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BMI Calculator

BMI
24.2
Average adult weight range

Formula

BMI = weight(kg) ÷ height(m)²

BMI (Body Mass Index) is calculated by dividing your weight in kilograms by the square of your height in meters. BMI categories: Under 18.5 = Underweight, 18.5-24.9 = Normal, 25-29.9 = Overweight, 30+ = Obese.

How to use

  1. Enter your Weight in kilograms.
  2. Enter your Height in centimeters.
  3. Read your BMI and compare it to the category ranges.

Example

A person weighing 70 kg at 170 cm has a BMI of 24.2 (70 ÷ 1.70²), which falls in the normal/healthy range.

Frequently Asked Questions

What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered normal/healthy weight by the WHO. However, BMI doesn't account for muscle mass, age, sex, or body composition.
Is BMI accurate for athletes?
No. BMI can be misleading for muscular people because muscle is denser than fat, so a lean, muscular person carries more weight for their height. A bodybuilder may have an 'overweight' BMI despite low body fat.
How do I convert lbs to kg for BMI?
Divide your weight in pounds by 2.205. For example, 154 lbs ÷ 2.205 = 70 kg.
What are the BMI categories?
Underweight: below 18.5. Normal: 18.5-24.9. Overweight: 25-29.9. Obese Class I: 30-34.9. Obese Class II: 35-39.9. Obese Class III: 40+.
Does BMI work the same for men and women?
The BMI formula and the standard category cutoffs are identical for adult men and women, since they're based only on height and weight. However, women naturally carry a higher percentage of body fat than men at the same BMI, so the number alone tells you less about body composition. For this reason BMI is best used as a general screening tool rather than a precise measure of health for any individual.
Is BMI used for children the same way as adults?
No. For children and teens aged 2 to 19, the same weight-to-height ratio is calculated but then compared against age- and sex-specific growth percentile charts rather than the fixed adult categories. A child's healthy range shifts as they grow, so a BMI of 19 could be normal for one age and overweight for another. Pediatricians use these percentile charts instead of the adult cutoffs shown here.

What BMI measures

Body Mass Index is your weight in kilograms divided by the square of your height in metres (kg/m²). It was designed in the 19th century as a quick population-level measure, and today it is used as a fast screening tool: under 18.5 is classed as underweight, 18.5–24.9 as normal, 25–29.9 as overweight, and 30 or above as obese.

Because it needs only height and weight, BMI is easy to calculate and compare — which is exactly why it became standard despite its bluntness.

What BMI does not tell you

BMI does not distinguish muscle from fat, so a lean, muscular athlete can register as "overweight" while carrying very little fat. It also says nothing about where fat is stored, which matters for health risk, and it is less reliable for the elderly, for very short or very tall people, and across different ethnic groups.

Treat the number as a starting point, not a diagnosis. Waist circumference, body-fat percentage, and a conversation with a doctor give a fuller picture. The value pages below show the BMI and category for specific height-and-weight pairs.

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