Significant Figures

There are some Concise rules for Significant Figures:

• All non-zero digits are considered significant

• Zeros between non-zero digits are significant

• Leadig zeros are never significant

• In a number with a decumal point, trailing zeros, those to the right of the last non-zero digit, are significant.

• In a number without a decimal point, trailing zeros may or may not be significant. More information through additional graphical symbols or explicit information on errors is needed to clarify the significance of trailing zeros.

To round to n significant figures:

• If the first non-significant figure is a 5 followed by other non-zero digits, round up the last significant figure (away from zero). For example, 1.2459 as the result of a calculation or measurement that only allows for 3 significant figures should be written 1.25.

• If the first non-significant figure is a 5 not followed by any other digits or followed only by zeros, rounding requires a tie-breaking rule. For example, to round 1.25 to 2 significangt figures:

• Round half up rounds up to 1.3. This is the default rounding method implied in many disciplines if not specified

• Round half to even, which rounds to the nearest even numebr, rounds down to 1.2 in this case. The same strategy applied to 1.35 would instead round up to 1.4.

• Replace non-significant figures in front of the decimal by zeros.

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