1. Start with geometry
Area and volume tools begin with transparent geometry: length × width, perimeter × height or length × width × depth. Dimensions are converted to compatible units before calculation.
2. Keep variable assumptions editable
Product coverage, bulk density, waste, pack size and stock length can vary by manufacturer, supplier and project. Where those values matter, the user can change them.
3. Round only when purchasing requires it
Geometric results can be decimal values. Bags, packs, boards and tiles are rounded up only at the purchasing stage.
4. Separate quantity from compliance
The toolkit deliberately avoids presenting material quantity calculations as structural design or regulatory approval. Where a decision depends on drawings, manufacturer instructions or professional design, the page says so.
5. Review and test
Calculator logic is tested against simple hand-checkable examples, including zero values and common unit conversions. Pages are reviewed when formulas, inputs or guidance change.
6. Sources and product data
For variable product values, we encourage users to enter the current value from the actual manufacturer or supplier instead of relying on a stale national average.