BMI Calculator
BMI is one division — weight over height squared — and yet it is the first number most doctors, insurers and sports programs ask for. This calculator handles both metric and imperial input, prints your BMI with the official WHO category, and converts the healthy range (18.5-24.9) back into an actual weight window for your height, which is the part that turns a score into a target.
The honest framing matters: BMI is a population screening tool, not a body composition scan. Muscle-heavy athletes read overweight; older adults with low muscle read healthy. Use the number as a checkpoint — if it sits outside the range and you don't know why, that's the moment to look at waist measurement or body fat rather than panic. The page remembers your inputs on this device for quick rechecks.
How to use
- Choose metric (cm, kg) or imperial (in, lb) — the placeholders follow your choice.
- Enter height and weight: BMI appears instantly with its WHO category and your healthy weight window.
- Share the number in one tap, or bookmark the page — inputs are remembered for next visit.
Frequently asked questions
How is BMI calculated?
BMI = weight (kg) ÷ height (m)². In imperial units, BMI = 703 × pounds ÷ inches². A 175 cm, 70 kg person lands at 22.9 — mid-range healthy. The calculator applies the formula exactly and shows both the score and its category.
What is a healthy BMI range?
The WHO defines 18.5-24.9 as healthy, below 18.5 underweight, 25-29.9 overweight and 30+ obese (classes I-III at 30/35/40). The healthy-weight stat converts that range into the actual weight window for your height — more actionable than the score alone.
Is BMI accurate for athletes and older adults?
Not by itself. BMI cannot tell muscle from fat, so muscular athletes often score overweight despite low body fat, and adults losing muscle with age can score healthy while carrying risk. Treat BMI as the cheap first screen; waist circumference or a body-fat measurement refines it.
Does BMI differ for men and women?
The formula and WHO cut-offs are identical for adult men and women — that is both its simplicity and its weakness. Body composition differs meaningfully by sex and age, which is why the healthy range here is the standard one and individual judgment (or a clinician) fills the gap.