TOOLEAD

Home›Health›BMI Calculator

Free BMI Calculator

cm
kg

Enter your height and weight to see your BMI

What Is BMI?

Body Mass Index (BMI) is a widely used screening number that relates your weight to your height. It offers a quick way to flag whether an adult's weight sits in a range linked to lower health risk. This free BMI calculator returns the value in seconds from just your height and weight.

The BMI Formula

Every Body Mass Index calculator uses one ratio:

BMI=weight (kg)height (m)2\text{BMI} = \dfrac{\text{weight (kg)}}{\text{height (m)}^2}

Working in pounds and inches instead? Multiply by 703:

BMI=703×weight (lb)height (in)2\text{BMI} = 703 \times \dfrac{\text{weight (lb)}}{\text{height (in)}^2}

Healthy BMI Range for Adults

CategoryBMI
Underweightbelow 18.5
Normal weight18.5 – 24.9
Overweight25.0 – 29.9
Obesity30.0 and above

What BMI Does and Doesn't Tell You

BMI is a population-level screen, not a diagnosis. It can't separate muscle from fat, so very muscular people may land in the "overweight" band without excess body fat, and it can understate risk in older adults who've lost muscle mass. Read the number alongside waist measurement and overall lifestyle, and talk to a clinician before acting on it.

FAQ

1. How do I calculate BMI?

Divide your weight in kilograms by the square of your height in meters: weight ÷ (height × height). In imperial units, multiply 703 × weight in lb ÷ (height in inches)².

2. What is a healthy BMI range?

For most adults, a BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above falls in the obesity range.

3. Is BMI accurate for athletes?

Not always. BMI can't tell muscle from fat, so muscular people may register as overweight despite low body fat. Body-fat percentage or waist-to-hip ratio gives a clearer picture in those cases.

4. Does BMI work for children?

Children and teens use percentile-based BMI-for-age charts rather than the adult cut-offs, so the same number means different things at different ages.

5. Is BMI a medical diagnosis?

No. BMI is a screening tool that flags possible weight-related risk; a clinician combines it with other measurements and history before drawing any conclusion.

How to Use

  1. Enter your height in centimeters (cm) or feet and inches for imperial.
  2. Enter your body weight in kilograms (kg) or pounds (lbs).
  3. Click calculate to see your BMI score and weight category instantly.