🚰 PSI to GPM Calculator
Use valve Cv and fluid specific gravity to estimate flow rate from pressure drop—or pressure drop from flow.
Enter the flow coefficient (Cv), specific gravity, and either pressure drop or flow to compute the other. This tool is useful for valve sizing, plumbing, and hydraulic calculations.
Flow Parameters
Cv is the flow rate in GPM that produces a 1 psi drop for water at 60°F.
Use relative density (fluid density ÷ water density). Water ≈ 1.0, gasoline ≈ 0.72.
Convert Between PSI & GPM
Differential pressure across the valve/orifice. Must be non-negative.
Enter flow to compute the required pressure drop or leave as-is to see the conversion from psi.
Flow from Pressure Drop
37.95 GPM
Only shown when pressure drop is specified.
Pressure Drop from Flow
10.03 psi
Only shown when flow rate is provided.
How to Use This Calculator
Enter the valve Cv and specific gravity
Cv is supplied by valve manufacturers. Specific gravity accounts for fluids heavier or lighter than water.
Provide either pressure drop or flow
Input the known value; leave the other field blank or zero to calculate it. You can also supply both to check consistency.
Review the computed result
Flow from pressure uses GPM = Cv × √(ΔP / SG). The reverse equation solves for required pressure drop.
Formula
GPM = Cv × √(ΔP / SG)
ΔP = (GPM ÷ Cv)² × SG
These standard valve sizing equations assume turbulent flow of liquids and CV referenced at 60°F water.
Use the formula breakdown to confirm the calculation logic or perform the conversion manually if needed.
Full Description
Valve and orifice manufacturers publish a flow coefficient (Cv) indicating how much water flows with a 1 psi drop. This calculator extends the relationship to arbitrary pressure drops and fluids by accounting for specific gravity.
Engineers and technicians can use it to estimate pump performance, balance hydronic systems, or approximate flow through irrigation equipment before running more detailed simulations.
Remember: results are approximations. For compressible fluids or highly viscous liquids, more advanced equations or empirical data may be required.
Frequently Asked Questions
Where do I find Cv values?
Check valve datasheets, manufacturer catalogs, or conduct laboratory testing. Cv depends on valve size, style, and trim position.
What if my fluid is not water?
Adjust the specific gravity input. For example, diesel ≈ 0.85, brine ≈ 1.2. The calculator scales the result accordingly.
Does this work for gases?
No. Gas flow requires compressibility corrections (Cv equations differ). Use specialized gas sizing formulas instead.
Can I set Cv or SG to zero?
No. Both values must be positive. A zero Cv implies no flow; zero specific gravity is not physically meaningful.