Gorlin Formula Calculator — Cardiac Valve Area
The Gorlin formula uses invasive haemodynamic measurements — cardiac output, heart rate, filling period and mean trans-valvular pressure gradient — to calculate the effective orifice area of a stenosed cardiac valve. Enter the catheterisation values and select the valve to get the area and stenosis grade.
Valve
L/min
bpm
s/beat
mmHg
Moderate stenosis
- 1
Cardiac output in mL/min
5 L/min × 1000 = 5,000 - 2
√(mean pressure gradient)
√(10) = 3.162 - 3
Denominator: HR × FP × K × √PG
75 × 0.44 × 37.7 × 3.162 = 3,934.19K = 37.7 (empirical Gorlin constant for mitral valve). - 4
Valve area = CO ÷ denominator
5,000 ÷ 3,934.19 = 1.27
How does this calculator work?
Gorlin Valve Area (cm²) = CO(mL/min) / [HR × FP(s) × K × √(gradient mmHg)], where K = 37.7 for mitral or 44.3 for aortic. Severe stenosis is typically < 1.0 cm² for both valves. Accuracy is highest at normal cardiac outputs; use echocardiography to cross-check, especially in low-flow states.
Formula
How this is calculated
The Gorlin formula, published in 1951, applies the hydraulic orifice equation to the cardiac valve: Valve Area = Flow Rate / (Constant × √ΔP), where flow rate is the mean volumetric flow across the valve during the relevant cardiac phase. Flow rate is derived from cardiac output — CO (mL/min) ÷ HR gives mL per beat, and dividing by the filling or ejection period gives mL/s through the valve. The constant K captures unit conversions and an empirical correction: 44.3 for the theoretical hydraulic constant, reduced to 37.7 for the mitral valve based on Gorlin's original empirical calibration against direct orifice measurements.
For the mitral valve, the relevant pressure and timing are the mean diastolic trans-mitral gradient and the diastolic filling period (DFP). For the aortic valve, use the mean systolic gradient and the systolic ejection period (SEP). Both are typically measured by simultaneous left-heart catheterisation with a transvalvular pullback manoeuvre, or by combined right and left heart catheterisation.
The Gorlin formula has known limitations: it underestimates valve area at low flow states (low-flow, low-gradient severe stenosis) and is most accurate at normal cardiac outputs. Modern echocardiography (continuity equation for aortic, pressure half-time or planimetry for mitral) has largely replaced invasive Gorlin assessment, but the formula remains valuable in ambiguous cases and in catheterisation laboratories.
Frequently asked questions
Normal mitral valve area is 4–6 cm²; severe stenosis is defined as < 1.0 cm². Normal aortic valve area is 3–4 cm²; severe stenosis is < 1.0 cm² (or indexed < 0.6 cm²/m² BSA). Tricuspid valve area is normally 7–9 cm²; significant stenosis is < 2.0 cm².
Gorlin & Gorlin (1951) found that the theoretical hydraulic constant of 44.3 overestimated mitral valve area compared to direct anatomical measurements at autopsy or surgery. They applied an empirical correction factor of 0.85, giving 44.3 × 0.85 ≈ 37.7 for the mitral valve. No such correction was needed for the aortic valve in their dataset.
It remains the reference method for valve area calculation from invasive catheterisation data, and is used when echocardiography is inconclusive, in low-flow states, or in interventional planning. However, it is flow-dependent — at cardiac outputs below about 3.5 L/min it tends to underestimate the true orifice area.
Also known as
TG we-Calculate Editorial Team. (2026). Gorlin Formula Calculator — Cardiac Valve Area [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/gorlin-formula-calculator
TG we-Calculate Editorial Team. "Gorlin Formula Calculator — Cardiac Valve Area." TG we-Calculate. 2026. https://we-calculate.com/calculator/gorlin-formula-calculator.
TG we-Calculate Editorial Team, "Gorlin Formula Calculator — Cardiac Valve Area," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/gorlin-formula-calculator
@misc{wecalculate_gorlin_formula_calculator, title = {Gorlin Formula Calculator — Cardiac Valve Area}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/gorlin-formula-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?