Ductulator is an engineering tool to calculate air duct dimensions based on given inputs including air-flow, duct material roughness and either air pressure static loss (friction method) or air velocity (velocity method).
This online ductulator calculates the dimensions for both round and rectangular duct options (one dimension should be entered by the user for rectangular duct). The output also includes air velocity when air static loss is an input (friction method) or it includes air static loss when velocity is an input (velocity method).
Note that when using velocity method, unlike conventional ductulators, this ductulator will calculate the dimensions of the rectangular duct based on the given velocity and it then calculates the static pressure loss for the rectangular duct based on the given velocity and dimensions. Most old calculators (including cardbox ones) will only use the given velocity to calculate the diameter of the round duct then it calculates the static pressure loss for the round duct and uses that static pressure to calculate the rectangular duct dimensions which is not the case here so getting more precise velocity output.