Valve Cv / Kv Calculator

Calculate the required valve flow coefficient for liquid applications using flow rate, Druckverlust, and specific gravity.

Required volumetric liquid flow.
Relative to water at the relevant reference condition.
Upstream gauge pressure.
bar
Downstream gauge pressure.
Anwendung: Preliminary calculation for single-phase, non-choked turbulent liquid flow. Not suitable for gas, Dampf, flashing or cavitating flow.

What Is a Valve Cv / Kv Calculator?

A valve Cv/Kv calculator estimates the required flow coefficient for a specified liquid flow rate and differential pressure. Engineers use flow coefficients to compare valve flow capacities and support preliminary valve selection.

Valve Cv and Kv Calculation Formulas

Kv = Q × √(SG / ΔP)

Q is liquid flow rate in m³/h. SG is the liquid specific gravity. ΔP is the differential pressure in bar. This simplified relationship applies to non-choked turbulent liquid flow.

Cv ≈ 1.1561 × Kv

Cv vs. Kv: Main Differences

Parameter Cv Kv
Measurement system US customary Metric
Reference flow unit US GPM m³/h
Pressure drop reference 1 psi 1 bar
Conversion Cv ≈ 1.1561 Kv Kv ≈ Cv / 1.1561

Valve Cv Calculation Example

Consider a water system with a liquid flow rate of 10 m³/h, an inlet pressure of 5 bar(g), and an outlet pressure of 4 bar(g). With specific gravity of 1.0, the pressure drop is 1 bar. The resulting required Kv is 10.0 and Cv is approximately 11.56.

How to Select a Valve Using Cv or Kv

Compare the required coefficient with the manufacturer's published valve capacity data at the intended operating position. Two valves with the same nominal diameter may have different flow coefficients.

Consider valve pressure rating, body and sealing materials, process temperature, fluid properties, valve characteristics and pressure recovery. Final valve sizing may require calculations according to IEC 60534-2-1.

Frequently Asked Questions

Can Cv determine valve diameter directly?

NEIN. Cv indicates flow capacity under specified reference conditions. The required valve size depends on the manufacturer's valve design and its available flow coefficients.

Is a higher Cv always better?

NEIN. Oversized control valves can provide poor regulation at low openings. A suitable valve must meet the required operating range.

Can this calculator size steam valves?

NEIN. Steam and gas are compressible fluids and require separate sizing equations and additional process data.

Does this tool check cavitation?

NEIN. This calculator does not evaluate cavitation, blinken, choked flow or viscosity corrections.

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Disclaimer: Calculation results are preliminary estimates and do not replace detailed engineering design, manufacturer valve sizing data, or qualified review.