PROJECT SUMMARY
Stairs project summary
Total rise36" · 5 risers @ 7.20"
- Run
- 3.7 ft · 4 treads @ 11"
- Width
- 36"
- Material
- Pressure-treated
- Stringers
- 3 × 2×12
- Handrail
- Included
- Difficulty
- Intermediate
- Build time
- 1–1.5 days
- Estimated materials
- $452–$611
Deck & Porch Stair Calculator
Risers, run, stringers and materials for code-aware deck or porch stairs.
Configure
Stairs calculator
Tread material
Advanced optionsfine-tune the details…
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ Where the stairs rise more than 30" above grade, a guard is generally required alongside the handrail. Confirm guard height and baluster spacing with local code.
Cost breakdown
Material only · national-average rates
| Lumber & Decking | $248–$336 |
| Fasteners & Hardware | $77–$105 |
| Concrete & Footings | $48–$64 |
| Connectors & Brackets | $45–$60 |
| Finishing & Sealant | $34–$46 |
| Total | $452–$611 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
Shopping list
Every item · grouped by store sectionThese are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
Lumber & Decking
- 3× 8 ftStair stringers — 2×12 PT — 5 risers @ 7.20" · 3 stringers
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- 9× cut to widthTread boards — Pressure-treated (2 per tread) — 4 treads · 36" wide
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- 5× lin ftGraspable handrail — one side min; both sides on wide stairs
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- 2× eaRail posts (4×4 or post kit)
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Concrete & Footings
- 8× bagsConcrete — 80 lb bags (landing pad) — 4" pad ≈ 4.0 × 2.9 ft at the base
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Connectors & Brackets
- 3× eaStair-stringer connectors — ties stringers to the deck rim / ledger
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- 15× eaBalusters / spindles — 4" max gap
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Fasteners & Hardware
- 1× boxStructural connector screws — stringer connectors + hangers
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- 1× boxDeck / tread screws (coated) — ≈ 54 fasteners
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Finishing & Sealant
- 1× galExterior stain / sealer — seal treads, stringers and cut ends
Find ↗
Tools
✓ required · ○ helpful
- Framing square + stair gauges — laying out stringers
- Circular saw
- Jigsaw or handsaw — finishing the notch cuts
- Cordless drill / impact driver
- Tape measure & speed square
- 4 ft level
- Clamps — holding stringers while you fasten
- Mixing tub or wheelbarrow — the landing pad
Project notes
- Estimates are a planning aid, not engineered drawings. Keep every riser within 3/8" of the others and the tread depths equal — uneven steps are the most common (and most cited) stair code failure.
- Cut one stringer first as a pattern with a framing square and stair gauges set to 7.20" rise and 11" run, test-fit it, then trace and cut the rest from it.
- Set the base on a solid, level footing or concrete pad so the stairs can't settle, and fasten the top securely to the deck rim or ledger with stringer connectors — not just nails.
- Common code targets: riser ≤ 7.75", tread ≥ 10", a graspable handrail 34–38" high for 4+ risers, and a guard where you're more than 30" above grade. Confirm against your local code.
About this calculator
How to estimate a stairs
Enter the total rise — the vertical height from the lower surface up to your deck or porch — and you get the whole flight laid out: the number of risers and the exact riser height, the tread depth and run, the stringer length and how many you need, plus tread boards, fasteners, an optional handrail and landing pad, with a cost range and build time.
It checks the riser height and tread depth against common code limits as you go, so you land on a comfortable, compliant step. Open advanced options to set your target riser, tread depth, stringer spacing, closed risers, a handrail and a base landing pad.
Step by step
How to build deck stairs
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
- 1
Measure the total rise
Measure straight down from the finished deck or porch surface to the ground where the stairs will land. This single number drives the whole layout, so take it where the stairs will actually sit, on firm ground.
- 2
Work out risers and treads
Divide the rise by about 7.5 inches and round to a whole number of risers; that sets the exact riser height. The treads are one fewer, and the run is the treads times your tread depth. The calculator above does this and flags anything outside code.
- 3
Pour or set the landing
Give the stairs a firm base — a small concrete pad or a compacted gravel footing — so they can't settle or kick out. Get it level before the stringers go down.
- 4
Lay out and cut one stringer
Set stair gauges on a framing square to your rise and run, step off the cuts down a 2×12, and cut the first stringer with a circular saw, finishing the inside corners with a jigsaw. Test-fit it before cutting the rest.
- 5
Trace and cut the rest
Use the first stringer as a template so every one matches exactly. Even small differences show up as wobbly, uneven steps.
- 6
Fasten the stringers
Attach the tops to the deck rim or ledger with stringer connectors, space the stringers evenly across the width, and anchor the bottoms to the landing. Check that they're plumb and square.
- 7
Install treads and risers
Screw down the tread boards with a consistent overhang and a small gap for drainage, adding closed risers first if you're using them. Keep the front edges aligned.
- 8
Add the handrail and finish
Mount a graspable handrail 34–38 inches above the tread nosings (both sides on wide stairs), add a guard if you're over 30 inches up, then seal the wood including the cut ends.
Equip the job
Recommended gear for this build
Hand-picked categories that match the shopping list above. Links open a current selection so you can compare brands and prices.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
Connectors & BracketsStair gauges (framing square stops)Clamp onto a framing square so every stringer is laid out identically.
$8–15
Connectors & BracketsStair stringer connectorsTie the stringers to the deck rim properly instead of relying on nails.
$4–7 ea
Fasteners & HardwareStructural connector screwsThe rated screws connectors are tested with — not deck or drywall screws.
$25–45/box
Lumber & DeckingGraspable handrail kitA code-profile rail your hand can fully close around, with brackets.
$15–25/ft
ToolsAdjustable stair gauge / templateSpeeds repeatable, accurate riser and tread layout on every stringer.
$20–40
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Answers
Frequently asked questions
How do I calculate stair stringers?
Start with the total rise (ground to deck surface) and divide by a comfortable riser height — around 7.5 inches — then round to a whole number of risers, which sets the exact riser height. The number of treads is one less than the risers. Multiply the treads by your tread depth to get the run, and the stringer length is the diagonal: the square root of run squared plus rise squared. This calculator does all of that and gives you the stringer length and count.
What are the code rules for stairs?
The most-cited residential limits are a maximum riser height around 7.75 inches, a minimum tread depth around 10 inches, and no more than 3/8 inch of variation between any two risers or treads. A graspable handrail is required once you have four or more risers, and a guard is required where you're more than 30 inches above grade. Always confirm the exact numbers with your local building department.
How many stringers do I need?
Spacing depends on what the treads are made of. Two-by pressure-treated or cedar treads carry 16 inches on center comfortably, so a 36-inch stair takes three stringers — one under each edge and one in the middle. Most composite and PVC treads are rated to only 12 inches on center on stairs, even where the same board spans 16 inches flat on a deck, so a 36-inch composite stair needs four. Run them further apart than the tread is rated for and the middle of each step flexes underfoot, the screws work loose, and the nosings crack or sag. Stringer count here follows the width and spacing you set.
How wide should outdoor stairs be?
Thirty-six inches is the common minimum and works for most deck and porch stairs. Going to 42–48 inches feels more generous and lets two people pass, but it needs an extra stringer and more tread material. Match the stair width to the deck opening and how the space will be used.