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BMI Calculator

Calculate body mass index from weight and height with category guidance.

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Formula

BMI = weight in kg / height in meters squared

Weight and height are converted to metric units and used to compute BMI.

Worked Example

Weight 70 kg and height 170 cm gives BMI around 24.2.

Understanding Body Mass Index (BMI)

BMI is a simple screening tool that uses your weight and height to estimate whether you fall into an underweight, normal weight, overweight, or obese category. It is widely used in clinical and public health settings.
  • BMI formula: weight in kilograms divided by height in meters squared (kg/m2)
  • WHO categories: underweight (below 18.5), normal weight (18.5 to 24.9), overweight (25.0 to 29.9), obese (30.0 and above)
  • BMI does not distinguish between muscle mass and fat mass, so it can overestimate body fat in muscular individuals
  • For a more complete picture, combine BMI with body fat percentage, waist circumference, and other health markers

BMI is a useful starting point but not a diagnosis. Consult a healthcare provider for personalized health assessment.

You can also calculate changes using our Body Fat Calculator, Ideal Weight Calculator, Calorie Calculator or TDEE Calculator.

Frequently Asked Questions

Is BMI a medical diagnosis?

No. BMI is a population-level screening tool. It indicates potential weight-related health risks but does not account for muscle mass, bone density, body composition, or individual health factors.

Does BMI work for athletes and bodybuilders?

BMI can overestimate body fat in very muscular individuals because muscle weighs more than fat per unit volume. Athletes with high muscle mass may have a "overweight" BMI despite low body fat.

What is a healthy BMI range?

The WHO defines normal weight as BMI 18.5 to 24.9. This range is associated with the lowest risk of weight-related health conditions for most adults.

Does BMI apply to children?

Children use age and sex-specific BMI percentiles rather than the adult categories. A pediatric BMI calculator is needed for accurate child assessment.

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