Deck joist span calculator: how far can a deck joist span?
14 ft 0 in
maximum span, 2 × 10 at 16 in on center · 16 ft 2 in at 12 in · 11 ft 5 in at 24 in · for 2 × 10 Southern pine, from IRC 2021 Table R507.6
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Enter it the way you measured it: 4.5, 4 1/2,
3/8 or 10' 6".
14 ft 0 in
maximum span, 2 × 10 at 16 in on center · 16 ft 2 in at 12 in · 11 ft 5 in at 24 in
Source: IRC 2021 Table R507.6, Maximum Deck Joist Spans (International Code Council), read October 1, 2026. Read the source
A 2 × 10 Southern pine deck joist at 16 inches on center spans up to 14 ft 0 in under a 40 psf live load (IRC 2021 Table R507.6): 16 ft 2 in at 12 inches and 11 ft 5 in at 24.
A worked example
A 2 × 8 hem-fir joist at 24 in on center, under a 50 psf ground snow load needs 8 ft 11 in. That is the IRC 2021 Table R507.6 cell for Douglas fir-larch, hem-fir and spruce-pine-fir, 2 × 8, 24 in, 50 psf snow; at 16 in the same joist spans 10 ft 7 in and at 12 in, 11 ft 7 in.
How far can a deck joist cantilever past the beam?
The same table gives it, in the columns on the right: a 2 × 10 Southern pine joist with an 8 ft back span can cantilever 2 ft 0 in, and with a 12 ft back span 3 ft 0 in, under the 40 psf live load. The cantilever is limited by the back span, the part of the joist between the ledger and the beam, and the table marks NP where the back span is too short to hold the overhang down. Read your row, then the column for your back span; the IRC allows interpolation between columns but not extrapolation past them.
What else it is called
A deck joist span calculator is also searched as a joist span table, a deck span chart or “how far can a 2 × 10 span”. On center (o.c.) is the distance from the middle of one joist to the middle of the next; the span is the clear distance between supports, from the ledger to the beam.
The full IRC table
| Load · species · joist | Span at 12 in o.c. | Span at 16 in o.c. | Span at 24 in o.c. | Cantilever, 4 ft back span | Cantilever, 6 ft back span | Cantilever, 8 ft back span | Cantilever, 10 ft back span | Cantilever, 12 ft back span | Cantilever, 14 ft back span | Cantilever, 16 ft back span | Cantilever, 18 ft back span |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 40 psf live load · Southern pine · 2 × 6 | 9-11 | 9-0 | 7-7 | 1-0 | 1-6 | 1-5 | NP | NP | NP | NP | NP |
| 40 psf live load · Southern pine · 2 × 8 | 13-1 | 11-10 | 9-8 | 1-0 | 1-6 | 2-0 | 2-6 | 2-3 | NP | NP | NP |
| 40 psf live load · Southern pine · 2 × 10 | 16-2 | 14-0 | 11-5 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-4 | 3-4 | NP |
| 40 psf live load · Southern pine · 2 × 12 | 18-0 | 16-6 | 13-6 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-6 | 4-0 | 4-1 |
| 40 psf live load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 6 | 9-6 | 8-4 | 6-10 | 1-0 | 1-6 | 1-4 | NP | NP | NP | NP | NP |
| 40 psf live load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 8 | 12-6 | 11-1 | 9-1 | 1-0 | 1-6 | 2-0 | 2-3 | 2-0 | NP | NP | NP |
| 40 psf live load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 10 | 15-8 | 13-7 | 11-1 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-3 | NP | NP |
| 40 psf live load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 12 | 18-0 | 15-9 | 12-10 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-6 | 3-11 | 3-11 |
| 40 psf live load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 6 | 8-10 | 8-0 | 6-10 | 1-0 | 1-4 | 1-1 | NP | NP | NP | NP | NP |
| 40 psf live load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 8 | 11-8 | 10-7 | 8-8 | 1-0 | 1-6 | 2-0 | 1-11 | NP | NP | NP | NP |
| 40 psf live load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 10 | 14-11 | 13-0 | 10-7 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 2-9 | NP | NP |
| 40 psf live load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 12 | 17-5 | 15-1 | 12-4 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-6 | 3-8 | NP |
| 50 psf ground snow load · Southern pine · 2 × 6 | 9-2 | 8-4 | 7-4 | 1-0 | 1-6 | 1-5 | NP | NP | NP | NP | NP |
| 50 psf ground snow load · Southern pine · 2 × 8 | 12-1 | 11-0 | 9-5 | 1-0 | 1-6 | 2-0 | 2-5 | 2-3 | NP | NP | NP |
| 50 psf ground snow load · Southern pine · 2 × 10 | 15-5 | 13-9 | 11-3 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-1 | NP | NP |
| 50 psf ground snow load · Southern pine · 2 × 12 | 18-0 | 16-2 | 13-2 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-6 | 3-10 | 3-10 |
| 50 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 6 | 8-10 | 8-0 | 6-8 | 1-0 | 1-6 | 1-4 | NP | NP | NP | NP | NP |
| 50 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 8 | 11-7 | 10-7 | 8-11 | 1-0 | 1-6 | 2-0 | 2-3 | NP | NP | NP | NP |
| 50 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 10 | 14-10 | 13-3 | 10-10 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-0 | NP | NP |
| 50 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 12 | 17-9 | 15-5 | 12-7 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-6 | 3-8 | NP |
