Sig figs in a nutshell

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.