ProjectCalc (working name)

Stair Calculator

Enter the total rise — get the riser count, exact riser height, treads, run and stringer length, plus a printable layout template for your stringer.

Inches — or feet/inches like 9'
Inches — code max is 7¾″ (IRC); 7–7½″ is comfortable
Inches — code minimum 10″; 11″ is comfortable
Sets the stringer count (16″ max spacing)

DimensionValue
Risers
Actual riser height (cut this)
Treads
Total run
Stringer length (minimum board)
Stringers needed
Comfort check (2 × riser + tread)

🛒 Shopping list

ItemQty
2×12 stringer boards
Tread boards (2 per tread, cut to width)
Stringer hangers / framing angles + structural screws

✅ Layout checklist

  • Measure total rise twice — finished floor to finished floor, not subfloor
  • Every riser must be identical; variation over 3/8″ in a flight fails code and trips people
  • Drop the first stringer mark by the tread thickness so the first step lands level
  • Cut one stringer, test-fit it, then use it as the template for the rest
  • Check headroom (6′8″ minimum) and handrail requirements before you finish

How the math works

Risers = total rise ÷ target riser height, rounded to a whole number; the *actual* riser height is then total rise ÷ that count, so every step is exactly equal. Treads = risers − 1 (the top landing is the last "tread"). Stringer length is the hypotenuse of total rise and total run. The comfort rule — two risers plus one tread should total 24–26″ — is what makes stairs feel right; the calculator checks it for you.

For estimation and layout only. Stair codes vary locally (max riser, min tread, headroom, railings) — confirm with your building department, especially for interior and egress stairs.