Obeche wood movement, board-foot & weight calculator
- Janka
- 430lbf
- Density
- 21lb/ft³
- T/R ratio
- 1.8
- Spec. gravity
- 0.3
Obeche (Triplochiton scleroxylon) is an imported species. It has a Janka side hardness of 430 lbf, a specific gravity of 0.3, and an air-dry density near 21 lb/ft³ (336 kg/m³) (mechanical values at 12% moisture content). It shrinks 5.4% tangentially and 3% radially from green to oven-dry (T/R ratio 1.8), so a 12-inch flatsawn board moves about 0.13 in (≈ 1/8 in) across a 6-point moisture swing (about 6%→12% MC).
Compute Obeche: movement, weight & board footage
Every number below is worked from Obeche'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″ | 0.022″ (≈ 1/32 in) | 0.012″ (≈ 0 in) |
| 3″ | 0.032″ (≈ 1/32 in) | 0.018″ (≈ 1/32 in) |
| 4″ | 0.043″ (≈ 1/32 in) | 0.024″ (≈ 1/32 in) |
| 6″ | 0.065″ (≈ 1/16 in) | 0.036″ (≈ 1/32 in) |
| 8″ | 0.086″ (≈ 3/32 in) | 0.048″ (≈ 1/16 in) |
| 10″ | 0.108″ (≈ 3/32 in) | 0.06″ (≈ 1/16 in) |
| 12″ | 0.13″ (≈ 1/8 in) | 0.072″ (≈ 1/16 in) |
| 16″ | 0.173″ (≈ 3/16 in) | 0.096″ (≈ 3/32 in) |
Need a different width or moisture swing? Run the movement calculator preloaded with Obeche. At a T/R ratio of 1.8, Obeche is stable — it moves moderately more across the face than through the thickness — normal behaviour for a furniture hardwood, and predictable if boards are acclimatised before milling.
Board footage & weight, standard sizes
| Nominal size × length | Board feet | Weight |
|---|---|---|
| 1×4 × 8′ | 2.67 bd ft | 4.7 lb |
| 1×6 × 8′ | 4 bd ft | 7 lb |
| 1×8 × 8′ | 5.33 bd ft | 9.3 lb |
| 1×10 × 8′ | 6.67 bd ft | 11.7 lb |
| 1×12 × 8′ | 8 bd ft | 14 lb |
| 2×4 × 8′ | 5.33 bd ft | 9.3 lb |
| 2×6 × 8′ | 8 bd ft | 14 lb |
| 2×8 × 8′ | 10.67 bd ft | 18.7 lb |
Different length or size? Run the board foot calculator or the weight calculator, both preloaded with Obeche.
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 | 0.099″ (≈ 3/32 in) |
| Chicago, IL | May · 12.3% | Dec · 15.1% | 2.8 pts | 0.06″ (≈ 1/16 in) |
| Miami, FL | Apr · 12.2% | Sep · 14.4% | 2.2 pts | 0.048″ (≈ 1/16 in) |
| Boston, MA | Apr · 11.5% | Sep · 12.8% | 1.3 pts | 0.028″ (≈ 1/32 in) |
| Denver, CO | Jul · 8% | Dec · 10.5% | 2.5 pts | 0.054″ (≈ 1/16 in) |
| Seattle, WA | Jul · 12% | Dec · 16.9% | 4.9 pts | 0.106″ (≈ 3/32 in) |
Driven by Obeche's tangential shrinkage of 5.4%. These are outdoor equilibrium-moisture figures, so they are an upper bound — a climate-controlled interior swings less. How this is calculated.
How Obeche compares
Ranked against the 196 species in the Wood Handbook tables this site carries.
- Hardness: at 430 lbf, Obeche is harder than 11% of the 157 species with a Janka figure — one of the softer woods here, easy to work and easy to dent.
- Weight: at 21 lb/ft³ it is heavier than 1% of the 170 species measured — an 8-foot 1×6 board weighs about 7 lb.
- Stability: its T/R ratio of 1.8 is more even than 54% of the 196 species here — as humidity changes, 46% of them hold their shape more evenly.
See Obeche plotted against every species we carry: the full Janka hardness chart and the full density chart .
Species with a similar working profile
Closest matches on hardness, weight and stability together — useful when Obeche is unavailable or priced out.
- Butternut is a common substitute for Obeche : 14% harder, 27% heavier, and similarly stable in service.
- Sitka Spruce is a common substitute for Obeche : 19% harder, 33% heavier, and similarly stable in service.
- Old Growth Redwood is a common substitute for Obeche : 12% harder, 33% heavier, and similarly stable in service.
- Yellow-poplar is a common substitute for Obeche : 26% harder, 40% heavier, and similarly stable in service.
| Species | Janka | Density | T/R |
|---|---|---|---|
| Butternut | 490 lbf | 26.6 | 1.88 |
| Sitka Spruce | 510 lbf | 28 | 1.74 |
| Old Growth Redwood | 480 lbf | 28 | 1.69 |
| Yellow-poplar | 540 lbf | 29.4 | 1.78 |
About Obeche
Obeche (Triplochiton scleroxylon) trees of west- central Africa reach a height of 50 m (150 ft) or more and a diameter of up to 2 m (5 ft). The trunk is usually free of branches for a considerable height so that clear lumber of considerable size can be obtained. The wood is creamy white to pale yellow with little or no difference between sapwood and heartwood. The wood is fairly soft, of uniform medium to coarse texture, and the grain is usually interlocked but sometimes straight. Air-dry wood weighs about 385 kg m–3 (24 lb ft–3). Obeche dries readily with little degrade. It is not resistant to decay, and green sapwood is subject to blue stain. The wood is easy to work and machine, veneers and glues well, and takes nails and screws without splitting. The characteristics of obeche make it especially suitable for veneer and corestock. Other uses include furniture, components, millwork, blockboard, boxes and crates, particleboard and fiberboard, patterns, and artificial limbs.
Durability & sustainability
Decay resistance: the Wood Handbook rates Obeche heartwood slightly or nonresistant to fungal decay . Ratings are for heartwood only and the table's own note cautions that resistance varies substantially within a species; treat this as a general indicator, not a guarantee, especially for ground contact. Wood Handbook, Chapter 14: Biodeterioration of Wood (Arango, Lebow, Glaeser), USDA Forest Products Laboratory, FPL-GTR-282 (2021), Table 14-1. Public domain.
Properties
| Specific gravity | 0.3 |
|---|---|
| Janka hardness (side) | 430 lbf |
| Density (air-dry, 12% MC) | 21 lb/ft³ (336 kg/m³) ovendry-weight basis: 18.7 lb/ft³ |
| Weight per board foot (air-dry) | 1.75 lb |
| Radial shrinkage (green→oven-dry) | 3% |
| Tangential shrinkage (green→oven-dry) | 5.4% |
| Volumetric shrinkage (green→oven-dry) | 9.2% |
| T/R ratio (stability indicator) | 1.8 |
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.
Data: USDA Forest Products Laboratory, Wood Handbook FPL-GTR-282 (2021), public domain.