Deck Stairs Calculator
Enter the height from ground to deck and the stair width. We'll size the steps, stringers, and material list — code-compliant rise/run included.
Advanced options
- Actual riser height
- 0 in
- Total run length
- 0 in
- Stringer count
- 0
- Stringer length (each)
- 0 in
- Treads needed
- 0
- Riser boards needed
- 0
- Estimated cost
- —
How the deck stair calculator works
A 36-inch drop from deck to ground takes 5 steps at a 7.2-inch riser, with 4 treads, 4 riser boards, and 4 stringers for a 4-ft-wide stair. The total run is 44 inches at an 11-inch tread depth, which makes each 2×12 stringer about 57 inches on the diagonal. A 7.2-inch riser and 11-inch tread are comfortably inside IRC limits of 7¾ inches max rise and 10 inches min tread.
The math: number of steps = total rise ÷ target riser height, rounded to the nearest whole number. The actual riser height is then total rise ÷ steps (so all risers are equal — code requires this to within ⅜").
Total run = (steps − 1) × tread depth. Stringer length = √(total rise² + total run²) for the diagonal cut. We round up to the next standard stringer length (12 ft / 3.6 m or 16 ft / 4.8 m for taller sets).
Code requirements (IRC, US residential)
- Riser height: 4" minimum, 7¾" maximum. All risers within ⅜" of each other.
- Tread depth: 10" minimum from front edge to back of nosing.
- Stair width: 36" minimum.
- Handrail: required on at least one side for 4+ risers; 34"–38" above tread nosing.
- Headroom: 6'8" minimum measured vertically from any tread.
Stringer count
One stringer per ~16" of stair width is the residential standard. A 36" wide stair gets 3 stringers; a 60" wide stair gets 4 or 5. Use the same lumber dimension as your deck joists (typically 2×12) to ensure proper notch depth without weakening the cut.
Common questions
What's the "ideal" stair?
The IRC magic number is a 7" rise + 11" tread. Walks comfortably, fits most decks, gives an exact 18" "rise + run" total which is the ergonomic sweet spot. If your rise/run combo lands close to this, you've designed well.
Can I make stringers DIY or buy pre-cut?
Both work. Pre-cut stringers from Lowe's/Home Depot come in 3-step, 4-step, 5-step, and 6-step versions. They're factory-sized for code-compliant 7¾" × 10" stair geometry — only useful if your total rise is an exact multiple of 7.75". Otherwise cut your own from 2×12.
Do I need risers or open-back stairs?
Code requires risers if there's a gap larger than 4" — that prevents a child from getting stuck. So below ~5" riser height you can leave them open; above that, you must close them. Most decks use closed risers regardless for the cleaner look.
For the deck surface itself, see the deck board calculator. For stain protection, the stain calculator.
Planning the full project?
These calculators usually get run in the same afternoon.