Calculate aortic root index from aortic root diameter and body surface area, or estimate BSA from height and weight using Mosteller.

Aortic Root Index Calculator

Enter aortic root diameter and body surface area to get the index.

I know BSA
Use height & weight

Aortic Root Index Formula

The aortic root index is the aortic root diameter adjusted for body surface area. The calculator reports the result in cm/m² and also shows the equivalent value in mm/m².

ARI = D_cm / BSAₘ2
BSAₘ2 = sqrt((H_cm * Wₖg) / 3600)
  • ARI = aortic root index, in cm/m²
  • D_cm = aortic root diameter, converted to centimeters
  • BSA_m2 = body surface area, in square meters
  • H_cm = height, converted to centimeters
  • W_kg = weight, converted to kilograms

If you choose I know BSA, the calculator converts the aortic root diameter to centimeters, converts BSA to m² if needed, then divides diameter by BSA.

If you choose Use height & weight, the calculator first estimates BSA with the Mosteller formula, then uses that BSA in the aortic root index formula.

Aortic Root Index Reference Ranges

These ranges match the interpretation used by the calculator. They are general adult reference ranges and should be interpreted with the imaging report, age, sex, clinical history, and measurement method.

Aortic root index Calculator interpretation
Less than 1.3 cm/m² Below typical adult range
1.3 to 2.1 cm/m² Within typical adult range
Greater than 2.1 to 2.5 cm/m² Mildly elevated
Greater than 2.5 cm/m² Elevated, suggests aortic root dilatation

Common Input Unit Conversions

Input Conversion used
Aortic root diameter in mm cm = mm × 0.1
Aortic root diameter in inches cm = inches × 2.54
BSA in ft² m² = ft² × 0.092903
Weight in lb kg = lb × 0.453592

Examples

Example 1: BSA is already known

You have an aortic root diameter of 34 mm and a BSA of 1.90 m².

Convert the diameter:

34 mm * 0.1 = 3.4 cm

Calculate the index:

ARI = 3.4 / 1.90 = 1.79 cm / m2

The result is about 1.79 cm/m², which is within the typical adult range used by the calculator.

Example 2: BSA from height and weight

You have an aortic root diameter of 4.2 cm, height of 175 cm, and weight of 75 kg.

First calculate BSA:

BSA = sqrt((175 * 75) / 3600) = 1.91 m2

Then calculate the index:

ARI = 4.2 / 1.91 = 2.20 cm / m2

The result is about 2.20 cm/m², which falls in the mildly elevated range used by the calculator.

FAQ

What does aortic root index mean?

Aortic root index is the aortic root diameter divided by body surface area. It adjusts the measured aortic root size for body size, so a measurement can be compared more fairly between people of different heights and weights.

Is a higher aortic root index always abnormal?

Not always. A higher value can suggest aortic root enlargement, but interpretation depends on the imaging method, exact measurement location, age, sex, body size, valve anatomy, and medical history. Use the result as a calculation aid, not as a diagnosis.

Should the aortic root diameter be entered in systole or diastole?

Use the value from the imaging report and keep the measurement method consistent when comparing results over time. Echocardiography, CT, and MRI reports may use different conventions, so follow the method used by the clinician or reporting lab.