Standard BMI Calculator
Calculate your Body Mass Index using the standard WHO formula. Get instant results with health category and personalized recommendations.
BMI Introduction
BMI is a measurement of a person's leanness or corpulence based on their height and weight, and is intended to quantify tissue mass. It is widely used as a general indicator of whether a person has a healthy body weight for their height.
Specifically, the value obtained from the calculation of BMI is used to categorize whether a person is underweight, normal weight, overweight, or obese depending on what range the value falls between. These ranges of BMI vary based on factors such as region and age, and are sometimes further divided into subcategories such as severely underweight or very severely obese.
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 Weight | 18.5 - 25 |
| Overweight | 25 - 30 |
| Obesity Class I | 30 - 35 |
| Obesity Class II | 35 - 40 |
| Obesity Class III | > 40 |
BMI Table for Children and Teens, Age 2-20
The Centers for Disease Control and Prevention (CDC) recommends BMI categorization for children and teens between age 2 and 20.
| Category | Percentile Range |
|---|---|
| Underweight | < 5% |
| Healthy Weight | 5% - 85% |
| At Risk of Overweight | 85% - 95% |
| Overweight | > 95% |
Risks Associated with Being Overweight
Being overweight increases the risk of a number of serious diseases and health conditions. Below is a list of said risks, according to the Centers for Disease Control and Prevention (CDC):
Cardiovascular Risks
- •High blood pressure
- •Higher levels of LDL cholesterol, lower levels of HDL cholesterol, and high levels of triglycerides
- •Coronary heart disease
- •Stroke
Metabolic Risks
- •Type II diabetes
- •Gallbladder disease
- •Sleep apnea and breathing problems
- •Osteoarthritis, a type of joint disease caused by breakdown of joint cartilage
Other Health Risks
- •Certain cancers (endometrial, breast, colon, kidney, gallbladder, liver)
- •Mental illnesses such as clinical depression, anxiety, and others
- •Low quality of life and body pains
- •Generally, an increased risk of mortality compared to those with a healthy BMI
Risks Associated with Being Underweight
Being underweight has its own associated risks, listed below:
- •Malnutrition, vitamin deficiencies, anemia (lowered ability to carry blood vessels)
- •Osteoporosis, a disease that causes bone weakness, increasing the risk of breaking a bone
- •A decrease in immune function
- •Growth and development issues, particularly in children and teenagers
- •Possible reproductive issues for women due to hormonal imbalances
- •Potential complications as a result of surgery
- •Generally, an increased risk of mortality compared to those with a healthy BMI
BMI Limitations
BMI doesn't distinguish between muscle and fat mass. Athletes and very muscular individuals may have high BMI despite being healthy. Age, sex, ethnicity, and body composition also affect interpretation.
In Adults
- •Older adults tend to have more body fat than younger adults with the same BMI
- •Women tend to have more body fat than men for an equivalent BMI
- •Muscular individuals and highly trained athletes may have higher BMIs due to large muscle mass
In Children and Adolescents
- •Height and level of sexual maturation can influence BMI and body fat among children
- •BMI could be a result of increased levels of either fat or fat-free mass
- •BMI is fairly indicative of body fat for 90-95% of the population
BMI Formula
Metric Formula
Standard international formula using kilograms and meters
Example:
Imperial Formula
US customary units formula with conversion factor
Example:
About BMI Prime
BMI Prime is the ratio of your BMI to the upper limit of normal BMI (25). A value of 1.0 means you're at the upper limit of normal weight.
BMI Prime Formula
Ratio of your BMI to the upper limit of normal 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 Weight | 18.5 - 25 | 0.74 - 1.0 |
| Overweight | 25 - 30 | 1.0 - 1.2 |
| Obesity Class I | 30 - 35 | 1.2 - 1.4 |
| Obesity Class II | 35 - 40 | 1.4 - 1.6 |
| Obesity 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. While BMI can be a useful tool when considering large populations, it is not reliable for determining leanness or corpulence in individuals.
Metric Formula
Ponderal Index using metric units
Imperial Formula
Ponderal Index using imperial units
Medical Disclaimer
BMI is a screening tool and may not reflect body composition. Consult healthcare professionals for personalized advice.