Enter the pressure drop, flow rate, Cv, and specific gravity into the calculator to determine the missing variable.

Cv To Pressure Drop Calculator

Enter any 3 values to calculate the missing variable

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Cv To Pressure Drop Formula

The following formula is used to calculate the pressure drop for a given flow rate, Cv, and specific gravity (for incompressible liquids, with Q in GPM and ΔP in psi).

\Delta P = \left(\frac{Q}{Cv}\right)^2 \cdot SG

Variables:

  • ΔP is the pressure drop
  • Q is the flow rate
  • Cv is the flow coefficient
  • SG is the specific gravity

To calculate the pressure drop, divide the flow rate by Cv, square the result, and then multiply by the specific gravity.

Cv to Pressure Drop Conversion Table (Q = 10 GPM, SG = 1.00)
Cv (unitless) Pressure Drop (psi)
1100.000
1.544.444
225.000
2.516.000
311.111
46.250
54.000
7.51.778
101.000
120.694
150.444
200.250
250.160
300.111
400.063
500.040
600.028
750.018
1000.010
1500.004
*Assumes flow rate Q = 10 GPM and water (SG = 1.00). Formula: ΔP (psi) = (Q / Cv)² × SG.

What is Cv?

Cv, or flow coefficient, is a measure of the capacity of a valve to pass fluid. It is defined as the flow rate of water in gallons per minute (GPM) at 60°F that will pass through a valve with a pressure drop of 1 psi. The higher the Cv, the greater the flow rate through the valve for a given pressure drop.

How to Calculate Pressure Drop?

The following steps outline how to calculate the pressure drop.

  1. First, determine the flow rate (Q).
  2. Next, determine the flow coefficient (Cv).
  3. Next, determine the specific gravity (SG).
  4. Finally, calculate the pressure drop using the formula ΔP = (Q / Cv)² × SG.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Flow rate (Q) = 10 GPM

Flow coefficient (Cv) = 5

Specific gravity (SG) = 1