Significant Figures Calculator
Enter a number to count its significant figures, and optionally round it to a chosen number of sig figs. The result keeps trailing zeros so the precision is unambiguous.
How to count and round significant figures
- Enter the number you want to analyze.
- Read how many significant figures it has.
- Optionally set how many sig figs to round to and copy the result.
Examples
Round to significant figures
12345 rounded to 3 sig figs
12300
Round a small decimal
0.0789 rounded to 2 sig figs
0.079
Frequently asked questions
What counts as a significant figure?
All non-zero digits are significant, zeros between them are significant, and trailing zeros after a decimal point are significant. Leading zeros, such as those in 0.0045, are never significant.
Why does the count sometimes look low for trailing zeros?
This tool reads a numeric input, and a value like 0.004560 is stored as 0.00456, so the final zero is lost and it counts as 3 significant figures. Trailing zeros on a whole number, like 1500, are genuinely ambiguous and are treated as not significant here.
How does rounding to significant figures work?
The calculator finds the place of the leading digit, then rounds so that exactly the requested number of significant digits remain, for example 12345 to 3 sig figs becomes 12300.
Why does the rounded result keep extra zeros?
The rounded string preserves trailing zeros so the precision is clear. Rounding 1 to 3 sig figs is shown as 1.00, which signals three significant figures.
How many significant figures does zero have?
Zero is a special case. This calculator reports it as having 1 significant figure by convention.
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