Calculator
Nominal to Actual Lumber Size Calculator
Compare common nominal lumber/timber names with approximate actual finished sizes. Use it before layout, joinery, cut lists, or material estimates so planned parts match the stock you can actually buy.
Nominal vs actual size calculator
Reference sizes are approximate. Actual lumber/timber dimensions vary by supplier, region, species, drying, milling, and product type.
Result
Select a nominal size, then calculate actual dimensions and volume.
These results are estimates only. Verify measurements, material specifications, structural requirements, safety requirements, and local building rules before buying materials or building.
| Nominal | Approx actual inches | Approx actual mm |
|---|---|---|
| 1x2 | 0.75 in x 1.5 in | 19 mm x 38 mm |
| 1x3 | 0.75 in x 2.5 in | 19 mm x 64 mm |
| 1x4 | 0.75 in x 3.5 in | 19 mm x 89 mm |
| 1x6 | 0.75 in x 5.5 in | 19 mm x 140 mm |
| 1x8 | 0.75 in x 7.25 in | 19 mm x 184 mm |
| 2x2 | 1.5 in x 1.5 in | 38 mm x 38 mm |
| 2x4 | 1.5 in x 3.5 in | 38 mm x 89 mm |
| 2x6 | 1.5 in x 5.5 in | 38 mm x 140 mm |
| 2x8 | 1.5 in x 7.25 in | 38 mm x 184 mm |
| 2x10 | 1.5 in x 9.25 in | 38 mm x 235 mm |
| 2x12 | 1.5 in x 11.25 in | 38 mm x 286 mm |
How this calculator works
Nominal lumber/timber names are not universal finished dimensions. Actual sizes vary by supplier, region, species, drying, milling, and product type.
Use the reference table as a common approximate guide only. If you know the actual dimensions of your stock, enter custom values to get a better board foot and volume estimate.
Formula
- Board feet = actual_thickness_inches x actual_width_inches x length_feet x quantity / 12.
- Cubic metres are estimated by converting board feet with 1 board foot approximately equal to 0.00235974 cubic metres.
Worked example
A common approximate 2x4 actual size is 1.5 inches x 3.5 inches.
Ten pieces at 8 feet long estimate as 1.5 x 3.5 x 8 x 10 / 12 = 35 board feet.
Common mistakes
- Assuming nominal sizes are universal global standards.
- Using nominal dimensions for joinery, cabinet parts, or finished layout.
- Forgetting that actual dimensions can vary by product type and supplier.
- Skipping measurement when mixing boards from different batches.
FAQs
Are these actual sizes guaranteed?
No. They are common approximate references only. Measure your own lumber/timber before building.
Why do nominal and actual dimensions differ?
Drying, surfacing, milling, species, supplier practices, and product type can all affect finished size.
Can I enter custom actual dimensions?
Yes. Custom dimensions override the reference table and should be used when you know the real stock size.
Does this replace supplier specifications?
No. Check supplier specifications and measure the material you will actually use.
Calculator disclaimer
These results are estimates only. Verify measurements, material specifications, structural requirements, safety requirements, and local building rules before buying materials or building.