Purpleheart wood movement, board-foot & weight calculator
- Janka
- 1,860lbf
- Density
- 46.8lb/ft³
- T/R ratio
- 1.9
- Spec. gravity
- 0.67
Purpleheart (Peltogyne spp.) is an imported species. It has a Janka side hardness of 1,860 lbf, a specific gravity of 0.67, and an air-dry density near 47 lb/ft³ (750 kg/m³) (mechanical values at 12% moisture content). It shrinks 6.1% tangentially and 3.2% radially from green to oven-dry (T/R ratio 1.9), so a 12-inch flatsawn board moves about 0.15 in (≈ 5/32 in) across a 6-point moisture swing (about 6%→12% MC).
Compute Purpleheart: movement, weight & board footage
Every number below is worked from Purpleheart'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″ | 0.024″ (≈ 1/32 in) | 0.013″ (≈ 0 in) |
| 3″ | 0.037″ (≈ 1/32 in) | 0.019″ (≈ 1/32 in) |
| 4″ | 0.049″ (≈ 1/16 in) | 0.026″ (≈ 1/32 in) |
| 6″ | 0.073″ (≈ 1/16 in) | 0.038″ (≈ 1/32 in) |
| 8″ | 0.098″ (≈ 3/32 in) | 0.051″ (≈ 1/16 in) |
| 10″ | 0.122″ (≈ 1/8 in) | 0.064″ (≈ 1/16 in) |
| 12″ | 0.146″ (≈ 5/32 in) | 0.077″ (≈ 1/16 in) |
| 16″ | 0.195″ (≈ 3/16 in) | 0.102″ (≈ 3/32 in) |
Need a different width or moisture swing? Run the movement calculator preloaded with Purpleheart. At a T/R ratio of 1.91, Purpleheart 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 | 10.4 lb |
| 1×6 × 8′ | 4 bd ft | 15.6 lb |
| 1×8 × 8′ | 5.33 bd ft | 20.8 lb |
| 1×10 × 8′ | 6.67 bd ft | 26 lb |
| 1×12 × 8′ | 8 bd ft | 31.2 lb |
| 2×4 × 8′ | 5.33 bd ft | 20.8 lb |
| 2×6 × 8′ | 8 bd ft | 31.2 lb |
| 2×8 × 8′ | 10.67 bd ft | 41.6 lb |
Different length or size? Run the board foot calculator or the weight calculator, both preloaded with Purpleheart.
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 | 0.112″ (≈ 1/8 in) |
| Chicago, IL | May · 12.3% | Dec · 15.1% | 2.8 pts | 0.068″ (≈ 1/16 in) |
| Miami, FL | Apr · 12.2% | Sep · 14.4% | 2.2 pts | 0.054″ (≈ 1/16 in) |
| Boston, MA | Apr · 11.5% | Sep · 12.8% | 1.3 pts | 0.032″ (≈ 1/32 in) |
| Denver, CO | Jul · 8% | Dec · 10.5% | 2.5 pts | 0.061″ (≈ 1/16 in) |
| Seattle, WA | Jul · 12% | Dec · 16.9% | 4.9 pts | 0.12″ (≈ 1/8 in) |
Driven by Purpleheart's tangential shrinkage of 6.1%. These are outdoor equilibrium-moisture figures, so they are an upper bound — a climate-controlled interior swings less. How this is calculated.
How Purpleheart compares
Ranked against the 196 species in the Wood Handbook tables this site carries.
- Hardness: at 1,860 lbf, Purpleheart is harder than 85% of the 157 species with a Janka figure — firmly in the hard quarter, which is what resists denting in flooring and worktops.
- Weight: at 46.8 lb/ft³ it is heavier than 79% of the 170 species measured — an 8-foot 1×6 board weighs about 15.6 lb.
- Stability: its T/R ratio of 1.91 is more even than 42% of the 196 species here — as humidity changes, 58% of them hold their shape more evenly.
See Purpleheart 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 Purpleheart is unavailable or priced out.
- Pecan Hickory is a common substitute for Purpleheart : nearly identical hardness, about the same weight, and similarly stable in service.
- White Oak is a common substitute for Purpleheart : 27% softer, about the same weight, and similarly stable in service.
- Post Oak is a common substitute for Purpleheart : 27% softer, about the same weight, and similarly stable in service.
- Sugar Maple is a common substitute for Purpleheart : 22% softer, about the same weight, and similarly stable in service.
| Species | Janka | Density | T/R |
|---|---|---|---|
| Pecan Hickory | 1,820 lbf | 46.1 | 1.82 |
| White Oak | 1,360 lbf | 47.5 | 1.88 |
| Post Oak | 1,360 lbf | 46.8 | 1.81 |
| Sugar Maple | 1,450 lbf | 44 | 2.06 |
About Purpleheart
Purpleheart, also referred to as amaranth, is the name applied to species in the genus Peltogyne. The center of distribution is in the north- central part of the Brazilian Amazon region, but the combined range of all species is from Mexico through Central America and southward to southern Brazil. Freshly cut heartwood is brown. It turns a deep purple upon exposure to air and eventually dark brown upon exposure to light. The texture is medium to fine, and the grain is usually straight. This strong and heavy wood (density of air-dried wood is 800 to 1,057 kg m–3 (50 to 66 lb ft–3)) is rated as easy to moderately difficult to air dry. It is moderately difficult to work with using either hand or machine tools, and it dulls cutters rather quickly. Gummy resin exudes when the wood is heated by dull tools. A slow feed rate and specially hardened cutters are suggested for optimal cutting. The wood turns easily, is easy to glue, and takes finishes well. The heartwood is rated as highly resistant to attack by decay fungi and very resistant to dry-wood termites. It is extremely resistant to treatment with preservatives. The unusual and unique color of purpleheart makes this wood desirable for turnery, marquetry, cabinets, fine furniture, parquet flooring, and many specialty items, such as billiard cue butts and carvings. Other uses include heavy construction, shipbuilding, and chemical vats.
Durability & sustainability
Decay resistance: the Wood Handbook rates Purpleheart heartwood very resistant 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 | 0.67 |
|---|---|
| Janka hardness (side) | 1,860 lbf |
| Density (air-dry, 12% MC) | 46.8 lb/ft³ (750 kg/m³) ovendry-weight basis: 41.8 lb/ft³ |
| Weight per board foot (air-dry) | 3.9 lb |
| Radial shrinkage (green→oven-dry) | 3.2% |
| Tangential shrinkage (green→oven-dry) | 6.1% |
| Volumetric shrinkage (green→oven-dry) | 9.9% |
| T/R ratio (stability indicator) | 1.9 |
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.