01
Measurements and units
Calculators preserve the physical quantity being measured, convert through fixed unit relationships, and label every input and output. Intermediate precision is retained; display values are rounded only at the end.
02
Theoretical versus purchase quantity
The theoretical result comes directly from geometry and selected coverage. The purchase recommendation then accounts for user-selected waste where applicable and rounds to practical package sizes. Both values remain visible.
03
Coverage and assumptions
Defaults are planning aids, not hidden facts. Editable coverage rates should be replaced with current information for the exact product and surface. Each calculator lists what it includes and excludes.
04
Costs
Cost tools use quantity multiplied by a user-entered unit price, plus explicit optional costs. We avoid presenting unsourced universal prices. When sourced defaults are introduced, the source and date will accompany them.
05
Verification
Core formulas are deterministic and tested for ordinary values, decimals, zero and invalid inputs, metric and imperial conversions, and rounding boundaries. Results should still be checked against actual site measurements and product documentation.