Guide
How to lay out a stair stringer with a framing square
By Uri Haramati · Updated November 13, 2026
Set stair gauges on a framing square at your riser height on the tongue and your tread depth on the blade. Step the square along a 2x12 and trace each notch. Then cut the bottom of the stringer short by one tread thickness, so every finished step comes out the same height.
Before you start
You need the number of risers, the riser height and the tread depth. If you do not have them yet, start with how to calculate stairs. Tools: a framing square, a pair of stair gauges, a pencil, a tape measure, a circular saw, and a handsaw or jigsaw for the corners.
Step 1: Pick the board
Use a straight 2x12, long enough for the stringer line plus the top and bottom cuts. Sight down the edge and find the crown, the slight hump. Lay out from the crown edge, so the crown faces up when the stringer is in place.
Step 2: Set the framing square
Clamp one stair gauge on the outside edge of the tongue at your riser height, and one on the outside edge of the blade at your tread depth. For a 7 5/16 in riser and a 10 1/2 in tread, set 7 5/16 on the tongue and 10 1/2 on the blade. No stair gauges? Clamp a straight strip of wood across the square at the same two marks.
Step 3: Mark the notches
- Lay the square on the board near the bottom end, with both gauges tight to the crown edge.
- Trace the outside of the tongue (a riser) and the outside of the blade (a tread).
- Slide the square up so the tongue starts where the last tread line ended, and trace again.
- Repeat until you have marked one riser line for every riser in the stair.
Mark lightly and count twice. A missed or extra step is the most common layout mistake.
Step 4: Mark the bottom and top cuts
At the bottom, draw a level line square to the first riser line. This is where the stringer sits on the floor, pad or landing.
Now make the first-step drop. Treads add their thickness to the top of every step. Without a correction, the first step comes out one tread thickness too tall and the last step one tread thickness too short. Move the bottom line up by the thickness of a tread and cut there. If the floor at the bottom will get its own flooring, move it up by the tread thickness minus the flooring thickness.
At the top, the last riser line becomes the cut that meets the rim joist or header. How the top is fastened (hangers, a hanger board or a ledger) depends on your framing and local rules.
Step 5: Check the throat
The throat is the narrowest strip of solid wood between the inside corner of a notch and the bottom edge of the board. It carries the load, so measure it square to the bottom edge. A common rule of thumb is at least 3 1/2 in, and some local rules ask for more. If it comes out thin, use a wider board or a different stair design.
Step 6: Cut and use it as a template
Cut along the lines with a circular saw and stop at the inside corners. Finish each corner with a handsaw or jigsaw, so you do not cut past the line and weaken the stringer. Test the first stringer in place, then trace it onto the other boards.
Example settings
| Setting | Value |
|---|---|
| Risers | 13 at 7 5/16 in |
| Treads | 12 at 10 1/2 in |
| Tongue (rise) | 7 5/16 in |
| Blade (run) | 10 1/2 in |
| Tread thickness | 1 in (5/4 deck boards) |
| Bottom riser on the stringer | 7 5/16 − 1 = 6 5/16 in |
See the stringer before you cut
Stair Once draws the stringer you are about to cut: every notch, the first-step drop for your tread thickness, the throat depth, the board length to buy and big framing square numbers for the tongue and blade.
Questions
Which side of the framing square is for the rise?
The rise goes on the tongue, the narrow 16 in leg. The tread goes on the blade, the wide 24 in leg. Set a stair gauge at each number on the outside edge of the square.
How much do I cut off the bottom of a stair stringer?
Cut off one tread thickness. With 1 in thick deck boards as treads, the bottom riser on the stringer is 1 in shorter than the others. If the floor at the bottom will get flooring, cut off the tread thickness minus the flooring thickness.
What size lumber do I need for stair stringers?
Cut stringers are usually 2x12. Notching removes a lot of the board, and a 2x12 leaves enough wood under the cuts for a typical stair. Check your local rules for deck and exterior stairs.
How many stringers does a stair need?
It depends on the stair width and how far your tread material can span. Many 36 in wide stairs use three stringers. Check the span rating for your tread boards.