Oak
Ring-porous hardwood, dense and hard wearing. White oak is the traditional choice for barrels, boatbuilding and heavy furniture; red oak is more common in cabinetry and flooring.
Properties
- Family
- Wood
- Category
- wood
- Species
- Quercus spp.
- Density
- 0.75 g/cm³ · 750 kg/m³
Densityhow oak compares
Wood propertiesUSDA clear-wood values at 12% moisture content
- Species measured
- White oak (Quercus alba)
- Specific gravity
- 0.68
- Janka side hardness
- 1,360 lbf · 6,050 N
- Modulus of rupture
- 15,200 psi · 104.8 MPa
- Modulus of elasticity
- 1.78 ×10⁶ psi · 12.27 GPa
- Shrinkage, green to oven-dry
- 5.6% radial · 10.5% tangential · 16.3% volumetric
White oak. Northern red oak is lighter (SG 0.63) and softer — 1,290 lbf, MOR 14,300 psi.
Source: USDA Forest Service, Wood Handbook — Wood as an Engineering Material (FPL-GTR-190, 2010), Table 5–3b, for clear straight-grained specimens at 12% moisture content. The grey figures are converted at 1 lbf = 4.448 N, 1 psi = 6.895 kPa and 1 GPa = 145,038 psi; the inch-pound numbers are the published ones. Specific gravity is oven-dry mass over volume at 12% moisture content, so it sits about 12% below the working density at the top of this page (0.68 × 1.12 ≈ 0.76 g/cm³). The two come from different sampling programmes, so a few species differ by more than that.
Applicationswhere oak is normally specified
Appearance & workabilitytrade experience, not measured values
- Origin
- Eastern North America (the commercial white oaks); Europe and Asia have their own species
- Appearance
- Pale straw to light brown heartwood with a straight grain; the coarse open pores show as a bold figure on quartersawn faces
- Working
- Planes and machines well, but the open pores need a filler before a smooth film finish. Damp oak corrodes steel, so outdoor work uses stainless or coated fixings.
Unlike the USDA figures above, these lines are not measurements: they carry no units and no single source. They describe how the timber is generally found to behave rather than what it is guaranteed to do — read them as the consensus of the trade, not as a specification.
Practical notes
- Density is for air-dried stock at about 12% moisture content
- Varies roughly ±10% with species, origin and growth conditions
- Green timber can be 50% or more heavier than air-dried
- White oak is notably denser than red oak — check which is specified
Lumber sizeswhat oak weighs in each nominal size
Lumber size databaseDressed sizes are the same for every species — a 2x4 is 1-1/2 x 3-1/2 in in oak as much as in spruce. What changes is the weight, and that is derived here from oak's density of 0.75 g/cm³.
Tools used on itmatched on the wood family, not on this page
All toolsWhich tools work a material is a property of the family (Wood), not of the individual species — so this list is the same on every wood page, and changes when the tool data changes rather than when this paragraph does.
Used in these projectsbuilds whose bill of materials calls for it
All projectsFrequently asked questionsthe questions this page answers about Oak
How hard is Oak?
Janka hardness is 1,360 lbf — the force needed to push a steel ball halfway into the wood. Higher is harder; this is the number quoted when a wood is specified for floors, worktops or butcher blocks.
How dense is Oak?
Density is 0.75 g/cm³, and the USDA table gives a specific gravity of 0.68.
How much does Oak move when it dries?
Green to oven-dry it shrinks 16.3% by volume — 5.6% radially and 10.5% tangentially. Movement across the grain is what opens joints, so a species that moves a lot wants room to move.
What is Oak used for?
Typical uses are Furniture, Flooring, Cabinetry, Barrels and Boatbuilding.
How does Oak work with hand and machine tools?
Planes and machines well, but the open pores need a filler before a smooth film finish. Damp oak corrodes steel, so outdoor work uses stainless or coated fixings.