Free tools
Deck framing calculators that cite their source
4 calculators, no signup, running the same engine that sizes framing inside deckpro.studio. Each one shows the table cell behind its answer — and stops answering where the prescriptive tables stop.
Joist span calculator
How far a 2x6, 2x8, 2x10 or 2x12 deck joist spans at 12", 16" or 24" on center — plus the overhang the same cell allows.
DCA6-2015 Table 2, p.4
Beam & footing calculator
Beam size, post spacing and footing diameter for one deck — including the post/footing combinations the table marks Not Permitted.
DCA6-2015 Table 3A + Table 4 · IRC R507
Deck stair calculator
Riser height, tread depth, stringer count and cut layout, screened against IRC R311.7 — including the 3/8" riser uniformity rule.
IRC R311.7 · R312.1
Ledger fastener spacing
On-centre spacing for ½" lags and through-bolts in a deck ledger, by the joist span it carries and the band joist behind it.
DCA6-2015 Table 5, p.15
Why every number here names its cell
A span number is only as useful as the cell it came from. Every number on these pages names one — the table, the footnote and the page, in a single dated edition you can download for free and read yourself. That is what makes an answer quotable at a permit desk. It is also what lets you catch us if we are wrong, which is the point.
These read transcribed tables from a single, identified document: AWC DCA 6-2015, Prescriptive Residential Wood Deck Construction Guide (based on the 2015 IRC), © 2018 American Wood Council. The 2015 edition matters — it carries the reduced Southern Pine design values published after 2013, and a calculator built on the 2012 edition returns longer Southern Pine spans that are not conservative.
The load basis on every structural page is the same: 40 psf live load + 10 psf dead load, No. 2 grade lumber, wet service conditions, L/360 deflection. And when an input lands outside those tables — a joist past 18 feet, a beam carrying more than the table covers, an interior beam line the table was never written for — these say so instead of extrapolating. That refusal is the most useful output a code calculator has.
Or skip the member-by-member part
The free 3D designer runs all three tables at once across a real footprint, then hands you the material list underneath it. No signup, no card.
Estimate only — not an engineered design. Spans, sizes, and quantities are screened against the AWC DCA 6-2015 / IRC prescriptive baseline at 40 psf live + 10 psf dead load. Local codes and amendments vary; your Authority Having Jurisdiction (AHJ) and a licensed design professional govern. Verify everything with a permit and a licensed pro before ordering or building.