Primary sources
- U.S. Department of Commerce / NIST — PS 20-25 American Softwood Lumber Standard. Used for common dry dressed softwood board and dimension-lumber sizes. NIST document.
- NIST Voluntary Product Standards Program. Used to confirm PS 20-25 as the current American Softwood Lumber Standard. NIST program page.
- USDA Forest Products Laboratory — Wood Handbook: Wood as an Engineering Material. Used as the scientific basis for wood density, moisture and dimensional-movement context. USDA FPL Wood Handbook.
What is a standard and what is an estimate?
WUDIM’s nominal-to-actual softwood size table is a reference derived from standardized dressed-size tables. Weight, panel mass and wood movement are estimates because natural and manufactured products vary. Calculator output is rounded to avoid suggesting precision the inputs cannot support.
Density assumptions
WUDIM stores a small set of representative planning densities rather than copying a large external database. They are intentionally rounded and are documented on the wood density reference. When the exact material matters, use a supplier’s product data or measured density.
Wood movement model
The movement tool uses published radial or tangential green-to-oven-dry shrinkage percentages as a species characteristic, then linearly scales movement with moisture change below a 30% planning fiber-saturation point. Real movement is not perfectly linear and individual boards vary, so the result is a sanity check rather than a design guarantee.
Cut-list model
The cut optimizer is original client-side code using a fast guillotine-style rectangle-packing heuristic. It includes kerf and optional rotation but does not model grain direction, defects, trim allowance, saw sequence or guarantee the mathematical optimum.
Editorial policy
We prefer primary standards and government technical references when they are available. Reference dates are reviewed when the underlying standard changes or a calculation method is updated. Corrections can be sent through the contact page.
Last methodology review: September 16, 2026.