Cv vs Kv
Side by side comparison: how they work, where each fits, and which to choose.
Quick answer: Cv and Kv both state valve capacity: Cv in US gpm of water at 1 psi, Kv in m³/h at 1 bar. Cv = 1.156 × Kv.
Cv vs Kv: Comparison Table
| Aspect | Cv | Kv |
|---|---|---|
| Units | US gpm, psi | m³/h, bar |
| Used mainly in | USA, ISA | Europe, IEC |
| Conversion | Cv = 1.156 Kv | Kv = 0.865 Cv |
| Full open value | Rated Cv | Kvs |
Choose Cv when
- ISA and US data sheets
Choose Kv when
- IEC 60534 and European data sheets
Key Differences Explained
Both use the same equation shape: flow equals coefficient times √(ΔP ÷ SG). The same corrections for piping, viscosity and choked flow apply.
Always check which coefficient a data sheet uses before comparing valves.
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Frequently Asked Questions
What is the difference between Cv and Kv?
Cv and Kv both state valve capacity: Cv in US gpm of water at 1 psi, Kv in m³/h at 1 bar. Cv = 1.156 × Kv.
Is Kvs the same as Kv?
Kvs is Kv at full rated travel.
Why 1.156?
It comes from converting gpm to m³/h and psi to bar.
Which does IEC 60534 use?
Both, with constants for each.
Learn more on the blog
Control valve flow coefficient (Cv and Kv)
A practical guide on instrumentationblog.in that goes deeper into this topic with field examples.
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