Your measurements
Ages 2–19 use sex-specific growth charts and completed months of age. From age 20, age and sex do not change the adult BMI category. Not for children under 2.
Results update automatically as you type.
Healthy weight
Your BMI falls between 18.5 and less than 25.
Your BMI on the scale
BMI 22.9 — Healthy weight. Your BMI falls between 18.5 and less than 25.
- Underweight
- Healthy weight
- Overweight
- Obesity
The scale shows BMI 10–45. Category boundaries use the unrounded result.
Adult BMI categories (ages 20+)
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 to below 25 |
| Overweight | 25 to below 30 |
| Obesity | 30 or higher |
| Category | BMI-for-age percentile |
|---|---|
| Underweight | Below 5th |
| Healthy weight | 5th to below 85th |
| Overweight | 85th to below 95th |
| Obesity | 95th or higher |
| Severe obesity | BMI ≥120% of the 95th-percentile BMI, or BMI ≥35 kg/m² |
The displayed BMI is rounded to one decimal place. The category uses the unrounded value.
What body mass index measures
Body mass index (BMI) expresses weight relative to height. It is used to screen weight status and to support decisions about further health assessment. It is not a body fat percentage or a diagnosis.
How to calculate BMI
Use kilograms and meters.
BMI = weight (kg) ÷ height (m)²
The factor 10,000 converts squared centimeters to squared meters.
BMI = 10,000 × weight (kg) ÷ height (cm)²
Convert feet to total inches first: feet × 12 + inches.
BMI ≈ 703 × weight (lb) ÷ height (in)²
The US factor 703 is rounded. This calculator converts pounds and inches to metric units before calculating, so a hand calculation using 703 may differ slightly.
Worked adult example: 70 kg and 175 cm
- Convert height: 175 ÷ 100 = 1.75 m .
- Square the height: 1.75 × 1.75 = 3.0625 m² .
- Divide weight by squared height: 70 ÷ 3.0625 = 22.857… kg/m² .
The displayed result is 22.9, within the adult healthy weight category. Keep the full value until the final step: rounding early can affect a result near a category boundary.
How height and weight affect the result
At a fixed height, BMI rises in direct proportion to weight. At a fixed weight, a taller person has a lower BMI because height is squared in the denominator.
View chart values
| Weight | 160 cm | 175 cm | 190 cm |
|---|---|---|---|
| 40 kg | 15.6 | 13.1 | 11.1 |
| 60 kg | 23.4 | 19.6 | 16.6 |
| 70 kg | 27.3 | 22.9 | 19.4 |
| 80 kg | 31.2 | 26.1 | 22.2 |
| 100 kg | 39.1 | 32.7 | 27.7 |
| 120 kg | 46.9 | 39.2 | 33.2 |
Why BMI is used — and its limits
Height and weight are easy to measure, making BMI a quick, inexpensive screening tool. Clinicians use it alongside medical history, physical examination and laboratory results, rather than as a complete assessment of health.
It cannot separate muscle from fat or show where fat is stored. A muscular person can have a high BMI without excess body fat. A result in the healthy weight range does not, by itself, establish that a person is healthy.
The adult categories apply from age 20. For ages 2–19, this calculator uses CDC sex-specific BMI-for-age percentiles. The scale is a reference, not a personalized target weight or treatment recommendation.
How the child and teen result is calculated
The BMI formula stays the same. The interpretation changes: the result is compared with the CDC reference for the child's sex and age in completed months. For example, age 9 years 6 months uses the 114.5-month reference row, representing ages 114 to less than 115 months.
A percentile describes position in that reference population. The 75th percentile means the BMI equals or exceeds approximately 75% of reference values for the same age and sex. It does not mean 75% body fat.
Below or at the 95th-percentile BMI, the calculator uses the CDC LMS method. Above it, the CDC 2022 extended method uses the age- and sex-specific sigma parameter. Values are approximate; categories are assigned before rounding. A percentile below 0.1 or above 99.9 is displayed as a range.
z = ((BMI ÷ M)^L − 1) ÷ (L × S)
For L = 0: z = ln(BMI ÷ M) ÷ S. Percentile = 100 × Φ(z). L, M and S come from the CDC reference table; Φ is the standard normal cumulative distribution function.
Above P95: percentile = 90 + 10 × Φ((BMI − P95) ÷ sigma)
P95 is the 95th-percentile BMI for the selected age and sex.
Child results are a screening aid. A pediatric clinician can assess growth over time; the result should not be used alone to set a child's target weight.
Child references: CDC child and teen categories; 2022 extended BMI-for-age method and data.
Using this calculator
Enter age in years and months, select sex, then enter height and weight in Metric or US units. Results, the scale marker and the highlighted category update as you type. Switching units converts the current measurements. For a consistent comparison over time, use the same measurement method.
Sources: CDC — BMI formulas and interpretation; Adult BMI categories; About BMI.