To supply fresh outside air into the room (supply ventilation), or remove exhaust air from the room (exhaust ventilation), ventilation ducts are used. Ventilation ducts are made of brick, simultaneously with the construction of walls or in the form of pipes with different cross-sections. Pipes are usually made of thin sheet steel. Exhaust ventilation pipes of smaller cross-sections are assembled into a pipe of a larger cross-section, while if the pipe cross-sections are round, the complexity of designing pipe connection units - branches increases.
The program on this page of the site will calculate the unfolded lateral surface of the vent tee branch and save your precious time.
The page will also be useful when designing large diameter gas ducts.

Unfolded lateral surface of the vent oblique tee branch with axes offset.
It is cut out on sheet metal with further circular rolling.

vent duct
Outer diameter (D) of tee header
Inner diameter (d) of tee branch
Tilt angle (a) of tee branch
Оffset of axes (C) of tee branch and tee header
Vertical height (H) of tee branch
Branch wall thickness (s)
Number (n) of separation parts - points - of surface
You can download a free program for working with files with the .dxf extension   here
You can download the DWGTrueView thumbnail viewer   here