Several highly-rated apps available on the Mac App Store replicate the McQuay experience: HVAC Duct Sizer:
If you prefer not to use workarounds, several native or web-based duct sizers exist for macOS. mcquay duct sizer for mac
If you're looking for a more manual or "paper" solution, you can refer to HVAC engineering textbooks or resources that provide duct sizing charts and methodologies for manual calculations. ASHRAE and other industry organizations publish guides and standards that can be used for manual duct sizing. The Quest for McQuay Duct Sizer for Mac:
A paid, user-friendly wrapper that allows you to run Windows executables without a full Windows license or virtual machine. Mac Hardware: Intel-based or Apple Silicon (M1/M2/M3) macOS
McQuay (now part of Daikin Applied) made a useful Duct Sizer utility that HVAC designers and contractors rely on to size ductwork quickly. If you’re a Mac user hunting for an accessible, Mac-friendly way to size HVAC ducts using McQuay’s tools or equivalents, here’s an engaging, practical piece you can use on a blog, product page, or newsletter.