The calculation
UniRuler converts the input into metres, then divides by the output reference’s length in metres.
Result = input quantity × input length in metres ÷ output length in metres
For combined inputs, it adds their lengths in metres before converting the total. Separate comparisons repeat the calculation for each input. Empty rows are unfinished; zero is a valid value. An invalid amount is explained before a total is shown.
For example, 5 inches × 0.0254 ÷ 0.3048 gives 0.416666… feet. The displayed 0.416667 is rounded. The inch-to-foot relationship itself is exact.
Exact units and defined objects
International feet, inches, yards and miles use their exact metre relationships. Metric units use decimal factors. The library links to the standards sources used for those definitions.
Objects need more context: an ID-1 card’s long edge, a particular aircraft model’s full wingspan, or a named fruit cultivar’s sample diameter. Nominal manufacturing sizes, rounded published measurements and natural variation remain qualified.
Ranges are not averages
A sample mean is labeled with its sample size and sampling date when known. A midpoint of a published range is labeled as a chosen midpoint. Neither becomes a universal average. A source range is not automatically an uncertainty interval or a confidence interval.
If a source’s units conflict or its dimension is unclear, the record is held out of the catalogue until that issue is resolved. We do not fill a missing measurement with a guess.
Precision and display
Calculations use decimal arithmetic. Exact-unit results display up to six significant digits; results involving object references use up to three. The approximation mark can therefore indicate an approximate reference, a rounded display, or both.
Extra decimal places do not make an object measurement more accurate. Calculations describe length, not area, mass, packing, physical fit or a calibrated on-screen ruler.
Older comparisons keep their definitions
Shared links contain the quantities, references and catalogue version. Supported earlier catalogues remain bundled and can be reopened. Editing an archived comparison continues to use that version; changing to the current catalogue is an explicit action.
Every catalogue edition has permanent reference pages, including the current edition. A damaged or unsupported link is explained rather than silently reinterpreted. A correction creates a new catalogue; it does not rewrite a preserved snapshot.