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Significant Figures

How to count how many significant figures a value has:

  1. Counting from the left, the first non-zero digit is the first significant figure.
  2. All figures following the first significant figure are also significant unless

    1. Final zeros in a whole number are not significant.
    2. Final zeros after the decimal point are significant.

Examples

How many significant figures do the following numbers have?

45

300

3020

1004000

0.0045

0.0450

0.004500

300.500

1004.0

0.00040

0.0102030

1.00

Rounding Examples

Round the following numbers to the given number of (significant figures):

6489 (2 s.f.)

34.8 (2 s.f.)

7.081 (2 s.f.)

7.981 (2 s.f.)

6489 (3 s.f.)

21.601 (3 s.f.)

748531 (3 s.f.)

952.9 (3 s.f.)

0.04774 (3 s.f.)

2.00094 (3 s.f.)

72.6 (1 s.f.)

99.61 (1 s.f.)