BMI Calculator: What Your Number Actually Means

Body Mass Index (BMI) is one of the most widely used health screening tools in the world. Our free BMI calculator gives you your number instantly, plus the context to understand what it actually means.

What is BMI?

BMI is a calculation using height and weight to estimate whether you are at a healthy body weight. Formula: BMI = weight (kg) divided by height (m) squared.

Example: 70kg and 1.75m tall. BMI = 70 divided by (1.75 x 1.75) = 70 divided by 3.0625 = 22.9.

How to use the BMI calculator

1. Select Metric (kg/cm) or Imperial (lb/ft+in)
2. Enter your weight
3. Enter your height
4. Click Calculate BMI

You will see your BMI number, category, visual scale, and healthy weight range for your height.

BMI categories

• Below 18.5: Underweight
• 18.5 to 24.9: Healthy weight
• 25.0 to 29.9: Overweight
• 30.0 and above: Obese

Real examples

Person A: Height 170cm, Weight 65kg. BMI 22.5 (Healthy weight). Healthy range for this height: 53 to 72kg.

Person B: Height 180cm, Weight 95kg. BMI 29.3 (Overweight). To reach healthy weight would need to be under 81kg.

Person C: Height 165cm, Weight 50kg. BMI 18.4 (Underweight). Healthy range: 50 to 68kg.

Important limitations of BMI

• BMI does not measure body fat directly. A muscular athlete may have high BMI but very low body fat.
• It does not account for age. Older adults naturally lose muscle mass.
• It does not account for where you carry weight. Abdominal fat carries more health risk.
• It may vary by ethnicity. Health risks associated with BMI differ between ethnic groups.

When to see a healthcare professional

If your BMI falls outside the healthy range, speak with a doctor or registered dietitian. They can assess health more comprehensively using body composition, blood work and blood pressure.

Frequently asked questions

Is BMI accurate? BMI is a population-level screening tool, not a precise individual diagnostic measure. It is useful as a starting point alongside other health indicators.

What is a healthy BMI for women vs men? The same BMI categories apply to both, though women naturally carry higher body fat percentage at the same BMI.

Can you be healthy with a BMI over 25? Yes. Many factors contribute to health. A physically active non-smoking person with normal blood pressure and BMI slightly above 25 may present very little health risk.

Is there a BMI calculator for children? BMI for children uses age and sex-specific growth charts. Standard adult BMI calculators are not appropriate for children under 18.

What BMI is considered obese? A BMI of 30 or above is classified as obese. A BMI of 40 or above is classified as severely obese. Both categories are associated with increased health risks.