African Ebony wood movement calculator
- Janka
- —
- Density
- —
- T/R ratio
- 1.2
- Spec. gravity
- —
African Ebony (Diospyros spp.) is an imported species. The Wood Handbook strength tables list no matched specific gravity or hardness for it, so those fields are shown as “—”. It shrinks 10.8% tangentially and 9.2% radially from green to oven-dry (T/R ratio 1.2), so a 12-inch flatsawn board moves about 0.26 in (≈ 1/4 in) across a 6-point moisture swing (about 6%→12% MC).
Compute African Ebony: movement, weight & board footage
Every number below is worked from African Ebony's own shrinkage and density figures, not looked up from a table — change the width, moisture swing, or board size in the calculators linked alongside.
Cross-grain movement by board width
| Board width | Flatsawn (tangential) | Quartersawn (radial) |
|---|---|---|
| 2″ | 0.043″ (≈ 1/32 in) | 0.037″ (≈ 1/32 in) |
| 3″ | 0.065″ (≈ 1/16 in) | 0.055″ (≈ 1/16 in) |
| 4″ | 0.086″ (≈ 3/32 in) | 0.074″ (≈ 1/16 in) |
| 6″ | 0.13″ (≈ 1/8 in) | 0.11″ (≈ 1/8 in) |
| 8″ | 0.173″ (≈ 3/16 in) | 0.147″ (≈ 5/32 in) |
| 10″ | 0.216″ (≈ 7/32 in) | 0.184″ (≈ 3/16 in) |
| 12″ | 0.259″ (≈ 1/4 in) | 0.221″ (≈ 7/32 in) |
| 16″ | 0.346″ (≈ 11/32 in) | 0.294″ (≈ 9/32 in) |
Need a different width or moisture swing? Run the movement calculator preloaded with African Ebony. At a T/R ratio of 1.17, African Ebony is very stable — it moves almost as much radially as tangentially, so flatsawn boards have little reason to cup and wide panels stay flat with ordinary care.
Board footage and weight aren't shown for African Ebony — the Wood Handbook strength tables carry no matched density for it, so a weight figure here would be invented rather than computed. The board foot calculator still works without a species; board feet don't depend on density.
Seasonal movement by city
| City | Driest month (EMC) | Most-humid month (EMC) | EMC swing | 12″ board movement |
|---|---|---|---|---|
| Phoenix, AZ | Jun · 4.4% | Dec · 9% | 4.6 pts | 0.199″ (≈ 3/16 in) |
| Chicago, IL | May · 12.3% | Dec · 15.1% | 2.8 pts | 0.121″ (≈ 1/8 in) |
| Miami, FL | Apr · 12.2% | Sep · 14.4% | 2.2 pts | 0.095″ (≈ 3/32 in) |
| Boston, MA | Apr · 11.5% | Sep · 12.8% | 1.3 pts | 0.056″ (≈ 1/16 in) |
| Denver, CO | Jul · 8% | Dec · 10.5% | 2.5 pts | 0.108″ (≈ 3/32 in) |
| Seattle, WA | Jul · 12% | Dec · 16.9% | 4.9 pts | 0.212″ (≈ 7/32 in) |
Driven by African Ebony's tangential shrinkage of 10.8%. These are outdoor equilibrium-moisture figures, so they are an upper bound — a climate-controlled interior swings less. How this is calculated.
How African Ebony compares
Ranked against the 196 species in the Wood Handbook tables this site carries.
- Stability: its T/R ratio of 1.17 is more even than 99% of the 196 species here — as humidity changes, 1% of them hold their shape more evenly.
Properties
| Specific gravity | — |
|---|---|
| Janka hardness (side) | — |
| Density (air-dry, 12% MC) | — |
| Weight per board foot (air-dry) | — |
| Radial shrinkage (green→oven-dry) | 9.2% |
| Tangential shrinkage (green→oven-dry) | 10.8% |
| Volumetric shrinkage (green→oven-dry) | 20% |
| T/R ratio (stability indicator) | 1.2 |
Shrinkage is total green-to-oven-dry (Table 4-4); strength values are at 12% MC. Full bases and the derivation formulas are on the methodology page. Values shown as “—” have no matched entry in the Wood Handbook strength tables (5-3b/5-5b).
Data: USDA Forest Products Laboratory, Wood Handbook FPL-GTR-282 (2021), public domain.