Rounding Calculator
Round numbers to decimal places
Rounding Calculator tool
(Use negative for tens, hundreds, etc.)
Result
—
Original
3.14159
Rounded to
2 decimal places
Direction
same
Step-by-step:
- 1.Number: 3.14159
- 2.Look at 3rd decimal: 1
- 3.1 < 5, so round down
- 4.Result: 0
Rounding Calculator: key facts
- What it does
- Round numbers to decimal places
- Category
- Math Calculators
- Cost
- Free, with no account, sign-up, or install.
- Your data
- Runs entirely in your browser — the files and text you enter are never uploaded to a server.
- Last reviewed
- . Report an incorrect result.
About the Rounding Calculator
Rounding seems simple until you need to round to a specific number of decimal places, or to the nearest ten, hundred, or thousand. This calculator rounds any number to the precision you choose and explains the decision — which digit it looked at and whether the value went up or down.
Students learning rounding rules use it to check their work; anyone presenting figures uses it to tidy decimals to a consistent precision. Support for negative decimal places means you can round to tens or hundreds, not just to decimal positions, covering both ends of the precision scale.
How to use it
- Enter the number you want to round.
- Enter the number of decimal places — use a negative value to round to tens, hundreds, and beyond.
- Read the rounded result.
- See which digit was examined and whether the value rounded up or down in the breakdown.
Shifting the decimal point and back
Rounding to a given number of decimal places is done by multiplying by a power of ten, rounding to the nearest integer, then dividing back. That shift-round-shift approach is how virtually every rounding implementation works, and it is why the number of places is expressed as a power rather than handled digit by digit.
The tool applies half-up rounding: a digit of exactly five rounds away from zero. That is the convention taught in schools and expected in most everyday contexts, though it is not the only one in use.
Alongside the rounded value, the tool shows the alternative treatments — rounding up, rounding down, and truncation — because they diverge for negative numbers in ways that catch people out. Rounding down and truncating are the same for positive values and opposite for negatives.
- The defaults — 3.14159 to 2 decimal places — give 3.14.
- The same number to 3 places gives 3.142, since the following digit is 5 and rounds up.
- −2.5 rounds to −3 under half-up away-from-zero, while truncation would give −2.
Why use this version
- It accepts negative decimal places, so you can round to the nearest ten, hundred, or thousand, not just decimal positions.
- It shows the digit it examined and the direction it rounded, making the rounding rule explicit.
- It reports the original and rounded values side by side so the change is clear.
- It computes instantly in your browser, free and without sign-up.
Banker's rounding, and accumulated bias
Always rounding a half upward introduces a small systematic bias, because halves consistently move in one direction. Across many values that bias accumulates, which is why financial and statistical systems frequently use round-half-to-even instead — known as banker's rounding. Under it 2.5 becomes 2 and 3.5 becomes 4, so halves split evenly between up and down and the bias cancels.
Rounding is also not safely repeatable. Taking 2.44 to one place gives 2.4, but rounding first to 2.5 and then to one place gives 3 — so intermediate rounding changes the answer. Keep full precision through a calculation and round only the final result.
One further subtlety specific to computers: binary floating point cannot represent many decimal fractions exactly, so a value stored as slightly under 2.675 will round to 2.67 rather than the 2.68 you might expect. It is not a bug in the rounding but a consequence of the representation, and it is why currency is usually handled in integer minor units rather than as decimals.
Frequently Asked Questions
What is the standard rounding rule?
Look at the digit just past your rounding position: if it is 5 or more, round up; if it is less than 5, round down. This calculator applies that rule and shows you the exact digit it checked.
How do I round to the nearest hundred?
Enter a negative number of decimal places — −2 rounds to the nearest hundred, −1 to the nearest ten, and −3 to the nearest thousand. The calculator supports these negative positions directly.
What does rounding to 2 decimal places mean?
It keeps two digits after the decimal point, rounding the rest away — so 3.14159 becomes 3.14. Entering 2 as the decimal places gives that result, with the breakdown showing why the third digit did not round it up.
What is the difference between rounding and truncating?
Rounding adjusts the last kept digit based on what follows it, so 3.78 rounded to one decimal becomes 3.8. Truncating simply chops off the extra digits, giving 3.7. This calculator rounds; it does not merely cut the number off.
