Free wood movement calculator with complete wood expansion chart. Calculate wood shrinkage and expansion for furniture design and joinery. Includes seasonal changes, species-specific data for oak, maple, cherry, and walnut. Prevent wood splitting, warping, and joint failures with accurate wood expansion and contraction calculations.
Enter wood specifications and environmental conditions to calculate expansion, contraction, and design allowances for your project.
Wood movement occurs because cell walls absorb and release moisture in response to environmental humidity changes. This process is reversible and predictable, following established scientific principles that allow accurate calculation of dimensional changes.
ΔDimension = Original Width × Shrinkage Coefficient × ΔMC | Environment | Expected MC | Relative Humidity | Notes |
|---|---|---|---|
| Kiln-Dried Lumber (Delivery) | 6-8% | 35-45% RH | Standard for indoor woodworking |
| Indoor Heated (Winter) | 6-7% | 35-40% RH | Lowest annual MC |
| Indoor (Summer) | 8-10% | 50-60% RH | Typical summer swell |
| Unheated/Garage Storage | 10-14% | Variable | Significant seasonal swing |
| Outdoor Covered | 12-18% | Variable | Region-dependent |
Wood movement is highly directional. Tangential movement (across growth rings, flat-sawn) is 1.5-2x greater than radial movement (along growth rings, quarter-sawn). Longitudinal movement (along grain) is negligible (0.1-0.3%).
12" Wide Oak Board, 4% MC Change (8% to 12%):
Design implication: Quarter-sawn boards are preferred for drawer fronts, raised panels, and tabletops despite the 20-40% cost premium.
Different wood species exhibit vastly different movement characteristics due to cell structure, density, and chemical composition. Professional woodworkers select species based on both aesthetic properties and dimensional stability requirements.
| Species | Tangential % | Radial % | T/R Ratio | Stability Rating |
|---|---|---|---|---|
| Mahogany | 5.0% | 3.2% | 1.6 | ⭐⭐⭐⭐⭐ Excellent |
| Teak | 5.7% | 2.5% | 2.3 | ⭐⭐⭐⭐⭐ Excellent |
| Cedar (Western Red) | 5.0% | 2.4% | 2.1 | ⭐⭐⭐⭐⭐ Excellent |
| Cherry | 7.2% | 3.8% | 1.9 | ⭐⭐⭐⭐ Good |
| Walnut | 7.7% | 5.3% | 1.5 | ⭐⭐⭐⭐ Good |
| White Oak | 8.6% | 5.6% | 1.5 | ⭐⭐⭐ Moderate |
| Red Oak | 9.0% | 4.8% | 1.9 | ⭐⭐⭐ Moderate |
| Maple (Hard) | 9.7% | 4.9% | 2.0 | ⭐⭐⭐ Moderate |
| Hickory | 10.8% | 7.2% | 1.5 | ⭐⭐ High Movement |
| Beech | 11.9% | 5.3% | 2.2 | ⭐⭐ High Movement |
Design decision: For tight-fitting cabinet doors, choose mahogany or cherry. For tabletops with breadboard ends, any species works with proper movement accommodation.
Professional furniture design incorporates wood movement from the initial concept. Ignoring movement leads to splits, warping, stuck doors, and joint failure.
Geographic location dramatically affects wood movement patterns. Northern heated climates experience the largest seasonal MC swings (4-5%), while desert climates have minimal variation.
| Region | RH Range | Indoor MC | Seasonal Swing | Strategy |
|---|---|---|---|---|
| Southwest Desert | 15-35% | 4-7% | 1-2% | Acclimate down; minimal movement |
| Southeast Humid | 60-90% | 10-14% | 2-4% | Use stable species; accept more movement |
| Northern Heated | 20-70% | 6-11% | 4-5% | Maximum clearances; build spring/fall |
| Pacific Northwest | 50-80% | 9-12% | 2-3% | Verify lumber is truly dry |
| Moderate (Mid-Atlantic) | 40-60% | 7-10% | 2-3% | Standard techniques work well |
Wood movement perpendicular to growth rings (across them). Greatest dimension change: 6-12% from green to oven-dry. Flat-sawn boards primarily exhibit tangential movement across their width.
Wood movement parallel to growth rings (toward tree center). Moderate dimension change: 3-6% from green to oven-dry. Quarter-sawn boards primarily exhibit radial movement — 40-50% less than tangential.
The MC (~28-30%) at which cell walls are fully saturated but cell cavities are empty. Below FSP, dimensional changes occur. Above FSP, wood absorbs water without changing dimensions.
The MC at which wood neither gains nor loses moisture in a given environment. Determined by temperature and relative humidity. Indoor EMC typically 6-11% depending on climate and season.
Tangential-to-Radial shrinkage ratio. Lower values (closer to 1.0) indicate more uniform shrinkage and less tendency to warp. Walnut (1.5) is better balanced than Hard Maple (2.0).
Lumber cut so growth rings are approximately perpendicular to the broad face (60-90°). Exhibits radial movement (more stable), prominent ray fleck pattern, and commands 20-40% price premium.
The most common sawing method. Growth rings meet the face at 0-30°. Shows cathedral grain pattern, exhibits tangential movement (more movement), and is the most economical cut.
A piece of wood attached cross-grain to the end of a panel (e.g., tabletop). Must be attached with center pin and elongated slots to allow seasonal panel movement. Prevents cupping while maintaining clean edge appearance.
For each 1% change in MC, wood moves 0.1-0.3% tangentially and 0.05-0.15% radially. A 12-inch wide oak board might move 1/8 to 1/4 inch across a full seasonal cycle. Use our calculator for precise species-specific values.
Tangential (across growth rings, flat-sawn) is typically 1.5-2x greater than radial (along growth rings, quarter-sawn). This is why quarter-sawn lumber is more dimensionally stable.
Use proper joinery: floating panels, figure-8 fasteners, slotted screw holes, breadboard ends with elongated slots. Orient grain consistently, use stable species for critical dimensions, and control your shop environment.
Target 6-8% MC for most indoor environments. Acclimate wood in the final environment for 2-4 weeks before construction. Use our moisture content calculator for environment-specific EMC values.
Mahogany (5.0% tangential), Teak (5.7%), and Cedar (5.0%) are among the most stable. Quarter-sawn boards of any species are more stable. Engineered materials (plywood, MDF) have minimal movement.
Northern heated climates have the largest seasonal swings (4-5% MC). Desert Southwest is driest with minimal variation (1-2%). Southeast is consistently humid. Design clearances should match your regional extremes.
Build in spring or fall when MC is at mid-season values. Size components at average dimensions so the piece will be centered between seasonal extremes. For critical projects, mill in winter (dry) and assemble in spring.
No. Finish slows moisture exchange but does not prevent it. Even thick film finishes only delay the process by days to weeks. All designs must accommodate movement regardless of finish. Unfinished end grain should be sealed to equalize moisture exchange rates.