How We Verify Our Calculators
A woodworking calculator is only useful if the numbers behind it are right. A wrong movement coefficient, a misread span table or an out-of-date hinge spec means wasted timber or a shelf that sags. This page explains where our figures come from and how we check them.
The process
- ✓Figures are checked against published sources: British and European timber standards (BS EN 338 strength classes, BS 8417 preservative treatment, Eurocode 5 fastener rules), the TDCA Code of Practice for decking, the USDA Wood Handbook for wood movement and mechanical properties, and current manufacturer specifications from the likes of Blum, Kreg, Titebond and West System.
- ✓Structural results such as shelf span and sag use standard beam-deflection theory, with material stiffness values taken from published timber data rather than rules of thumb.
- ✓Every calculator is tested against hand-worked examples: we derive the expected answer from the source by hand, then check the calculator produces it. These checks run as automated tests across desktop and mobile browsers before every release.
- ✓Calculators are adversarially re-checked: an independent pass re-derives each result from the underlying source and compares it back to the code. When the check and the code disagree, we fix the code.
- ✓Errors reported through the feedback buttons are investigated against the original source, fixed, and re-verified before the correction goes live. When a report shows a genuine error, the fix lands on the affected page itself, with a dated correction note where it matters.
- ✓When a standard is revised or a manufacturer updates a data sheet, we review the affected calculators and update the figures. Each calculator carries a last-updated date.
Verified, not guaranteed
These calculators give estimates to plan a project from, not professional advice. Timber varies by species, grade and moisture content, so confirm quantities and sizes with your timber merchant before ordering. For structural work such as decks, load-bearing frames and anything fixed to a building, have the design confirmed by a structural engineer or a suitably qualified builder.
Spotted an error?
Every calculator page has feedback buttons. If a figure looks wrong, tell us what you entered and what you expected: we investigate against the original source, fix anything that fails the check, and re-verify before the correction goes live.