Stair stringer layout
Divide the rise evenly, lay out the notches, and see the throat you are leaving in the board. Checked against the model code, with nothing adjusted behind your back to make a check pass.
Finished surface to finished surface
7 is comfortable
= 10.5"
Overhang past the riser
What the tread will span
8 risers, 7 treads
Rise per step
7 1/8"
7.1250"
Run per step
10 1/2"
Total run
73 1/2"
Stair angle
34.2°
Throat left
5 3/8"
Cut the bottom short
Take 1" off the bottom of every stringer after you lay out the notches — the thickness of one tread. Treads sit on top of the notches, so without this the first step finishes a full tread taller than the rest of them.
That single step is the most common way a set of stairs fails inspection, and it is the hardest to fix afterwards. Lay the notches out from the top of the board, then move the bottom cut up.
Against the model code
- Riser at most 7.75" — passesYours is 7.125".
- Tread depth at least 10" — passesYours is 10.500", measured nosing to nosing.
- Nosing 0.75"–1.25" where treads are under 11" — passesTreads are 10.50" deep, so a 0.75"–1.25" nosing is required. Yours is 1.00".
- No more than 151" of rise without a landing — passesYours is 57.0".
- Stair at least 36" wide — passesYours is 42.0".
- At least 5" of stringer left under the notch — passesYours is 5.35".
- Rise plus run between 17" and 18" (rule of thumb, not code) — passesYours is 17.63".
Checked against the 2021 IRC for residential stairs. Your jurisdiction amends this — some allow an 8" riser, some require 11" treads, some treat exterior deck stairs differently again. Ring your building department before you cut, not after.
Cutting the stringers
- Framing square settingsRise on the tongue, run on the blade
- 7 1/8" × 10 1/2"
- Plumb cutsTop of the stringer and every riser face
- 34.2° off square
- Level cutsThe heel, and every tread seat
- 55.8° off square
- Stringer stock93" of sawtooth, plus the end cuts
- 9 ft
- StringersNo more than 16" apart
- 4
- Treads11 1/2" deep — 10 1/2" of run plus the nosing
- 7 at 42" long
Marks along the top edge
- Step 1
- 12 11/16"
- Step 2
- 25 3/8"
- Step 3
- 38 1/16"
- Step 4
- 50 3/4"
- Step 5
- 63 7/16"
- Step 6
- 76 1/8"
- Step 7
- 88 13/16"
- Step 8
- 101 1/2"
Measured along the sloped edge from the toe of the bottom cut, every one from the same end. Stepping a framing square down the board eight times accumulates every small error you make; these marks do not.
This is a calculator, not an engineer
It divides the rise evenly, works out the cuts, and checks the result against the model code. It does not know your soil, your span, your handrail, your headroom, or what your inspector asked the last person to change. Stairs are the part of a build where getting it wrong hurts somebody — use this to lay out, and have the design checked.
About building stairs
- What is the maximum riser height?
- 7.75" under the 2021 IRC for residential stairs, with a minimum tread depth of 10". More importantly, the difference between the tallest and shortest riser in a flight may not exceed 0.375" — a stair with one odd step is the kind people fall down, because after two steps your feet stop looking. Local codes amend these numbers, so check with your building department.
- Why do I cut the bottom of the stringer short?
- Because the treads sit on top of the notches. Lay out a stringer from its bottom without thinking about it and every tread surface ends up one tread-thickness above the notch it rests on — which is fine for every step except the first, where the ground does not move up to match. So the first riser finishes a full tread taller than the rest. The fix is to cut the thickness of one tread off the bottom of the stringer after laying out the notches.
- How many stringers do I need?
- At least three for a stair up to 36" wide, and enough after that to keep the spacing under whatever the tread material will span — 16" on centre for 5/4 decking, up to 24" for 2x stock. A springy stair is not a code failure, it just feels wrong under your feet, and adding a stringer is far cheaper than living with it.
- Can I cut stringers from a 2x10?
- Usually not. Notching removes a triangle whose depth is rise × run divided by the hypotenuse, which for a typical 7 1/2" by 10" step is 6". A 2x12 is 11 1/4" wide and keeps 5 1/4" under the notch; a 2x10 is 9 1/4" and keeps only 3 1/4", well under the 5" of sound material a cut stringer wants. Use 2x12, or hang the treads off uncut stringers with cleats or brackets.
- What is a comfortable rise and run?
- Rise plus tread depth between 17" and 18" is the old carpenter's rule, and it holds up. A 7" rise with an 11" tread is close to ideal for a main stair; deck stairs often go a little steeper. The rules are about stride length — too shallow and you shuffle, too steep and you have to look at your feet on the way down.