Check Your BMI & Healthy Weight Range
Calculate your Body Mass Index (BMI) using your height, weight, age, and preferred measurement system. Get your BMI result and learn what it means.
Calculate Your BMI
Find out how your weight compares with your height using our free, international BMI Calculator.
Your BMI
0.0
Your entered information
- Age
- Gender
- Height
- Weight
This calculator is provided for general educational and informational purposes only. BMI is a screening measure and is not a diagnosis of health, disease, or body-fat percentage. It does not account for every factor that affects health. If you have concerns about your weight, health, pregnancy, a child's growth, or a medical condition, consult a qualified healthcare professional.
What Is BMI?
Body Mass Index (BMI) is a simple screening number calculated from height and weight. It is widely used around the world — in the USA, Canada, the UK, Australia, India, and beyond — as a quick way to place an adult's weight relative to their height into a general category. BMI does not measure body fat directly and is not a diagnosis; it is a starting point for a broader conversation about health.
Why Use a BMI Calculator?
Health Monitoring
A BMI calculator gives you a quick, free reference point you can discuss with a healthcare professional alongside other measurements such as waist circumference, blood pressure, and blood work.
Fitness and Weight Management
If you are working toward a fitness or weight-management goal, BMI can act as one of several markers you track alongside strength, endurance, energy levels, and how your clothes fit.
Tracking Changes Over Time
Because the calculation is quick and consistent, many people find it useful to recheck their BMI periodically to see the general direction of change, rather than relying on a single reading in isolation.
How Is BMI Calculated?
Metric BMI Formula
BMI = weight in kilograms ÷ (height in metres × height in metres). For example, a person weighing 72 kg at 1.75 m tall has a BMI of roughly 72 ÷ (1.75 × 1.75) ≈ 23.5.
Imperial BMI Formula
BMI = (weight in pounds × 703) ÷ (height in inches × height in inches). This formula is commonly used in the United States and produces the same result as the metric formula once units are converted.
BMI Categories for Adults
| BMI Range | Category | General Interpretation |
|---|---|---|
| < 18.5 | Underweight | Below the typical range; may warrant a conversation with a healthcare professional. |
| 18.5 – 24.9 | Healthy Weight | Commonly used reference range for adults, used as a general screening guide. |
| 25.0 – 29.9 | Overweight | Above the typical range; worth considering alongside other health indicators. |
| 30.0+ | Obesity | Higher screening range associated with increased likelihood of certain health considerations; a professional assessment is recommended. |
BMI is a screening measure, not a diagnosis. It should be interpreted alongside other health information rather than on its own.
BMI for Children and Teenagers
Children and teenagers grow at different rates depending on their age and sex, so a single adult-style BMI category does not apply to them. Instead, a child's or teenager's BMI is typically compared against an age- and sex-specific growth reference, expressed as a percentile. A percentile shows how a young person's BMI compares with others of the same age and sex, rather than comparing it to a fixed adult cut-off. This calculator can compute a BMI number for ages 2–19, but a proper percentile assessment should come from a pediatrician or an official growth chart.
BMI for Men and Women
The standard adult BMI formula and the standard adult BMI categories are the same for men and women. Gender does not change the maths. That said, men and women often carry weight differently, so many health professionals look at BMI together with other measures, such as waist circumference, when forming a fuller picture.
BMI and Muscle Mass
BMI is calculated from height and total body weight, and it cannot tell the difference between weight from muscle and weight from fat. Because muscle is denser than fat, a muscular person — such as a strength athlete or bodybuilder — can have a BMI in the "overweight" or "obesity" range while carrying relatively little body fat. For this reason, BMI is often less informative for highly muscular individuals and athletes.
Limitations of BMI
- BMI does not directly measure body fat — it is calculated only from height and weight.
- BMI does not show where fat is distributed on the body, which can matter for health risk.
- BMI cannot distinguish muscle mass from fat mass.
