Significant Figures Calculator
Count the significant figures in any number and round it to a chosen number of sig figs. Shows the result in standard and scientific notation, with the rules explained.
Significant figures in your number
5
Rounded to 3 sig figs
0.0245
Scientific notation
2.45e-2
Counting honors trailing zeros after a decimal point. Trailing zeros in a whole number (like 1200) are treated as ambiguous and not counted โ write it in scientific notation to make them significant.
Frequently Asked Questions
How do I count significant figures?
Count from the first non-zero digit to the last reported digit. All non-zero digits count, zeros between non-zero digits count, and trailing zeros count only when there is a decimal point. Leading zeros never count โ they only mark the decimal place.
Do trailing zeros count as significant?
Trailing zeros count when the number has a decimal point (1.200 has four sig figs) but are ambiguous without one (1200 may have two, three, or four). Writing the number in scientific notation removes the ambiguity.
How do I round to a number of significant figures?
Keep that many significant digits starting from the first non-zero digit, then round the last kept digit based on the next digit. For example, 0.024519 rounded to 3 sig figs is 0.0245, and 31870 to 2 sig figs is 32000.
Are leading zeros significant?
No. Leading zeros in numbers like 0.0042 are not significant; they only position the decimal point. The number 0.0042 has two significant figures (the 4 and the 2).
What are significant figures used for?
They communicate the precision of a measurement. The result of a calculation should not be reported with more significant figures than the least precise input, so sig-fig rules keep answers from implying false accuracy.