Species data
Koa
Acacia koa - a hardwood from hawaii. Also sold as hawaiian koa.
Properties at a glance
| Janka hardness | 1,170 lbf |
| Stiffness (MOE) | 1,503,000 psi |
| Specific gravity | 0.61 |
| Density | 38.1 lb/ft3 (610 kg/m3) |
| Weight per board foot | 3.17 lb |
| Shrinkage, green to oven-dry | 6.2% tangential / 5.5% radial |
| Indicative price | $50.00 per board foot (estimated) |
Values are at about 12% moisture content. Density is specific gravity times 62.4; a board foot is one twelfth of a cubic foot, so weight per board foot is that density divided by twelve. Anything marked estimated is our own figure, not a measured one.
How Koa compares
Measured against the 113 solid woods in this database: it is harder than 55% of them, heavier than 50%, and stiffer than 38%.
What that means in the shop
A 4/4 board 8 inches wide and 8 feet long is 5.33 board feet, so in Koa it weighs about 16.9 lb. A stack of ten is 169 lb - worth knowing before you load a rack or a car.
Against red oak, the trade's usual yardstick at 1,220 lbf, Koa is about 96% as hard and 87% as heavy.
Its shrinkage is 6.2% tangential against 5.5% radial, a ratio of 1.1 to 1. The wider that ratio, the more unevenly a flatsawn board moves across its width as humidity changes, and the more it wants to cup; anything near or above 2 to 1 is worth quartersawing or restraining for panels and wide tops. This one moves comparatively evenly.
Woods of similar hardness
Closest to Koa on hardness in this database: Oregon Ash (1,160 lbf), Iroko (1,190 lbf), Makore (1,200 lbf), Chestnut Oak (1,130 lbf). Similar hardness does not mean similar behaviour - check density and movement before substituting one for another.
Working with it
Workability. Mostly easy, though figured interlocked grain gets tricky; finishes, stains and turns well
Durability. Non-durable to perishable, with termites a persistent threat
Typical uses. furniture, cabinetry, musical instruments, veneer, turning.
Related calculators
Sources
MOE, SG (12% MC), Janka and shrinkage from The Wood Database (cites USDA FPL Wood Handbook). CT/CR omitted: koa is not listed in the FPL/Hoadley dimensional change coefficient table. Uses, region, durability and workability summarized from The Wood Database. Price indicative.
These calculators are for planning and estimation. Engineering results (shelf sag, wood movement) use published average material properties; real boards vary by grade, grain, moisture and defects. Verify load-bearing designs with a professional.