1. Select Wood Species: Different woods move different amounts. Choose your species from the list.
2. Enter Initial & Final Moisture Content (MC): Input the wood's starting MC and the MC of the environment it will end up in. For example, going from an air-dried state (15%) to an indoor, heated environment (8%).
3. Enter Board Width: Input the width of your board. Wider boards will exhibit more total movement.
4. Calculate & Analyze: The calculator shows the total dimensional change for both flatsawn and quartersawn boards. Note how much more a flatsawn board moves, which is why it's more prone to cupping.

• Warp: Any distortion in a piece of lumber from its true plane. The four main types are bow, cup, crook, and twist.
• Cup: A warp across the width of a board, where the edges are higher or lower than the center. Most common in flatsawn boards.
• Bow: A warp along the length of the board's face, from end to end.
• Crook: A warp along the edge of a board, from end to end.
• Twist: A warp where the four corners are not in the same plane.
• T/R Ratio: The ratio of Tangential to Radial shrinkage. A higher ratio indicates that a flatsawn board will be much less stable than a quartersawn board of the same species.

"You can't stop wood from moving. Period. The best woodworkers don't try to stop it; they build in ways that accommodate it. Frame and panel construction, breadboard ends on tabletops, elongated screw holes—these are all classic solutions to the age-old problem of wood movement. Understand the movement, and you'll understand the joinery." - Fine Woodworking Magazine Editor

Example: A Wide Red Oak Panel
You are building a 24-inch wide tabletop from flatsawn Red Oak. You build it in your shop at 12% MC, and it will live in a home at 7% MC.
MC Change: 5%.
Estimated Shrinkage (Flatsawn): `24" * (8.6/100) * (5/30) ≈ 0.344 inches`. The panel will shrink by over 1/3 of an inch. If it's rigidly attached, it will likely crack.

• Gluing a Solid Wood Panel to a Plywood Substrate: Plywood is stable and doesn't move, while solid wood does. Gluing them together will cause the solid wood to tear itself apart as it tries to shrink.
• Screwing Down a Tabletop Rigidly: Driving screws through the center of a wide tabletop into its base will prevent it from shrinking and swelling, leading to splits and cracks. Use special fasteners like Z-clips or figure-8 clips that allow for movement.
• Ignoring Grain Orientation: Making a large panel from flatsawn lumber and not alternating the growth rings can lead to a severely cupped panel.

• Furniture Design: Designing joints and structures that allow for seasonal wood movement.
• Material Selection: Choosing more stable, quartersawn lumber or species with a low T/R ratio for applications demanding stability.
• Failure Analysis: Understanding why an old piece of furniture may have cracked or warped over time.
• Educational Tool: Visually demonstrating the dramatic difference in movement between flatsawn and quartersawn lumber.