Nonzero digits are always significant.
Zeros on the other hand will depend on the placement.
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If the zeros are between nonzero values, then those zeros are significant.
Examples
- 207 has 3 sig figs.
- 2007 has 4 sig figs.
- 12300.450067 has 11 sig figs
- 1023040 has 6 sig figs (the zero at the end doesn't count).
"sig fig" is shorthand for "significant figures".
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If the zeros are after nonzero values, and the zeros are to the right of a decimal point, then those zeros are significant. The leading zeros, if present, are not considered significant.
Examples
- 1.2300 has 5 sig figs
- 0.123400 has 6 sig figs
- 0.1234000 has 7 sig figs
- 0.000000012340 has 5 sig figs
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If the zeros are between a nonzero value and the decimal point, then the zeros are significant. Zeros after the decimal point are also considered significant as well
Examples
- 1234500. has 7 sig figs
- 123450.00 has 8 sig figs
The decimal point may be tricky to see in the first example.
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Here are some examples where the zeros aren't significant
- 800 has 1 sig fig
- 0.0000000000123 has 3 sig figs
If ever in doubt, then search out "sig fig calculator" and there are a ton of options to choose from. Some of those calculators may also explain each of the rules mentioned above.