About the rounding calculator
This rounding calculator rounds a number to a chosen decimal place (including tens, hundreds and thousands) or to the nearest fraction, using the rule you choose: standard half away from zero, half up, half down, banker's rounding (half to even), half to odd, always up, always down and more.
Rounding is exact and works on the digits, so numbers like 1.005 round correctly instead of being affected by floating-point error.
Who should use the rounding calculator
- Accountants and analysts who need a specific rounding convention.
- Programmers comparing rounding modes.
- Students and teachers working with decimals.
How to use the rounding calculator: what each input means
- Number to round
- Any decimal number of any length.
- Round to
- A decimal place or the nearest fraction such as 1/8 or 1/16.
- Rounding rule
- How ties and remainders are handled.
How the rounding calculator works: method and formula
The number is scaled so the rounding position becomes a whole number, rounded using your rule, then scaled back. Because the arithmetic is on exact fractions, the result is not affected by binary floating-point behaviour.
- Round to p places
- round(x × 10^p) ÷ 10^p using the chosen rule
How to read your rounding calculator result
Different rules only disagree on exact ties (like 2.5) and for the directed modes (floor, ceiling). Banker's rounding sends ties to the nearest even digit and is often used to avoid bias when many values are rounded and added.
Rounding Calculator worked example
Round 3.14159 to 2 decimal places, and 1.005 with two different rules.
- 3.14159 to 2 places is 3.14.
- 1.005 to 2 places with the standard rule is 1.01, because the exact value is a tie that rounds up.
- With banker's rounding, 2.5 to the nearest whole number is 2, and 3.5 is 4.
3.14159 rounds to 3.14 at two decimal places.
Practical uses of the rounding calculator
- Following a specific rounding rule in accounting or tax.
- Rounding measurements to the nearest 1/8 or 1/16.
- Comparing how modes affect a set of values.
Assumptions and limitations of this calculator
- Rounds to a decimal place or a fraction, not to significant figures.
- The standard rule may differ from what a particular programming language or spreadsheet does by default.