BMI Calculator







Advanced BMI Calculator


BMI Calculator










Underweight (<18.5)
Normal (18.5-24.9)
Overweight (25-29.9)
Obese (30+)
Your BMI
0
Normal

About Your BMI

BMI is a measurement of body fat based on height and weight.
It provides a reliable indicator of body fatness for most people.

The Body Mass Index (BMI) Calculator can be used to calculate BMI value and corresponding weight status while taking age into consideration. Use the “Metric Units” tab for the International System of Units or the “Other Units” tab to convert units into either US or metric units. Note that the calculator also computes the Ponderal Index in addition to BMI, both of which are discussed below in detail.

BMI Introduction

BMI (Body Mass Index) is a measurement of a person’s leanness or corpulence based on their height and weight, intended to quantify tissue mass. It serves as a general indicator of whether a person has a healthy body weight for their height. The calculated BMI value categorizes individuals as underweight, normal weight, overweight, or obese. These ranges vary based on factors like region and age, and may include subcategories. While imperfect, BMI is a useful screening tool to determine if additional testing or lifestyle changes are needed.

BMI Table for Adults (WHO Classification)

This is the World Health Organization’s recommended body weight classification for adults (20+ years):

Classification BMI Range (kg/m²)
Severe Thinness < 16
Moderate Thinness 16 – 17
Mild Thinness 17 – 18.5
Normal weight 18.5 – 25
Overweight 25 – 30
Obese Class I 30 – 35
Obese Class II 35 – 40
Obese Class III > 40

 

BMI Chart for Adults

[Visual graph showing BMI categories with dashed lines indicating subdivisions]

BMI Table for Children/Teens (CDC Classification, Ages 2-20)

Category Percentile Range
Underweight <5%
Healthy weight 5% – 85%
At risk of overweight 85% – 95%
Overweight >95%

BMI Chart for Children/Teens

[Growth charts showing BMI-for-age percentiles for boys and girls]

Health Risks

Risks Associated with Being Overweight (CDC)

  • High blood pressure

  • Abnormal cholesterol (high LDL, low HDL, high triglycerides)

  • Type 2 diabetes

  • Coronary heart disease

  • Stroke

  • Gallbladder disease

  • Osteoarthritis

  • Sleep apnea

  • Certain cancers (endometrial, breast, colon, etc.)

  • Reduced quality of life

  • Mental health disorders

  • Increased mortality risk

Risks Associated with Being Underweight

  • Malnutrition and vitamin deficiencies

  • Osteoporosis

  • Weakened immune system

  • Developmental issues (in children/teens)

  • Reproductive problems in women

  • Surgical complications

  • Increased mortality risk

BMI Limitations

While useful, BMI has limitations:

  • Doesn’t distinguish between muscle and fat

  • Affected by age, sex, ethnicity, and activity level

  • Less accurate for:

    • Athletes (may show false overweight)

    • Elderly (may underestimate fat)

    • Children (must use age/sex percentiles)

For 90-95% of the population, BMI correlates well with body fat when used with other measures.

BMI Calculations

Standard Formulas
Metric Units:

BMI = mass (kg) / height² (m)

US Units:

BMI = 703 × mass (lbs) / height² (in)

Example (5’10”, 160 lbs):

BMI = 703 × 160 / 70² = 23.0

BMI Prime

Ratio of actual BMI to upper normal limit (25 kg/m²):

BMI Prime = BMI / 25

Classification BMI Prime
Underweight < 0.74
Normal 0.74 – 1
Overweight > 1
Obese > 1.2
Ponderal Index

Alternative to BMI that cubes height instead of squaring it:

Metric:

PI = mass (kg) / height³ (m)

US:

PI = height (in) / ∛mass (lbs) Example (5’10”, 160 lbs): PI = 70 / ∛160 ≈ 12.9  

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