Significant Figures Calculator
Count significant figures and round a number to a chosen number of them.
The meaningful digits
Significant figures are the digits in a number that carry real meaning about its precision. This counts the significant figures in a number and rounds to a chosen number of them, which matters throughout science for reporting measurements honestly.
Enter a number to count or round its significant figures.
Why significant figures matter in science
Significant figures exist to communicate how precise a measurement is. If you measure something as 4.5 units, writing the answer to a calculation as 4.53891 falsely implies a precision you never had — the extra digits are meaningless. The rule is that a result should not be reported to more significant figures than the least precise measurement it came from, since a calculation cannot create precision that was not in the inputs. The rules for which digits count — leading zeros do not, trailing zeros are tricky — trip people up, which is exactly where counting them mechanically helps. Reporting the right number of significant figures is a mark of honest, careful science, neither overstating nor throwing away real precision.
Frequently asked questions
Why can't I keep all the digits from a calculation?
Because a calculation cannot create precision the measurements did not have — reporting extra digits falsely implies accuracy you never measured.
Which digits are significant?
Non-zero digits always count, leading zeros never do, and trailing zeros are context-dependent — which is why counting them mechanically helps.
Is anything uploaded?
No. The calculation happens in your browser.