Joist Span Calculator

For help, simply click on the(?) beside the section you need help with, Or watch this Tutorial Video.

Select the species of wood you will be using. Each species has its own unique physical characteritics and properties which in turn affect its ability to span distances. Generally the softer the wood, the shorter distance it can span and the greater its dimensions must be in order to span an identical distance compared to a harder wood.

Select the type of beam configuration you will be using for your deck or floor structure (Pictured to the right)

Select the nominal dimension of your joists.


Joists are typically spaced at 12", 16" and 24" apart from the center of one joist to the next. The closer joists are spaced, the farther they can span between supporting beams.