Methodology
Calculation Methodology
How exact calculations, estimates, ranges and models are distinguished, and how assumptions, units, rounding and displayed precision are handled.
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Calculation classes
- Exact: deterministic arithmetic where the defined inputs determine one mathematical result.
- Estimate: a deterministic calculation that depends on explicit planning assumptions such as waste, density, coverage or package size.
- Range: an output represented by lower and upper bounds rather than a single false-precision value.
- Model or data-based result: an output whose meaning depends on a named model, dataset or external factual source.
Inputs and assumptions
Material assumptions that change the result should be explicit inputs or clearly disclosed named conventions. A calculator should not silently introduce a default density, waste rate, product coverage or packaging size when those values can materially vary.
Units and conversions
Dimensional conversions should preserve the meaning of the quantity being converted. Unit labels are part of the calculation contract, not presentation-only decoration.
Rounding
Internal arithmetic should preserve enough precision for the method. Display rounding is applied to communicate a useful result; discrete purchase quantities such as whole bags, tiles or packages use explicit whole-unit rules rather than ordinary decimal display rounding.
Displayed precision
Results are calculated at full precision and only shortened for display. A value that is not zero is never displayed as zero: very small results are shown with enough decimal places to keep three significant digits, and results too large or too small to print exactly are shown in scientific notation. When a displayed value has been shortened, the result says so.