The Kv value expresses the amount of flow in a regulating valve at a given valve position with a pressure loss of 1 bar. The special situation with a fully open valve determines the Kvs value.

The amount of flow at a lower pressure loss (Kv) can be calculated using the formula:
Kv = Q / √ΔP
where
Kv: Kv value [m³/h]
Q: Flow [m³/h]
ΔP: Pressure loss over regulating valve [bar]

The Kvs value expresses the amount of flow in a regulating valve at a fully-open valve position and a pressure differential of 1 bar. The Kvs value is a special case of the Kv value, which indicates the flow at a given valve position and a pressure differential of 1 bar.

The flow at a lower pressure loss can be calculated by rearranging the equation:
Kvs = Q / √ΔP
where
Kvs: Kvs value [m³/h]
Q: Flow [m³/h]
ΔP: Pressure differential across a regulating valve [bar]