BMI Calculator

Adjust the values and click "Calculate" to see your results.
Units: US Units | Metric Units | Other Units

Age: 25 (Range: 2 - 120 years)
Gender:
Height: 180 cm
Weight: 65 kg

Result:
BMI = 20.1 kg/m² (Normal)

BMI Categories:

• Underweight: < 18.5
• Normal: 18.5 - 25
• Overweight: 25 - 30
• Obesity: > 30

Details:

• Healthy BMI Range: 18.5 kg/m² - 25 kg/m²
• Healthy Weight for Height: 59.9 kg - 81 kg
• BMI Prime: 0.8
• Ponderal Index: 11.1 kg/m³

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About the BMI Calculator

The Body Mass Index (BMI) Calculator helps determine your BMI value and corresponding weight status, taking age into account. Use the "Metric Units" tab for the International System of Units or the "Other Units" tab to convert units into US or metric measurements. The calculator also computes the Ponderal Index alongside BMI, both explained in detail below.

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What is BMI?

BMI is a measure of a person's leanness or corpulence based on their height and weight. It serves as a general indicator of whether someone has a healthy body weight for their height. The BMI value categorizes individuals as underweight, normal weight, overweight, or obese, depending on the range it falls into. These ranges can vary by region, age, and other factors, and are sometimes further divided into subcategories like severely underweight or very severely obese.

While BMI is not a perfect measure of healthy body weight, it is a useful tool for identifying whether additional testing or lifestyle changes may be needed.

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BMI Table for Adults

This table reflects the World Health Organization's (WHO) recommended body weight categories based on BMI for adults aged 20 and 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

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BMI Table for Children and Teens (Ages 2-20)

The Centers for Disease Control and Prevention (CDC) provides BMI percentiles for children and teens:

Category	Percentile Range
Underweight	< 5%
Healthy Weight	5% - 85%
At Risk of Overweight	85% - 95%
Overweight	> 95%

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Health Risks of Being Overweight

Being overweight increases the risk of numerous health conditions, including:

• High blood pressure
• High LDL cholesterol, low HDL cholesterol, and high triglycerides
• Type 2 diabetes
• Coronary heart disease
• Stroke
• Gallbladder disease
• Osteoarthritis
• Sleep apnea and breathing problems
• Certain cancers (e.g., endometrial, breast, colon)
• Reduced quality of life
• Mental health issues like depression and anxiety
• Increased risk of mortality

Maintaining a BMI below 25 kg/m² is generally recommended, but consult a doctor for personalized advice.

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Health Risks of Being Underweight

Being underweight also carries risks, such as:

• Malnutrition, vitamin deficiencies, and anemia
• Osteoporosis and weakened bones
• Weakened immune function
• Growth and development issues in children and teens
• Reproductive issues in women, including hormonal imbalances and miscarriage
• Increased risk of complications from surgery
• Higher mortality risk

If you suspect being underweight is due to an underlying condition, consult a healthcare professional.

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Limitations of BMI

While BMI is a useful indicator, it has limitations:

• It does not account for body composition (muscle vs. fat).
• Factors like age, sex, ethnicity, muscle mass, and activity level can influence BMI accuracy.
• Athletes or individuals with high muscle mass may have higher BMIs despite being healthy.
• Older adults and women may have more body fat at the same BMI compared to younger adults or men.

For children and teens, height and sexual maturation can also affect BMI interpretation. Despite these limitations, BMI remains a helpful tool for assessing body weight in most individuals.

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BMI Formula

BMI is calculated using the following formulas:

Metric Units:
[ \text{BMI} = \frac{\text{Weight (kg)}}{\text{Height (m)}^2} ]

US Units:
[ \text{BMI} = 703 \times \frac{\text{Weight (lbs)}}{\text{Height (in)}^2} ]

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BMI Prime

BMI Prime is the ratio of a person's BMI to the upper limit of the normal BMI range (25 kg/m²). It is calculated as:
[ \text{BMI Prime} = \frac{\text{BMI}}{25} ]

Classifications:

• Underweight: < 0.74
• Normal: 0.74 - 1
• Overweight: 1 - 1.2
• Obese: > 1.2

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Ponderal Index

The Ponderal Index (PI) is similar to BMI but uses height cubed instead of squared. It is more reliable for very tall or short individuals.

Formula:
[ \text{PI} = \frac{\text{Weight (kg)}}{\text{Height (m)}^3} ]

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Conclusion

BMI is a valuable tool for assessing body weight and identifying potential health risks. However, it should be used alongside other measurements and professional advice for a comprehensive evaluation of health.