BMI Calculator
Calculate your Body Mass Index, healthy weight range and ideal weight using metric or imperial units.
Example: 175 cm · 70 kg
🎨 BMI Visual Zone Chart
Colour-coded BMI zones per WHO standards. Enter your measurements above and click Calculate to see your position.
↑ your BMI marker will appear here after calculating
📊 BMI Classification (WHO Standard)
| BMI Range | Category | Health Risk |
|---|---|---|
| < 18.5 | Underweight | Increased |
| 18.5–25 | Normal weight | Minimal |
| 25–30 | Overweight | Increased |
| 30–35 | Obese Class I | High |
| 35–40 | Obese Class II | Very High |
| > 40 | Obese Class III | Extremely High |
📖 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.