Easy Duct

Easy Duct is an air duct sizing calculator built by an HVAC engineer for real design work. Enter what you know and get a buildable duct size in seconds, on site or at your desk. Easy Duct solves for whatever is missing: airflow, head loss, velocity or duct size. Set a maximum head loss and a maximum velocity together, and the duct is sized to whichever limit is reached first. The governing limit is always named, so you know exactly why you got that size. SIZE THE WAY YOU DESIGN - Head loss and velocity limits checked at the same time - Rectangular and round duct, with aspect ratio shown for every size - Buildable size steps (½, 1 or 2 in) so results match what gets fabricated - EN 1506 standard sizes for metric round duct - Pick any duct size and see its spare capacity live SAFETY FACTOR AND ADD TO FLOW - Apply a flow safety factor that is built into the design flow - Adding a branch or outlet? Type the extra airflow and it goes straight onto the total CROSS-CHECK: TWO SCENARIOS, ONE DUCT Size a single duct against two sets of conditions, such as normal and peak operation. Link Scenario B to Scenario A by percentage, added value, equal or absolute, and see side-by-side results with the scenario that governs named up front. UNITS YOUR WAY - Switch between IP and SI with one tap - Tap any unit to change it, field by field: a mm duct with L/s or cfm airflow is fine ENGINEERING YOU CAN CHECK - Darcy-Weisbach with your choice of friction model: Colebrook, Haaland or Altshul - Duct wall roughness by material - Air density and viscosity from temperature and altitude - Full results: design flow, velocity, head loss, equivalent diameter, required round size, cross-section, Reynolds number, friction factor and velocity pressure SIMPLE AND FAST - Minimal interface with results that fold away until you need them - Works fully offline - Also available on Windows and Android Easy Duct is for HVAC and mechanical engineers, designers, estimators and students who size ductwork every day and want a quick, reliable answer.