Significant Figures Calculator – Sig Fig Calculator

Calculate the significant figures in a number or round a number using the sig fig calculator below.

Results:

Count of Significant Figures:

 

The Significant Figures Are:

 


What are Significant Figures?

Significant figures of a number, also referred to as its significant digits, are the digits in a number that are meaningful in expressing a number’s precision. In other words, these are the digits that provide meaning to the overall number.

Significant figures are the important digits that tell us something about the accuracy number and are often used to simplify or round a number without losing precision.

Significant figures do not quantify the size of a number but rather the level of precision, which is useful in converting from decimal to scientific notation.

How to Find How Many Significant Figures

You might be curious how to find the significant figures in a number or find how many of them there are. Since not all digits in a number are significant, there are a series of rules to follow to find significant digits in a number.

Significant Figures Rules

These are the rules for finding significant figures:[1]

  • All non-zero numbers ARE significant. There are three digits in the number 3.14 that are significant because each digit is non-zero.
  • Zeros between non-zero digits ARE significant. The zero in the number 4.605 is significant because it’s between two non-zero numbers.
  • Leading zeros are NOT significant. Any zero to the left of non-zero digits are not significant. The zero in the number 0.47 is not significant.
  • Trailing zeros in a number with a decimal point ARE significant, but trailing zeros in a number without a decimal point are NOT significant. The zero in the number 470 is not significant, but the zero in 47.0 is significant.
illustration showing how to find significant figures in the number 0.03750

When a number has a decimal point but no trailing digits, the decimal point indicates that there is at least one zero following it. For instance, the number 75. is treated as 75.0 and has three significant digits.

You can use an overline to indicate the last significant figure in a number. However, some people choose to use an underline in place of an overline.

Examples

Table showing the significant figures for various numbers
Count of Significant Figures Significant Figures
23 2 2, 3
7.5 2 7, 5
0.00025 2 2, 5
10.7 3 1, 0, 7
-12.208 5 1, 2, 2, 0, 8
63500 3 6, 3, 5
63500. 5 6, 3, 5, 0, 0
63500.0 6 6, 3, 5, 0, 0, 0

How to Round Significant Figures

It is common to round a number to a significant figure, and the process is similar to decimal round. Follow these steps to round a number using the sig fig rules above.

Step One: Find Significant Figures

The first step to round a number to a sig fig is to find the significant digits in a number. Follow the rules above to find the figures that are significant, then move to the next step.

Step Two: Use Rounding Rules

Once you’ve found the significant figures, use standard rounding rules to round the number to the specified precision. The difference between sig fig rounding and standard decimal rounding is that the rounding point is the significant digit indicated by the precision rather than the decimal place.

Putting it all Together

Let’s follow the steps above to round 03570 to two significant figures.

The number 03540 has four significant digits: [3, 5, 7, 0]

Round the number to the position of the second sig fig, which is 5:

03570 -> 3600

Sig Fig Rounding Examples

Table showing a number rounded to various significant figures
Precision Rounded to Significant Figures
375.09 0
375.09 1 400
375.09 2 380
375.09 3 375
375.09 4 375.1
375.09 5 375.09
375.09 6 375.090
375.09 10 375.0900000

References

  1. Columbia Center for Teaching and Learning, Significant Figures, https://ccnmtl.columbia.edu/projects/mmt/frontiers/web/chapter_5/6665.html