Stair Stringer Calculator
Riser and tread cut list, throat depth and stock length — checked against the reference you choose.
Stair dimensions
= 48" (4')
= 10"
Advanced
= 11 1/4"
Results update as you typeLive
Stair Stringer · Result
CalculatedRISERS × TYPICAL RISER
7 risers at 6 7/8"
- Total run
- 5' 0"
- Throat
- 5 5/8"
- Cut length
- 6' 0 3/4"
- Stock
- 8'
2021 IRC reference check — within the limits checked. Local requirements may differ.
Reference profile 2021 IRCA reference check is not a compliance determination; local amendments differ.
SettingChangeStandard stock lengths 8/10/12/14/16/20 ft are a market convention, UNVERIFIED
SUGGESTED DEFAULTCode references & assumptions · 7
How this result is supported
- ASSUMPTIONTotal rise is finished floor to finished floor, so the top riser takes no adjustment; a top-riser finished-floor rule was not sourced
- INTERPRETED
- ASSUMPTIONThe bottom riser is cut short by the tread thickness so every finished step matches
- CROSS-VERIFIED
- ASSUMPTIONLine length is the geometric diagonal; no allowance for plumb and level cut waste
- UNVERIFIED
- SUGGESTED DEFAULTStandard stock lengths 8/10/12/14/16/20 ft are a market convention, UNVERIFIED
- ASSUMPTION
- CODE REFERENCEApplication defaults to deck, so the DCA 6 cut-stringer span limit applies. DCA 6 states it for residential deck stairs on 11.25 in (2x12) minimum stock under its own design basis (40 psf live / 10 psf dead; 300 lb concentrated load, L/288, No. 2 grade, wet service), measured on the horizontal span
- PRIMARY-VERIFIED
- CODE REFERENCEAttachment defaults to hung for a deck stair: deck stringers hang from the rim joist with the deck surface as the top tread (DCA 6 Figure 31), interior stringers carry the top riser to the header
- PRIMARY-VERIFIED
- ASSUMPTIONThe cut length is the notched board's geometric diagonal; no allowance is made for plumb or level cut waste
- DERIVED
What do these evidence labels mean?
- PRIMARY-VERIFIED
- directly supported by one authoritative primary source, quoted with section/page/figure
- CROSS-VERIFIED
- independently supported by two or more appropriate authoritative sources
- DERIVED
- mathematically derived from PRIMARY-VERIFIED values; the derivation is preserved in data and in code
- INTERPRETED
- a source exists but translating it into calculator behaviour required interpretation
- CONVENTION
- recognised trade practice, not a mandatory provision
- ASSUMPTION
- product/design assumption or useful default with no authoritative basis
- UNVERIFIED
- insufficient authoritative evidence
Code references and product data are quoted in the units their source uses.
Reference checks are informational, not compliance determinations.
How stair stringer is calculated
The riser count is yours to choose; everything else follows from it. The calculator divides the total rise evenly, lays the treads out across the run, and reports what is left of the stock behind the notches — the throat, which is what actually decides whether a stringer is strong enough to cut.
The reference check reports what the selected standard says about riser height, tread depth and the guidance's span limit. It is informational: it tells you which provision a number is close to, not whether your stair may be built.
unit rise = total rise ÷ riser count
total run = (riser count − 1) × unit run
throat = stock width − (rise × run) ÷ √(rise² + run²)
The timber left behind the notches, measured perpendicular to the cut line.