Butterfly Valve Dimensions & Cv Flow Chart
This reference gives typical flow coefficients (Cv) for resilient-seated wafer butterfly valves by nominal size, plus notes on bore and face-to-face dimensions. Use it to confirm a valve will control flow in a useful range — not just near full open.
What Cv means
Cv is the flow coefficient: the gallons per minute of 60°F water that pass through a fully open valve at 1 psi of pressure drop. Higher Cv means less restriction. A butterfly valve reaches most of its rated Cv only in the last ~30–70° of opening, so for throttling you want to operate in that controllable band.
Typical Cv by size
Approximate full-open values for resilient-seated butterfly valves. Always confirm against the manufacturer datasheet for the specific valve.
| Nominal size | Typical full-open Cv (approx.) |
|---|---|
| 2" | ~120 |
| 2-1/2" | ~190 |
| 3" | ~340 |
| 4" | ~630 |
| 5" | ~1,000 |
| 6" | ~1,500 |
| 8" | ~2,900 |
| 10" | ~4,900 |
| 12" | ~7,400 |
Bore and face-to-face
Wafer butterfly valves have a near-full bore (the disc sits in the flow path). For reference, our 4" stainless-disc valve has a 4.10" bore and the 10" has a 9.87" bore. Face-to-face (lay length) follows API 609 / MSS SP-67 for wafer valves, so they drop into standard ANSI 125/150 flange gaps. Confirm exact lay length on the datasheet before finalizing pipe spool dimensions.
Sizing tips
For on/off service, size the valve to the line. For throttling, pick a size where your normal flow falls in the 30–70° open range — an oversized valve does all its control in a narrow, twitchy band near closed. When in doubt, share your flow rate and pressure drop and we'll help size it.
Shop butterfly valves
See sizes and configurations: Butterfly Valves. Related: selection guide and lever vs gear operators.