Rounding Calculator
Round any number to decimal places, or to the nearest 5, 10 or 100.
Good to know. Banks sometimes round 2.5 down to 2 (banker’s rounding), so errors don’t pile up. Pick your side.
How it works
In plain words
Look at the digit just after the place you’re rounding to. 5 or more rounds up; less than 5 rounds down. Other methods treat exact halves differently, or always go in one direction.
The formula
result = round(x ÷ step) × step standard: 2.5 → 3, −2.5 → −3 banker’s: 2.5 → 2, 3.5 → 4
Worked example
3.14159 to 2 decimal places: the next digit is 1, which is less than 5, so it rounds down to 3.14.
Sources
No outside data or rates: this is plain arithmetic.
10 automated tests check its answers on every change.
About the rounding calculator
Rounding makes numbers easier to read and use. Prices are rounded to cents, measurements to the nearest millimetre, and statistics to one or two decimal places.
The standard rule is the one taught in school: look at the next digit. If it is 5 or more, round up; otherwise round down. So 3.14159 rounded to two decimal places is 3.14, and 2.675 is 2.68. Halfway values round away from zero, so −2.5 becomes −3.
Banker’s rounding, also called round-half-to-even, treats exact halves differently: they go to the nearest even number, so 2.5 becomes 2 and 3.5 becomes 4. Over many values this avoids a slight upward bias, which is why it is used in accounting, statistics and many programming languages.
Always up (ceiling) and always down (floor) ignore the next digit entirely. Use "up" when you can’t have a fraction left over: you need 3.2 tins of paint, so you buy 4. Use "down" for things like counting complete units.
Rounding to the nearest 5, 10, 100 or 0.05 works the same way. Rounding to the nearest 0.05 is used for cash in countries without 1- and 2-cent coins.
This calculator avoids a common computer glitch: many calculators and spreadsheets round 1.005 down to 1.00 because of how decimals are stored in binary. Here it correctly becomes 1.01.
Questions people ask
How do I round to 2 decimal places?
Look at the third decimal digit. If it is 5 or more, add one to the second digit; otherwise leave it. 3.14159 becomes 3.14, and 2.675 becomes 2.68.
What is banker’s rounding?
A method where exact halves round to the nearest even number: 2.5 → 2, 3.5 → 4. It reduces bias when rounding many values.
Does 0.5 round up or down?
With standard rounding, up (away from zero). With banker’s rounding, to the nearest even number, so 0.5 becomes 0.