Too many digits can distract from a useful difference and imply more certainty than the information supports. Too few can hide the change the reader is trying to understand.
Choose a display rule that fits the quantity and the purpose. Keep the underlying values available where exact detail matters, and explain any formatting that turns a value into a range or an abbreviated label.
Check totals and small values after rounding. Displayed parts may not add exactly to a displayed total, and a small positive value may appear as zero. A brief note can resolve that confusion without filling the page with unnecessary decimals.
Picture this situation.
Consider showing an estimated duration to the nearest useful minute. Extra decimal places may suggest precision the underlying observation cannot support.
A second way to look.
Keep the question beside the number. A measure is easier to interpret when the reader knows which decision or comparison it was intended to support.
- Match precision to the reader’s task.
- Keep exact values available when needed.
- Check the effect on totals and small values.
Follow a related question
Assess the content rather than the fluent style.
Prediction and the appearance of understandingDistinguish an amount from a rate.
Energy and power answer different questionsKeep learning
Related background to continue exploring this subject.
NIST: statistical engineering W3C: accessibility, usability, and inclusion