BMI turns height and weight into a standardized screening ratio: weight in kilograms divided by height in meters squared, or the equivalent imperial formula. This BMI Calculator applies that arithmetic so you can see the result and the commonly used adult screening category without working through the equation manually.
The number needs context. BMI does not directly measure body fat, muscle mass, bone density, metabolic health, or fat distribution, and ordinary adult cut points are not designed for children, teenagers, or pregnancy. It is most useful as a broad screening measure or discussion point, not as a diagnosis or a stand-alone reason to make major health or weight-change decisions.
How to use this tool
How is BMI calculated?
Metric: BMI = weight (kg) ÷ height² (m²). Imperial: BMI = 703 × weight (lb) ÷ height² (in²).
How to use BMI Calculator
- Enter your current height and weight using one consistent measurement system.
- Check that the height and weight units match the labels shown by the calculator.
- Calculate BMI and read the result together with the adult screening category shown on the page.
- Treat the category as a screening reference rather than a diagnosis.
- For children, teenagers, pregnancy, or medical decisions, use population-appropriate clinical guidance instead of ordinary adult BMI cut points.
What does a BMI result mean?
For most adults, standard screening cut points are under 18.5, 18.5–24.9, 25.0–29.9, and 30.0+. Clinical interpretation can differ by individual circumstances and population. BMI-for-age percentiles are used for children and teenagers rather than adult cut points.
Methodology reference
Adult BMI categories and interpretation should be treated as screening guidance. Reference: CDC – Adult BMI Categories.
Examples
Metric BMI example
70 ÷ (1.70 × 1.70) ≈ 24.2, which falls in the commonly used healthy-weight screening range for adults.
Higher adult BMI example
82 ÷ (1.65 × 1.65) ≈ 30.1. This crosses the standard adult obesity screening threshold, but BMI alone is not a diagnosis.
Lower adult BMI example
58 ÷ (1.80 × 1.80) ≈ 17.9, below the standard adult healthy-weight range.
Imperial example
703 × 175 ÷ 70² ≈ 25.1, just above the standard healthy-weight screening range.
Common use cases
- General adult weight screening
- Preparing for a wellness discussion
- Tracking BMI over time
- Fitness assessments
- Public-health education
Frequently asked questions
How is BMI calculated?
For metric inputs, BMI is weight in kilograms divided by height in meters squared. For imperial inputs, the equivalent formula is 703 × weight in pounds ÷ height in inches squared.
What do adult BMI categories mean?
Adult BMI categories are screening ranges, not diagnoses. A BMI result should be interpreted with other health information because the calculation does not directly measure body fat, muscle mass, fat distribution, or metabolic health.
Can a muscular person have a high BMI?
Yes. BMI uses only height and weight, so substantial muscle mass can raise BMI even when body-fat levels are not high.
Should children or teenagers use adult BMI categories?
No. Children and teenagers are assessed with age- and sex-specific BMI-for-age methods rather than ordinary adult cut points.
Is BMI suitable during pregnancy?
Ordinary adult BMI interpretation is not designed to assess pregnancy-related weight changes. Pregnancy should be interpreted with appropriate prenatal guidance.
Why can two BMI calculators differ slightly?
Differences usually come from unit conversion, rounding, or the values entered. The underlying adult BMI formula itself is straightforward.