Stairs Calculator

This calculator is intented as a guide. Even though we have based the calculations on the IRC, you must always check with local building codes to ensure there are no variances.

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

Step 1

Input the total elevation change from the top of the decking material surface to the landing area the stairs will rest on.


Step 2


Select the size of the nosing you prefer. Nosing is the distance that the tread overhangs beyond the rise of the next step.


Step 3

Select the construction style of stairs you prefer. The style of construction is based on whether you intend to connect your stairs on the outside or inside of the deck framing. You may also choose whether you wish the first step level with the top of the deck or the first rise below the deck surface.

Outside Frame - Level with deck
Outside Frame - First rise below deck
Inside Frame - First rise below deck

Input the size of joist you plan to use. The most common joist sizes are 2x8 and 2x10. 2x6 joists are very rarely used and not recommended because of their reduced spans but you may select this if you wish.


Double Rim Joist?

Some decks have a second rim joist (also called perimeter or band joist) around the deck framing. Select this option if you choose to use a double rim joist configuration.

Input the size of the stringer you will use. The 2x10 is more common, but sometimes a 2x12 is a good idea in order to increase the minimum distance between the corner of the tread notches and the underside of the stringer.


Be sure to recalculate any changes before printing.

*All results given in inches

**After stringer is measured, cut thickness of one tread from bottom