McQuay Duct Sizer – Free Download

About McQuay Duct Sizer

McQuay Duct Sizer (now part of Daikin) is a free, lightweight Windows utility for sizing HVAC air ducts by the equal-friction and equal-velocity methods. Enter the airflow (CFM or L/s) and a friction rate, and it instantly returns the round duct diameter, the equivalent rectangular size, air velocity and pressure loss — the digital version of the classic ductulator wheel.

Key features

• Round & rectangular duct sizing by equal-friction or velocity method
• Instant velocity and friction-loss readout for every size
• Metric (Pa/m, L/s, mm) and Imperial (in.wg/100ft, CFM, in) units
• Round-to-rectangular equivalent conversion built in
• Tiny footprint, works offline, no licence key needed

Prefer to size ducts in your browser with no install? Use our free online duct size calculator (ductulator) or read how to size HVAC ductwork.

System Requirements

• OS: Windows 7 / 8 / 10 / 11 (32 & 64-bit)
• RAM: 512 MB or more
• Disk: ~10 MB free space
• Other: No internet connection required to run

How to Install McQuay Duct Sizer

1. Click the Download button and save the ZIP/installer to your PC.
2. Right-click the downloaded file and choose Extract All (if zipped).
3. Run Setup.exe and follow the on-screen prompts, or run the extracted DuctSizer.exe directly (portable).
4. If Windows SmartScreen appears, click More info → Run anyway (the tool is unsigned freeware).
5. Launch the app, choose your units, and start sizing ducts.

Always scan any downloaded installer with your antivirus. MEPMate links to freeware for convenience and is not affiliated with McQuay/Daikin.