4-Step Stair Stringer: Dimensions, Length & Cut Angle
Four steps is where deck stairs get serious: this is the first step count that requires a handrail, and it covers the very common 2-foot deck height. Every row is computed by the same engine as our interactive calculator.
4-step stringer dimensions · 10.5" tread
| Total Rise | Rise per Step | Total Run | Stringer Length | Cut Angle |
|---|---|---|---|---|
| 24" (2') | 6.00" (6") | 31.5" | 39.6" (39 5/8") | 29.7° |
| 25" (2' 1") | 6.25" (6 1/4") | 31.5" | 40.2" (40 3/16") | 30.8° |
| 26" (2' 2") | 6.50" (6 1/2") | 31.5" | 40.8" (40 7/8") | 31.8° |
| 27" (2' 3") | 6.75" (6 3/4") | 31.5" | 41.5" (41 1/2") | 32.7° |
| 28" (2' 4") | 7.00" (7") | 31.5" | 42.1" (42 1/8") | 33.7° |
| 29" (2' 5") | 7.25" (7 1/4") | 31.5" | 42.8" (42 13/16") | 34.6° |
| 30" (2' 6") | 7.50" (7 1/2") | 31.5" | 43.5" (43 1/2") | 35.5° |
| 31" (2' 7") | 7.75" (7 3/4") | 31.5" | 44.2" (44 3/16") | 36.4° |
Total run is fixed at 31.5" for 4 steps with a 10.5" tread: (steps − 1) × tread, because the upper floor or deck acts as the top step. For a different tread depth, total run = 3 × tread.
Rise per step is floored to the nearest 1/16" for framing-square layout. Different total rise? Use the interactive stringer calculator.
When do you need 4 steps?
Four steps is where deck stairs get serious: this is the first step count that requires a handrail, and it covers the very common 2-foot deck height.
A 4-step stringer covers total rises from 24" (2') to 31" (2' 7") while keeping every riser at or under the IRC maximum of 7¾" (R311.7.5.1). Below 24", use a 3-step stringer; above 31", move to 5 steps.
What board do you need?
The longest stringer in the table is 44.2", so a 8-foot 2×12 covers every case with layout margin. Use solid, straight-grained 2×12 stock — after notching, the remaining "throat" must keep at least 3.5" of material for structural integrity.
Code checkpoints for a 4-step stair
- Handrail required. 4 risers is at or over the 4-riser threshold — a graspable handrail is required on at least one side (IRC R311.7.8).
- Guards depend on height. Rises above 30" in this range trigger the guard requirement on open sides (IRC R312.1.1); at or below 30" they are optional.
- Riser uniformity: the largest and smallest riser may differ by no more than 3/8" (IRC R311.7.5.1) — divide total rise by 4 and mark every notch from the same reference edge.
- Drop the bottom riser by one tread thickness so the first step matches the rest after treads go on.