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Gorlin Formula Calculator

Health

Calculate aortic or mitral valve area from invasive cardiac catheterization data using the classic Gorlin formula, based on cardiac output and mean gradient.

Reviewed by the thecalcu.com team · Last updated August 1, 2026

Valve
Cardiac Output
L/min
Heart Rate
bpm
Systolic Ejection Period
ms
Mean Gradient
mmHg

Aortic Valve Area

0cm²

Severity

—

Not a substitute for clinical interpretation. Catheterization-derived valve area should be reviewed alongside the full hemodynamic study by a qualified cardiologist.

What is a Gorlin Formula?

The Gorlin Formula Calculator computes aortic or mitral valve area using the classic invasive cardiac catheterization method, based on measured cardiac output, the systolic ejection period (aortic) or diastolic filling period (mitral), heart rate, and the mean pressure gradient across the valve. This catheterization-derived formula has been a cornerstone of hemodynamic valve assessment since 1951.

Select the valve type and enter your catheterization data below to see the calculated valve area and severity classification. For the non-invasive Doppler equivalent for the aortic valve, see the Aortic Valve Area Calculator; for the cardiac output input this formula requires, see the Doppler Echo Cardiac Output Calculator.

Why Use a Gorlin Formula Calculator?

Converting cardiac output and a flow period per beat into a flow-rate-per-minute term, then dividing by an empirical constant and the square root of the mean gradient, involves several unit conversions and an easily-fumbled square root step. This calculator performs the full calculation instantly, automatically applying the correct constant for your selected valve type.

It's useful for reviewing a catheterization report's underlying hemodynamic numbers, or for cardiology fellows and students practicing the classic Gorlin formula calculation.

Who Should Use This Calculator?

Cardiology fellows, cath lab staff, and nursing students learning invasive hemodynamic assessment can use this calculator to check worked Gorlin formula examples against measured catheterization data. Patients reviewing their own catheterization report who want to understand how their valve area figure was derived may also find this a useful educational reference.

This calculator is for informational and educational purposes only. It is not a substitute for a qualified cardiologist's clinical interpretation of an actual invasive hemodynamic catheterization study, always discuss your specific results and treatment options with a healthcare provider.

What Insights Does the Gorlin Formula Calculator Give You?

Valve Area is the primary result, the calculated cross-sectional area of the selected valve in square centimeters, based on your entered catheterization data.

Severity translates that area into a plain-language normal/mild, moderate, or severe stenosis classification, using standard ACC/AHA and ASE valve disease severity thresholds.

How to use this Gorlin Formula calculator

  1. Select the Valve, aortic or mitral.
  2. Enter the Cardiac Output in L/min, as measured during catheterization.
  3. Enter the Heart Rate in beats per minute.
  4. Enter the Systolic/Diastolic Period per beat in milliseconds (systolic ejection period for aortic, diastolic filling period for mitral).
  5. Enter the Mean Gradient in mmHg across the valve.
  6. Review the calculated Valve Area and Severity classification.
Show formula & methodology ↓Show less ↑

Formula & Methodology

Aortic Valve Area (cm²) = Cardiac Output (mL/min) ÷ (Systolic Ejection Period (s/min) × 44.3 × √Mean Gradient)

Mitral Valve Area (cm²) = Cardiac Output (mL/min) ÷ (Diastolic Filling Period (s/min) × 37.7 × √Mean Gradient)

Where the flow period in seconds-per-minute equals the period per beat (in seconds) multiplied by heart rate. Severity bands: for the aortic valve, 2.0 cm² or higher is normal/mild, 1.0-1.5 cm² is moderate, and under 1.0 cm² is severe; for the mitral valve, 1.5 cm² or higher is normal/mild, 1.0-1.5 cm² is moderate, and under 1.0 cm² is severe (Gorlin R, Gorlin SG. Am Heart J. 1951;41(1):1-29).

Worked example: For an aortic valve assessment with cardiac output of 5 L/min (5000 mL/min), heart rate of 70 bpm, systolic ejection period of 300ms per beat (giving 0.3 × 70 = 21 s/min), and mean gradient of 40 mmHg: AVA = 5000 ÷ (21 × 44.3 × √40) ≈ 5000 ÷ (21 × 44.3 × 6.32) ≈ 5000 ÷ 5878 ≈ 0.85 cm², consistent with severe aortic stenosis.

