Significant Figures Calculator

Significant figures:
Least significant decimal:
Always display scientific notation.


Enter the number that you wish to have formatted with significant figures and the calculator will display the formatted version in the box to the left.

Significant figures are used. Results are shown only with as many significant figures as the quantity that was entered. Scientific notation may be used for large results or if the number of significant digits would be ambiguous otherwise. The calculator follows proper rounding rules for scientific purposes.

A significant figure is any non-zero digit or any embedded or trailing zero. Leading zeros are not significant. The number may be rounded or padded with zeros to give it the correct number of significant figures. When multiplying values together, your result is only as significant as your least significant value.

The least significant decimal is the place that holds the last significant digit. For example, 243.3's least significant decimal is -1 (10^-1 for the 1/10ths place). When adding values together, your result is only as significant as your value with the least significant decimal in the highest place.

The calculator rounds number in the proper scientific way. It rounds up if the next digit is greater than five. Rounds down if the next digit is less than five. If the next digit is five it rounds up half the time and down half the time based on whether the previous digit is even or odd. This ensures that cumulative rounding errors do not skew the data.


This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

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Copyright Stephen Ostermiller 2001-2021