PSI to GPM Calculator
Calculate flow rate (GPM) from pressure (PSI) using the orifice flow equation or Cv coefficient method — for valves, nozzles, and pipe systems.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
Flow Rate
35.827 GPM
L/min (LPM)
135.619
m³/hr
8.137
Formula: Q = 29.84 × Cd × d² × √P (Cd = 0.62)
This tool provides general unit conversions for everyday and educational use. For regulated, legal, or scientific applications, verify conversion factors against the applicable official standard.
About the PSI to GPM Calculator
The PSI to GPM calculator estimates water flow in US gallons per minute from pressure. It offers two methods: an orifice method, Q = 29.84 × Cd × d² × √P, for water flowing through a round opening of known diameter, and a valve method, Q = Cv × √ΔP, using the flow coefficient published by valve manufacturers. Real systems lose pressure in hoses and pipes, so treat the orifice result as a theoretical maximum.
How to use it
- 1Choose the orifice or Cv method.
- 2Enter the pressure in PSI.
- 3Enter the orifice diameter in inches or the valve Cv value.
- 4Copy, share or print the result with the buttons below it.
Worked example
water through a 0.5-inch sharp-edged orifice at 60 PSI flows at about 29.84 × 0.62 × 0.25 × √60 ≈ 35.8 GPM. A valve with Cv = 2 at a 25 PSI drop passes 2 × 5 = 10 GPM.
How it works
Methods
Orifice method: Q = 29.84 × Cd × d² × √ΔP (Q in GPM, d in inches, P in PSI, Cd ≈ 0.62 for sharp edge)
Cv method: Q = Cv × √ΔP — Cv is the flow coefficient provided by valve manufacturers.
Typical flow rates
- Garden hose (5/8 in nozzle, 60 PSI): ≈ 9 GPM
- Shower head (60 PSI): 1.5–2.5 GPM (restricted)
- Fire hydrant: 250–1500 GPM
Common use cases
- Sizing nozzles and orifices
- Estimating flow through a valve
- Irrigation and pump planning
Frequently asked questions
A:Flow rate is proportional to the square root of pressure differential (Bernoulli principle). Doubling the pressure increases flow by ~41%, not 2×.
A:Cv is the flow coefficient: the volume of water (in GPM) that passes through a valve at 1 PSI pressure drop. Higher Cv = less restrictive valve.
Reviewed for accuracy · Last updated October 7, 2026
Conversion factors are based on internationally defined SI units and standard metric/imperial equivalence tables.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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