| 50 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 6 | 8-3 | 7-6 | 6-6 | 1-0 | 1-4 | 1-1 | NP | NP | NP | NP | NP |
| 50 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 8 | 10-10 | 9-10 | 8-6 | 1-0 | 1-6 | 2-0 | 1-11 | NP | NP | NP | NP |
| 50 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 10 | 13-10 | 12-7 | 10-5 | 1-0 | 1-6 | 2-0 | 2-6 | 2-9 | NP | NP | NP |
| 50 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 12 | 16-10 | 14-9 | 12-1 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-5 | 3-5 | NP |
| 60 psf ground snow load · Southern pine · 2 × 6 | 8-8 | 7-10 | 6-10 | 1-0 | 1-6 | 1-5 | NP | NP | NP | NP | NP |
| 60 psf ground snow load · Southern pine · 2 × 8 | 11-5 | 10-4 | 8-9 | 1-0 | 1-6 | 2-0 | 2-4 | NP | NP | NP | NP |
| 60 psf ground snow load · Southern pine · 2 × 10 | 14-7 | 12-9 | 10-5 | 1-0 | 1-6 | 2-0 | 2-6 | 2-11 | 2-11 | NP | NP |
| 60 psf ground snow load · Southern pine · 2 × 12 | 17-3 | 15-0 | 12-3 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-6 | 3-7 | NP |
| 60 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 6 | 8-4 | 7-6 | 6-2 | 1-0 | 1-6 | 1-4 | NP | NP | NP | NP | NP |
| 60 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 8 | 10-11 | 9-11 | 8-3 | 1-0 | 1-6 | 2-0 | 2-2 | NP | NP | NP | NP |
| 60 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 10 | 13-11 | 12-4 | 10-0 | 1-0 | 1-6 | 2-0 | 2-6 | 2-10 | NP | NP | NP |
| 60 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 12 | 16-6 | 14-3 | 11-8 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-5 | 3-5 | NP |
| 60 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 6 | 7-9 | 7-0 | 6-2 | 1-0 | 1-4 | NP | NP | NP | NP | NP | NP |
| 60 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 8 | 10-2 | 9-3 | 7-11 | 1-0 | 1-6 | 2-0 | 1-11 | NP | NP | NP | NP |
| 60 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 10 | 13-0 | 11-9 | 9-7 | 1-0 | 1-6 | 2-0 | 2-6 | 2-7 | NP | NP | NP |
| 60 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 12 | 15-9 | 13-8 | 11-2 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-2 | NP | NP |
| 70 psf ground snow load · Southern pine · 2 × 6 | 8-3 | 7-6 | 6-5 | 1-0 | 1-6 | 1-5 | NP | NP | NP | NP | NP |
| 70 psf ground snow load · Southern pine · 2 × 8 | 10-10 | 9-10 | 8-2 | 1-0 | 1-6 | 2-0 | 2-2 | NP | NP | NP | NP |
| 70 psf ground snow load · Southern pine · 2 × 10 | 13-9 | 11-11 | 9-9 | 1-0 | 1-6 | 2-0 | 2-6 | 2-9 | NP | NP | NP |
| 70 psf ground snow load · Southern pine · 2 × 12 | 16-2 | 14-0 | 11-5 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-5 | 3-5 | NP |
| 70 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 6 | 7-11 | 7-1 | 5-9 | 1-0 | 1-6 | NP | NP | NP | NP | NP | NP |
| 70 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 8 | 10-5 | 9-5 | 7-8 | 1-0 | 1-6 | 2-0 | 2-1 | NP | NP | NP | NP |
| 70 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 10 | 13-3 | 11-6 | 9-5 | 1-0 | 1-6 | 2-0 | 2-6 | 2-8 | NP | NP | NP |
| 70 psf ground snow load · Douglas fir-larch / Hem-fir / Spruce-pine-fir · 2 × 12 | 15-5 | 13-4 | 10-11 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-3 | NP | NP |
| 70 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 6 | 7-4 | 6-8 | 5-10 | 1-0 | 1-4 | NP | NP | NP | NP | NP | NP |
| 70 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 8 | 9-8 | 8-10 | 7-4 | 1-0 | 1-6 | 1-11 | NP | NP | NP | NP | NP |
| 70 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 10 | 12-4 | 11-0 | 9-0 | 1-0 | 1-6 | 2-0 | 2-6 | 2-6 | NP | NP | NP |
| 70 psf ground snow load · Redwood / Western cedars / Ponderosa pine / Red pine · 2 × 12 | 14-9 | 12-9 | 10-5 | 1-0 | 1-6 | 2-0 | 2-6 | 3-0 | 3-0 | NP | NP |
IRC 2021 Table R507.6, Maximum Deck Joist Spans, as printed: feet-inches (9-11 is 9 ft 11 in), NP = not permitted. Dead load = 10 psf. Snow load not assumed to be concurrent with live load. No. 2 grade, wet service factor included. Interpolation allowed. Extrapolation is not allowed.
Where the numbers come from
- Spans: 2021 International Residential Code, Section R507.6 Deck joists and Table R507.6, Maximum Deck Joist Spans, printed in full above. The table assumes No. 2 grade lumber with the wet service factor, a dead load of 10 psf, deflection limited to L/360 at the main span and to L/180 at a cantilever with a 220 lb point load on the end, and allows interpolation but not extrapolation. Read on the ICC public access site October 1, 2026. Source
- Nothing here is calculated: the page looks up the cell for your species, size, spacing and load, and for a span you type it lists the sizes whose cell is at least that long.
This is the IRC's table for a residential deck at the loads shown. It does not cover a hot tub, heavy planters or a roof over the deck, which are engineered loads, and a joist set at 24 in may be limited by the decking (IRC Table R507.7). Your state or county adopts a version of the IRC and can amend the table: the span your inspector accepts is the one in your adopted code.
By Javier Miralles · Last updated . How this site is made.
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