When selecting industrial valves, many people get confused by the CV value and KV value. Both parameters describe how much flow a valve can handle, yet the numbers are different. If you mix them up or convert them incorrectly, you may end up selecting a valve with insufficient flow—affecting production—or one that is oversized and wastes money. In some cases, it may even increase the system’s energy consumption.This article explains the definitions, usage, and conversions of these two parameters to help you make the right choice during valve selection.

CV Value & KV Value: Two“Flow Measuring Rulers”with Different Uses

In essence, CV and KV values represent the same concept: a measure of a valve’s flow capacity.

The difference lies in the measurement units and the regions where they are used:

CV Value: The “Imperial Measuring Ruler” used in North America

The CV value (Flow Coefficient) is commonly used in the U.S. and other imperial-unit regions.It is defined based on the following test conditions:Water at 60°F (≈15.6°C), under a pressure drop of 1 psi.The CV value equals the number of U.S. gallons per minute (gpm) that can pass through the valve when it is fully open.For example, if a valve has a CV of 10, it means that with a 1 psi pressure drop, 10 gpm of 60°F water can pass through it.For applications using imperial units, CV is the universal standard.

KV Value: The “Metric Measuring Ruler” used internationally

The KV value is the flow coefficient under the metric system.The test conditions are:Water at 20°C, under a pressure drop of 1 bar.The KV value equals the cubic meters per hour (m³/h) of water flowing through a fully open valve.

For example, a valve with KV = 5 can deliver 5 m³/h of water under a 1 bar pressure drop.Most regions using SI units—Asia, Europe, Southeast Asia—commonly rely on the KV value for valve selection.

 In short, CV and KV are like “inches” and “centimeters”: they measure the same thing but in different unit systems.

Why Are CV and KV Values So Important?

Many people think “close enough is fine,” but an incorrect CV/KV value can cause multiple problems.Its importance mainly lies in three areas:

1. Meeting flow requirements

If the required flow is 10 units but the selected valve only delivers 8, pressure will fluctuate and production may become unstable.If the valve is oversized, costs increase and installation becomes more complicated.

2. Energy consumption

A mismatched valve forces equipment—such as air compressors—to work harder.If a valve with insufficient flow stays open above 90% for long periods, energy costs rise significantly.With the correct CV/KV value, the valve may only need to open 50%, reducing energy usage.

3. Precision and process control

Industries like pharmaceuticals and food processing often require high flow accuracy.CV/KV values determine how much medium passes through the valve at different opening percentages (10%, 30%, 70%, etc.).Accurate flow control ensures consistent purity and product quality.

Conversion Between CV and KV Values

Engineers working on international projects often need to switch between the two systems.

The conversion formula is simple:

CV → KV: KV = CV × 0.865

KV → CV: CV = 1.156 × KV

Note:This formula applies to standard water conditions.For gases, steam, or high-temperature liquids, corrections must be made based on density and viscosity.

Practical Selection Tips

Step 1: Determine the region , choose the correct parameter

North America / Americas → use CV

Asia / Europe / Southeast Asia → use KV

International projects → use CV + KV to avoid conversion errors

Step 2: Consider the actual working conditions

Do not rely solely on the standard CV/KV values.

You must factor in:Medium type (liquid, gas, steam) , Temperature , Pressure , Density / viscosity (for non-water fluids).

Correct CV/KV selection is the foundation of valve sizing. A properly selected valve ensures system stability, reduces energy consumption, and minimizes long-term costs.

If you also need to use any type of pneumatic valves in your system, you can contact us directly.

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