DuctFlow Lite is a fast, offline HVAC duct-sizing calculator for mechanical engineers, HVAC designers, and building-services technicians.

Enter the airflow rate and your target friction loss, and DuctFlow Lite returns the required round duct diameter and equivalent rectangular duct dimensions, plus air velocity and pressure drop per unit length — all calculated with the classic equal-friction duct-sizing method used in industry design charts.

KEY FEATURES
- Equal-friction duct sizing
- Round duct diameter output in mm / inches
- Equivalent rectangular duct sizing with user-selectable aspect ratio
- Velocity and pressure-drop per meter / per 100 ft reporting
- Supports SI (L/s, Pa/m, mm) and Imperial (CFM, in.wg/100 ft, inches) units
- Clean, single-screen workflow — enter values, get results instantly
- Works fully offline — no account, no sign-up, no ads, no tracking

WHO IT'S FOR
- HVAC design engineers working on commercial, industrial, or residential ducted systems
- Site engineers and technicians checking duct sizing on the job
- Engineering students learning HVAC duct design and the equal-friction method
- Anyone who needs a quick sanity check on a duct size without opening a full design suite

WHY DUCTFLOW LITE
Other duct calculators are either stripped-down demos or riddled with ads and sign-up walls. DuctFlow Lite is a no-account, no-tracking engineering tool — purpose-built to do one job well. It runs entirely on your device, so your project data never leaves your phone.

ABOUT THE METHOD
The equal-friction method sizes duct sections so that pressure loss per unit length remains approximately constant throughout the system, which gives a reasonably balanced design with modest effort. DuctFlow Lite implements this standard approach, making results directly comparable to hand calculations and to results from established commercial tools.

PRIVACY
DuctFlow Lite does not collect, store, or transmit any personal information. There are no user accounts, no analytics, no ads, and no third-party SDKs. Calculations run entirely on your device.

This app is provided as an engineering productivity tool. For feedback or questions, visit engineershouse.org.

Engineers House

Additional Information