Counting Significant Figures

Identify the number of significant figures in each of the following measurements.

Rules for Zeroes


Rule

Examples

Zeros appearing between nonzero digits are significant


  • 40.7 L has three sig figs
  • 87 009 km has five sig figs

Zeros appearing in front of nonzero digits are not significant


  • 0.095 987 m has five sig figs
  • 0.0009 kg has one sig fig

Zeros at the end of a number and to the right of a decimal are significant


  • 85.00 g has four sig figs
  • 9.000 000 000 mm has 10 sig figs

Zeros at the end of a number but to the left of a decimal may or may not be significant. If such a zero has been measured, or is the first estimated digit, it is significant. On the other hand, if the zero has not been measured or estimated but is just a placeholder, it is not significant. A decimal placed after the zeros indicates that they are significant.


  • 2000 m may contain from one to four sig figs, depending on how many zeros are placeholders. For measurements given in this text, assume that 2000 has one sig fig.
  • 2000. m contains four sig figs, indicated by the presence of the decimal point

Scientific notation - All digits expressed before the exponential term are signicant.


  • 5.060 x 10-3 m has four sig figs.
  • 9.00 x 102 g has three sig figs.

 
  1. 2.37 x 10-2 m