Counting Significant Figures (Sig Figs)

Vocabulary flashcards covering how to count and round significant figures, including rules for decimal presence, Pacific/Atlantic sides, and common examples.

Significant figures (sig figs)

The digits in a number that carry meaning about its precision; include all nonzero digits, zeros between nonzero digits, and trailing zeros if a decimal point is present.

Leading zeros

Zeros that precede the first nonzero digit; not significant.

Zeros between nonzero digits

Zeros between nonzero digits are significant.

Trailing zeros without decimal point

Zeros at the end of a number with no decimal point are not significant.

Trailing zeros with decimal point

Zeros at the end of a decimal number are significant.

Pacific side rule (decimal present)

When a decimal point is present, count sig figs starting from the left (Pacific side).

Atlantic side rule (no decimal point)

When there is no decimal point, count sig figs starting from the right (Atlantic side).

Example: 100.0

Has 4 sig figs because the decimal point makes the trailing zero significant.

Example: 123000

Has 3 sig figs since there is no decimal point and trailing zeros are not significant.

Rounding to N sig figs

Keep the first N significant digits and round the (N+1)th digit, then drop the remaining digits.

Scientific notation and sig figs

The number of sig figs is determined by the significand; multiplying by powers of ten does not change the sig fig count.

Showing significance after rounding

If rounding creates trailing zeros, adding a decimal point can show those zeros are significant (e.g., 50. vs 50).

Counting method: skip leading zeros

When counting sig figs, ignore leading zeros; they do not count toward precision.