treat the number as a starting point, not a verdict.
What is BMI Prime? ›
BMI Prime is your BMI divided by 25 (the upper limit of the healthy range). A value below 1.0 means you are under 25; above 1.0 means you exceed it. It is handy for tracking progress because a drop from 1.20 to 1.10 is intuitively "10% closer to healthy".
How is the ideal body weight calculated? ›
This tool uses the Devine formula, a common clinical estimate: 50 kg + 2.3 kg per inch over 5 feet for males, and 45.5 kg + 2.3 kg per inch over 5 feet for females. It is a rough guideline and ignores frame size and body composition.
Why do my values change when I switch units? ›
Switching between metric and imperial converts your height and weight automatically and rounds to one decimal place, which can cause a tiny rounding difference (usually under 0.1). The BMI itself is always computed from the metric values, so the result stays consistent.
Does this work for children? ›
No. Children and teens (under 20) use BMI-for-age percentiles rather than the adult categories shown here. For anyone under 20, consult a pediatric growth chart or a doctor.