DuctSizer: Duct Calculator
HVAC sizing: friction & CFM
Free · In‑App Purchases
Rebuilt for iOS 26: native tab bar, system lists, and a Home Screen widget with your last duct size. Airflow in, sizes out — live. One-time Pro, no subscription.
Size ducts in seconds — right from the ladder.
DuctSizer turns airflow into duct sizes instantly. Enter CFM (or L/s) and a friction rate or velocity target, and read every valid size at a glance: round diameter plus rectangular options for the joist depth you actually have.
SIZING, FREE
• Round and rectangular results, live as you type
• Friction and velocity for every option, with clear limit warnings
• Imperial and SI units (CFM, L/s, m³/h · in.wg/100 ft, Pa/m)
• Material roughness shown for galvanized, spiral, duct board, and flex
DUCTSIZER PRO — ONE-TIME PURCHASE
• Reverse mode: pick a size, get its max airflow — including flex with honest compression derating, and flat-oval ducts
• Fittings & pressure loss: total effective length and Manual D friction rate (FR = ASP × 100 / TEL)
• Altitude and temperature density correction, always visible
• Saved jobs: group runs by project and export CSV or PDF
THE MATH, DONE RIGHT
Calculations follow the ASHRAE friction chart with Darcy–Weisbach and Haaland for material roughness, and Huebscher equivalents for rectangular and flat-oval ducts. Results match the cardboard wheel you trained on — with the steps the wheel can't do.
BUILT FOR THE FIELD
• Works 100% offline — no account, no sign-in
• No analytics or tracking; your data stays on your device
• Dark, glare-friendly interface with big touch targets
• iPhone and iPad, iOS 17 or later
Pro is a single one-time purchase. No subscription, ever.
DuctSizer is an independent app and is not affiliated with or endorsed by ASHRAE, ACCA, or Trane.
Privacy Policy: https://ductsizer.app/privacy
Terms of Use: https://ductsizer.app/terms
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Rebuilt on native iOS controls.
• New Home Screen widget shows the last duct size you worked out
• “Size a duct” now works from Shortcuts, Spotlight and Siri
• Every screen moved to the system tab bar, lists and pickers
• Numeric keyboards now have a Done button
• Full Dynamic Type support — numbers scale with your text size
• Fixed decimal separators on non-US region formats
The developer, Alican Basak, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Purchases
- Identifiers
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Alican Basak
- Size
- 7.7 MB
- Category
- Utilities
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- DuctSizer Pro $9.99
- Copyright
- © 2026 Alican Basak