Rounding Calculator
Round any number to decimal places, whole numbers, tens, hundreds or thousands. Free rounding calculator showing round half up, round down and round up results.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the rule used
How the Rounding Calculator Works
This calculator rounds any number to the precision you choose — a set number of decimal places, the nearest whole number, or the nearest ten, hundred or thousand. It shows three results at once: the standard round-half-up value, the floor (rounded down) and the ceiling (rounded up), so you can see exactly how the number behaves.
The Method
Rounding to a place value uses a simple scale-and-round approach:
rounded = round(value × 10^place) ÷ 10^place
Here place is the number of decimal places (use negative values for tens, hundreds and thousands). The classic by-hand rule is: look at the first digit you are about to drop. If it is 5 or more, round up; if it is 4 or less, round down.
Worked Example
Round 3.14159 to 2 decimal places:
- The digit after the second decimal is the third decimal, 1.
- Since 1 is less than 5, you round down and keep 3.14.
- Result: 3.14
Now round 1,247 to the nearest hundred:
- The tens digit is 4, which is below 5.
- So you round down: 1,200.
Rounding Rules at a Glance
| Number | Nearest whole | 1 decimal | Nearest ten |
|---|---|---|---|
| 3.14159 | 3 | 3.1 | 0 |
| 47.5 | 48 | 47.5 | 50 |
| 152.49 | 152 | 152.5 | 150 |
| 999.6 | 1,000 | 999.6 | 1,000 |
When Rounding Matters
Rounding keeps numbers readable and avoids false precision. Use it for money (two decimal places), measurements (matching your instrument’s precision), statistics (reporting to a sensible number of significant figures), and estimates where the nearest ten or hundred is close enough. Always round at the very end of a calculation, not partway through, to avoid compounding small errors.
Frequently asked questions
How do you round a number to a decimal place?+
Look at the digit immediately to the right of the place you are rounding to. If it is 5 or more, round the place value up by one; if it is 4 or less, leave it unchanged and drop the remaining digits. For example, 3.14159 rounded to two decimals is 3.14 because the third decimal (1) is below 5.
What does rounding half up mean?+
Round half up is the most common rule: when the digit being dropped is exactly 5, you round the kept digit up. So 2.5 rounds to 3 and 7.45 rounds to 7.5. This calculator uses round half up, which matches how most schools and everyday math teach rounding.
How do I round to the nearest ten or hundred?+
Choose 'Nearest ten' or 'Nearest hundred' in the calculator. To do it by hand, look at the digit one place to the right: 1,234 to the nearest hundred checks the tens digit (3), which is below 5, so it stays 1,200. To the nearest ten it checks the ones digit (4) and rounds to 1,230.
What is the difference between rounding, flooring and ceiling?+
Rounding sends a number to the nearest target value. Floor always rounds down toward negative infinity, and ceiling always rounds up toward positive infinity. For 3.2, round and floor both give 3, while ceiling gives 4; for 3.8, round and ceiling give 4 while floor gives 3.
Why does my calculator round 2.675 to 2.67 instead of 2.68?+
Because 2.675 cannot be stored exactly in binary floating point — it is actually slightly less than 2.675 in the computer, so it rounds down. This is a known limitation of floating-point math, not a rounding error in the rule itself, and it affects most digital calculators and spreadsheets.