Deck Stair Calculator
Calculate deck stair rise, run, and cost with IRC code compliance checking. Get instant dimensions for stringers, treads, and landings based on your deck height.
30" rise, ground-level deck
Estimated Total Cost
$347 – $944
$87 – $236 per step
Stair Dimensions
Stringers
$45–$120
Treads
$72–$144
Hardware
$30–$80
Landing
—
Labor
$200–$600
Pressure Treated Pine: Most affordable, requires staining. 15-20 year lifespan. Tread cost: $3–$6/LF.
Handrails Required: IRC requires handrails on at least one side for stairs with 4 or more risers. Budget $15–$30/LF for handrails.
IRC Code Reference: Max rise 7.75", min run 10", min stair width 36", max rise variation 3/8" between steps.
Not included: Handrails ($15–$30/LF), post bases and caps ($20–$50 each), staining/sealing ($1–$3/sqft), concrete footings ($50–$150 each), or permits.
IRC Stair Code Requirements
| Dimension | Requirement | Notes |
|---|---|---|
| Riser Height (Rise) | Max 7.75", Min 4" | Ideal is 7–7.5" for comfort |
| Tread Depth (Run) | Min 10" | 10–11" typical, nose to nose |
| Stair Width | Min 36" | Clear width, handrail to handrail |
| Rise Variation | Max 3/8" | Between any two risers |
| Headroom | Min 6'8" | Measured vertically from tread nosing |
| Landing | Required >12 risers | Min 36" in direction of travel |
Deck Stair Cost by Material
| Tread Material | Cost Per LF | Cost Per Step (3' wide) |
|---|---|---|
| Pressure Treated Pine | $3–$6 | $70–$170 |
| Cedar | $5–$10 | $85–$210 |
| Redwood | $8–$15 | $110–$260 |
| Composite Decking | $8–$18 | $110–$300 |
| Tropical Hardwood (Ipe) | $15–$30 | $150–$400 |
*Cost per step includes 2 tread boards, stringer cost allocation, and labor
How We Calculate
Our deck stair calculator uses IRC (International Residential Code) standards to determine safe, code-compliant stair dimensions:
Number of Steps = Total Rise ÷ 7.5"
Actual Rise = Total Rise ÷ Number of Steps
Stringer Length = √(Total Rise² + Total Run²)
Step-by-Step Process
- Measure total rise — deck surface to ground level
- Calculate number of steps — divide by 7.5" ideal rise
- Calculate actual rise — must be under 7.75" max
- Determine run — standard 10.5" per step
- Calculate stringer length — use Pythagorean theorem
Stringer Requirements
Use 2×12 pressure-treated lumber for stringers. After cutting notches, at least 5" of solid wood must remain below the notches. Space stringers maximum 16" apart — 3 stringers for 36" wide stairs, 4 for 48" wide.
Handrail Requirements
IRC requires handrails on at least one side for stairs with 4 or more risers. Handrails must be 34–38" above the stair nosing, graspable (1.25–2" diameter), and continuous for the full length of the stairs.
Data Sources
Cost data verified from HomeGuide, Angi, Home Depot, and Lowe's (February 2026). IRC code requirements per 2021 International Residential Code Section R311.7. Local codes may vary — check with your building department.
Frequently Asked Questions
How do I calculate the number of stairs I need? +
Divide total rise (deck height) by ideal rise of 7–7.5 inches. For example, 36" total rise ÷ 7.5" = 4.8, rounded to 5 steps. Then calculate actual rise: 36" ÷ 5 = 7.2" per step (within code).
What is the maximum rise for deck stairs per code? +
IRC code allows maximum 7.75" rise per step. Minimum is 4". The ideal comfortable rise is 7–7.5". All risers must be within 3/8" of each other in height.
How much do deck stairs cost? +
Deck stairs cost $50–$150 per step for basic pressure-treated wood, or $100–$250 per step for composite. A typical 4-step staircase costs $300–$800 including labor and materials.
What is the minimum tread depth for deck stairs? +
IRC requires minimum 10" tread depth (run). Standard is 10–11". This is measured from nose to nose of consecutive treads, not including any nosing overhang.
How many stringers do I need for deck stairs? +
3 stringers for stairs up to 36" wide. Add one stringer for every additional 16" of width. A 4-foot wide staircase needs 4 stringers for proper support.
Do deck stairs require a landing? +
IRC requires a landing for stairs with more than 12 risers (steps). Landings must be at least 36" in the direction of travel. They're also recommended for any staircase making a turn.
What size lumber do I need for stair stringers? +
2×12 pressure-treated lumber is standard for stringers. This provides enough material after cutting the notches. Never use 2×10 — it doesn't leave adequate wood after cuts.
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