Starting from a finished design, not a blank one
This tool assumes the planning stage is already done. If you don't yet have a riser, tread and step count, start with the Rise and Run Calculator and bring those three numbers back here.
Enter your finished riser, tread and riser count
These should already be uniform and code-checked. This calculator doesn't re-derive them from a total rise — it turns them into a cuttable stringer.
Pick your mount type
Cut/notched is the traditional approach — the tread sits directly in a triangular notch. Housed/closed hides the cut from below with a routed dado. Bracket-hung skips notching entirely with surface-mounted metal stair connectors.
Set your board and check the throat depth
Pick a 2×10 or 2×12 (or enter a custom width) and watch the Throat Depth Left result — this is the wood remaining after the deepest notch, and it's the number that decides whether your board is strong enough.
Read off the notch points and cut list
Scroll to the Notch Points table or download the full cut sheet — it lists the rise and run to mark for every notch, plus the board length to buy and the bottom drop to apply before the first cut.
The five formulas behind every result
Nothing on this page is a black box. Here's exactly what runs when you change a number.
Notch Point (for step i)
Cumulative height and horizontal distance from the bottom-front starting corner to the inside corner of notch i, marked with a framing square.
Stringer Length
The straight-line hypotenuse of the full stair triangle — the board length before waste, notching, and end cuts.
Throat Depth Remaining
Board width minus the perpendicular depth of the deepest notch corner. This is the wood actually left to carry load after cutting — the number a thin board can fail on. [VERIFY: minimum accepted throat depth for a residential cut stringer — commonly cited near 3.5", confirm against your local code or engineer]
Board Length to Buy
Add roughly 14" for the birdsmouth cut at the top and notch waste, then round up to a stocked length — 8', 10', 12', 14', 16', 18' or 20'.
Cutting the stringer for a 108" basement stair
Picking up exactly where the Rise and Run Calculator's default example leaves off: 14 risers at 7.71", a 10" tread, 108" total rise.
Total rise, run & stringer length
14 risers × 7.71" = 108.0" total rise. 13 treads × 10" = 130" total run. Stringer length: √(108² + 130²) ≈ 169.0" — the same figure the Rise and Run Calculator's stringer output shows, since it's the same triangle.
Board length to buy
169.0" + 14" waste allowance = 183" needed. The next stocked length up is a 16' (192") board — again matching the sibling calculator's own board-length result for this exact design.
Throat depth — where the board size actually matters
On a 2×12 (11.25" actual width): 11.25 − (7.71 × 10) ÷ 12.63 ≈ 5.1" remaining, comfortably clear of the commonly cited 3.5" minimum. Drop to a 2×10 (9.25" actual) for the exact same notch and only ≈3.1" is left — under that minimum. The riser and tread haven't changed at all; only the board width has, and that alone is enough to fail the check. This is why a stringer calculator has to check the board, not just the stair.
Bottom drop
With a 1" tread material thickness, the bottom of the stringer gets trimmed down 1" before the first cut, so the first step — measured from the finished floor, with no tread underneath it — ends up the same height as the other 13.
Same riser and tread numbers, two different board outcomes — the throat check is the one result on this page that depends on a decision (board width) the Rise and Run Calculator never asks about.
Notch points, marked from the bottom-front corner
Each row is one notch: how far up and how far over to mark it with a framing square, measured from a single reference corner at the bottom-front of the board.
| Notch # | Rise (up from bottom) | Run (over from front) |
|---|
Nominal vs. actual board width
Dimensional lumber always measures smaller than its nominal name — this is the actual width the throat-depth check uses.
| Nominal | Actual Width | Typical Use on a Stringer |
|---|---|---|
| 2×8 | 7.25" | Shallow-angle or short-flight stairs only — thin margin for most notch depths. |
| 2×10 | 9.25" | Common on gentler stairs with shallower risers; check throat depth before committing. |
| 2×12 | 11.25" | The default choice for most residential cut stringers — clears the throat check on nearly every code-legal riser/tread combination. |
| 2×14 | 13.25" | Steep stairs or extra-deep notches. [VERIFY: 2×14 dimensional lumber stocking varies by region/supplier] |
Notching, mounting & the bottom drop
A calculated stringer length is only half the job. These three details are where a technically-correct stringer still ends up wrong on the wall.
| Mount Type | Notch Cut? | Visible From Below? | Typical Use |
|---|---|---|---|
| Cut / notched | Yes, full depth | Yes — open underneath | Standard framed stairs, decks, basements. |
| Housed / closed | Yes, routed dado | No — finished skirt hides it | Finished interior stairs against a wall. |
| Bracket-hung | No notch | Depends on bracket style | Retrofit, engineered stringers, some code-required connector installs. |
Why bracket-hung skips the throat check
Metal stair stringer connectors let the tread sit on a bracket fastened to the face of an un-notched board, so the full board width carries load. The tradeoff is connector load rating and fastening pattern, not board geometry — [VERIFY: connector load capacity and spacing against the specific hardware's published data].
The bottom drop, explained
Every riser above the first has a tread sitting on top of its notch, which effectively raises the walking surface by the tread's thickness. The first step has no tread underneath it — just the floor — so the whole stringer gets trimmed down by that same thickness at the bottom, or the first riser ends up taller than the rest.
Open vs. closed riser & the cut list
A closed riser adds one riser-board piece per step to the cut list, sized to riser height × stair width. An open riser skips that piece entirely, but check local code — some jurisdictions cap the open gap for fall protection.
Common mistakes when cutting a stringer
These five account for most of the "why doesn't this fit" callbacks on an otherwise correctly-measured stair.
Forgetting the bottom drop
Skip the tread-thickness trim at the bottom and the first step comes out taller than every other riser — a classic first-step trip hazard, and it's invisible until the tread goes on.
Confusing riser count with notch count
A "14-step" stair has 14 risers but only 13 tread notches on the stringer — the 14th riser is the top landing itself, with nothing to cut there.
Cutting the throat too thin
Dropping from a 2×12 to a 2×10 without re-checking throat depth is the single most common way a stringer ends up structurally undersized — same notch, less wood left to carry it.
Marking nosing onto the notch line
Nosing overhang belongs to the tread board, not the stringer notch. Cutting the notch itself deeper to "add" nosing throws off every riser height above it.
Not checking the pattern stringer before tracing the rest
Cut and test-fit one stringer first. Tracing a mismeasured pattern onto two or three more boards multiplies a single small error across the whole stair.
When to use a stair stringer calculator
This is the last stop before cutting — used once the layout numbers are locked in, not while they're still being decided.
Continuing from a Rise & Run plan
Taking a finalized riser, tread and step count straight to a cut-ready stringer.
Replacing a single damaged stringer
Matching an existing stair's exact riser and tread when only one stringer needs replacing.
Deck & outdoor stair builds
Laying out and cutting pressure-treated stringers before assembling deck stairs.
Pre-cutting off-site
Marking and cutting stringers in a shop before delivering them to a job site.
Ordering lumber before a job
Getting an exact board length and stringer count before a lumber yard run.
DIY basement or attic builds
Walking through the notch-by-notch layout for a first-time stringer cut.