⚪ Rounding Calculator
Rounding trims a number to a chosen precision: π becomes 3.14 at two decimal places. Half-up rounding — the kind taught in schools — pushes a trailing 5 away from zero, so 2.5 becomes 3 and −2.5 becomes −3.
Enter the number and how many decimal places to keep (0–15). The result is shown both as a value and exactly as written, trailing zeros included.
How to use this calculator
Type the number and how many decimal places to keep, then press Calculate.
- Type the number into the Number field.
- Type the decimal places to keep into the Decimal places field, from 0 to 15.
- Press Calculate and read the rounded value as the headline result.
- Check the As written line to see the result with its exact trailing zeros.
Frequently asked questions
What rounding rule does this use?
Half-up rounding, the school standard: look at the first dropped digit; 5 or more rounds up, 4 or less rounds down. A trailing 5 rounds away from zero, so 2.5 becomes 3 and -2.5 becomes -3.
What does 0 decimal places do?
It rounds to the nearest whole number: 3.7 becomes 4, 3.2 becomes 3, and 2.5 becomes 3 under half-up rounding.
Why does the As written line matter?
As a plain value, 2.50 and 2.5 look identical, but in money or measurements the trailing zero carries meaning. The As written line preserves it, showing 2.50 exactly.
Can you show a worked example?
Rounding 3.14159 to 2 decimal places: the third decimal is 1, which is less than 5, so the result is 3.14.