Lumber Dimensions Converter
Look up actual versus nominal lumber sizes from 1x2 to 6x6.
A 2x4 really measures 1.5 by 3.5 inches, and board feet are priced on the nominal size.
Select a nominal lumber size to see actual dimensions, or calculate board feet below.
Enter the nominal size, the one printed on the tag, not the dressed measurement. Board footage is a pricing convention and the trade prices a 2x4 as a full 2 by 4.
In North America, lumber is sold by nominal size, but the actual dimensions are smaller. This is because wood shrinks when dried and is planed smooth after cutting.
Standard softwood lumber (dry, dressed):
| Nominal (in) | Actual (in) | Actual (mm) |
|---|---|---|
| 1 × 2 | 0.75 × 1.5 | 19 × 38 |
| 1 × 4 | 0.75 × 3.5 | 19 × 89 |
| 1 × 6 | 0.75 × 5.5 | 19 × 140 |
| 1 × 8 | 0.75 × 7.25 | 19 × 184 |
| 1 × 10 | 0.75 × 9.25 | 19 × 235 |
| 1 × 12 | 0.75 × 11.25 | 19 × 286 |
| 2 × 2 | 1.5 × 1.5 | 38 × 38 |
| 2 × 4 | 1.5 × 3.5 | 38 × 89 |
| 2 × 6 | 1.5 × 5.5 | 38 × 140 |
| 2 × 8 | 1.5 × 7.25 | 38 × 184 |
| 2 × 10 | 1.5 × 9.25 | 38 × 235 |
| 2 × 12 | 1.5 × 11.25 | 38 × 286 |
| 4 × 4 | 3.5 × 3.5 | 89 × 89 |
| 4 × 6 | 3.5 × 5.5 | 89 × 140 |
| 6 × 6 | 5.5 × 5.5 | 140 × 140 |
Board Feet: Board feet is the standard unit for buying lumber by volume.
- 1 board foot = 1 inch thick × 12 inches wide × 12 inches long
- Board feet = (thickness_in × width_in × length_in) ÷ 144
Use the nominal size in that formula, not the actual size. This is the single most expensive mistake on this page, and it is easy to make precisely because the table above has just taught you that a 2x4 is really 1.5 by 3.5. Board footage is a pricing convention, not a measurement of the wood in front of you, and the trade prices a 2x4 as though it were a full 2 by 4. Run an 8-foot 2x4 the honest way and you get 2 × 4 × 96 ÷ 144 = 5.33 board feet. Run it with the actual dressed dimensions and you get 3.5, which is 34% short. Order a thousand board feet that way and you are a third of a delivery light.
The exception is rough-sawn stock straight off a sawmill, which really is full nominal size, and hardwood, which is sold by actual thickness in quarters.
Hardwood quarter sizing: Hardwood does not come in 2x4s. It is sold in random widths and lengths, at thicknesses quoted in quarters of an inch:
| Quarter | Rough thickness | Surfaced two sides |
|---|---|---|
| 4/4 | 1 in | 13/16 in |
| 5/4 | 1.25 in | 1-1/16 in |
| 6/4 | 1.5 in | 1-5/16 in |
| 8/4 | 2 in | 1-3/4 in |
| 12/4 | 3 in | 2-3/4 in |
“Four-quarter” is the standard starting thickness and the one most projects use. You pay for the rough figure even after surfacing takes some of it away, which is the hardwood version of the same convention that makes a 2x4 measure 1.5 by 3.5.
Metric countries sell lumber by actual dimensions in millimeters, and the numbers here are close but not identical to a straight conversion. A European C24 stud is 38 × 89 mm, the same as a North American 2x4, because the milling standards converged. Widths above that diverge: a 45 × 95 mm or 45 × 145 mm section is common in Scandinavia and has no exact North American twin.
One last thing before you cut. The actual dimensions in the table are for dry, dressed lumber. Green (unseasoned) framing lumber is milled slightly larger, around 1-9/16 by 3-9/16 for a 2x4, on the assumption that it will shrink to the dressed size as it dries. If a board measures a little over and you were expecting exactly 1.5 inches, it is probably green rather than mismarked.
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This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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