What Size Inside Door Header Should I Use?

This door header size calculator is a tool designed to help determine the appropriate size of wood beam for your door or window. It provides a comprehensive look at header design and discusses how to figure out the right-size header for different spans. For example, a 3 to 4 foot span should use 4″×4″ lumber, while a 5 to 6 foot span should use 4″×6″ lumber. The door header size calculator is a specialized tool designed to help you determine the appropriate size for the header over door openings in a construction setting.

The size of the header will vary depending on the size of the new window or door opening. For example, with openings up to 3 feet wide, 2×4’s may be used, while for openings up to 5 feet, 2×6’s should be. A typical header width with single jack studs is cut 3″ larger than the rough opening. Double or triple jack should also be considered.

For an interior door, make a header with two 2-by-4s laid flat together on the 4-inch faces. Most new doors are 6 ft. 8 in. tall. Cut the header to fit between the king studs, check the thickness of the studs, and install a cripple stud between the header and the top. If on the top floor, use 2 2×4’s (unless the building is 36′ wide) or 2 2×6’s (unless the building is 36′ wide).

Double 2×12 headers are still the standard for window and door openings, but the IRC lists other options for headers that save lumber. Interior doors need headers to be either 2″ x 4″ or 2″ x 6″, while exterior doors require a minimum of 2″ x 10″.