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PSI to GPM Calculator

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### Fluid Dynamics & Hydrostatic Orifice Flow Pressure (pounds per square inch) and volumetric flow rate (gallons per minute) are governed by **Torricelli's Law** and the **Bernoulli Energy.

Reviewed by Sheraz Share · BSCS
Last updated:
Editorial Guidelines

⚙ Input Values

PSI
in

📊 Results

Water Flow Rate (GPM)
116.28
GPM
Flow Rate (Metric LPM)
440.15
L/min
Flow Rate (GPH)
6,976.5
GPH
Jet Velocity
84.47
ft/s
Hydraulic Power (HHP)
3.39
hp
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📐 Formula

Freeman's Nozzle Formula: Q = 29.83 * Cd * d^2 * sqrt(P)
Velocity V = 12.19 * sqrt(P) in ft/s for water (Torricelli)
NFPA Fire Sprinkler: Q = K * sqrt(P)
Valve Cv: Q = Cv * sqrt(dP)
Hydraulic Horsepower HHP = (P * Q) / 1714

💡 Practical Example

✅

Discharging water at 50.0 PSI through a 0.75-inch smooth bore nozzle: Generates 116.27 GPM and 3.39 Hydraulic Horsepower.

📖 About PSI to GPM Calculator

Fluid Dynamics & Hydrostatic Orifice Flow

Pressure (pounds per square inch) and volumetric flow rate (gallons per minute) are governed by Torricelli's Law and the Bernoulli Energy Equation. Fluid cannot flow through a pipe or orifice without a pressure differential Δ P.

Core Hydraulic Flow Equations

  • Freeman's Nozzle Orifice Discharge: Q = 29.83 × C_d × d^2 × √(P)
  • NFPA Fire Sprinkler Equation: Q = K × √(P) P = ((Q) / (K))^2
  • Control Valve Sizing: Q = C_v × √((Δ P) / (SG))
  • Torricelli Theoretical Jet Velocity: v = √(2 g h) = 12.19 × √(P)
  • Hydraulic Horsepower: HHP = (P × Q) / (1,714)

Standard Orifice Discharge Coefficients (C_d)

  • Smooth Bore Nozzle / Fire Monitor: C_d ≈ 0.97 - 0.99
  • Standard Short Pipe / Spigot: C_d ≈ 0.80 - 0.82
  • Square Sharp-Edged Orifice: C_d ≈ 0.60 - 0.

62.

How to Use This Calculator

Enter your Hydraulic System Model — choose from Nozzle / Orifice: Q = 29.83 × Cd × d² × √P, Fire Sprinkler / Hose: Q = K × √P, Control Valve: Q = Cv × √(ΔP / SG), Differential Water Pressure (PSI) (e.g. 50.0 in PSI), Orifice / Nozzle Diameter (d) (e.g. 0.75 in in), Discharge Coefficient (Cd) — choose from 0.98 - Smooth Bore Fire Nozzle / Well-Rounded, 0.80 - Short Pipe / Standard Tap, 0.62 - Sharp-Edged Orifice / Restriction Plate, and Valve Flow Coefficient (Cv) or Sprinkler K-Factor (e.g. 5.6). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Freeman's Nozzle Formula: Q = 29.83 Cd d^2 * sqrt(P)

Velocity V = 12.19 * sqrt(P) in ft/s for water (Torricelli)

NFPA Fire Sprinkler: Q = K * sqrt(P)

Valve Cv: Q = Cv * sqrt(dP)

Hydraulic Horsepower HHP = (P * Q) / 1714

Worked Example

Discharging water at 50.0 PSI through a 0.75-inch smooth bore nozzle: Generates 116.27 GPM and 3.39 Hydraulic Horsepower.

Understanding Your Result

Unit conversion precision: round to the same number of significant figures as your original measurement. Converting 6 feet to meters gives 1.8288 m — but if your measurement was approximate (±1 inch), expressing more than 2 decimal places is false precision. For international trade and technical specifications, SI units (meters, kilograms, liters) are the standard. US customary units (feet, pounds, gallons) differ from Imperial UK units: 1 US gallon = 3.785 L vs. 1 UK gallon = 4.546 L.

💡 Methodological Standards & Calculation Accuracy

  • All calculations are performed client-side in your browser using verified, standards-compliant mathematical algorithms.
  • Results are provided for educational and informational analysis; verify critical applications with certified domain specialists.
  • Ensure input values are entered in consistent units matching the selector options to guarantee accurate outputs.
  • Periodic recalibration is recommended whenever baseline assumptions, operating parameters, or external conditions change.

Results are for informational and educational purposes only. Always verify critical decisions with a qualified professional.

❓ Frequently Asked Questions

Can you convert PSI directly to GPM without knowing pipe or nozzle size?

No. PSI measures force per unit area (pressure), while GPM measures volume over time (flow rate). You must know the restriction diameter, Cv, or K-factor to calculate flow.

What is Freeman's Formula for water flow?

Freeman's Formula is Q = 29.83 Cd d² * √P, used by municipal water utilities and fire departments to calculate water discharge from hydrants and hoses.

What is a fire sprinkler K-Factor?

The K-Factor is a discharge coefficient rating for fire sprinkler heads; flow is calculated as Q = K * √P.

How does doubling water pressure affect GPM flow rate?

Because flow scales with the square root of pressure (√P), doubling pressure (e.g. from 25 to 50 PSI) increases flow rate by approximately 41.4% (√2 ≈ 1.414).

What is Hydraulic Horsepower (HHP)?

Hydraulic horsepower represents the actual fluid mechanical energy delivered by a pump or water jet, calculated as / 1,714.

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