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Significant figures

The significant figures are the digits of a given number, ignoring the leading zeros (the zeros on the left). Significant figure can be abbreviated as s.f. or sig fig.

$$0.0\Tred{1}\Tblue{230}$$ has four significant figures: 1, 2, 3 and 0. The first s.f. is $$\Tred{1}$$.

Numbers can be truncated or rounded to fewer significant figures so that they are easier to use in calculations. The significant figures that are no longer wanted are replaced by 0.

$$\Tblue{18}6$$ truncated to two significant figures is $$\Tblue{18}0$$.

$$\Tblue{18}6$$ rounded to two significant figures is $$\Tblue{19}0$$.

Here is a summary of the truncation and rounding of $$19.283$$

S.F. 1 2 3 4 5 6
Truncation $$\Tblue{1}0$$ $$\Tblue{19}$$ $$\Tblue{19.2}$$ $$\Tblue{19.28}$$ $$\Tblue{19.283}$$ $$\Tblue{19.283}$$
Rounding $$\Tblue{2}0$$ $$\Tblue{19}$$ $$\Tblue{19.3}$$ $$\Tblue{19.28}$$ $$\Tblue{19.283}$$ $$\Tblue{19.283}$$