Kv to Cv Converter
Per ISA 75.01 Annex D and IEC 60534-2-1, the conversion between metric Kv (m³/h at 1 bar ΔP, water at 5-40°C) and US Cv (GPM at 1 psi ΔP, water at 60°F) is: Cv = 1.156 × Kv, or...
Formula
Source: ISA 75.01-2012 Annex D; IEC 60534-2-1 | Last reviewed: July 3, 2026
Examples
10 kV
= 11.56 cv
Kv 10 → Cv 11.56 (small chemical injection valve)
50 kV
= 57.8 cv
Kv 50 → Cv 57.8 (typical process valve)
100 kV
= 115.6 cv
Kv 100 → Cv 115.6 (large chiller valve)
500 kV
= 578 cv
Kv 500 → Cv 578 (cooling tower header)
Quick Reference Table
| Kv (m³/h) | Cv (GPM) | Typical Valve | Application |
|---|---|---|---|
| 0.1 | 0.12 | 1/4" needle | Lab / analytical |
| 1 | 1.16 | 1/2" globe | Small process |
| 4 | 4.6 | 3/4" globe | Instrument air |
| 10 | 11.6 | 1" globe | Small chemical |
| 25 | 28.9 | 1.5" globe | Process cooling |
| 63 | 72.8 | 2" globe | Heat exchanger |
| 160 | 185 | 3" globe | Large chiller |
| 400 | 462 | 4" globe | Cooling tower |
| 1000 | 1156 | 6" globe | Main header |
Where is this used?
European manufacturers (Samson, Siemens, KSB) typically specify valves in Kv; US manufacturers (Fisher, Emerson, Flowserve) specify in Cv.
Process control engineers in the US working with European equipment must convert.
The conversion is linear, not pressure-dependent, because both Kv and Cv are defined as flow at 1 unit of pressure drop (water).
The 1.156 factor is exact and should not be approximated as 1.16 or 1.2 — these introduce 0.4% and 3.8% error respectively.
Real-World Usage Scenarios
European Valve Specified in US Project
A US specifier receives a quotation from Samson (Germany) for a Type 3241 globe valve sized as Kv 100. The US specifier must convert to Cv to use the company's standard ISA 75.01 sizing procedure. Cv = 1.156 × 100 = 115.6. The corresponding US sizing at 15 psi ΔP: GPM = 115.6 × √15 = 447.7 GPM. The specifier notes that this is a borderline 3-inch valve (typical Cv range 100-300 for 3") and selects the 4-inch body with appropriate trim for better control rangeability.
Common Mistakes to Avoid
Using 1.16 or 1.2 as the conversion factor
The exact ISA 75.01 factor is 1.156. Using 1.16 gives 0.4% error (small but accumulates in process audits). Using 1.2 gives 3.8% error (significant for control valve sizing). The exact factor comes from the unit conversion: 4.4029 GPM/m³/h divided by √(14.504 psi/bar).
Confusing Kv with Kvs or Kvr
Kv is the valve flow coefficient. Kvs is the maximum Kv when the valve is fully open (often used in datasheets). Kvr is the rated Kv at a specific stroke position. The Kv-to-Cv formula applies to all three, but the engineer must know which Kv is being specified.
Industry Standards Referenced
Frequently Asked Questions
What is the exact formula to convert Kv to Cv?
Cv = 1.156 × Kv. The factor 1.156 is exact per ISA 75.01 Annex D. Reverse: Kv = 0.865 × Cv. The conversion is linear and does not depend on pressure or fluid (because both Kv and Cv are defined as flow at 1 unit ΔP of water).
Are Kv and Cv the same physical quantity?
Yes, they represent the same physical quantity (valve flow coefficient) in different units. Kv uses m³/h at 1 bar ΔP, water at 5-40°C. Cv uses GPM at 1 psi ΔP, water at 60°F. The 1.156 factor is the unit conversion ratio between these two reference conditions.
Does the conversion change for different fluids?
No. The Kv-to-Cv conversion is purely a unit conversion between metric and US. For different fluids (gas, steam, viscous), you use different sizing formulas entirely, not different unit conversion factors. The 1.156 factor is constant for all fluids and all pressures.
Reviewed for accuracy
Cross-referenced against ISA 75.01 Annex D and IEC 60534-2-1 · 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.