Calculate your Body Mass Index from height and weight, watch the figure on the measuring station respond live, and see the healthy weight range for your height.
The healthy range is the weight that corresponds to a BMI of 18.5–24.9 for your height. It updates as you change your height.
Body Mass Index (BMI) is a quick, globally recognised screening tool that estimates a person's total body fat from their height and weight. It applies to most adult men and women aged 20 and over. While it does not measure body fat directly, BMI is a fast, non-invasive way to sort weight into four primary ranges, underweight, normal weight, overweight and obesity, and it correlates reasonably well with health risk across large populations, which is why clinicians, public-health agencies and fitness professionals use it as a starting point.
This calculator works for adult men and women, accepts both metric and imperial units, and instantly shows your BMI, your weight category, and the healthy weight range for your height. The figure on the height-and-weight station and the gauge update live as you change the inputs, so you can see exactly where any height and weight combination lands without scrolling.
Tip: pair this with our BMR Calculator to also estimate the calories your body burns at rest and each day.
Once you calculate your score it falls into one of the standard classifications defined by the World Health Organization (WHO). Obesity is split into three classes because health risk tends to rise with each step.
| BMI range (kg/m²) | Weight status | Health risk level |
|---|---|---|
| Below 18.5 | Underweight | Minimal to moderate |
| 18.5 – 24.9 | Normal / healthy weight | Low (optimal) |
| 25.0 – 29.9 | Overweight | Increased |
| 30.0 – 34.9 | Obesity class 1 | High |
| 35.0 – 39.9 | Obesity class 2 | Very high |
| 40.0 and above | Obesity class 3 (severe) | Extremely high |
The formula is the same worldwide; only the units differ. In metric units you divide your weight in kilograms by your height in metres squared. In imperial units you multiply your weight in pounds by 703, then divide twice by your height in inches. The 703 factor simply converts pounds and inches into the metric result.
Tracking your BMI is a useful starting point for understanding your general health trajectory. Falling outside the normal range can be an early flag for potential health risks that are worth discussing with a professional.
A BMI of 18.5 to 24.9 is considered the healthy range for most adults and is linked with fewer weight-related health problems than the categories above and below it. Because the range is defined by BMI, you can turn it around to find the healthy weight for any height: multiply 18.5 and 24.9 by the square of your height in metres. This calculator shows that span automatically as you change your height, so you see a realistic range rather than a single "perfect" number, which does not exist.
It is vital to remember that BMI is a general screening tool, not a definitive medical diagnostic. Because the formula relies purely on total weight, it cannot distinguish weight from fat from weight from lean muscle. Athletes and bodybuilders frequently score as "overweight" or "obese" despite very low body fat. Keep these blind spots in mind:
The underlying equation and the adult category cut-offs are identical for men and women. However, body-fat distribution varies between the sexes: on average women carry a higher body-fat percentage than men at the same BMI value, so a healthcare professional will contextualise the score by sex and age rather than treating it as the final word.
BMI is calculated the same way for children and teens, but it is interpreted very differently. Because healthy body fat changes a lot with age and differs between boys and girls as they grow, a child's BMI is compared against age- and sex-specific growth charts and expressed as a percentile rather than placed in the fixed adult categories. For anyone aged 2 to 19, use a dedicated child and teen BMI tool and review the result with a healthcare provider.
If you want a fuller picture, BMI pairs well with measures of where weight is carried and what it is made of. Waist circumference and the waist-to-height ratio both capture abdominal fat, which is more closely tied to metabolic risk. Body-fat percentage, estimated with calipers, bioimpedance scales or other methods, describes body composition that BMI cannot see. Blood pressure, cholesterol, blood sugar, diet and activity levels round out the assessment your clinician would actually use.
According to the World Health Organization (WHO), a healthy BMI for adults aged 20 and over is 18.5 to 24.9. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30.0 or above points to obesity.
Metric: divide your weight in kilograms by your height in metres squared. Imperial: multiply your weight in pounds by 703, then divide by your height in inches squared.
No. Because the formula evaluates total weight against height, it cannot tell dense lean muscle from body fat, so very fit, muscular people are frequently misclassified as "overweight" or "obese".
Once every few months is plenty for tracking overall health and trends. Checking daily or weekly is unnecessary, because BMI shifts gradually through sustained nutrition, strength and cardiovascular changes.
The equation is identical for adult men and women. Body-fat distribution differs by sex, so a professional contextualises the same numerical score differently based on sex and age.
Yes. An elevated BMI is correlated with metabolic trends and acts as a screening flag for high blood pressure, cardiovascular strain, insulin resistance and joint stress, prompting deeper clinical assessment.
It is calculated the same way but interpreted using age- and sex-specific percentiles, not the adult categories. Use a child and teen tool and consult a provider.
It is the weight that gives a BMI of 18.5 to 24.9 for your height. This calculator displays that range as you enter your height.
Category definitions and formulas follow the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC). For authoritative guidance see the CDC BMI resources, the WHO obesity topic, and the NHS BMI healthy weight calculator. This page is for general information and is not medical advice.