Timber Finished Size Calculator: Rough to Finished Dimensions
Estimate finished timber dimensions by subtracting explicit machining and trimming allowances from rough stock. Use separate allowances for thickness, width and length so the finishing assumptions remain visible.
Rough and finishing dimensions
Finished timber dimensions
How rough-to-finished timber conversion works
The model is intentionally simple: each finished dimension equals the rough dimension minus the user-specified removal allowance.
Finished width = rough width − width allowance
Finished length = rough length − trimming allowance
Why the allowances are separate
Thickness and width may be changed by planing or surfacing, while length may require end trimming. Treating them separately makes the calculation more useful for workshop planning.
Worked example
A 50 × 150 × 3,000 mm rough piece with 3 mm thickness removal, 4 mm width removal and 20 mm end trimming produces an estimated 47 × 146 × 2,980 mm finished size.
Important manufacturing limitation
Real timber processing may involve moisture changes, warping, defects, grading requirements, minimum machining stock and tolerances. Use supplier and machine-specific process information when the final dimension matters.
Frequently Asked Questions
Can allowances be zero?
Yes.
Can finished dimensions be negative?
No; the calculator blocks any allowance that consumes the entire rough dimension.
Does this model moisture shrinkage?
No.
Can I calculate multiple pieces?
Yes. Total finished volume is also shown.