General BMI screening tool
BMI Calculator
Choose the correct age group, then calculate Body Mass Index from height and weight. Adults receive standard BMI categories; children and teens use age- and sex-specific BMI-for-age percentiles.
Your result
A clear result without the clutter.
Enter only your height and weight. Your measurements are calculated locally in this browser and are not added to the page URL.
23.4
kg/m²
Healthy weight
Your BMI is within the standard healthy-weight range for adults.
Your positionAdult BMI scale
UnderweightHealthyOverweightObesity
Standard healthy-weight range
53.5–72.0 kg
Calculated from BMI 18.5 to below 25 for your height.
Current position
Within range
Your current weight is within this calculated range.
Weight-change scenarios
Mathematical examples5% lower weightBMI 22.266.5 kg
Current weightBMI 23.470.0 kg
5% higher weightBMI 24.673.5 kg
These scenarios show how BMI changes mathematically. They are not personal targets, recommendations, or predictions.
BMI-for-age result
One calculator, one consistent experience.
Enter age, reference sex, height, and weight. The BMI-for-age estimate is calculated locally without loading an outside website.
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kg/m²
Approx. percentile
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Calculate a result
BMI-for-age uses age- and sex-specific reference values.
BMI-for-age positionPercentile screening scale
<5th5th–<85th85th–<95th95th+
Profile—Age and reference sex
Percentile result—Estimated BMI-for-age position
95th-percentile BMI—Age- and sex-specific reference
How to read this result
The category is a screening estimate and should be considered with growth history and specialist guidance.
How to useChoose the appropriate age group, enter the required measurements, and review the result using the correct interpretation method.
Select age groupChoose Adult 20+ or Child & teen 2–19.
Select unitsChoose Metric or US units in the selected calculator.
Enter measurementsAdd height and weight; child mode also needs age and sex.
CalculateReview BMI with the correct age-specific category method.
Use the resultPreview, print, or save the age-appropriate report; discuss concerns with a qualified healthcare provider.
What your result meansBMI compares weight with height. Adults use fixed BMI ranges, while children and teenagers use age- and sex-specific BMI-for-age percentiles.
Adult categories · age 20+
Standard fixed ranges used for adult screening.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 to below 25.0 |
| Overweight | 25.0 to below 30.0 |
| Obesity | 30.0 or higher |
Child and teen categories · ages 2–19
Percentile categories compare BMI with children of the same age and sex.
| Category | BMI-for-age percentile |
|---|---|
| Underweight | Below 5th |
| Healthy weight | 5th to below 85th |
| Overweight | 85th to below 95th |
| Obesity | 95th or higher |
Additional Asian adult health-risk guidance
Some Asian public-health guidance uses BMI 23.0 and 27.5 as additional adult risk action points. This applies to adult interpretation only and does not replace child and teen BMI-for-age percentiles.
FormulaThe BMI equation is the same in both unit systems. The interpretation method changes according to age.
Metric
BMI = weight (kg) ÷ height² (m²)
US units
BMI = 703 × weight (lb) ÷ height² (in²)
Worked example: For 70 kg and 1.75 m, BMI = 70 ÷ 1.75² = 22.9. Adults use the standard BMI ranges; ages 2–19 require BMI-for-age percentile interpretation.
Tips and common mistakesConsistent measurements and correct unit entry matter more than adding extra fields. These checks improve calculation quality without complicating the calculator.
Measurement tips
- Measure height without shoes and stand upright.
- Use a recently calibrated scale where possible.
- Compare results under similar measurement conditions.
- Retake measurements when a result appears unexpected.
- Review trends rather than reacting to one isolated result.
- Interpret BMI together with other health information.
Common mistakes
- Entering centimetres as metres.
- Entering decimal feet instead of feet and inches.
- Mixing pounds with the metric formula.
- Rounding height before the calculation.
- Applying adult categories to children or teenagers.
- Treating BMI as a diagnosis or direct body-fat measurement.
- Calling the calculated range an “ideal weight.”
Frequently asked questionsCommon questions about BMI calculation, age-specific interpretation, accuracy, and limitations.
BMI, or Body Mass Index, compares weight with the square of height. The formula is the same across age groups, but the category method differs for adults and for children and teens.
Adults use fixed BMI ranges, including 18.5 to below 25.0 for the standard healthy-weight category. Children and teens use age- and sex-specific BMI-for-age percentiles.
No. BMI is a screening measure and should be interpreted with other information when assessing an individual’s health.
The BMI formula is the same. Adult categories do not use sex, while child and teen percentiles are sex-specific because growth patterns differ.
BMI may overestimate body fat in some people with greater muscular mass. Additional body-composition and health information may be more useful.
Yes. Select Child & teen for ages 2 through 19. That mode interprets BMI using age- and sex-specific BMI-for-age percentiles. Children under age 2 need different growth standards.
Small differences usually come from rounding, unit conversion, or the number of decimal places displayed.
No. BMI does not measure fitness, body-fat distribution, blood pressure, blood glucose, or many other individual health factors.