# Gorlin Formula Calculator (Valve Area)

URL: https://speedycalculator.com/calculators/health/gorlin-formula/
Last updated: 2026-10-30

> The Gorlin formula calculator estimates aortic or mitral valve area from cardiac catheterisation data – cardiac output, heart rate, systolic ejection or diastolic filling period, and the mean pressure gradient – and gives the simpler Hakki estimate.

## Inputs

- Valve
- Cardiac output (L/min)
- Heart rate (bpm)
- Systolic ejection or diastolic filling period (s per beat)
- Mean pressure gradient (mmHg)

## Results

- Valve area (Gorlin)
- Valve area (Hakki)

## Formula

```
Valve area (cm²) = CO (mL/min) ÷ (HR × ejection or filling period (s) × C × √mean gradient)
C = 44.3 for the aortic valve, 37.7 for the mitral valve
Hakki: area ≈ CO (L/min) ÷ √mean gradient
```

## Explanation

The Gorlin equation (1951) applies fluid hydraulics to blood flow through a narrowed valve. It is still the reference method in the catheter lab, although it is less accurate at low cardiac output.

### How to use the Gorlin Formula Calculator

- **Valve**
- **Cardiac output**
- **Heart rate**
- **Systolic ejection or diastolic filling period**
- **Mean pressure gradient**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Choose the valve and enter cardiac output, heart rate, the systolic ejection period (aortic) or diastolic filling period (mitral) per beat and the mean gradient.

### Inputs explained

FieldWhat to enterValveChoose one: Aortic, MitralCardiac outputIn L/minHeart rateIn bpmSystolic ejection or diastolic filling periodIn s per beatMean pressure gradientIn mmHg

### What each result means

- **Valve area (Gorlin)** = [Cardiac output]×1000÷([Heart rate]×[Systolic ejection or diastolic filling period]×[Valve]×sqrt([Mean pressure gradient]))
- **Valve area (Hakki)** = [Cardiac output]÷sqrt([Mean pressure gradient])

### Example values

How the main result changes when **Cardiac output** changes and everything else stays at the example values above:

Cardiac output (L/min)Valve area (Gorlin) (cm²)2.50.343.750.5150.686.250.857.51.02101.36
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Valve: Aortic; Cardiac output: 5 L/min; Heart rate: 75 bpm; Systolic ejection or diastolic filling period: 0.33 s per beat; Mean pressure gradient: 45 mmHg.

Results — **Valve area (Gorlin) = 0.68 cm²**; Valve area (Hakki) = 0.75 cm².

## Key terms

- **SEP**: Systolic ejection period.
- **DFP**: Diastolic filling period.

## FAQ

**What is the Gorlin constant?**
44.3 for the aortic valve and 37.7 (44.3 × 0.85) for the mitral valve.

**Why might Gorlin be inaccurate?**
At low cardiac output it underestimates valve area.

**What is the Hakki formula?**
A simplified version: cardiac output divided by the square root of the gradient.


## Sources

- [Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve. Am Heart J, 1951](https://pubmed.ncbi.nlm.nih.gov/14799434/)
- [Hakki AH et al. A simplified valve formula for the calculation of stenotic cardiac valve areas. Circulation, 1981](https://pubmed.ncbi.nlm.nih.gov/7471786/)