Number

Significant figure

A digit that contributes to the precision of a number. Leading zeros do not count.

Definition

In 0.00342, the first significant figure is 3. The second is 4. The third is 2. In 1500, all four digits are significant unless the trailing zeros are placeholders. Rounding to 1 s.f. means keeping only the first non-zero digit.

Example

1234 to 2 s.f. is 1200. 0.0567 to 2 s.f. is 0.057.

Related terms

Decimal place

The position after the decimal point. "To 2 d.p." means two digits after the decimal point.

Estimate

Round every value to 1 significant figure, then calculate. Do not use the exact values.

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