This rounding calculator rounds a number to a chosen decimal place and shows the floor and ceiling values alongside.
Math
Rounding Calculator
Round numbers to a chosen decimal place and show floor/ceil results.
Calculator
About this calculator
Formula notes
Standard rounding goes to the nearest step (0.5 rounds up); floor always rounds down to the step; ceiling always rounds up.
Worked examples
- Example: 3.1415926 to 2 decimal places is 3.14, with floor 3 and ceiling 4 at integer level — matching the defaults.
- Rounding 12.345 to 2 decimal places gives 12.35 under the usual half-up rule, while flooring gives 12.34 and ceiling gives 12.35.
How to use it
- Enter the number you want to round.
- Set the number of decimal places to keep.
- Compare rounded, floor, and ceiling results.
Frequently asked questions
How does it round a value ending in exactly 5?
It uses round-half-up: 2.5 to whole numbers becomes 3.
Can decimal places be negative?
A negative value rounds to tens, hundreds, and so on — useful for rough estimates.
Limits and interpretation
- Tie-breaking rules differ: half-up, half-away-from-zero, and half-to-even can produce different results at exact midpoints.
- Binary floating-point may store a decimal such as 2.675 only approximately, affecting edge-case rounding.