How to Cut Stair Stringers (Step by Step)

Updated October 2026

Cutting stair stringers comes down to three things: an accurate total rise, a careful layout with a framing square, and cuts that stop exactly at your lines. Get the first stringer right and it becomes the template for the rest.

What you need

2x12 pressure-treated lumber rated for ground contact if the stringers will sit near soil or on a pad that stays wet. A 2x10 leaves too little wood below the notches for most outdoor stairs.
Framing square and a pair of stair gauges (small clamps that lock onto the square)
Circular saw plus a handsaw or jigsaw to finish the inside corners
Tape measure, pencil, a 4 ft level and a long straightedge
End-cut preservative (copper naphthenate) for the freshly cut treated wood

Step 1: Measure the total rise

Total rise is the vertical distance from the surface the stairs will land on up to the top of the deck boards, not the top of the joists.

On flat ground, measure straight down from the deck surface. On sloping ground, the landing spot is usually several feet out from the deck and lower than the ground at the rim. Rest a long straightedge on the deck, extend it level to roughly where the bottom step will land, and measure down to the ground (or the top of your planned concrete pad) there. Then recheck the landing distance once you know the total run (step 2), because a different landing spot changes the rise.

Step 2: Work out risers and treads

Divide the total rise by 7.75” (the IRC maximum riser height) and round up. That’s your number of risers.
Divide the total rise by that number for the exact riser height.
Treads = risers − 1. The deck itself is the top step.
Total run = treads × tread depth (10” minimum; 10½–11” is more comfortable).

For a 36” rise: 36 ÷ 7.75 = 4.65, so 5 risers of 7.2” (about 7 3/16”), 4 treads, and 40” of run with 10” treads. The stair stringer calculator does this for you and also checks throat depth and code limits.

Step 3: Lay out the first stringer

Lay the 2x12 across sawhorses, crown (the slight upward bow) facing up.
Clamp the stair gauges to the framing square: riser height on the tongue (the short, narrow leg) and tread depth on the blade (the long, wide leg).
Starting near the bottom end, set the square on the board with both gauges tight against the top edge. Trace along the outside of the tongue and blade.
Slide the square up so the tongue mark lines up with the end of the previous tread line, and trace again. Repeat for every step.
At the bottom, draw a level line where the stringer will sit on the pad. At the top, draw a plumb line where it meets the rim joist.

Double-check that you’ve drawn the right number of risers and that every riser and tread measures the same. The code allows only ⅜” variation between the largest and smallest riser.

Step 4: Drop the stringer

Every step will get a tread on top, but the bottom of the stringer sits directly on the pad. Without an adjustment, the first step would be one tread thickness taller than the rest.

Cut the bottom riser shorter by the thickness of one tread: about 1” for 5/4 deck boards or composite, 1½” for 2x lumber. Mark this new level line before you cut anything.

Step 5: Make the cuts

Cut along the lines with a circular saw, but stop the blade before it reaches the inside corner of each notch. Overcutting into the corner weakens the stringer right where it’s narrowest.
Finish each corner with a handsaw or jigsaw, keeping the blade vertical.
Cut the bottom level line and the top plumb line.
Brush end-cut preservative on every cut surface of treated lumber.

Step 6: Test-fit, then copy

Set the first stringer in place against the rim and check each tread with a level. If it’s right, trace it onto the remaining 2x12s and cut them the same way. Most deck stairs need three stringers for a 36” wide stair. See how many stringers you need.

Attaching the stringers

At the top: hang stringers from the rim joist with stringer connectors rated for the load, or from a hanger board fastened to the rim per your local code.
At the bottom: set the stringers on a level concrete pad or footing, not directly on soil, so they stay dry and don’t settle.
Space stringers evenly and keep the tops aligned. A string line across the notches shows any that sit high or low.

Common mistakes

Measuring rise to the joists instead of the finished deck surface. Every step comes out wrong.
Forgetting to drop the stringer. The bottom step ends up taller than the rest, and that’s a trip hazard.
Using 2x10s. A 7”+ riser with a 10” run notches away more than 5” of a 2x10, leaving almost nothing for the throat.
Overcutting the notches. It cracks stringers over time.

Before you build, review the deck stair code requirements your inspector will check.