Classic BMI calculator

Your body mass index from two measurements.

Your body mass index

Complete to see your result

Weight
Height
Confirmation

Enter your weight and height, then confirm the adult setting. Supported ranges: 20 to 350 kg and 100 to 250 cm, or their imperial equivalents.

BMI

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Understand the calculation

BMI relates your weight to the square of your height. It provides a general reference for adults without distinguishing muscle from fat. The thresholds shown are from the standard adult classification and are not enough to establish a diagnosis.

BMI = weight in kg / (height in meters × height in meters). Waist-to-height ratio = waist circumference / height, in the same unit.

Fictional calculation example

For 75 kg and 1.75 m: 75 / 1.75² = 24.49 kg/m². This result falls within the standard adult range of 18.5 to under 25.

Scientific sources

National Institute for Health and Care Excellence. Overweight and obesity management. NG246, recommendations 1.9.5-1.9.15. Updated 8 January 2026.

Adult BMI categories

Adult BMI categories
Category	BMI (kg/m²)
BMI below 18.5	< 18.5
BMI in the standard reference range	18.5-24.9
BMI in the overweight category	25-29.9
BMI in the class 1 obesity category	30-34.9
BMI in the class 2 obesity category	35-39.9
BMI in the class 3 obesity category	≥ 40

Your questions

Why can BMI seem high when you’re muscular?

BMI does not distinguish between tissues: two people of the same height and weight have the same result, even with different body compositions. Significant muscle mass is therefore context for interpretation, not proof that all risk is absent.

Is BMI reliable when you are muscular?

A high amount of muscle can increase BMI without reflecting excess fat. The WorkoutGen method BMI tool complements this number with estimates of fat mass and lean mass.

How does this differ from the WorkoutGen method BMI?

Classic BMI uses only weight and height. The WorkoutGen method keeps this BMI and breaks weight down into fat mass and lean mass, based on measurements or an already measured body fat percentage. This addition remains an estimate.

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