How hard is koa wood?

Koa has a Janka hardness of 1170 lbf (5,180 N), a side-hardness measurement reflecting the force needed to embed a half-inch steel ball halfway into the wood. That figure is a USDA Forest Products Laboratory value at 12% moisture content.

Can koa be used outdoors?

No. Koa is only moderately durable, has moderate insect resistance, and is not suited for ground contact, so it is best kept indoors. It is traditionally used for furniture, cabinetry, ukuleles and acoustic guitars, bowls and turnings, paddles, and outrigger canoe hulls.

Is koa hard to work with?

Working koa is generally good, and it turns, carves, glues, and finishes beautifully, taking oil and lacquer better than almost anything. The catch is figured stock tears out, so use sharp tooling and light cuts and plan on scraping or sanding; Acacia dust carries documented sensitizers that can cause respiratory and skin irritation.

ExoticAcacia koa

Koa

The wood of the canoe and the warrior — and the wood of every conversation about Hawaiian sourcing.

Koa (Acacia koa) is an exotic hardwood endemic to the Hawaiian Islands, with a Janka hardness of 1170 lbf. Its heartwood runs golden brown to deep reddish brown with frequent dark streaks, and curly, fiddleback, or quilted figure with high luster is what defines it commercially.

Category: Exotic
Janka: 1,170 lbf
Botanical: Acacia koa
Shipped at: 6–8% MC

Acacia koa Hawaiian Koa · Hawaiian Koa · Endemic to the Hawaiian Islands; found on Hawaii

Endemic to the Hawaiian Islands; found on Hawaii.

Koa means "brave" or "warrior" in Hawaiian. Heartwood golden brown to deep reddish brown to near chocolate, with frequent dark streaks.

Detail of Koa grain — figured wood texture, photographed at Raw Heartwood — A close read on the grain. Detail of this specimen

What you see.

Heartwood golden brown to deep reddish brown to near chocolate, with frequent dark streaks. Curly, fiddleback, quilted, fish-scale figure is what people pay for and what defines the wood commercially. Pale sapwood, sharp line.

Heartwood color detail of Koa (Acacia koa)

Heartwood, this specimen

How the grain runs.

Straight to deeply interlocked or wavy. The wave is what you want — that is the figure. Medium uniform texture, high luster. Koa glows under finish.

Closer in

On the bench.

Moderately durable. Not for ground contact. Moderate insect resistance. Indoors. Generally good. Figured stock tears out — sharp tooling, light cuts, plan on scraping or sanding. Turns, carves, glues, and finishes beautifully. Takes oil and lacquer better than almost anything. Mild and faintly sweet at the cut. Little odor when dry. Reactions are uncommon. Acacia carries documented sensitizers, so some workers report respiratory and skin irritation from the dust.

The numbers, looked at directly.

Janka Hardness

0lbf

5,180 N. Side-hardness — force to embed a half-inch steel ball halfway into the wood.

Average Dried Weight

0lbs/ft³

610 kg/m³. At 12% MC.

Specific Gravity

0.49/ 0.61 at 12% MC

Basic over green volume; second number at 12% moisture content.

Hardness, in context

A side-hardness measurement. Higher number, harder wood.

Shrinkage — radial / tangential / volumetric

3.0%radial

5.5%tangential

8.5%volumetric

On sourcing

Koa is the sustainability flashpoint among Hawaiian woods.

Koa is the sustainability flashpoint among Hawaiian woods. Not on CITES. IUCN Least Concern at present. The species has lost roughly 90% of its historical range to agriculture, ranching, and fire. Old-growth stands are rare and protected. Hawaii heavily restricts harvest from state forest reserves and regulates commercial cutting on public land. Most legal koa lumber on the market is private-ranchland salvage, small private forestry, or certified plantation. Verify legal-origin paperwork. Raw log export is restricted.

What it's for.

Furniture & cabinetry
Ukuleles & acoustic guitars
Bowls & turnings
Gunstocks
Paddles & surfboards
Outrigger canoe hulls
Veneer
Fine craft

Worth knowing.

Koa means "brave" or "warrior" in Hawaiian. Traditional wood for waʻa (voyaging canoes), papa heʻe nalu (surfboards), and royal artifacts. Old-growth was reserved for aliʻi. The species sits at the meeting point of cultural heritage, conservation, and a global tonewood market — sourcing matters.

Sources & references.

Acacia koa — Wikipedia contributors
Growing Koa: A Hawaiian Legacy Tree — CTAHR, University of Hawaii at Manoa — Wilkinson, K.M.; Elevitch, C.R. (2003)
Hawaiian Koa (Acacia koa) — The Wood Database
Acacia koa (koa) — Species Profiles for Pacific Island Agroforestry — Elevitch, C.R.; Wilkinson, K.M.; Friday, J.B. (2006)
Hawaii Administrative Rules, Title 13, Chapter 104 — Forest Reserves (DLNR/DOFAW)
Hawaii Division of Forestry and Wildlife — Forestry Program
Acacia koa — Plants of the World Online (Kew)

Common questions.

How hard is koa wood?: Koa has a Janka hardness of 1170 lbf (5,180 N), a side-hardness measurement reflecting the force needed to embed a half-inch steel ball halfway into the wood. That figure is a USDA Forest Products Laboratory value at 12% moisture content.
Can koa be used outdoors?: No. Koa is only moderately durable, has moderate insect resistance, and is not suited for ground contact, so it is best kept indoors. It is traditionally used for furniture, cabinetry, ukuleles and acoustic guitars, bowls and turnings, paddles, and outrigger canoe hulls.
Is koa hard to work with?: Working koa is generally good, and it turns, carves, glues, and finishes beautifully, taking oil and lacquer better than almost anything. The catch is figured stock tears out, so use sharp tooling and light cuts and plan on scraping or sanding; Acacia dust carries documented sensitizers that can cause respiratory and skin irritation.

From the library to your bench