Rounding Calculator
Round any number to decimal places, the nearest 10, 100 or 1,000, or significant figures. Exact decimal maths, so 2.675 rounds to 2.68 as it should.
About this tool
Works on the exact decimal digits you type, not on binary floating-point numbers, so halves are always treated as halves. Negative numbers round symmetrically with the half-up method (−2.5 becomes −3).
Round a number to a set number of decimal places, to the nearest 10, 100 or 1,000, or to a number of significant figures. Choose the rounding method too: the half-up method taught at school, banker’s rounding used in some finance and statistics software, or always rounding up or down. The calculator works on the exact digits you type, so results match working on paper.
How to use the Rounding Calculator
- Type the number, for example 3.14159 or 1,234.5.
- Choose what to round to: decimal places, the nearest 10, 100 or 1,000, or significant figures.
- Choose the method. Leave it on round half up unless you need another one.
- Read the rounded number, the rounded-down and rounded-up values, and how much the number changed.
Rounding 3.14159 and 2.675
3.14159 to 2 decimal places is 3.14, because the next digit (1) is less than 5. To 3 decimal places it is 3.142, because the digit after the 1 is 5 or more. 2.675 to 2 decimal places is 2.68: the dropped part is exactly a half, and the half-up method rounds it away from zero. With banker’s rounding (round half to even), 2.665 becomes 2.66 and 2.675 becomes 2.68, because a tie goes to the even digit.
3.14159 rounded different ways
Worked out with this calculator using round half up.
| Round to | Result |
|---|---|
| Whole number | 3 |
| 1 decimal place | 3.1 |
| 2 decimal places | 3.14 |
| 3 decimal places | 3.142 |
| 4 decimal places | 3.1416 |
| 3 significant figures | 3.14 |
How rounding works
Look at the first digit you are dropping. If it is 5 or more, round up; if it is 4 or less, keep the digit before it. Rounding to the nearest 100 works the same way on whole numbers: 1,234.5 becomes 1,200. Significant figures count from the first non-zero digit, so 0.004567 to 2 significant figures is 0.0046 and 83,456 to 3 significant figures is 83,500. Programming languages store most decimals in binary, so some of them round 1.005 to 1.00. This calculator uses the decimal digits as typed and gives 1.01.
Common mistakes
- Rounding in steps. 2.345 to 1 decimal place is 2.3; rounding first to 2.35 and then to 2.4 gives the wrong answer.
- Dropping zeros that matter. 7 rounded to 2 decimal places is 7.00 when you report money or measurements to that precision.
- Mixing up decimal places and significant figures. 0.004567 to 2 decimal places is 0.00, but to 2 significant figures it is 0.0046.
Frequently asked questions
What is 2.5 rounded to the nearest whole number?
3 with the school method (round half up). With banker’s rounding it is 2, because ties go to the nearest even number.
How do you round a negative number?
With round half up, halves go away from zero, so −2.5 becomes −3. Rounding down (towards −∞) also gives −3, while truncating gives −2.
What does round half to even mean?
When the dropped part is exactly a half, the number is rounded to the nearest even digit: 2.5 becomes 2 and 3.5 becomes 4. Over many numbers, ties then round up and down equally often.
Why does my code or calculator app round 1.005 to 1.00?
Many programs store 1.005 as a binary number slightly below 1.005, so it rounds down: JavaScript’s toFixed(2) and Python’s round(1.005, 2) both give 1.00. Spreadsheet ROUND functions correct for this and give 1.01. This calculator rounds the decimal digits exactly and gives 1.01.