Count the significant figures in any measurement and round it to a chosen number of sig figs, with the exact rule that was applied explained.. Significant Figures Calculator is a free online tool from the ToolsRift Study & Education Tools collection. It runs entirely in your browser — nothing to install, no signup, and your data never leaves your device.
Type a measurement such as 0.004520 or 1.230e4 and the significant figure count appears with a digit-by-digit explanation. Set a target number of sig figs to see the correctly rounded value.
All non-zero digits count, zeros between non-zero digits count, leading zeros never count, and trailing zeros count only when there is a decimal point. That is why 0.00450 has three significant figures while 4500 has an ambiguous two, three or four.
Write it in scientific notation as 4.500 × 10³, or add a decimal point as 4500. — both make the trailing zeros unambiguous. The tool flags ambiguous trailing zeros rather than silently guessing what you meant.
Keep the required number of significant digits and look at the next one: round up at five or above, down below five. The tool shows the rounded value in both plain and scientific notation so trailing-zero significance is never lost.