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BMI Calculator

Calculate your Body Mass Index (BMI) to determine if your weight is in a healthy range for your height.

How to Use

  1. 1

    Select your unit system: Metric (kg, cm) or Imperial (lbs, inches)

  2. 2

    Enter your biological sex and whether you have an athletic body type

  3. 3

    Input your weight

  4. 4

    Input your height

  5. 5

    View your BMI score, category, health risk, healthy weight range, and BMI Prime

Examples

Good Examples

Average adult (metric)

70 kg ÷ (1.70 m)² = 24.2 (Normal weight)

Average adult (imperial)

154 lbs ÷ (71 in)² × 703 = 21.5 (Normal weight)

Bad Examples

Using BMI for athletes

A bodybuilder with 80 kg muscle at 170 cm has BMI 27.7 "overweight" despite low body fat

Mixing metric and imperial

Entering weight in kg but height in inches gives a meaningless result

Common Mistakes

  • Using BMI as the sole health indicator — it doesn't distinguish between muscle and fat mass
  • Mixing unit systems — use either metric (kg, cm) or imperial (lbs, inches), not a mix
  • Applying adult BMI to children — children need age-specific BMI percentile charts
  • Ignoring body frame size — people with larger frames naturally weigh more
  • Forgetting that BMI doesn't account for fat distribution — where fat is stored matters for health

Frequently Asked Questions

Q

Is BMI accurate for everyone?

BMI is a useful screening tool but not a perfect measure. It does not distinguish between muscle and fat mass, so athletes and muscular individuals may have a high BMI despite low body fat. For a more complete picture, combine BMI with other measurements like waist circumference.

Q

What is a healthy BMI?

According to the WHO, a BMI between 18.5 and 24.9 is considered normal weight for adults. A BMI below 18.5 is underweight, and 25-29.9 is overweight. Obesity starts at 30.

Q

What is BMI Prime?

BMI Prime is your BMI divided by 25 (the upper limit of normal BMI). A BMI Prime of 1.0 means you are at the upper boundary of normal weight. Below 1.0 is underweight or normal; above 1.0 is overweight or obese.

Q

Does BMI differ for men and women?

The BMI formula is the same for men and women. However, women typically have more body fat than men at the same BMI. Some health professionals adjust BMI interpretation based on sex.

Q

Can children use this BMI calculator?

No — this calculator is for adults (18+). Children and teens need age- and sex-specific BMI percentile charts. Consult a pediatrician for children's BMI assessment.