HVAC Duct Calculator·Ductwork

Stop calculating one duct at a time. Ductwork models the whole critical path—supply and return in series—and shows whether the run fits the pressure the equipment actually has left for duct. Build the run, choose the airflow for each leg, and see where the pressure goes. Ductwork sizes round or rectangular duct, accounts for every length and fitting, identifies the element with the biggest loss, and shows a remedy when a larger stock size fixes the problem. WHOLE-RUN DUCT SIZING Supply and return are calculated together through the air handler, while each leg keeps its own airflow and duct size. Choose the equipment pressure budget from a preset or enter a custom value. Filter, coil, supply register, return grille, and other losses are taken out before the duct is sized. TWO CALCULATION METHODS Use either: • Equivalent length, where fittings are charged as additional straight-duct length • Loss coefficients, where fittings are charged from their velocity pressure Straight duct is calculated with Darcy-Weisbach and Colebrook-White friction factors. BUILD THE ACTUAL RUN Add straight duct and supported fittings including elbows, starting collars, offsets, and register boots. Choose: • round or rectangular duct • galvanized, flexible, or lined material • automatic stock sizing or a hand-set size • imperial or metric units • design temperature and elevation Automatic sizing walks the available stock sizes and keeps 15% of the pressure budget in reserve. SEE WHAT COSTS THE MOST Ductwork shows: • available and used pressure • duct size and velocity • friction and fitting losses • the highest-loss element • fits, fits but tight, or does not fit • a larger stock size when one resolves the problem The run is drawn to scale with supply, return, fittings, and the device in place. REPORT THE RUN The report uses the same solve as the calculator. It includes the drawing, verdict, pressure breakdown, both legs, every element and its loss, the calculation method, and the assumptions used. The PDF is formatted for paper and can be sent through the iOS share sheet to Mail, Print, or Save to Files. OFFLINE AND PRIVATE All calculations work offline. Runs, saved jobs, and settings stay on the device. Nothing you enter about a run leaves the phone. FREE The free version includes the complete calculator: all supported fittings and materials, both calculation methods, imperial and metric units, the equipment pressure budget, run drawing, verdict and remedy, plus one saved job with unlimited edits. ONE-TIME UNLOCK A one-time in-app purchase unlocks additional saved jobs, job duplication, the full report, and PDF export. There are no subscriptions. Ductwork models one linear residential critical path. It does not calculate loads, select equipment, balance branch systems, calculate duct leakage, perform psychrometrics, or provide CFM capacity for a chosen duct size. Ductwork is a calculation aid for US residential practice. It is not ACCA-approved software and does not replace a Manual J/S/D package, permit submittal, inspection, design engineer, or professional judgment. Privacy Policy: https://vexor.digital/legal/ductwork/privacy.html Terms of Use: https://vexor.digital/legal/ductwork/terms.html