True Mahogany — wood data
- Janka
- 800lbf
- Density
- 31.4lb/ft³
- T/R ratio
- 1.4
- Spec. gravity
- 0.45
True Mahogany (Swietenia macrophylla) is an imported species. It has a Janka side hardness of 800 lbf, a specific gravity of 0.45, and an air-dry density near 31 lb/ft³ (503 kg/m³) (mechanical values at 12% moisture content). It shrinks 4.1% tangentially and 3% radially from green to oven-dry (T/R ratio 1.4), so a 12-inch flatsawn board moves about 0.1 in (≈ 3/32 in) across a 6-point moisture swing (about 6%→12% MC).
Properties
| Specific gravity | 0.45 |
|---|---|
| Janka hardness (side) | 800 lbf |
| Density (air-dry, 12% MC) | 31.4 lb/ft³ (503 kg/m³) ovendry-weight basis: 28.1 lb/ft³ |
| Weight per board foot (air-dry) | 2.62 lb |
| Radial shrinkage (green→oven-dry) | 3% |
| Tangential shrinkage (green→oven-dry) | 4.1% |
| Volumetric shrinkage (green→oven-dry) | 7.8% |
| T/R ratio (stability indicator) | 1.4 |
Shrinkage is total green-to-oven-dry (Table 4-4). Specific gravity basis: estimated average clear wood SG (ovendry weight); volume basis per source, FPL-GTR-282 Table 5-5b. Janka side hardness at 12% MC. Primary density is air-dry at 12% MC: 62.4 × specific gravity × 1.12 (includes the ~12% bound-water mass — how dried lumber is actually weighed). The ovendry-weight figure (62.4 × SG, wood substance only) is shown beneath it.
Data: USDA Forest Products Laboratory, Wood Handbook FPL-GTR-282 (2021), public domain.
Estimated movement by board width
| Board width | Flatsawn (tangential) | Quartersawn (radial) |
|---|---|---|
| 4″ | 0.033″ (≈ 1/32 in) | 0.024″ (≈ 1/32 in) |
| 6″ | 0.049″ (≈ 1/16 in) | 0.036″ (≈ 1/32 in) |
| 8″ | 0.066″ (≈ 1/16 in) | 0.048″ (≈ 1/16 in) |
| 12″ | 0.098″ (≈ 3/32 in) | 0.072″ (≈ 1/16 in) |
Need a different width or moisture swing? Run the movement calculator preloaded with True Mahogany. A T/R ratio near 1 means the wood moves evenly in both directions and tends to stay flat; higher ratios cup and distort more as moisture changes.
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 | 0.075″ (≈ 1/16 in) |
| Chicago, IL | May · 12.3% | Dec · 15.1% | 2.8 pts | 0.046″ (≈ 1/32 in) |
| Miami, FL | Apr · 12.2% | Sep · 14.4% | 2.2 pts | 0.036″ (≈ 1/32 in) |
Computed with ΔD = D × (S ÷ 30 ÷ 100) × ΔEMC, where S is True Mahogany's total green-to-oven-dry tangential shrinkage (4.1%) and 30% is the fiber-saturation-point convention. The EMC figures are USDA Table 13-1 monthly equilibrium moisture content for outdoor exposure (through 2010); a climate-controlled interior swings less, so treat these as an upper-bound seasonal range for each location.
Sources & method
Shrinkage, specific gravity, and hardness values follow the USDA Forest Products Laboratory Wood Handbook (FPL-GTR-282, 2021); derived figures (movement, weight per board foot, T/R ratio, kg/m³, density from specific gravity) are computed with the formulas documented on the methodology page.