- BMI may be less informative for athletes and highly muscular individuals.
- BMI is not designed to assess weight status during pregnancy.
- Ethnicity, age, body frame, and individual health factors can affect how a given BMI value should be interpreted.
Health Risks Associated With Higher BMI
Population-level research associates higher BMI ranges with an increased likelihood of certain health considerations, such as elevated blood pressure and blood sugar. These are associations observed across large groups of people, not certainties for any one individual, and BMI alone does not diagnose any condition. A healthcare professional can help interpret your BMI alongside your personal and family health history.
Health Considerations for Lower BMI
A BMI below the typical healthy-weight range can sometimes be associated with insufficient energy or nutrient intake, and in some cases with an underlying health condition. If your BMI is low, especially alongside unintended weight loss, fatigue, or other symptoms, it is worth discussing with a qualified healthcare professional.
BMI During Pregnancy
BMI is not an appropriate tool for assessing weight status during pregnancy. Healthy weight gain during pregnancy varies by individual and is best assessed by a midwife, obstetrician, or other qualified healthcare provider using pregnancy-specific guidance.
BMI vs Body Fat Percentage
BMI is calculated only from height and weight, while body fat percentage estimates the proportion of your body that is made up of fat, typically using methods such as skinfold calipers, bioelectrical impedance, or DEXA scanning. Two people with an identical BMI can have very different body fat percentages depending on muscle mass, bone density, and body composition. Body fat percentage generally gives a more direct picture of composition, while BMI remains a faster, more accessible screening tool.
Frequently Asked Questions
BMI, or Body Mass Index, is a screening number calculated from your height and weight. It is used as a quick, general indicator of whether your weight falls within a typical range for your height.
Enter your height and weight into the calculator above in either metric (cm, kg) or imperial (ft, in, lb) units and select "Calculate BMI." The calculator applies the standard formula instantly in your browser.
For most adults, a BMI between 18.5 and 24.9 falls within the commonly used healthy-weight range. This is a general screening range rather than an individual target.
The commonly used adult reference range is 18.5–24.9. Below 18.5 is categorized as underweight, 25.0–29.9 as overweight, and 30.0 and above as obesity for screening purposes.
Yes. The standard BMI formula and adult BMI categories are identical for men and women. Gender is used on this page only for contextual messaging, never to change the calculation.
BMI can be less informative for athletes and very muscular people, because it cannot distinguish muscle weight from fat weight. A muscular athlete may show a higher BMI while having relatively low body fat.
No. BMI is calculated only from height and weight and does not directly measure body fat. Methods such as skinfold measurements, bioelectrical impedance, or DEXA scans are used to estimate body fat percentage.
Divide your weight in kilograms by your height in metres squared: BMI = kg ÷ (m × m).
Multiply your weight in pounds by 703, then divide by your height in inches squared: BMI = (lb × 703) ÷ (in × in).
For children and teenagers, BMI is interpreted using age- and sex-specific percentiles rather than the fixed adult categories, because growth patterns vary significantly with age and sex. A pediatrician or an official growth chart can provide a proper percentile assessment.
No. BMI is not designed to assess weight status during pregnancy. A midwife, obstetrician, or other qualified healthcare provider can advise on healthy weight gain using pregnancy-specific guidance.
A BMI above the typical range is a prompt to look at your overall health picture. Consider speaking with a qualified healthcare professional, who can look at your BMI alongside other factors such as waist circumference, activity level, and personal health history.
A BMI below the typical range, especially with unintended weight loss or other symptoms, is worth discussing with a qualified healthcare professional to check for possible underlying causes.
Yes. Because BMI is calculated directly from your current weight and height, it changes whenever your weight changes. Many people recheck their BMI periodically to see the general direction of change over time.
No. BMI is only one screening measure. Overall health depends on many factors, including diet, physical activity, sleep, body composition, family history, and existing medical conditions. Use BMI as a starting point, not a complete health assessment.