Sloped roof rafters where the ceiling is not attached to the rafters (30 psf ground snow load). Rafter spans are the horizontal projection. A blank cell in the Select Structural, No. 1 or No. 2 rows means the source table gives a note rather than a span for that size. No. 3 rafter spans are published in the source table but are not reproduced here - look them up in the cited table.
Source: International Residential Code (IRC), 2018 - Table R802.4.1(3) - Rafter Spans, 30 psf Ground Snow Load (ceiling not attached, L/180). Published by International Code Council.
Edition: These values are transcribed from the IRC 2018 tables. The ICC has since published IRC 2021 and IRC 2024, and the edition in force varies by jurisdiction - confirm the table and edition adopted by your local building department before relying on a span.
Not sure whether this is even the right member? Rafter vs joist follows one 2x8 through this table and the joist tables, including why rafter spans are horizontal projections rather than member lengths.
Spacing
Species & grade
2x4
2x6
2x8
2x10
2x12
12″ o.c.
Douglas Fir-Larch · SS
10′-0″
15′-9″
20′-9″
-
-
12″ o.c.
Douglas Fir-Larch · #1
9′-8″
14′-9″
18′-8″
22′-9″
-
12″ o.c.
Douglas Fir-Larch · #2
9′-6″
14′-0″
17′-8″
21′-7″
25′-1″
12″ o.c.
Douglas Fir-Larch · #3
-
-
-
-
-
12″ o.c.
Hem-Fir · SS
9′-6″
14′-10″
19′-7″
25′-0″
-
12″ o.c.
Hem-Fir · #1
9′-3″
14′-6″
18′-5″
22′-6″
26′-0″
12″ o.c.
Hem-Fir · #2
8′-10″
13′-7″
17′-2″
21′-0″
24′-4″
12″ o.c.
Hem-Fir · #3
-
-
-
-
-
12″ o.c.
Spruce-Pine-Fir · SS
9′-3″
14′-7″
19′-2″
24′-6″
-
12″ o.c.
Spruce-Pine-Fir · #1
9′-1″
13′-9″
17′-5″
21′-4″
24′-8″
12″ o.c.
Spruce-Pine-Fir · #2
9′-1″
13′-9″
17′-5″
21′-4″
24′-8″
12″ o.c.
Spruce-Pine-Fir · #3
-
-
-
-
-
12″ o.c.
Southern Pine · SS
9′-10″
15′-6″
20′-5″
-
-
12″ o.c.
Southern Pine · #1
9′-6″
14′-10″
19′-0″
22′-3″
-
12″ o.c.
Southern Pine · #2
8′-7″
12′-11″
16′-4″
19′-5″
22′-10″
12″ o.c.
Southern Pine · #3
-
-
-
-
-
16″ o.c.
Douglas Fir-Larch · SS
9′-1″
14′-4″
18′-10″
24′-1″
-
16″ o.c.
Douglas Fir-Larch · #1
8′-9″
12′-9″
16′-2″
19′-9″
22′-10″
16″ o.c.
Douglas Fir-Larch · #2
8′-3″
12′-1″
15′-4″
18′-9″
21′-8″
16″ o.c.
Douglas Fir-Larch · #3
-
-
-
-
-
16″ o.c.
Hem-Fir · SS
8′-7″
13′-6″
17′-10″
22′-9″
-
16″ o.c.
Hem-Fir · #1
8′-5″
12′-7″
15′-11″
19′-6″
22′-7″
16″ o.c.
Hem-Fir · #2
8′-0″
11′-9″
14′-11″
18′-2″
21′-1″
16″ o.c.
Hem-Fir · #3
-
-
-
-
-
16″ o.c.
Spruce-Pine-Fir · SS
8′-5″
13′-3″
17′-5″
22′-1″
25′-7″
16″ o.c.
Spruce-Pine-Fir · #1
8′-2″
11′-11″
15′-1″
18′-5″
21′-5″
16″ o.c.
Spruce-Pine-Fir · #2
8′-2″
11′-11″
15′-1″
18′-5″
21′-5″
16″ o.c.
Spruce-Pine-Fir · #3
-
-
-
-
-
16″ o.c.
Southern Pine · SS
8′-11″
14′-1″
18′-6″
23′-8″
-
16″ o.c.
Southern Pine · #1
8′-7″
13′-0″
16′-6″
19′-3″
22′-10″
16″ o.c.
Southern Pine · #2
7′-6″
11′-2″
14′-2″
16′-10″
19′-10″
16″ o.c.
Southern Pine · #3
-
-
-
-
-
19.2″ o.c.
Douglas Fir-Larch · SS
8′-7″
13′-6″
17′-9″
22′-1″
25′-7″
19.2″ o.c.
