CalcVitalsBMI Calculator
BMI is your weight in kilograms divided by your height in metres squared. For example, at 70 kg and 175 cm, BMI is 22.86 — inside the healthy 18.5–24.9 band, which at 175 cm means a weight between 56.7 and 76.3 kg.
How it works
Body mass index was designed as a population statistic: one number, worked out from height and weight alone, that sorts large groups of people into bands that correlate with health risk. It does that job well, which is why the World Health Organization cut-offs — underweight below 18.5, healthy to 24.9, overweight to 29.9, obese above 30 — are still the standard screen in most clinics.
What BMI cannot do is see inside the body. Two people at 175 cm and 90 kg share a BMI of 29.4 whether the extra weight is muscle or fat, and risk follows the fat, not the number. Treat your result as a first signal: inside the healthy band is reassuring, outside it is a prompt to look at the fuller picture — waist size, body fat percentage, blood pressure, blood sugar — most of which have their own calculators on this page's family shelf.
The healthy range printed with your result is simply the 18.5–24.9 band converted back into kilograms for your height. It is a wide target on purpose: at 175 cm it spans nearly 20 kg, because healthy bodies at the same height genuinely do come in that many shapes.
The method
BMI = weight (kg) ÷ height (m)², with WHO adult categories (underweight <18.5, healthy 18.5–24.9, overweight 25–29.9, obese ≥30). The healthy weight range is 18.5 × height² to 24.9 × height². BMI does not apply cleanly to children, pregnancy, or very muscular builds.
Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9. Below 18.5 is classed as underweight, 25 to 29.9 as overweight, and 30 or above as obese. These are screening bands from the World Health Organization, not personal verdicts.
Why does my BMI look wrong for my build?
Because BMI only sees height and weight. Muscle is denser than fat, so a strength athlete can land in the overweight band with low body fat, while someone with little muscle can sit in the healthy band carrying more fat than is ideal. The waist-to-height ratio and body fat calculators on this site look at the picture from other angles.
Is BMI different for men and women?
The formula and the adult cut-offs are the same for both. What differs is what a given BMI typically means in body composition — at the same BMI, women on average carry a few percentage points more body fat than men.
Should children use this calculator?
No — children and teenagers are assessed against growth-chart percentiles for their age and sex, not the adult bands used here.