Support

Does DuctSizer Pro need an internet connection?

No. The app is 100% offline — every calculation runs on your device, instantly, anywhere on a job site with no signal.

What can DuctSizer Pro do?

Size mode: enter airflow plus a target friction rate or velocity to get a recommended round duct diameter, its nearest standard size, and a rectangular equivalent. Analyze mode: enter airflow and existing duct dimensions (round or rectangular) to get velocity, friction rate, velocity pressure, and Reynolds number for a duct you already have.

What formulas does it use?

Calculations follow ASHRAE Fundamentals (Duct Design chapter): the Colebrook–White equation for the friction factor, Darcy–Weisbach for pressure loss, and the Huebscher correlation for round-to-rectangular equivalent diameter (equal-friction basis, not equal-velocity).

What duct materials are supported, and what roughness values do they use?

Material	Roughness (ε)
Smooth (PVC, aluminum)	0.03 mm
Galvanized steel (default)	0.09 mm
Average (fibrous glass, lined)	0.15 mm
Medium rough (flex, fabric)	0.90 mm
Rough (flex, fully extended)	3.00 mm

Can I switch between metric and imperial units?

Yes — go to Settings → Units to toggle SI/IP globally, and Settings → Airflow Unit to pick L/s, m³/h, or CFM independently.

Is DuctSizer Pro available in other languages?

Yes — English and Japanese are supported. Switch under Settings → Language.

Is this a subscription?

No. DuctSizer Pro is a one-time purchase. There are no subscriptions, no ads, and no in-app purchases beyond the initial download.

Does the app collect any of my data?

No — see the Privacy Policy for details.