Enter total rise and target tread run the layout solves risers, stringer length, and live IRC code checks instantly.
Floor-to-floor vertical height.
Over 36″ gets a 4th stringer.
Key IRC R311.7 checks riser & tread
Covers riser height and tread depth only. Full R311.7 compliance also requires riser/tread uniformity (⅜″), 6′-8″ headroom, 36″ stairway width, landings, and handrails verify on site.
Riser OK
7.71″ vs max 7.75″ (R311.7.5.1)
Tread OK
10.5″ vs min 10″ (R311.7.5.2)
Steep / shallow
2R+T = 25.93″ (target 24–25″)
Labor (optional)
Step count
14
RISERS
Bill of materials+0% waste
2×12 stringers (16-ft stock)
3 stringers @ 36″ wide
Net 14.51 ft cut · Waste —
Treads
Top tread is the landing (14 risers − 1)
Net 13 ea · Waste —
Cost projection
Saved on this device · No account · No cloud
Total · $335.60
14 × 7.71″ risers
Riser count = round(total rise ÷ 7.5); unit rise = total rise ÷ count. Treads = risers − 1 (the top tread is the landing).
Enter total rise and target tread run the layout solves risers, stringer length, and live IRC code checks instantly.
IRC R311.7: risers ≤ 7¾″, treads ≥ 10″. The comfort rule 2R + T should land between 24″ and 25″.
Stringer boards round up to stock 10/12/14/16-ft 2×12s; widths over 36″ get a fourth stringer.
Risers = total rise ÷ 7
The IRC caps residential risers at 7-3/4 inches maximum, with treads at least 10 inches deep. The calculator targets about 7.5 inches per riser for comfort and flags any layout over the code maximum.
Riser count = round(total rise / 7.5); unit rise = total rise / count; treads = risers - 1, since the top tread is the landing. Stringer boards round up to stock 10, 12, 14, or 16-ft 2x12s.
From the total rise and total run — the calculator solves the stair's slope length and rounds up to the next stock 2x12 length. Widths over 36 inches get a fourth stringer.
108 / 7.5 = 14.4, so 14 risers at 7.71 inches each, with 13 treads (the top tread is the landing). The calculator checks each riser against the 7-3/4 inch IRC maximum.
Twice the riser height plus the tread run should land between 24 and 25 inches for a comfortable stair. It is a comfort guideline, not a code requirement.
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