Every estimate starts with a measurable assumption.
Our formulas are intentionally understandable. The goal is not false precision—it is a defensible order quantity you can verify.
Area and volume
Rectangular area equals length multiplied by width. Wall area uses the room perimeter multiplied by height, minus entered openings. Volume adds a finished depth and converts units before rounding.
Waste allowance
Waste is applied after the base quantity. It represents cuts, pattern alignment, breakage, settling, and imperfect site conditions. Defaults are starting points, not product requirements.
Purchasable quantities
A store cannot sell a fraction of a carton, roll, board, can, or bag. Package counts are therefore rounded up only after waste has been included. Cost uses that rounded purchase quantity.
Review process
Formulas are covered by automated tests for representative imperial and metric projects. We review copy and defaults when tools or product conventions change.
Last reviewed: July 21, 2026