How to use this calculator
Enter a finite number and choose decimal places or significant figures. Select the rounding direction where available, then compare the rounded result with the original value.
Decimal places versus significant figures
Decimal places count digits after the decimal point. Significant figures count meaningful digits starting at the first nonzero digit. The calculator supports 0–12 decimal places or 1–12 significant figures. These choices can give different results for very large or very small numbers.
Direction and precision
Upward rounding moves toward positive infinity and downward rounding toward negative infinity, so their behavior for negative numbers differs from rounding away from zero. Nearest rounding follows the implemented JavaScript rounding convention. Binary floating-point representation can affect values near a halfway boundary; do not treat this tool as an arbitrary-precision decimal ledger.
Example: rounding 12.345
Rounding 12.345 to two decimal places gives 12.35. Rounding it to three significant figures gives 12.3 because the first three significant digits are 1, 2 and 3.