How we calculate
Every calculator on this site uses documented coverage rates, manufacturer specifications, and industry-standard waste allowances — not a live pricing feed.
Coverage and quantities
Material quantities (tiles, boxes, bags, gallons) are derived from your room dimensions and a coverage rate — how much area or volume one purchase unit typically covers. Coverage rates come from common manufacturer packaging specs for each material (for example, a standard box of 12x12 inch tile covering roughly 15 sq ft). Where a calculator lets you pick a size or preset, the coverage figure updates to match.
Waste allowances
Every quantity includes a waste margin to cover cuts, breakage, and mistakes, because buying exactly the measured amount almost always leaves a project short. For flooring and tile, waste guidance follows general industry norms of roughly 5-15% for straight layouts, rising to 15-20% for diagonal or herringbone patterns. For concrete, mix and placement guidance draws on ACI 318 (Building Code Requirements for Structural Concrete) and typical contractor practice. You can always override the default waste percentage in the calculator itself.
Cost estimates
Cost ranges shown on each calculator are static, periodically reviewed typical-US price bands — a low, expected, and high price per purchase unit — not live retail or regional pricing. Actual prices vary by region, retailer, brand, and time of purchase. Every calculator lets you enter your own price per unit, which overrides the default band with your real number.
Review and updates
Calculators are periodically reviewed for accuracy as coverage specs, pricing bands, and industry guidance change. Where available, each tool page shows who reviewed it and when it was last updated, along with the specific sources behind its numbers.