Douglas Fir-Larch · #1
7′-11″
11′-8″
14′-9″
18′-0″
20′-11″
19.2″ o.c.
Douglas Fir-Larch · #2
7′-7″
11′-0″
14′-0″
17′-1″
19′-10″
19.2″ o.c.
Douglas Fir-Larch · #3
-
-
-
-
-
19.2″ o.c.
Hem-Fir · SS
8′-1″
12′-9″
16′-9″
21′-4″
24′-8″
19.2″ o.c.
Hem-Fir · #1
7′-10″
11′-6″
14′-7″
17′-9″
20′-7″
19.2″ o.c.
Hem-Fir · #2
7′-4″
10′-9″
13′-7″
16′-7″
19′-3″
19.2″ o.c.
Hem-Fir · #3
-
-
-
-
-
19.2″ o.c.
Spruce-Pine-Fir · SS
7′-11″
12′-5″
16′-5″
20′-2″
23′-4″
19.2″ o.c.
Spruce-Pine-Fir · #1
7′-5″
10′-11″
13′-9″
16′-10″
19′-6″
19.2″ o.c.
Spruce-Pine-Fir · #2
7′-5″
10′-11″
13′-9″
16′-10″
19′-6″
19.2″ o.c.
Spruce-Pine-Fir · #3
-
-
-
-
-
19.2″ o.c.
Southern Pine · SS
8′-5″
13′-3″
17′-5″
22′-3″
-
19.2″ o.c.
Southern Pine · #1
8′-0″
11′-10″
15′-1″
17′-7″
20′-11″
19.2″ o.c.
Southern Pine · #2
6′-10″
10′-2″
12′-11″
15′-4″
18′-1″
19.2″ o.c.
Southern Pine · #3
-
-
-
-
-
24″ o.c.
Douglas Fir-Larch · SS
8′-0″
12′-6″
16′-2″
19′-9″
22′-10″
24″ o.c.
Douglas Fir-Larch · #1
7′-1″
10′-5″
13′-2″
16′-1″
18′-8″
24″ o.c.
Douglas Fir-Larch · #2
6′-9″
9′-10″
12′-6″
15′-3″
17′-9″
24″ o.c.
Douglas Fir-Larch · #3
-
-
-
-
-
24″ o.c.
Hem-Fir · SS
7′-6″
11′-10″
15′-7″
19′-1″
22′-1″
24″ o.c.
Hem-Fir · #1
7′-0″
10′-3″
13′-0″
15′-11″
18′-5″
24″ o.c.
Hem-Fir · #2
6′-7″
9′-7″
12′-2″
14′-10″
17′-3″
24″ o.c.
Hem-Fir · #3
-
-
-
-
-
24″ o.c.
Spruce-Pine-Fir · SS
7′-4″
11′-7″
14′-9″
18′-0″
20′-11″
24″ o.c.
Spruce-Pine-Fir · #1
6′-8″
9′-9″
12′-4″
15′-1″
17′-6″
24″ o.c.
Spruce-Pine-Fir · #2
6′-8″
9′-9″
12′-4″
15′-1″
17′-6″
24″ o.c.
Spruce-Pine-Fir · #3
-
-
-
-
-
24″ o.c.
Southern Pine · SS
7′-10″
12′-3″
16′-2″
20′-0″
23′-7″
24″ o.c.
Southern Pine · #1
7′-1″
10′-7″
13′-5″
15′-9″
18′-8″
24″ o.c.
Southern Pine · #2
6′-1″
9′-2″
11′-7″
13′-9″
16′-2″
24″ o.c.
Southern Pine · #3
-
-
-
-
-
Rafters - 30 psf Ground Snow Load. Live load 30 psf, dead load 10 psf, deflection limit L/180. Spans in feet-inches; “-” means the source leaves that cell blank.
L/180. The L is the span itself and the number underneath is the fraction of that span the member is allowed to bend under the table's design load, so two tables can cover the same lumber and the same load and still publish different spans purely because one allows more bend than the other.
What loading does this table use?
30 psf live load plus 10 psf dead load. That load case is what the table was published for: Sloped roof rafters where the ceiling is not attached to the rafters (30 psf ground snow load).
Can I interpolate between joist spacings?
No. The source table (International Residential Code (IRC), 2018 - Table R802.4.1(3) - Rafter Spans, 30 psf Ground Snow Load (ceiling not attached, L/180) (International Code Council).) publishes a separate span only at the listed on-center spacings, and every figure on this site is a verbatim cell from that table - nothing is computed or interpolated. If your layout falls between two published spacings, the wider spacing's shorter span is the one the table supports.