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BMI Calculator

Know your health status in seconds
⚠️ Result is for informational purposes only. Consult your doctor for a proper health assessment.

BMI Classification Table

Category Range Status
Underweight < 18.5 ⚠️ Below normal
Normal weight 18.5 – 24.9 ✅ Ideal
Overweight 25 – 29.9 ⚠️ Above normal
Obese ≥ 30 ⛔ High risk

What is BMI (Body Mass Index)?

Body Mass Index (BMI) is a simple measurement used to estimate body fat based on weight and height. Developed by the World Health Organization (WHO), it is the most widely used tool globally for screening healthy weight.

BMI is calculated by dividing weight in kilograms by the square of height in meters. The result is classified into four categories: underweight, normal weight, overweight, and obese.

Note that BMI does not differentiate between fat and muscle, so it may not accurately reflect the situation of athletes, children, or the elderly. Use it as a general indicator, not a medical diagnosis.

How is BMI calculated?

The mathematical formula for calculating BMI is:

BMI = Weight (kg) ÷ Height² (m)

Example: A person weighing 75 kg and 175 cm tall (1.75 m):

BMI = 75 ÷ (1.75 × 1.75) = 75 ÷ 3.0625 ≈ 24.5

The result 24.5 falls in the normal range (18.5 – 24.9). If using pounds and inches: BMI = (weight in lbs ÷ height in inches²) × 703

Frequently Asked Questions about BMI

BMI is a useful general indicator for most adults, but may be less accurate for athletes (muscle weighs more than fat), pregnant women, children, and older adults. For a more accurate assessment, consult a doctor and consider additional measurements like waist circumference or body fat percentage.
According to WHO, a BMI between 18.5 and 24.9 is considered ideal for adults. Children and adolescents use separate growth charts that account for age and sex. Some research suggests the optimal range may vary by ethnicity and body composition.
If your weight is in pounds and height in inches, use: BMI = (weight in lbs ÷ height in inches²) × 703. Quick conversion: 1 kg = 2.205 lbs, 1 inch = 2.54 cm. This calculator uses metric units (kg and cm) only.
The BMI formula is the same for both sexes, but body composition differs. Women typically have a higher fat percentage than men at the same BMI. Some doctors recommend supplementing BMI with waist circumference or waist-to-hip ratio for a more accurate assessment.
A high BMI (≥30) is linked to increased risk of type 2 diabetes, heart disease, high blood pressure, and some cancers. A low BMI (<18.5) is associated with weakened immunity, osteoporosis, and malnutrition. In both cases, consult a doctor.
How is BMI calculated — with a worked example?

BMI formula: weight (kg) ÷ height² (m). Example: a person weighing 75 kg and 175 cm tall: 75 ÷ (1.75 × 1.75) = 75 ÷ 3.0625 ≈ 24.5. This falls in the Normal range (18.5–24.9) per WHO standards.

What is the ideal weight for my height?

Ideal weight = normal BMI range (18.5–24.9) × height² in metres. Example for 170 cm (1.70 m): lower = 18.5 × (1.70²) ≈ 53.5 kg, upper = 24.9 × (1.70²) ≈ 71.9 kg. Any weight between 53.5 and 71.9 kg is ideal for this height.

Is BMI suitable for children?

No. Children and adolescents under 18 use specialised growth charts (BMI-for-age) that account for sex and age. Adult BMI values (18.5–24.9 normal) do not apply to children. Consult a paediatrician for an accurate assessment.

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BMI Calculator — How to Interpret Your Result

Body Mass Index (BMI) is calculated from your height and weight using the formula: weight (kg) ÷ height² (m). For example, 70 kg at 1.75 m = 70 ÷ 3.0625 = 22.9. It gives a quick indication of whether you may be underweight, at a healthy weight, overweight, or in the obese range — but it is a screening tool, not a diagnosis.

BMI ranges (WHO standard)

  • Under 18.5 — Underweight
  • 18.5 to 24.9 — Normal weight
  • 25.0 to 29.9 — Overweight
  • 30.0 and above — Obese

What BMI doesn't tell you

BMI does not measure body fat directly. A muscular athlete may score in the "overweight" range despite low body fat. Older adults may have a normal BMI but carry excess fat. Always combine BMI with other health markers and consult a doctor for a complete assessment.

Last updated: September 2026