Choose the calculator for the job
Use the plywood and sheet calculator for broad surface coverage, the timber calculator for repeated pieces and stock volume, and the linear metre calculator when width and thickness do not affect the total. The mitre calculator handles equal flat angles, while the compound mitre calculator is only for sprung cornice or crown moulding cut flat on the saw table. The cut list optimiser places rectangular parts on sheet material. Shelf spacing and drawer-front spacing have separate calculators because they produce different workshop marks.
What happens when you change an input
- Required values must be numbers and stay inside the range shown by the input.
- Piece, shelf and drawer-front quantities must be whole numbers.
- Changing any value clears the previous result until you calculate again.
- The result repeats the material dimensions and allowances used.
- Inputs are calculated in your browser and are not sent to the site.
What each formula leaves out
The sheet calculator covers one rectangle with a simple rectangular grid; it does not nest individual parts. The timber and linear metre calculators check how many identical pieces fit after entered kerf and end trim, but they do not optimise a mixture of different lengths. The flat mitre calculator joins two equal flat pieces or plans a regular frame; it does not estimate bevels or three-dimensional joints. Shelf marks do not calculate load, sag or support spacing. Drawer-front results size equal inset fronts, not drawer boxes, overlays or runners. The cut list optimiser produces one workable rectangular sheet layout rather than claiming no tighter layout exists.
Rounding
Calculations keep their full precision until the result is displayed. Piece, stock and sheet quantities round upwards because a part of a purchasing unit cannot cover the remainder. Marking schedules accumulate positions from the unrounded value so a small display rounding does not grow down a bank of shelves or drawer fronts.
Safety and professional limits
The calculators do not size load-bearing members, choose blades, set machinery, approve a cutting sequence or decide whether a method is safe. Check the actual stock, the machine instructions, support and guarding before cutting. The sources page links to the HSE material used for this surrounding workshop context.
How the tools are checked
Before a calculator is published, its formula is worked independently for the example shown on the page. Empty, impossible and out-of-range entries are tested to make sure they return a clear message rather than an old or misleading number. The worked example, printed record and no-JavaScript version are also read through as a woodworker would use them. These checks are repeated whenever a formula changes, and the review date is shown on each calculator.