Valve Pressure Drop Calculator
Find the pressure drop across a valve from the flow rate, valve Cv, and fluid specific gravity.
Method
ΔP = SG × (Q / Cv)² (Q in gpm, ΔP in psi)
Rearranged from the liquid sizing equation Q = Cv√(ΔP/SG).
Tip
If the calculated drop is high, the valve is undersized for the flow — choose a higher-Cv valve. Keep the valve operating below ~80% of rated Cv.
Frequently Asked Questions
How do I calculate valve pressure drop?
Use ΔP = SG × (Q/Cv)² with flow in gpm; the result is in psi.
What if the drop is too high?
The valve is undersized — select one with a higher Cv to reduce the drop.
Does this apply to gas?
This form is for liquids; compressible flow uses different equations.
What Cv should I enter?
The valve’s rated Cv at the operating opening, from its datasheet.
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