BMI calculator.
Work out your body mass index from your height and weight, in metric or US units. See which BMI category you fall in and the healthy weight range for your height.
Your measurements
LiveBMI uses only height and weight, so it does not account for muscle. Switch units any time.
Body mass index
24.7
Normal weight
BMI is a screening tool, not a diagnosis, and does not measure body fat directly. Calculations run in your browser; nothing is stored.
How it works
Height and weight, one number
BMI divides your weight in kilograms by your height in metres squared. The result places you on a standard scale: under 18.5 is underweight, 18.5 to 24.9 is a normal weight, 25 to 29.9 is overweight, and 30 or above is in the obese range.
For someone 180 cm and 80 kg, that is 80 divided by 1.8 squared, which is about 24.7, near the top of the normal range. The calculator also shows the weight range that would keep your BMI between 18.5 and 25.
The full guide
The complete BMI guide.
What BMI measures, what the categories mean, and where the number falls short.
What is BMI?
Body mass index is a quick estimate of whether your weight is in a healthy range for your height. It was designed for populations rather than individuals, but it is a useful first check because it needs only two measurements and no special equipment.
A normal-range BMI is associated with lower risk for several weight-related conditions, which is why doctors use it as a starting point.
The BMI categories
The World Health Organization scale is: under 18.5 underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, and 30 and above obese, which is sometimes split into classes one, two and three. The calculator shows your category and the weight range that keeps you in the normal band.
Where BMI falls short
Because BMI uses only height and weight, it cannot tell muscle from fat. A very muscular athlete can have a high BMI while carrying little fat, and an older person can have a normal BMI yet little muscle. It also does not show where fat is stored, which matters for health.
Treat BMI as one signal among several, alongside waist measurement, body-fat percentage and how you feel and function.
BMI for adults versus children
This calculator uses the adult interpretation. For children and teens, BMI is read against age and sex percentiles rather than fixed numbers, so a paediatric BMI tool or a clinician is the right reference for under-18s.
Using BMI sensibly
If your BMI sits outside the normal range, it is a prompt to look closer, not a verdict. Small, steady changes to eating and activity move the number safely over time. For tailored advice, especially if you have a health condition, speak with a doctor or dietitian.
The formula
Two numbers,
one index.
BMI is weight over height squared. Use metres and kilograms, or let the calculator convert your US units for you.
Try the body fat calculator ›# Metric
BMI = weight(kg) / height(m)²
# US units
BMI = 703 × weight(lb) / height(in)²
# worked example
80 / 1.8² = 24.7Questions
BMI questions.
How do I calculate my BMI?
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Divide your weight in kilograms by your height in metres squared. In US units, multiply your weight in pounds by 703 and divide by your height in inches squared. Just enter your height and weight and the calculator does it.
What is a healthy BMI?
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A BMI from 18.5 to 24.9 is considered a normal, healthy weight for most adults. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese.
Is BMI accurate for everyone?
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BMI is a useful screen but not perfect. It does not distinguish muscle from fat, so it can misclassify very muscular people, and it is read differently for children, who use age and sex percentiles.
What is the healthy weight range for my height?
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It is the weight that keeps your BMI between 18.5 and 25. The calculator shows that range for your exact height in your chosen units.
Is this BMI calculator free and private?
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Yes. It is completely free with no sign-up, and every calculation runs locally in your browser, so nothing you enter is stored or sent anywhere.
About the developer
Jean Borg
Jean builds and maintains every calculator on freecalculators.pro from Malta. The BMI calculator uses the standard WHO formula and categories and is provided for general information, not medical advice.