Free online valve sizing tool — calculates the required flow coefficient (Cv) for liquid, gas, or steam service using Miller Valve's own sizing methodology, with choked-flow detection and an indicative valve size.
The flow coefficient (Cv) is the standard measure of a valve's flow capacity. It's defined as the volume of water (60°F) in US gallons per minute that passes through a fully-open valve with a pressure drop of 1 psi across it.
Higher Cv means more flow capacity. Sizing a control valve correctly is critical: undersized valves can't pass design flow at acceptable ΔP, and oversized valves cycle in a small portion of their range — accelerating wear and degrading control quality.
For a quick reference: a typical 1" ball valve has a Cv around 50, a 4" ball valve roughly Cv 1,000, and a 12" ball valve Cv ~10,000+. Globe and control valves are typically 30–50% lower at the same nominal size.
Cv = Q × √(SG / ΔP) (Q gpm, ΔP psi)Cv = Q × √(SG · T) / (1360 · √(ΔP · P1)) (Q scfh, T °R, P psia)These follow Miller Valve & Controls' own sizing methodology and reference library — CRANE Flow of Fluids, the Emerson Control Valve Handbook, and Miller's internal Cv procedure. The size shown is an indicative reference for scale only; our engineers select the exact valve, size, trim, and materials for your service.
For initial sizing. Final selection accounts for piping geometry, valve style factors (FL, Fp, Y), specific-heat ratio, cavitation, and rangeability via our full sizing program. Send us your conditions for a verified, engineered selection.
Our engineers verify Cv with full ISA-75 factor corrections, recommend trim packages, and match the right valve from our 16 vendor partners.
In loving memory of our founders and friends, Wayne and Lawton Miller