BMI Calculator

📖 What is BMI?

Body Mass Index (BMI) is a simple numerical value calculated from a person's weight and height. It provides a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health problems.

The formula is: BMI = weight (kg) / height² (m²). For example, a person who is 175 cm tall and weighs 70 kg has a BMI of 22.86 — in the Normal range.

📈 Understanding the BMI Chart

The BMI chart maps your height and weight to a specific zone. The colour-coded zones (blue, green, yellow, orange, red) immediately communicate where you fall relative to healthy ranges defined by the World Health Organization (WHO).

🔢 What is the Ponderal Index?

The Ponderal Index (PI) is an alternative to BMI that uses the cube of height rather than the square: PI = weight (kg) / height³ (m³). It is considered a more accurate measure for very tall or very short individuals where BMI may overestimate or underestimate body fatness.

⚠️ Limitations of BMI

• BMI does not distinguish between muscle and fat mass.
• Athletes may be classified as overweight due to high muscle density.
• BMI does not account for fat distribution (e.g., abdominal fat is riskier).
• Age and ethnicity can affect what BMI values are considered healthy.
• It is not suitable for use with pregnant women or children without adjusted charts.

📏 Alternative Body Measurements

Alongside BMI and PI, consider these complementary measures for a fuller picture of health:

• Waist-to-Height Ratio — waist circumference divided by height; values above 0.5 indicate increased risk.
• Body Fat Percentage — measured via DEXA, skinfold calipers, or bioelectrical impedance.
• Waist Circumference — > 88 cm (women) or > 102 cm (men) signals higher cardiovascular risk.
• Basal Metabolic Rate (BMR) — calories your body burns at rest; key to any weight management plan.