What is the difference between Cv and Kv in control valves?

Cv and Kv both describe a valve's flow coefficient but use different units: Cv is the flow in US GPM of 60°F water through the valve with a 1 PSI pressure drop, while Kv is the flow in m³/h of water at 5–40°C with a 1 bar pressure drop. The conversion is: Cv = 1.156 × Kv, or Kv = 0.865 × Cv — so a valve with a Kv of 10 has a Cv of approximately 11.6. When specifying valves for international projects, always confirm whether the manufacturer's catalog uses Cv or Kv to avoid undersizing errors. For HVAC applications, typical control valve Cv values range from 0.3 (small reheat coil) to 160+ (large chiller bypass), and selection tables are available from Belimo, Siemens, and Honeywell that map required flow and pressure drop to the appropriate valve size.