Cv to Kv Converter
Per ISA 75.01 Annex D and IEC 60534-2-1, the conversion from US Cv (GPM at 1 psi ΔP) to metric Kv (m³/h at 1 bar ΔP) is: Kv = 0.865 × Cv, or equivalently Kv = Cv / 1.156. The...
Formula
Source: ISA 75.01-2012 Annex D; IEC 60534-2-1 | Last reviewed: July 3, 2026
Examples
25.8 cv
= 22.3 kV
Cv 25.8 (100 GPM at 15 psi) → Kv 22.3
100 cv
= 86.5 kV
Cv 100 → Kv 86.5 (typical chiller)
500 cv
= 432.5 kV
Cv 500 → Kv 432.5 (large process)
Quick Reference Table
| Cv (GPM) | Kv (m³/h) | Typical Valve | Application |
|---|---|---|---|
| 0.5 | 0.43 | 1/4" needle | Lab |
| 5 | 4.33 | 1/2" globe | Small process |
| 25 | 21.6 | 1" globe | Instrument air |
| 100 | 86.5 | 2" globe | Process cooling |
| 500 | 432.5 | 4" globe | Cooling tower |
| 2000 | 1730 | 6" globe | Main header |
Where is this used?
The conversion is exact and linear.
European process control engineers working with US equipment (e.g., Fisher, Emerson) need to convert Cv to Kv to use European sizing software.
The 0.865 factor is exact per ISA 75.01 Annex D and should not be approximated.
Real-World Usage Scenarios
US Spec for European Manufacturer
A US engineering firm specifies a Fisher ED valve (Cv 200) in their P&ID. The European EPC contractor (working in IEC 60534 units) needs the Kv equivalent: Kv = 0.865 × 200 = 173. The European contractor specifies a Samson Type 3241 with Kv ≥ 173 (typically Kv 200 trim for 30% margin).
Common Mistakes to Avoid
Using 0.83 as the conversion factor
The exact ISA 75.01 factor is 0.865. Using 0.83 gives 4% error. Common source: some textbooks print 'Cv × 0.853' or 'Cv × 0.86' due to rounding. Verify with ISA 75.01 Annex D (current 2012 edition): Kv = 0.865 × Cv.
Industry Standards Referenced
Frequently Asked Questions
What is the exact formula to convert Cv to Kv?
Kv = 0.865 × Cv, or equivalently Kv = Cv / 1.156. The factor 0.865 is exact per ISA 75.01 Annex D. Reverse: Cv = 1.156 × Kv.
Is the conversion affected by pressure or fluid?
No. The conversion is purely between metric and US units at the same reference condition (1 unit ΔP, water). For non-water or non-1-unit pressure drops, use the full ISA 75.01 formula.
Why do some vendors use 1.17 instead of 1.156?
ISA 75.01 value is 1.156 (4.4028/√14.5038). SAMSON rounds to 1.17 for catalog simplicity. Difference is 1.2%. Use 1.156 for precise work.
Reviewed for accuracy
Cross-referenced against ISA 75.01 Annex D · Last reviewed: July 3, 2026
All calculations are for reference only. Always verify with manufacturer data and a qualified engineer for critical applications. Learn about our editorial process.