Rounding Calculator
Round a number to a given number of decimal places, or up/down.
Assumptions used in this calculation
- Tie-breaking: In "nearest" mode, ties (a trailing 5) round away from zero rather than to even (banker's rounding).
About this calculator
Rounding seems trivial until you hit an edge case, a value that lands exactly on .5, a negative number, or a need to round to the nearest ten or hundred rather than a decimal place, and different rounding conventions (round-half-up vs. round-half-to-even, round toward zero vs. round toward negative infinity) can quietly produce different answers. This calculator rounds a number to a specified number of decimal places, or, using a negative number of places, to the nearest ten, hundred, thousand and so on, with three modes: nearest (standard round-half-up, so 2.5 rounds to 3 and −2.5 rounds to −2, away from zero on ties), always up, or always down. Internally it scales the value by 10^decimalPlaces, applies the rounding rule, then scales back, matching the standard algorithm taught for rounding by hand. That removes ambiguity about which convention is being applied and handles negative numbers and negative decimal-place counts correctly, which manual rounding often gets wrong.
Worked example
3.14159 to 2 decimal places
Result: 3.14
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