A.1.1—Significant figures

Significant figures communicate the precision supported by a measurement or calculation. Zeros between non-zero digits count; leading zeros only locate the decimal point.

Keep guard digits during working, then round the final result to match the least precise relevant measurement. State a value such as 2.40 to show its precision.

A mean based on readings recorded to 0.1 s should not be reported as 2.437891 s; 2.4 s or 2.44 s may be appropriate depending on the data.

More digits do not make a result more accurate, and exact counted quantities are not limited by instrument precision.