Stair Stringer Calculator
Lay out a stair stringer for a deck or porch: riser count and height, treads, total run, stringer length, angle, and the exact cuts to mark with your framing square.
Deck surface to ground, plumb
IRC minimum 10″ including nosing
2× material ≈ 1.5″
IRC 7.75″ · IBC 7″
Risers4
Actual riser height7.5″
Treads3
Total run30″
Stringer length (hypotenuse)3.54 ft (42.43″)
Stair angle45°
Stringer cut — vertical6″
Mark stringers with a framing square: horizontal cut = tread run (10″), vertical cut = riser minus tread thickness (6″). Cut the bottom riser shorter by the tread thickness so the treads land level. Check local code — riser max 7.75″ (IRC) or 7″ (IBC), and all risers must be within 3/8″ of each other.