Rounding Calculator
Enter a number to round it to a chosen number of decimal places and significant figures.
How rounding to decimals vs. significant figures differs
Rounding to a number of decimal places keeps a fixed number of digits after the decimal point, regardless of the number's size — rounding 3.14159 to 2 decimal places gives 3.14.
Rounding to significant figures instead keeps a fixed number of meaningful digits starting from the first non-zero digit, regardless of where the decimal point falls — this matters more in science and engineering, where it reflects the precision of a measurement rather than an arbitrary decimal cutoff.
Frequently asked questions
What's the difference between decimal places and significant figures?
Decimal places count digits after the decimal point only; significant figures count all meaningful digits in a number, starting from the first non-zero digit, whether before or after the decimal point.
How does standard rounding handle a 5?
This calculator uses standard "round half up" rounding — a digit of exactly 5 rounds the preceding digit up, so 2.5 rounds to 3 at zero decimal places.
Why would I use significant figures instead of decimal places?
Significant figures better represent the precision of a measurement — a value of 1,230,000 with 3 significant figures (rounds to 1,230,000 but implies precision only to the nearest 10,000) communicates something different than specifying a fixed number of decimal places would for a number that large.