Significant Figures Calculator
Count significant figures.
Input
Result
What is a Significant Figures Calculator?
A Significant Figures Calculator counts the number of meaningful digits (sig figs) in a number and rounds results to the correct precision. It is essential for scientific measurements and calculations where accuracy matters.
How to count significant figures manually (the formula)
Apply the standard rules: (1) All non-zero digits are significant. (2) Zeros between non-zero digits are significant. (3) Leading zeros are not significant. (4) Trailing zeros after a decimal point are significant. (5) Trailing zeros in a whole number without a decimal are not significant.
Example calculation
Count the significant figures in 0.004050. The leading zeros (0.004) are not significant. The digits 4, 0, 5, and the trailing 0 after the decimal are significant. So 0.004050 has 4 significant figures.
Common mistakes
- Counting leading zeros — Leading zeros only indicate place value and are never significant.
- Ignoring trailing zeros after a decimal — These zeros indicate precision and are significant (e.g., 2.50 has three sig figs).
- Treating all zeros the same — The significance of a zero depends on its position and whether a decimal point is present.
Frequently asked questions
What are significant figures?
Significant figures (sig figs) are the meaningful digits in a number that contribute to its precision.
How do I count significant figures?
Count all non-zero digits, zeros between non-zero digits, and trailing zeros after a decimal point.
How many significant figures are in 100?
100 has 1 significant figure (unless written as 100. or 1.00 × 10²).
What are the rules for significant figures in calculations?
For multiplication/division, round to the least number of sig figs. For addition/subtraction, round to the least decimal places.
Why do significant figures matter?
They communicate the precision of a measurement without overstating accuracy.