Frequently Asked Questions

What is the Gorlin formula used for?
The Gorlin formula calculates the cross-sectional area of a stenotic (narrowed) heart valve, either the aortic or mitral valve, using data obtained during invasive cardiac catheterization, including cardiac output, the flow period per beat, and the mean pressure gradient across the valve. It has been a foundational tool in invasive hemodynamic valve assessment since 1951.
How is the Gorlin formula different from the Doppler continuity equation?
The Gorlin formula requires invasive catheterization data, measured cardiac output and directly measured pressure gradients from catheters placed across the valve, while the continuity equation used in the [Aortic Valve Area Calculator](/aortic-valve-area-calculator/) relies entirely on non-invasive Doppler echocardiography velocities. Both estimate valve area but from fundamentally different data sources.
What is the systolic ejection period and why does it matter for the aortic valve?
The systolic ejection period is the portion of each cardiac cycle during which blood is actively flowing forward through the aortic valve, measured in milliseconds per beat. Because flow only occurs during this window, the formula needs it to convert total cardiac output into the flow rate specifically during valve opening.
What is the diastolic filling period and why does it matter for the mitral valve?
The diastolic filling period is the portion of each cardiac cycle during which blood flows forward through the mitral valve from the left atrium into the left ventricle. Similar to the aortic valve's systolic ejection period, this value is needed to convert total cardiac output into the flow rate specifically during mitral valve opening.
Why do the aortic and mitral valve calculations use different constants?
The Gorlin formula uses an empirically derived constant of 44.3 for the aortic valve and 37.7 for the mitral valve, reflecting differences in valve geometry and flow characteristics observed in the original derivation studies. Selecting the correct valve type in this calculator automatically applies the appropriate constant.
What do the severity categories mean?
This calculator uses the same general severity framework applied across most valve area assessments: an area of 2.0 cm² or higher (aortic) or 1.5 cm² or higher (mitral) is considered normal or mild, while progressively smaller areas indicate moderate and then severe stenosis. These bands broadly align with ACC/AHA and ASE valve disease guidelines.
Is the Gorlin formula still used in modern cardiology practice?
Yes, though less frequently than non-invasive Doppler methods for routine assessment, the Gorlin formula remains clinically relevant when catheterization is performed for other reasons, or when Doppler-derived valve area estimates are inconclusive or discordant with the clinical picture. It's also foundational to understanding hemodynamic valve assessment.
Why does the Gorlin formula require a square root of the gradient?
The relationship between pressure gradient and flow velocity across a fixed orifice follows a squared relationship (per the simplified Bernoulli principle), so the formula takes the square root of the mean gradient to convert it back into a velocity-equivalent term needed for the area calculation. This mathematical relationship is shared with the Doppler continuity equation.
Can low cardiac output affect the accuracy of a Gorlin-calculated valve area?
Yes, the Gorlin formula can underestimate true valve area in patients with low cardiac output states, sometimes called 'low-flow, low-gradient' aortic stenosis, because the formula assumes a fixed relationship between flow and gradient that doesn't hold as well at very low flow rates. Cardiologists often use additional testing, such as dobutamine stress echocardiography, in these specific cases.
Can this calculator replace a formal catheterization report?
No, this calculator is for informational and educational purposes only and simply performs the standard Gorlin formula calculation from values you enter. Actual measurement of cardiac output, ejection or filling period, and mean gradient requires an invasive cardiac catheterization performed and interpreted by a qualified cardiologist.
How does this relate to the Doppler Echo Cardiac Output Calculator?
The [Doppler Echo Cardiac Output Calculator](/doppler-echo-cardiac-output-calculator/) estimates cardiac output non-invasively, which is one of the required inputs for this Gorlin formula calculation. In an actual catheterization lab, cardiac output is more commonly measured directly via thermodilution or the Fick method rather than echocardiography.
How does this relate to the Aortic Valve Area Calculator?
The [Aortic Valve Area Calculator](/aortic-valve-area-calculator/) calculates the same underlying measurement, aortic valve area, but uses the non-invasive Doppler continuity equation instead of invasive catheterization data. Comparing results from both methods for the same patient can highlight discordance worth discussing with a cardiologist.
Also known as
Gorlin equation calculatorinvasive valve area calculatorcardiac catheterization valve area calculatorGorlin formula aortic valve calculatorGorlin formula mitral valve calculator