[header] How to measure stair stringers [title] Determine the overall height of the stairs. [step] Extend a level out across the upper edge of the deck or porch (or the entry point, if you're building stairs for a shed or similar structure). Stretch your tape measure from the bottom of the board to the ground. 
This will tell you exactly how high the new stairs will reach. [substeps] The stringers are the notched, sloping boards that will go on either side of the stairs to hold the steps and support the weight that's placed on them.