How Do Significant Figures Work?
We count the number of significant figures in a number by looking at whether or not your number contains leading zeros.
Rule
Significant Figures
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When the number begins with a , count the number of digits from the first non-zero digit.
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When the number doesn’t begin with a , count all the number’s digits.
Example 1
Significant figures:
| 1 | has 1 significant figure |
| 10 | has 1 or 2 significant figures |
| 100 | has 1, 2 or 3 significant figures |
| has 2 significant figures | |
| has 3 significant figures | |
| has 4 significant figures | |
| 1 | has 1 significant figure |
| 10 | has 2 significant figures |
| 100 | has 3 significant figures |
Some numbers can be ambiguous in terms of how many significant figures they have. You then need to consider the context. For instance, the number 100, can have one, two, or three significant figures, depending on how it is described. If it is rounded to the nearest hundred, it has one significant figure. If it is precise to the ones place, then it has three significant figures.
Example 2
You have L of juice you pour equally into three bottles. How much juice is in each bottle?
To find the answer, you need to divide by . You get
Even though the result has more digits, you round it so that the answer has the precision of the original numbers. In this case, two significant figures.
