DuctCalc - HVAC Ductulator

Size and check HVAC ductwork with guided steps made for installers, sheet-metal workers, and residential designers. DuctCalc works on iPhone and iPad, and its calculators work without an internet connection. SIZE DUCTWORK Enter airflow, then size by design friction or target velocity. Review the exact diameter, recommended standard round size, velocity, friction, and nearby round options. Select up to three rectangular heights for equivalent sizes, set fabrication width increments, and apply a configurable flex-duct factor when your design calls for one. CHECK AN EXISTING DUCT Choose round, rectangular, or flat oval. Use known airflow to calculate velocity and friction, or use known velocity to calculate airflow. Add an optional run length to estimate total friction loss. Results also include velocity pressure. CONVERT DUCT SHAPES AND UNITS Calculate equivalent round and rectangular dimensions, solve a missing rectangular side, size from an aspect ratio, and find a flat-oval equivalent diameter. Add airflow for a velocity comparison. A separate flex correction helper and converters for airflow, pressure, length, velocity, and friction cover common imperial-to-metric field conversions. QUICK JOBSITE CALCULATIONS Estimate airflow from cooling tons, divide system CFM evenly across registers and size each branch, or estimate round and rectangular duct surface area and sheet-metal weight by gauge with a waste allowance. SAVE, SHARE, AND SET DEFAULTS Save Size and Check results to searchable local history, revisit or delete saved work, and share calculation text through the iOS share sheet. Set units, rectangular width increment, flex factor, velocity-warning preset, decimal places, and haptics. PAY ONCE, WORK OFFLINE No account, ads, in-app purchases, or subscriptions. Calculations, history, and settings are stored locally on your device. Sharing, feedback, rating, and privacy-policy links open only when you choose them. DuctCalc uses standard ASHRAE equations for clean galvanized duct and standard air. Actual system performance depends on fittings, material, elevation, and installation quality. Sizing shown here is a starting point; verify with an approved design method (for example, ACCA Manual D) and applicable codes.