What is the formula to convert PSI to GPM?

The formula depends on the method used. For nozzles with K-factor: GPM = K × √PSI. For pipes using Bernoulli's principle: Calculate velocity from pressure difference, then multiply by cross-sectional area.

Can I convert GPM back to PSI?

Yes, this calculator supports bidirectional conversion. Enter your GPM value and pipe diameter or K-factor to calculate the required pressure in PSI.

What is a K-factor in fire sprinklers?

K-factor is a discharge coefficient that represents the flow characteristics of a nozzle or sprinkler head. It's calculated as K = Q/√P where Q is flow rate and P is pressure.

How does pipe diameter affect flow rate?

Larger pipe diameters allow for greater flow rates at the same pressure. Flow rate increases with the square of the diameter - doubling the diameter quadruples the flow capacity.

What is Cv in valve sizing?

Cv is the flow coefficient that measures a valve's capacity to pass fluid. It's defined as the flow rate in GPM of water at 60°F that will pass through a valve with a 1 PSI pressure drop.

Does fluid density affect the calculation?

Yes, fluid density affects flow calculations. This calculator defaults to water (62.4 lb/ft³) but allows custom density input for other fluids like oil or chemicals.

PSI to GPM Calculator — Convert Pressure to Flow Rate

Conversion Direction

Pressure

Calculation Method

Pipe Diameter

Fluid

Result Unit

Flow Rate

44.27

GPM

Velocity: 5.68 ft/s | Area: 3.14 sq in | Formula: Bernoulli

⮟ Advanced Options

Friction Factor

Pipe Length

Decimal Places

Show Velocity

PSI to GPM Calculator — Quickly convert pressure (PSI) to gallons per minute (GPM) using pipe diameter, K-factors or Cv. Use this free CalculatorCave tool for fast, accurate flow estimates for plumbing, irrigation, fire protection, and industrial applications.

How It Works

This calculator uses three main methods to convert between pressure and flow rate:

1. K-factor Method (Nozzles & Sprinklers)

For nozzles and sprinkler heads, flow is calculated using: GPM = K × √PSI

Where K is the nozzle discharge coefficient. This is the most accurate method for fire sprinklers and spray nozzles.

2. Cv Method (Valves)

For control valves, flow is calculated using: GPM = Cv × √ΔP

Where Cv is the valve flow coefficient and ΔP is the pressure drop across the valve in PSI.

3. Bernoulli Method (Pipes)

For pipes, we use a simplified Bernoulli equation assuming incompressible flow:

v = √(2 × ΔP / ρ) where v is velocity, ΔP is pressure difference, and ρ is fluid density

Q = v × A where Q is volumetric flow and A is cross-sectional area

This method provides a good estimate for short pipe sections with minimal friction loss.

Worked Examples

Example 1: K-factor Nozzle

Input: K-factor = 5.6, Pressure = 50 PSI

Calculation: GPM = 5.6 × √50 = 5.6 × 7.071 = 39.6 GPM

Result: 39.60 GPM

Example 2: Pipe Flow

Input: Diameter = 2 inches, Pressure = 50 PSI, Downstream = 14.7 PSI

Calculation: ΔP = 35.3 PSI, Area = 3.14 sq in, Velocity = 14.1 ft/s

Result: 44.27 GPM

Example 3: GPM to PSI (Reverse)

Input: GPM = 10, Diameter = 1 inch

Calculation: Solve Bernoulli equation for pressure

Result: 5.03 PSI required

Frequently Asked Questions

What is the difference between K-factor and Cv?

K-factor is used for nozzles and sprinklers (GPM = K × √PSI), while Cv is used for valves (GPM = Cv × √ΔP). K-factor is dimensionless, while Cv has units of GPM/√PSI.

Can this calculator handle different fluids?

Yes! The calculator includes presets for water, oil, and gasoline, plus a custom density option. Fluid density affects flow calculations since heavier fluids require more pressure to achieve the same flow rate.

Why do I need to enter downstream pressure?

Flow is driven by pressure difference (ΔP), not absolute pressure. For open systems discharging to atmosphere, downstream pressure is 14.7 PSI. For closed systems between two vessels, you need both upstream and downstream pressures.

How accurate are the pipe flow calculations?

The basic Bernoulli method assumes no friction loss and is accurate for short pipe sections. The advanced mode includes friction factor for more accurate results in longer pipelines. For precise engineering, consult a professional.

What units can I use?

Pressure: PSI, bar, kPa. Flow: GPM, LPM, m³/h, GPH. Diameter: inches, mm. Area: sq in, sq mm. The calculator automatically converts between units for consistent results.

Is this calculator suitable for fire protection systems?

Yes! The K-factor method is specifically designed for fire sprinkler calculations. Fire protection engineers commonly use this calculator for hydraulic calculations of sprinkler systems per NFPA 13 standards.