About the Rounding Calculator
This rounding calculator rounds a number to the precision you choose, either a number of decimal places (including negative ones for tens and hundreds) or a number of significant figures. It offers seven rules, from the usual school method of rounding halves away from zero to banker's rounding, truncation, and always rounding up or down. The arithmetic is exact, using the digits you typed rather than the binary approximation that most programming languages use, so a value like 1.005 rounds to 1.01 just as you would on paper.
Updated October 2026
How to use the Rounding Calculator
- 1Type the number you want to round. A minus sign, decimal point and scientific form like 1.2e5 are accepted.
- 2Choose whether to round to decimal places or significant figures.
- 3Enter how many places or figures to keep. Use a negative number to round to tens or hundreds.
- 4Pick the rounding rule, or leave the usual half-up rule selected.
- 5Read the rounded number and copy it.
Choosing the right rounding rule
Most everyday and school work uses the half-up rule: a digit of 5 or more rounds up, in size, away from zero. Finance and statistics sometimes prefer round half to even to keep long sums unbiased. Engineering and safety work often use directed rounding, always up when you must not underestimate, such as the number of boxes you need, and always down when you must not overestimate, such as a weight limit.
The seven rules at a glance
- Half away from zero: 2.5 becomes 3 and -2.5 becomes -3.
- Half to even: 2.5 becomes 2 and 3.5 becomes 4.
- Half toward zero: 2.5 becomes 2 and -2.5 becomes -2.
- Away from zero: any leftover digit moves the number further from zero.
- Toward zero (truncate): extra digits are simply cut off.
- Ceiling: always toward positive infinity, so -2.1 becomes -2.
- Floor: always toward negative infinity, so -2.1 becomes -3.
Reporting precision honestly
A rounded answer should not claim more accuracy than the data behind it. If a length was measured as 12.3 centimetres, writing the result of a calculation as 4.87654321 suggests a precision that does not exist. Round the final answer, not the steps along the way, to avoid errors building up. Use the Scientific Notation Converter for very large or small values, the Percentage Calculator for percentage results, and the Average Calculator when you need a mean before rounding it.
Features
- Decimal places from -30 to 60, including tens and hundreds
- Significant figures from 1 to 60
- Seven rounding rules in one place
- Exact decimal arithmetic with no floating-point errors
- Trailing zeros kept so you can see the precision
- Works with negative numbers and scientific notation
- Runs in your browser
Frequently asked questions
How do I round to a certain number of decimal places?
Look at the digit just after the place you want to keep. If it is 5 or more, increase the last kept digit by one; if it is less than 5, leave it. To round 3.14159 to two places, the third decimal is 1, so the answer is 3.14. To round 2.678 to two places, the third decimal is 8, so the answer is 2.68.
What are significant figures?
Significant figures are the meaningful digits in a number, counted from the first non-zero digit. The number 0.004560 has four significant figures: 4, 5, 6 and the final 0. Rounding to three significant figures gives 0.00456. They are used in science to show how precisely something was measured.
What is banker's rounding?
Banker's rounding, also called round half to even, sends an exact half to the nearest even digit. So 2.5 becomes 2 and 3.5 becomes 4. Over many values this avoids the slight upward bias of always rounding halves up, and it is the default in some accounting and programming systems.
What is the difference between rounding down and truncating?
For positive numbers they are the same, as both drop the extra digits. For negative numbers they differ: truncating -2.7 gives -2 because it moves toward zero, while rounding down to the floor gives -3 because it moves toward negative infinity. The rule list lets you pick either.
Why does my phone or spreadsheet sometimes round 1.005 to 1.00?
Computers store most decimals as binary fractions, and 1.005 is actually stored as a number a tiny bit below 1.005, so it rounds down. This calculator works on the digits you type, so 1.005 correctly rounds to 1.01 under the half-up rule.
How do I round to the nearest ten or hundred?
Enter a negative number of decimal places. Use -1 for the nearest ten, -2 for the nearest hundred and -3 for the nearest thousand. For example 1,284 rounded to -2 places gives 1,300.