What Is the Control Valve Flow Coefficient (Cv) Calculator?
The flow coefficient (Cv) is a standardized measure of a valve’s capacity to pass fluid flow.
By definition, a valve with a Cv of 1.0 will pass 1.0 US GPM of water at 60°F with a 1.0 PSI pressure drop.
How Does the Control Valve Flow Coefficient (Cv) Calculator Work?
Evaluates the ratio of fluid specific gravity to allowable pressure drop.
Multiplies by flow rate to calculate Cv.
Converts to metric Kv (m³/hr with 1 bar ΔP) via dividing by 1.156.
Control Valve Flow Coefficient (Cv) Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Cv is defined as the flow of 60°F water in GPM through a valve with a pressure drop of 1 PSI.
How to Use the Control Valve Flow Coefficient (Cv) Calculator
- Enter required flow rate in GPM.
- Enter available pressure drop across the valve in PSI.
- Specify liquid specific gravity.
Step-by-Step Example Calculation
45 GPM of Water across a 5 PSI Pressure Drop
Input Values:
Understanding Your Result
Choose a catalog valve with a maximum full-open Cv approximately 25%–30% larger than the calculated requirement.
Factors That Affect the Result
- Choked flow, cavitation index, and pipe reducer swage corrections.
When Should You Use This Calculator?
- Sizing 2-way and 3-way modulating control valves for HVAC air handlers, chillers, and industrial autoclaves.
Assumptions & Limitations
- Applies to turbulent liquid flow without flashing or cavitation.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard ISA-75.01.01 / IEC 60534 control valve sizing standard.