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Bmi Calculator

Body Mass Index (BMI) is a quick screening number that compares your weight to your height. It is used worldwide by clinicians, insurers and fitness coaches as a rough indicator of whether someone is underweight, in a healthy range, overweight, or obese. Our free BMI calculator handles both metric (kg/m) and imperial (lb/ft-in) units, shows the WHO category your result lands in, and tells you the weight gain or loss needed to reach the healthy range.

BMI Scale

Underweight
<18.5 Normal
18.5–24.9 Overweight
25–29.9 Obese
≥30

Your BMI

BMI
Category
Healthy weight range
Weight to lose/gain

Enter height and weight above

BMI Categories (WHO Standard)

Underweight Below 18.5
Normal weight 18.5 – 24.9
Overweight 25.0 – 29.9
Obese (Class I) 30.0 – 34.9
Obese (Class II) 35.0 – 39.9
Obese (Class III) 40.0 and above
Note: BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, age, or ethnicity. Consult a healthcare professional for a complete health assessment.
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About the BMI Calculator

Body Mass Index (BMI) is a quick screening number that compares your weight to your height. It is used worldwide by clinicians, insurers and fitness coaches as a rough indicator of whether someone is underweight, in a healthy range, overweight, or obese. Our free BMI calculator handles both metric (kg/m) and imperial (lb/ft-in) units, shows the WHO category your result lands in, and tells you the weight gain or loss needed to reach the healthy range.

How to use it

  1. Select your preferred unit system — metric (kg/cm) or imperial (lb/ft).
  2. Enter your weight and height into the labeled fields.
  3. Your BMI and WHO weight category appear instantly as you type.
  4. Read the healthy weight range and the weight change needed to reach it.
  5. Use the metric/imperial toggle to switch between unit systems.

Formula & methodology

BMI = weight (kg) / [height (m)]². In imperial: BMI = [weight (lb) / height (in)²] × 703.

Common use cases

  • Checking your weight category before a doctor visit or health screening
  • Tracking BMI changes during a weight loss or muscle gain program
  • Assessing health risk factors for insurance or wellness programs
  • Calculating BMI for family members including children and teenagers
  • Understanding the weight range needed for a specific BMI target

Frequently asked questions

A BMI between 18.5 and 24.9 is considered healthy by WHO standards. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese. BMI is a screening tool, not a diagnostic — athletes with high muscle mass may have a high BMI despite low body fat.
BMI is a useful population-level screening tool but has limitations for individuals. It does not account for muscle mass, bone density, body composition, or fat distribution. Athletes, older adults, and pregnant women may get less accurate results. For a full health assessment, consult your doctor.
The formula is different but the result is identical. Metric uses kilograms and meters (BMI = kg/m²). Imperial uses pounds and inches (BMI = [lb/in²] × 703). Our calculator handles both automatically — just pick your preferred units.

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