Enter your height and weight to get your Body Mass Index, weight category and healthy weight range instantly. Free, based on WHO categories, and calculated privately in your browser.
Quick answer: BMI (Body Mass Index) equals weight in kilograms divided by height in meters squared. For adults, a BMI of 18.5 to 24.9 is classed as normal weight, 25 to 29.9 as overweight and 30 or higher as obese (WHO). Example: 70 kg at 175 cm is a BMI of 22.9. Last updated September 2026.
Body Mass Index (BMI) is a number calculated from height and weight that estimates whether an adult's weight is healthy for their height. It is one of the most widely used weight screening measures and is the same formula for men and women.
The formula is BMI = weight (kg) ÷ height (m)². The result places you in one of four ranges: underweight, normal weight, overweight or obese. It is a quick screening measure, not a diagnosis.
Why calculate BMI regularly? Tracking your BMI over time gives you a simple benchmark for weight changes and can flag when it is worth talking to a doctor. It works best together with other measures such as waist circumference.
Your BMI
Healthy Weight Range for Your Height
-- kg
BMI divides your weight by the square of your height. Use whichever unit system you prefer:
Metric example: a person who weighs 70 kg and is 175 cm (1.75 m) tall has a BMI of 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9, which is normal weight.
Imperial example: a person who weighs 160 lbs and is 70 inches tall has a BMI of 703 × 160 ÷ 70² = 112,480 ÷ 4,900 = 23.0, which is also normal weight.
Rearrange the formula to work out the weights that match a BMI of 18.5 and 24.9 at your height:
At 1.75 m, that is 18.5 × 3.0625 = 56.7 kg up to 24.9 × 3.0625 = 76.3 kg.
BMI Prime is your BMI divided by 25, the upper limit of the normal range. A value below 1 means you are under that limit, and above 1 means you are over it. For a BMI of 22.9, BMI Prime = 22.9 ÷ 25 = 0.92.
These are the standard adult BMI ranges used by the World Health Organization. They apply to men and women aged 20 and over.
| Category | BMI (kg/m²) |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 - 24.9 |
| Overweight | 25.0 - 29.9 |
| Obesity class I | 30.0 - 34.9 |
| Obesity class II | 35.0 - 39.9 |
| Obesity class III | 40.0 or higher |
Some health bodies use lower cut-offs for people of Asian descent, because health risks can rise at a lower BMI. Ask your doctor which thresholds apply to you.
The weights below correspond to a BMI of 18.5 to 24.9 at each height.
| Height | Healthy weight (kg) | Healthy weight (lbs) |
|---|---|---|
| 150 cm (4'11") | 41.6 - 56.0 kg | 92 - 124 lbs |
| 155 cm (5'1") | 44.4 - 59.8 kg | 98 - 132 lbs |
| 160 cm (5'3") | 47.4 - 63.7 kg | 104 - 141 lbs |
| 165 cm (5'5") | 50.4 - 67.8 kg | 111 - 149 lbs |
| 170 cm (5'7") | 53.5 - 72.0 kg | 118 - 159 lbs |
| 175 cm (5'9") | 56.7 - 76.3 kg | 125 - 168 lbs |
| 180 cm (5'11") | 59.9 - 80.7 kg | 132 - 178 lbs |
| 185 cm (6'1") | 63.3 - 85.2 kg | 140 - 188 lbs |
| 190 cm (6'3") | 66.8 - 89.9 kg | 147 - 198 lbs |
BMI does not measure body fat directly. It cannot separate muscle from fat, and it does not show where fat is stored. Very muscular people may be classed as overweight, and older adults may carry excess body fat at a normal BMI. Pregnancy and some medical conditions also make BMI unreliable.
This calculator provides general information only and is not medical advice. Speak to a doctor or registered dietitian before making health decisions. Category definitions follow the World Health Organization and guidance from the CDC.
A healthy BMI for adults is 18.5 to 24.9 kg/m². Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or higher is obese, according to the World Health Organization. BMI is a screening tool, not a diagnosis, so talk to a healthcare provider about what it means for you.
Divide your weight in kilograms by your height in meters squared (kg ÷ m²). In imperial units, divide weight in pounds by height in inches squared, then multiply by 703. Example: 70 kg at 175 cm gives 70 ÷ 1.75² = 22.9, which is in the normal range.
BMI is a useful screening tool for most adults, but it cannot tell muscle from fat or show where fat is stored. Athletes and muscular people can have a high BMI while being healthy, and older adults can have excess body fat at a normal BMI. Use it alongside waist circumference, body fat percentage and advice from a healthcare professional.
No. The BMI formula and the adult categories are the same for men and women. Women tend to carry more body fat than men at the same BMI, which is why BMI is best treated as a starting point rather than a full health assessment.
This calculator is designed for adults aged 20 and over. For children and teens aged 2 to 19, the CDC uses BMI-for-age percentiles that compare a child with others of the same age and sex, so a fixed adult category does not apply. Ask a pediatrician to interpret a child's BMI.
Checking once a month is enough for most people. Weigh yourself at the same time of day, ideally in the morning, in light clothing and on the same scale, so that changes you see reflect real trends rather than daily water and food fluctuations.
BMI changes as your weight changes. Water retention, meals and hormones can shift your weight and BMI by a point or two from day to day, so focus on monthly trends. To plan changes to your weight, try our Calorie Calculator.
Yes. All calculations run in your browser. Your height and weight are not sent anywhere or stored by the calculator, and no login is required.