How far can a 2×6 Southern Pine deck joist span at 16″ on center?

2x6 Southern Pine at 16″ o.c.

9′ 0″maximum span

IRC Table R507.5 — 40 psf live, 10 psf dead, No. 2 grade, wet service, no cantilever

Maximum joist span9 ft	9′ 0″
Maximum cantileverone quarter of the actual span, IRC R507.5.1	2′ 3″
Joists across that spanfor a deck as wide as the span is long, at 16″ o.c.	7joists
Species groupthe strongest of the common deck species, and the usual choice in the south-east	Southern Pine
— Same size, other spacings —
2x6 at 12″ o.c.	9′ 11″
2x6 at 16″ o.c.the combination on this page	9′ 0″
2x6 at 24″ o.c.	7′ 7″
— Other sizes at 16″ o.c. —
2x6 at 16″ o.c.	9′ 0″
2x8 at 16″ o.c.	11′ 10″
2x10 at 16″ o.c.	14′ 0″
2x12 at 16″ o.c.	16′ 6″

Notes

Four assumptions, and all four have to hold. IRC Table R507.5 is written for 40 psf live load plus 10 psf dead, No. 2 grade lumber, wet service conditions, and no cantilever. Change any one and the number changes. A hot tub, a heavy planter wall or a roof over the deck all put you outside the table entirely.
Spacing buys more than you would guess. The same 2x6 goes from 7′ 7″ at 24″ o.c. to 9′ 11″ at 12″ — a gain of 2′ 4″ for twice the joists. Going up a size is usually cheaper: a 2x8 at 16″ reaches 11′ 10″.
Species matters more than most people expect. The same 2x6 at 16″ spans 9′ 0″ in Southern Pine and 8′ 0″ in redwood or cedar. Buying "whatever the yard has" can quietly cost you a foot of span.
Cantilever is capped at a quarter of the actual span, not the maximum. If your joists span 10 ft, the overhang can be 2½ ft even though this row says 2′ 3″.
The inspector has the last word. Local codes amend the IRC, and high-snow jurisdictions use higher live loads. Pull the permit before you buy the lumber, not after — a deck built to the wrong table comes apart, and it usually comes apart with people on it.

The answer

9′ 0″ — a 2×6 Southern Pine joist at 16″ on center, from IRC Table R507.5.

The four assumptions, and all four have to hold

40 psf live load plus 10 psf dead. No. 2 grade lumber. Wet service conditions. No cantilever.

Change any one and the number changes. A hot tub, a heavy planter, a roof over the deck or a snow-load jurisdiction all put you outside this table entirely, and outside it you need an engineer rather than a web page.

What spacing actually buys

The same 2×6 spans 7′ 7″ at 24″ o.c. and 9′ 11″ at 12″ — twice the joists for a gain of a few feet.

Going up a size is usually the cheaper route to more span. Compare the rows below before you decide to halve the spacing.

Species is worth a foot

The same 2×6 at 16″ spans 9′ 0″ in Southern Pine and 8′ 0″ in redwood or cedar. Buying whatever the yard has in stock can quietly cost you a foot of span, and nobody mentions it at the register.

Cantilever

Up to a quarter of the actual span, not the maximum — so 2′ 3″ only if your joists really run 9′ 0″. Joists spanning 10 ft cantilever 2½ ft, whatever this table says.

The inspector has the last word

Local codes amend the IRC. High-snow jurisdictions use higher live loads. Pull the permit before you buy lumber, not after: a deck built to the wrong table comes apart, and it comes apart with people standing on it.

Nearby sizes

How to Tell if a Deck Is Unsafe: The Seven Checks, in Order of What Kills PeopleDeck collapses are almost never a broken board. They are the ledger letting go, all at once, with everyone standing on it.
Deck Post Size by Height: When 4×4 Stops Being AllowedThe 8 ft line is where 4×4 stops. Above it the question is not only size but bracing, and the connection at each end matters more than the post between them.
Deck Beam Span Table: Why the Span Depends on the Joists, Not the DeckA beam span table has two inputs, and the one people forget is the joist span the beam is carrying. Read it with one input and the answer is wrong by feet.
Deck Joist Cantilever: One Quarter of the Actual Span, Not the MaximumThis is the most misread line in the deck code, and it is misread in the direction that puts the beam too far in.