Rounding rules compared
Most people round half up: 2.5 → 3, 2.45 → 2.5 at one decimal. Accountants and statisticians often use half even ("banker's rounding"): ties go to the even neighbour, so 2.5 → 2 and 3.5 → 4, which avoids pushing totals upward when many values are rounded. Up and down always move away from or towards zero; floor and ceiling always move down or up on the number line, which matters for negative numbers.
Significant figures
Rounding to significant figures keeps a fixed number of meaningful digits regardless of size: 123,456 to 2 significant figures is 120,000, and 0.0012345 to 3 is 0.00123.
Why 1.005 rounds to 1.00 elsewhere
Computers store 1.005 in binary as 1.00499999999…, so many calculators and spreadsheets round it to 1.00. This page rounds the digits you typed, so 1.005 to two decimals is 1.01.
How this works
The page reads your number as text and converts it to an exact whole number with a decimal scale, avoiding binary floating point. It finds the position to round at (a number of decimals, or the place giving the chosen number of significant figures), looks at the remainder beyond it, and applies the rule: ties away from zero for half up, ties to even for half even, always away from or towards zero for up and down, and towards minus or plus infinity for floor and ceiling. The result keeps trailing zeros. Everything runs in your browser.
Frequently asked
What is banker's rounding?
Rounding ties to the nearest even digit: 0.5 → 0, 1.5 → 2, 2.5 → 2. It avoids a systematic upward bias.
How do I round to 2 significant figures?
Keep the first two non-zero digits and round the rest: 0.04567 → 0.046.
What is the difference between floor and down?
For positive numbers none. For negatives, down goes towards zero (−1.7 → −1) and floor goes lower (−1.7 → −2).
Why does Excel round 1.005 differently?
Spreadsheets work in binary floating point, where 1.005 is slightly below 1.005. This page uses the decimal digits exactly.
Sources
Reviewed Oct 17, 2026 · test vectors fixtures/calculators/math/rounding-calculator/