Pick the direction
Size a valve from duty, predict the drop across an installed Cv, or predict the flow it will pass — one equation, solved three ways.
Free tools · Industrial
Right valve, first time.
Size Cv/Kv, predict drop or flow for liquids per IEC 60534 — computed on your device, never uploaded.
Size · drop · flow
Right valve, first time.
Size Cv/Kv from duty, or predict drop and flow for an installed valve — liquids, turbulent non-choked, IEC 60534. Everything computes on your device.
Solve for
Liquids only, turbulent non-choked (Q = 0.865 · Cv · √(ΔP/G)). Add margin per your valve vendor's practice.
How it works
Three steps, all on your device.
The same N1 equation behind every valve schedule, solved three ways without accounts or uploads.
Enter the duty
Flow with independent volume and time units, differential pressure in any unit, and specific gravity (water is 1). Fields you don't need stay out of the way.
Read Cv and Kv
Both coefficients with the full basis trail, ready to copy into datasheets and requisitions — with a margin reminder per vendor practice.
Questions
Sizing valves, answered.
If you manage servers by hand, see the engineering services behind this tools series.
Is my data uploaded anywhere?
No. Sizing runs entirely in your browser — the page makes no network requests with your data. You can verify this in your browser's developer tools or disconnect from the network after the page loads.
What is the difference between Cv and Kv?
Two dialects of the same number: Kv is metric (m³/h of water across 1 bar), Cv is US customary (gpm of water across 1 psi), and Cv = 1.156 × Kv. The tool reports both, so datasheets match whatever the vendor quotes.
When does this equation not apply?
Liquids in turbulent, non-choked flow only. It does not cover gases or steam (compressible — needs xT and expansion factors), flashing or cavitation (vapor pressure matters), or laminar viscous flow (Reynolds correction). Choked or flashing service needs full IEC 60534 treatment with the fluid's vapor pressure.
How much margin should I add to the calculated Cv?
Size so the valve normally operates at 60–80% open: practice varies by vendor and service, and control quality collapses near fully open or nearly closed. Treat the computed Cv as the hydraulic answer, then select the next standard trim up with your vendor.
Gauge or absolute for the pressure drop?
Either — a difference is a difference. Enter the differential directly in any unit; atmospheric pressure cancels out of ΔP.
Can it handle gas or steam flow?
Not yet — compressible sizing needs the gas expansion factor and critical-flow data per fluid. Gas and steam modes are separate tools on the roadmap in the Industrial family.