Significant figures (also known as significant digits and often abbreviated to “sig figs”, and occasionally “sign figs” or “sig digs”) represents a way of rounding a number so that we only use the digits of value or that contribute meaningfully to the numbers precision, in a scientific experiment, for example.

To work out the significant figures for a number we ignore:

• leading and trailing zeros (unless a decimal point is present) where they serve merely as placeholders to indicate the scale of the number.
• spurious digits introduced, for example, by calculations carried out to greater accuracy than that of the original data, or measurements reported to a greater precision than the equipment supports. You cannot add sig figs by converting from one type of unit (lbs) to kilograms (kg), in other words.

The concept of significant figures is often used in connection with rounding. Rounding to “n” significant figures is a more general-purpose technique than rounding to “n” decimal places, because it handles numbers of different scales in a uniform way. A practical calculation that uses any irrational number necessitates rounding the number, and hence the answer, to a finite number of significant figures.

The term “significant figures” can also refer to a crude form of error representation based around significant figure rounding.

Examples of sig figs calculations

• Num Sig
• Sig Figs Calculator
• Sign. Figs

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