PSI to GPM Conversion Calculator

PSI to GPM Calculator

Enter pressure of system in pounds per square inch in psi to gpm calculator and input pipe diameter in inches. Select appropriate discharge coefficient (Cd) based on pipe characteristics.

The calculator will compute the flow rate in gallons per minute based on formula.

  • PSI: 40
  • Flow Coefficient (C): 0.5
    GPM = 0.5 × √(40) = 0.5 × 6.32 ≈ 3.16 GPM

PSI to GPM Conversion Chart

PSI (Pressure)C (Flow Coefficient)GPM (Gallons Per Minute)
10 PSI0.51.58
20 PSI0.52.24
30 PSI0.52.74
40 PSI0.53.16
50 PSI0.53.54
100 PSI0.55.00
200 PSI0.57.07
300 PSI0.58.66
1000 PSI0.515.81
10 PSI0.72.21
20 PSI0.73.13
30 PSI0.73.82
40 PSI0.74.43
50 PSI0.74.93
100 PSI0.77.00
200 PSI0.79.90
1000 PSI0.722.14
10 PSI1.03.16
20 PSI1.04.47
30 PSI1.05.48
40 PSI1.06.32
50 PSI1.07.07
100 PSI1.010.00
200 PSI1.014.14
1000 PSI1.031.62

How to Convert PSI to GPM

To convert PSI to GPM, first measure water pressure in system using a pressure gauge. Note internal diameter of your pipe in inches. Consider discharge coefficient based on your pipe type and condition, typically ranging from 0.6 for sharp edges to 0.9 for streamlined entries.

Use these values in the flow rate formula to calculate GPM, making sure to account for the conversion factor from seconds to minutes.

  • PSI: 1000
  • Flow Coefficient (C): 1.0
    GPM = 1.0 × √(1000) = 1.0 × 31.62 ≈ 31.62 GPM

PSI to GPM Conversion Formula

GPM = 60 × Cd × A × √(2g × P × 144 ÷ 62.4)

Where:

GPM = Flow Rate (gallons per minute)
Cd = Discharge Coefficient (typically 0.6-0.9)
A = Pipe Area (square inches)
g = Gravity (32.2 ft/s²)
P = Pressure (PSI)

Standard Garden Hose

  • Inputs: Pressure = 40 PSI, Pipe diameter = 0.75 inches, Discharge coefficient = 0.7
  • Calculations: Area = Ï€(0.75/2)² = 0.442 in². GPM = 60 × 0.7 × 0.442 × √(2 × 32.2 × 40 × 144 ÷ 62.4) = 12.3
  • Result: The flow rate is 12.3 GPM

Fire Hydrant Flow

  • Inputs: Pressure = 60 PSI, Pipe diameter = 2.5 inches, Discharge coefficient = 0.8
  • Calculations: Area = Ï€(2.5/2)² = 4.909 in². GPM = 60 × 0.8 × 4.909 × √(2 × 32.2 × 60 × 144 ÷ 62.4) = 209.4
  • Result: The flow rate is 209.4 GPM

Industrial Pipeline

  • Inputs: Pressure = 80 PSI, Pipe diameter = 4 inches, Discharge coefficient = 0.85
  • Calculations: Area = Ï€(4/2)² = 12.566 in². GPM = 60 × 0.85 × 12.566 × √(2 × 32.2 × 80 × 144 ÷ 62.4) = 624.8
  • Result: The flow rate is 624.8 GPM

Residential Water Main

  • Inputs: Pressure = 50 PSI, Pipe diameter = 1.5 inches, Discharge coefficient = 0.75
  • Calculations: Area = Ï€(1.5/2)² = 1.767 in². GPM = 60 × 0.75 × 1.767 × √(2 × 32.2 × 50 × 144 ÷ 62.4) = 65.2
  • Result: The flow rate is 65.2 GPM

Sprinkler System

  • Inputs: Pressure = 30 PSI, Pipe diameter = 1 inch, Discharge coefficient = 0.65
  • Calculations: Area = Ï€(1/2)² = 0.785 in². GPM = 60 × 0.65 × 0.785 × √(2 × 32.2 × 30 × 144 ÷ 62.4) = 18.9
  • Result: The flow rate is 18.9 GPM

What is PSI and GPM?

PSI (Pounds per Square Inch): A unit of pressure that measures the force applied over one square inch of area. In fluid systems, PSI indicates water pressure in pipes, pumps, and hydraulic systems.

PSI = Force (pounds) ÷ Area (square inches)

GPM (Gallons per Minute): A unit of flow rate measuring the volume of water passing through a point in one minute. This measurement is essential for sizing pumps, pipes, and water systems.

GPM = Volume (gallons) ÷ Time (minutes)

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