Rounding Calculator
Pick what to round to and which rule to use. Rounding is done on the decimal digits you typed, so 1.005 rounds correctly to 1.01.
Round a number
Rounding rules compared
| Value | Half away from zero | Half to even | Up | Down | Truncate |
|---|---|---|---|---|---|
| 2.5 | 3 | 2 | 3 | 2 | 2 |
| 3.5 | 4 | 4 | 4 | 3 | 3 |
| −2.5 | −3 | −2 | −2 | −3 | −2 |
| 2.4 | 2 | 2 | 3 | 2 | 2 |
Significant figures
Significant figures count from the first non-zero digit. 0.004567 to 2 significant figures is 0.0046; 123,456 to 3 significant figures is 123,000. Use them when the precision of a measurement matters more than a fixed number of decimal places.
Worked example
Round 3.14159 to 2 decimal places
- Look at the third decimal digit: 1
- 1 is less than 5, so the second digit stays the same
3.14159 → 3.14
Why 1.005 is tricky
Many calculators round 1.005 to 1.00 because the binary floating-point value of 1.005 is actually 1.00499999999999989… This tool shifts the decimal point on the digits themselves before rounding, so the answer is the expected 1.01.