Rounding Calculator
Enter a number and choose the place to round to. The calculator rounds half up, the method taught in school, and also shows the value rounded down and up.
Result
- Rounded down (floor)
- 3.14
- Rounded up (ceiling)
- 3.15
- Original number
- 3.14159
Halves are rounded away from zero, so 2.5 becomes 3 and −2.5 becomes −3.
Formula
- Look at the digit to the right of the place you are rounding to
- If it is 5 or more, round up. If it is 4 or less, round down
- Digits to the right are dropped, or replaced by zeros left of the decimal point
How the Rounding Calculator works
Rounding replaces a number with a nearby one that has fewer digits. Find the digit in the place you are keeping, then look one digit to its right. Five or more raises the kept digit by one, and anything less leaves it alone.
This calculator works on the decimal digits directly. That avoids the errors of binary floating point, where a value such as 1.005 is stored as slightly less than 1.005 and would round the wrong way.
Worked example
Rounding 3.14159 to the nearest hundredth: the hundredths digit is 4 and the next digit is 1, which is below 5, so the result is 3.14. To the nearest thousandth the next digit is 5, so 3.141 rounds up to 3.142.
Frequently asked questions
How do I round to the nearest tenth?
Keep one digit after the decimal point and look at the second. 4.36 rounds to 4.4 because 6 is 5 or more. 4.34 rounds to 4.3.
What does 0.5 round to?
With the standard round half up rule it becomes 1. Some fields use round half to even, known as banker's rounding, where 0.5 becomes 0 and 1.5 becomes 2.
How do I round to the nearest hundred?
Look at the tens digit. 1,250 rounds to 1,300 and 1,249 rounds to 1,200.
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