Water Pressure to GPM Calculator by Tons of Concrete

Water Flow Formulas:

\[ V = \sqrt{\frac{2 \times (P_1 - P_2) \times 144}{\rho}} \] \[ Q = V \times A \times 448.83 \]

Inlet Pressure (P₁):

psi

Outlet Pressure (P₂):

psi

Water Density (ρ):

lb/ft³

Pipe Diameter:

inches

Velocity (V): ft/s

Flow Rate (Q): GPM

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is a Water Pressure to GPM Calculator?

Definition: This calculator estimates water flow rate in gallons per minute (GPM) based on pressure difference and pipe diameter.

Purpose: It helps plumbers, engineers, and irrigation specialists determine water flow through pipes for system design and troubleshooting.

2. How Does the Calculator Work?

The calculator uses these formulas:

\[ V = \sqrt{\frac{2 \times (P_1 - P_2) \times 144}{\rho}} \] \[ Q = V \times A \times 448.83 \]

Where:

\( V \) — Water velocity (feet per second)
\( P_1 \) — Inlet pressure (psi)
\( P_2 \) — Outlet pressure (psi)
\( \rho \) — Water density (lb/ft³, default 62.4)
\( Q \) — Flow rate (gallons per minute)
\( A \) — Pipe cross-sectional area (ft²)

Explanation: The pressure difference creates velocity, which when multiplied by pipe area gives volumetric flow rate.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate estimation ensures proper pipe sizing, pump selection, and system performance in plumbing, irrigation, and industrial applications.

4. Using the Calculator

Tips: Enter pressure values (P₁ > P₂), water density (default 62.4 lb/ft³), and pipe diameter in inches. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: Why is pressure difference important?
A: Flow occurs due to pressure differential, not absolute pressure. Higher differences create faster flow.

Q2: What affects water density?
A: Temperature primarily - colder water is denser (62.4 lb/ft³ at 50°F, 61.9 at 100°F).

Q3: Does this account for pipe friction?
A: No, this is theoretical maximum. Real systems have friction losses reducing actual flow.

Q4: How does pipe diameter affect flow?
A: Flow increases with the square of diameter - double diameter gives ~4x flow at same pressure.

Q5: When would this calculation not apply?
A: For viscous fluids, very small pipes (capillary flow), or compressible fluids like air.