Control Valve · Free Calculator
Valve Pressure Drop from Cv Calculator
Find the pressure drop across a fully open valve, strainer or any component rated with a Cv or Kv value, for a given liquid flow.
ΔP from CvΔP from KvLiquidsStrainers and valves
SG
Pressure drop0.5939 bar
Pressure drop8.614 psi
Pressure drop59.39 kPa
Equivalent Kv51.9
How this result was calculated
- Kv = 51.9 (Cv ÷ 1.156)
- ΔP = SG × (Q ÷ Kv)² = 1 × (40 ÷ 51.9)² = 0.5939 bar
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Pressure Drop from Flow Coefficient
ΔP (bar) = SG × (Q ÷ Kv)², Q in m³/h
ΔP (psi) = SG × (Q ÷ Cv)², Q in US gpm
ΔP (psi) = SG × (Q ÷ Cv)², Q in US gpm
Worked example
40 m³/h of water through a valve with Cv 60 (Kv 51.9): ΔP = (40 ÷ 51.9)² = 0.59 bar.
Key insight: pressure drop rises with the square of flow, so doubling flow through a strainer quadruples its pressure drop. Size isolation valves and strainers for a small drop at maximum flow.
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Frequently Asked Questions
How do I calculate pressure drop from Cv?
ΔP (psi) = SG × (gpm ÷ Cv)². In metric units use Kv, m³/h and bar.
Does this apply to gases?
Only approximately at small pressure drops. Use the gas valve sizing calculator for gas service.
Can I use it for strainers and check valves?
Yes, any component with a published Cv or Kv, for turbulent liquid flow.
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Control valve flow coefficient (Cv) explained
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