Maximum Duct Length Calculator
Parameters- Input values in yellow boxes
Result
Please select a Design Flow Rate to display your results.
Result
0 ft
"NL" = No limit on duct length for the specified system.
"X" = Specified system is not likely to achieve the design flow. Please vary the inputs to identify a compliant system.
- This tool may be used to comply with the requirements of 2015 IRC Section M1506.2 and 2018 IRC Section M1504.2.
- Duct length is calculated with the same formulas used to develop 2015 IRC Table M1506.2 and 2018 IRC Table M1504.2 (i.e., the Darcy-Weisbach-Colebrook equations). Assumptions are consistent with these tables (i.e., 15' for elbows, 30' for a termination fitting, standard temperature and pressure, and roughness factors of 0.0055' for flex ducts and 0.00038' for smooth ducts).
- Actual results may vary based on differences in equipment, materials, and installation. Compression of flex ducts by as little as 5% can significantly reduce flow.
- Fan curves are based on test data determined in accordance with ANSI/AMCA 210-ANSI/ASHRAE 51 and HVI 916.