BMI Calculator

Modify the values and click the Calculate button to use

US Units
Metric Units
ages: 2 - 120
feet inches
pounds

Result

BMI = 23 kg/m2
(Normal)
23.0
BMI Score
BMI = 23
Healthy BMI range
18.5 kg/m2 - 25 kg/m2
Healthy weight for the height
128.9 lbs - 174.2 lbs
BMI Prime
0.92
Ponderal Index
12.9 kg/m3

BMI Introduction

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 Table for Adults

This is the World Health Organization's (WHO) recommended body weight based on BMI values for adults. It is used for both men and women, age 20 or older.

Classification BMI range - kg/m²
Severe Thinness < 16
Moderate Thinness 16 - 17
Mild Thinness 17 - 18.5
Normal 18.5 - 25
Overweight 25 - 30
Obese Class I 30 - 35
Obese Class II 35 - 40
Obese Class III > 40

BMI Formula

Below are the equations used for calculating BMI in the International System of Units (SI) and the US customary system (USC) using a 5'10", 160-pound individual as an example:

USC Units:
BMI = 703 × mass (lbs) / height² (in) = 703 × 160 / 70² = 23.0
SI, Metric Units:
BMI = mass (kg) / height² (m) = 72.57 / 1.778² = 23.0

BMI Prime

BMI prime is the ratio of a person's measured BMI to the upper limit of BMI that is considered "normal," by institutions such as the WHO and the CDC. Though it may differ in some countries, such as those in Asia, this upper limit, which will be referred to as BMIupper is 25 kg/m².

BMI prime = BMI / 25
Classification BMI BMI Prime
Severe Thinness < 16 < 0.64
Moderate Thinness 16 - 17 0.64 - 0.68
Mild Thinness 17 - 18.5 0.68 - 0.74
Normal 18.5 - 25 0.74 - 1
Overweight 25 - 30 1 - 1.2
Obese Class I 30 - 35 1.2 - 1.4
Obese Class II 35 - 40 1.4 - 1.6
Obese Class III > 40 > 1.6

Ponderal Index

The Ponderal Index (PI) is similar to BMI in that it measures the leanness or corpulence of a person based on their height and weight. The main difference between the PI and BMI is the cubing rather than squaring of the height in the formula.

USC Units:
PI = height (in) / ∛mass (lbs) = 70 / ∛160 = 12.9
SI, Metric Units:
PI = mass (kg) / height³ (m) = 72.57 / 1.778³ = 12.9

Risks Associated with Being Overweight

  • High blood pressure
  • Higher levels of LDL cholesterol
  • Type II diabetes
  • Coronary heart disease
  • Stroke
  • Gallbladder disease
  • Osteoarthritis
  • Sleep apnea and breathing problems
  • Certain cancers
  • Low quality of life
  • Mental illnesses
  • Body pains and difficulty with physical functions
  • Increased risk of mortality

Risks Associated with Being Underweight

  • Malnutrition, vitamin deficiencies, anemia
  • Osteoporosis
  • Decrease in immune function
  • Growth and development issues
  • Reproductive issues for women
  • Potential complications from surgery
  • Increased risk of mortality

Limitations of BMI

Although BMI is a widely used and useful indicator of healthy body weight, it does have its limitations. BMI is only an estimate that cannot take body composition into account. Due to a wide variety of body types as well as distribution of muscle, bone mass, and fat, BMI should be considered along with other measurements rather than being used as the sole method for determining a person's healthy body weight.