BMI Introduction:

Your Body Mass Index (BMI) is a quick and reliable way to estimate whether your body weight is healthy for your height. It’s a simple calculation using your height and weight that helps assess whether you are underweight, at a healthy weight, overweight, or obese.

The BMI value is the same for both men and women and can be used for adults of all ages. However, while BMI is a good general indicator of body fat, it does not directly measure body composition (like muscle mass vs fat).

BMI Table for Adults:

BMI Range	Weight Status
Below 18.5	Underweight
18.5 – 24.9	Healthy weight
25.0 – 29.9	Overweight
30.0 – 34.9	Obesity Class I
35.0 – 39.9	Obesity Class II
40.0 and above	Obesity Class III (Severe)

BMI Chart for Adults:

A visual BMI chart helps you quickly identify where your height and weight place you within BMI categories.

• If your BMI is below 18.5, you fall into the underweight zone.
• A BMI between 18.5 and 24.9 means you’re within the healthy range.
• 25 and above indicates overweight or obesity, depending on how high the number goes.

Age Calculator

Tip: Use the BMI calculator to know your exact BMI value, then refer to the chart to interpret it correctly.

BMI Table for Children and Teens (Ages 2–20):

For children and adolescents, BMI is age- and sex-specific because body fat changes with age and differs between boys and girls. The result is expressed as a percentile rather than a single number.

BMI Percentile	Weight Status
Below 5th percentile	Underweight
5th – 84th percentile	Healthy weight
85th – 94th percentile	Overweight
95th percentile and above	Obese

Risks Associated with Being Overweight:

Carrying excess body weight can increase the risk of several health issues, including:

• Type 2 diabetes
• High blood pressure
• Heart disease and stroke
• Sleep apnea
• Joint pain and osteoarthritis
• Certain types of cancer (colon, breast, kidney)

Maintaining a healthy BMI through balanced nutrition and regular physical activity helps reduce these risks.

Risks Associated with Being Underweight:

Being underweight can also have serious health consequences, such as:

• Nutritional deficiencies (especially iron, calcium, and protein)
• Weakened immune system
• Fatigue and poor concentration
• Increased risk of osteoporosis
• Fertility issues
• Slow growth and development in children and teens

A balanced diet with adequate calories and nutrients is essential for maintaining a healthy weight.

Limitations of BMI:

While BMI is a useful screening tool, it has several limitations:

• It doesn’t distinguish between muscle and fat mass—athletes may have a high BMI but low body fat.
• It doesn’t account for body fat distribution (waist vs. hip).
• It may not accurately reflect health status in older adults who have lost muscle mass.
• For children and teens, BMI must be interpreted relative to age and sex.

In Children and Adolescents:

BMI for children and adolescents works differently than for adults.

• It’s calculated in the same way but compared to percentile growth charts that take into account age and sex.
• Pediatricians use these charts to track growth patterns over time.
• A consistent rise or fall outside the healthy percentile range may require medical advice.

BMI Formula:

The basic formula for calculating BMI is:

For metric units:
BMI = Weight (kg) / [Height (m)]²

For imperial units:
BMI = (Weight (lbs) × 703) / [Height (in)]²

Example:
If you weigh 70 kg and are 1.75 m tall,
BMI = 70 / (1.75 × 1.75) = 22.9 (Healthy range)

BMI Prime:

BMI Prime is a ratio of your BMI to the upper limit of the healthy BMI range (which is 25).
It shows how close or far you are from being overweight.

Formula:
BMI Prime = BMI / 25

Interpretation:

• BMI Prime < 1.0 → Below healthy range
• BMI Prime = 1.0 → Upper limit of healthy range
• BMI Prime > 1.0 → Overweight

Example:
If your BMI is 22.9, BMI Prime = 22.9 / 25 = 0.916 → within the healthy range.

Ponderal Index (PI):

The Ponderal Index is another measure used to evaluate body composition, especially useful for tall individuals where BMI may overestimate body fat.

Formula:
PI = Height (m) / [Weight (kg)]^(1/3)

Higher PI values generally indicate a leaner physique.