Free Engineering Tool
Valve Flow Coefficient Calculator
Bidirectional Kv/Cv calculator for valve sizing. Calculate Kv from flow + ΔP, flow from Kv + ΔP, or ΔP from Kv + flow. For liquid flow.
Results
Kv for Liquid Flow
The flow coefficient Kv (European standard) is defined as the flow of water in m³/h through a valve at 1 bar pressure drop:
- Kv — flow coefficient (m³/h at ΔP = 1 bar)
- Q — volumetric flow rate (m³/h)
- SG — specific gravity (water = 1.0; hydraulic oil ≈ 0.87)
- ΔP — pressure drop across valve (bar)
Kv ↔ Cv Conversion
Cv is the US/imperial equivalent: flow in US GPM of water at ΔP = 1 psi and 60°F.
Valve Sizing Guide
| Valve Type | Typical Kv Range | Notes |
|---|---|---|
| Ball valve DN15 | 10 – 40 | Full bore preferred for hydraulics |
| Ball valve DN25 | 50 – 200 | Low pressure drop at full open |
| Ball valve DN50 | 250 – 800 | Most common in process |
| Globe valve DN25 | 8 – 15 | Good for throttling/control |
| Globe valve DN50 | 25 – 50 | Higher ΔP than ball |
| Butterfly DN100 | 300 – 600 | Compact, large flows |
| Needle valve | 0.1 – 5 | Fine flow adjustment |
Practical Example
Given: Q = 60 L/min hydraulic oil (SG = 0.87), ΔP = 5 bar
Convert: Q = 60 / 1000 × 60 = 3.6 m³/h
Kv = 3.6 × √(0.87 / 5) = 3.6 × 0.417 = 1.50
Cv = 1.50 × 1.156 = 1.74
Recommended valve Kv ≥ 1.50 × 1.3 = 1.95 (with safety margin)
⚠️ Note: For critical applications, also check: cavitation index (FL factor), noise level, rangeability, and dynamic response. Consult the valve manufacturer’s sizing software for final selection.
The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.
Professional field balancing instruments and software. Used in 50+ countries.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
