# Flow Coefficient *C*_{v} versus Flow Factor *K*_{v}

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## Comparing flow coefficient *C*_{v} and flow factor *K*_{v}

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The flow coefficient - *C*_{v} - or the flow factor - *K*_{v} - are commonly used to specify capacities of control valves.

### Flow Coefficient - *C*_{v}

It is often convenient to express the capacity and flow characteristic of a control valve in terms of the

- Flow Coefficient -
*C*_{v}

The flow coefficient - *C*_{v} - is based on the imperial units system and is defined as:

*the flow of water through a valve at 60*^{o}F in US gallon/minute at a pressure drop of 1 lb/in^{2}

The flow coefficient is commonly used in the U.S.

### Flow Factor - *K*_{v}

The metric equivalent of the flow coefficient - *C _{v}* - is based on the SI-system and is called the

- Flow Factor -
*K*_{v}

The flow factor - *K _{v}* - is defined as

*the flow of water with temperature ranging 5 - 30*^{o}C through a valve in cubic meters per hour (m^{3}/h) with a pressure drop of 1 bar

The flow factor is commonly used outside U.S.

### Converting between Flow Coefficient *C*_{v} and Flow Factor *K*_{v}

The relationship between *C*_{v} and *K*_{v} can be expressed as:

*C*_{v}= 1.16 K_{v}*(1)**K*_{v}= 0.862 C_{v}*(2)*