BMI (Body Mass Index) is a simple estimate of body size based on weight and height. It does not directly measure body fat.

What is a healthy BMI range?

For many adults, a BMI from 18.5 to 24.9 is considered a healthy range. Individual health can vary.

Why do athletes sometimes have a high BMI?

BMI does not distinguish muscle from fat. People with more muscle may have a higher BMI even when healthy.

Home › BMI Calculator

BMI Calculator

Calculate your Body Mass Index (BMI) and see the category plus an estimated healthy weight range.

Privacy: All calculations run locally in your browser. We do not send your inputs to any server.

Tip: your entries are never placed in the page URL.

Export summary downloads a .txt file created in your browser. Copy page link copies only the page address (no inputs).

About BMI

Body Mass Index (BMI) is a number based on your height and weight. It’s commonly used to describe weight status in adults and to provide a quick, consistent way to compare results over time.

How BMI is calculated

BMI is computed as weight divided by height squared. In metric units: BMI = kg / m². In U.S. units, the formula uses a 703 multiplier to account for inches and pounds.

Adult BMI categories

Underweight: below 18.5
Healthy range: 18.5 to 24.9
Overweight: 25.0 to 29.9
Obesity: 30.0 and above

These categories are widely used for adults aged 20 and over. Your result also shows an estimated healthy weight range for your height (based on BMI 18.5–24.9).

Children and teens

For ages 2–19, the same BMI number can mean different things at different ages. If you enter Age (under 20) and Sex, this calculator estimates a BMI‑for‑age percentile and updates the scale using percentile cut‑offs.

How the percentile is computed (LMS method): the CDC growth chart provides three age‑ and sex‑specific parameters (L, M, S). We convert your BMI (X) into a z‑score, then into a percentile.

If L ≠ 0: z = ((X/M)^L − 1) / (L·S)
If L = 0: z = ln(X/M) / S
Percentile = Φ(z)·100, where Φ is the standard normal CDF

Percentile categories (ages 2–19): Underweight < 5th, Healthy weight 5th–<85th, Overweight 85th–<95th, Obesity ≥ 95th. On the gauge, the color boundaries are the BMI values at the 5th, 85th and 95th percentiles for your chosen age and sex.

If you leave age or sex empty, the calculator uses the standard adult category thresholds.

Tips for accurate inputs

Measure height without shoes and stand straight.
Use a recent weight measurement and similar conditions (time of day, clothing).
If you’re using imperial units, enter both feet and inches for best accuracy.