Stair Stringer Dimensions by Step Count
Pre-computed stringer tables for 2 to 16 steps: rise per step, total run, stringer length, and cut angle at a 10.5″ tread. Find your total rise, pick your step count.
Which step count do you need?
| Steps | Total Rise Range | Longest Stringer | 2×12 Needed |
|---|---|---|---|
| 2-step | 8–15" (0' 8" to 1' 3") | 18.3" | 8 ft |
| 3-step | 16–23" (1' 4" to 1' 11") | 31.1" | 8 ft |
| 4-step | 24–31" (2' to 2' 7") | 44.2" | 8 ft |
| 5-step | 32–38" (2' 8" to 3' 2") | 56.6" | 8 ft |
| 6-step | 39–46" (3' 3" to 3' 10") | 69.8" | 8 ft |
| 7-step | 47–54" (3' 11" to 4' 6") | 83.0" | 8 ft |
| 8-step | 55–62" (4' 7" to 5' 2") | 96.2" | 10 ft |
| 9-step | 63–69" (5' 3" to 5' 9") | 108.7" | 10 ft |
| 10-step | 70–77" (5' 10" to 6' 5") | 121.9" | 12 ft |
| 11-step | 78–85" (6' 6" to 7' 1") | 135.1" | 12 ft |
| 12-step | 86–93" (7' 2" to 7' 9") | 148.3" | 14 ft |
| 13-step | 94–100" (7' 10" to 8' 4") | 160.9" | 14 ft |
| 14-step | 101–108" (8' 5" to 9') | 174.1" | 16 ft |
| 15-step | 109–116" (9' 1" to 9' 8") | 187.3" | 16 ft |
| 16-step | 117–123" (9' 9" to 10' 3") | 199.8" | landing/LSL |
Measure your total rise (finished floor or deck surface to finished landing, in inches), find the matching row, and open the step-count page for the full dimension table. Ranges keep every riser at or under the IRC 7¾" maximum (R311.7.5.1).
Need exact numbers for your measurements? Use the stair stringer calculator or, for outdoor stairs, the deck stair calculator.
How these tables are computed
Every row is generated by the same calculation engine as the interactive calculators: rise per step = total rise ÷ steps; total run = (steps − 1) × tread; stringer length = √(rise² + run²); cut angle = arctan(step rise ÷ tread). Tables assume a 10.5" tread — two 5.5"-wide deck boards with a ½" gap, and comfortably over the IRC 10" minimum (R311.7.5.2). The engine is verified by an automated test suite that runs before every release.
Rules of thumb across all step counts
- 4 or more risers → a graspable handrail is required on at least one side (IRC R311.7.8).
- Walking surface more than 30" up → guards required on open sides (IRC R312.1.1) — from about 5 steps on, that is every stair.
- Riser uniformity: largest and smallest riser within 3/8" of each other (IRC R311.7.5.1).
- Comfort rule: rise + run between 17" and 18" feels natural underfoot.
- Past a 16-foot 2×12 (around 16 steps), plan a mid-flight landing or use LSL stringer stock.