Last updated: July 10, 2026
For questions, bug reports, or feature requests about Duct Calc Pro, please contact:
goonobu@gmail.com
We review all messages and reply as soon as we can (please allow some time for a response).
Q. What formulas does the app use?
A. Round duct sizing and friction loss use the standard equal-friction duct chart equation (ΔP = 0.109136 × CFM^1.9 / D^5.02, in.wg per 100 ft, for galvanized round duct). Round/rectangular conversion uses the ASHRAE Fundamentals (Huebscher) equivalent diameter equation: De = 1.30 × (a×b)^0.625 / (a+b)^0.25. Each calculation screen shows the formula it used.
Q. Is this a substitute for a full engineered duct design?
A. No. Duct Calc Pro is a fast field-reference and preliminary-sizing tool. Final duct design must follow applicable codes, project specifications, and a qualified engineer's judgment.
Q. Are there any ads?
A. No. The App does not include any advertising SDK.
Q. Where is my calculation history stored?
A. Entirely on your device. The App performs no network communication and has no account or sign-in.
Q. How do I delete my history?
A. Swipe to delete individual entries in the History tab, or uninstall the App to remove all data stored on your device.
Q. Are there any in-app purchases?
A. No. This is a one-time paid app — all features are available after purchase with no additional charges.
See the Privacy Policy.