About the Rounding Calculator
This rounding calculator rounds, rounds up or rounds down (truncates) a number to any precision: to the nearest tenth, hundredth or thousandth, to a whole number, or to the nearest ten, hundred, thousand and beyond. It is handy for prices, measurements, homework and spreadsheet checks.
Many apps round 1.005 to two decimals as 1.00, because the computer stores 1.005 as 1.00499999…. This calculator works on the digits exactly as you typed them, so 1.005 → 1.01 every time.
How to use
- Enter a number. Thousands separators and minus signs are fine.
- Choose Round, Round up or Round down.
- Pick the precision from the list or tap a shortcut (2 decimals, whole number, nearest 10, 100, 1,000…).
- Read the result and the difference from the original value. The table compares all three methods at every precision – tap a row to select it.
Rounding examples
| Value / precision | Round | Round up | Round down |
|---|---|---|---|
| 3.14159 / 2 decimal places (nearest hundredth) | 3.14 | 3.15 | 3.14 |
| 2.5 / whole number | 3 | 3 | 2 |
| $12.345 / nearest cent | $12.35 | $12.35 | $12.34 |
| $1,234,567 / nearest $1,000 | $1,235,000 | $1,235,000 | $1,234,000 |
| −1.25 / 1 decimal place | −1.3 | −1.3 | −1.2 |
Round half up vs. banker’s rounding
This calculator uses round half away from zero, the rule taught in school and used by Excel’s ROUND: a 5 in the first dropped digit always rounds up (2.5 → 3, −2.5 → −3). Banker’s rounding (round half to even) sends exact halves to the nearest even digit instead (2.5 → 2, 3.5 → 4) and is used by some programming languages and financial systems to avoid bias. This tool does not apply banker’s rounding.
Rounding negative numbers
Round up and round down follow Excel’s ROUNDUP and ROUNDDOWN: round up moves away from zero (−1.21 → −1.3) and round down moves toward zero (−1.29 → −1.2), which is the same as truncating. The mathematical ceiling and floor functions (CEILING/FLOOR) use the number line instead, so for negative numbers the result is the opposite. When you enter a negative number, the calculator shows that alternative too.
FAQ
Why does my spreadsheet round 1.005 to 1.00 but this calculator gives 1.01?
1.005 cannot be stored exactly in binary floating point; internally it is 1.00499999…, so some programs round it down. This calculator rounds the decimal digits you typed, so you get the mathematically correct 1.01.
What is the difference between rounding down and truncating?
For positive numbers they are the same: you simply drop the extra digits (7.89 → 7.8). Here, round down always truncates toward zero, also for negative numbers.
How do I round to the nearest hundred?
Choose Round and tap “Nearest 100”. 12,345 becomes 12,300, and 12,350 becomes 12,400.
Can it handle very large numbers or many decimals?
Yes. The calculation uses exact integer arithmetic, so numbers with more than 20 digits are rounded precisely.