Rounding and Significant Digits in Measurement Results: How to Report Values Without Losing Meaning

Rounding is often treated as a final formatting step, but it can affect the meaning of a measurement result and even change a conformity decision. Too many digits suggest a level of knowledge that the measurement does not provide. Too few digits can hide useful information or create avoidable numerical error. This working paper explains how measurement results and uncertainties should be rounded, why calculations should retain additional digits, and how significant digits differ from decimal places and instrument resolution. It also discusses values close to specification limits, repeated calculations, unit conversion, software behaviour, and examples from medical metrology. The main conclusion is that rounding should be planned as part of the measurement and reporting process, not applied casually at the end.