Methodology
Every calculator shows its formula on the page. Here's the shared approach behind the numbers.
Area & volume
Areas are computed from the shape you select (rectangle, circle, or triangle). Volumes multiply area by depth. All dimensions are converted to a common unit before calculating, then results are converted to cubic feet, cubic yards, and cubic meters.
Waste factor
Real projects waste material. We apply a waste factor you control: roughly 5% for simple jobs, 10% for normal DIY, 15% for irregular layouts, and 20% for complex projects. The waste-adjusted total is what you should actually order.
Bags, tons & coverage
Where relevant we convert volume into bags (using standard bag yields) or weight in tons (using typical material densities). These vary by supplier, so treat them as close estimates and confirm with your product's label.
Rounding
Quantities you buy in whole units (bags, boards, sheets, pavers) are rounded up — you can't buy half a bag. Continuous quantities are rounded to a sensible precision for readability.
Reference values used across the site are collected in our charts & resources.