Rounding replaces a number with a nearby, simpler one — to a set number of decimal places or to the nearest multiple like 10 or 100. The everyday rule, round half up, looks at the next digit: 5 or more rounds up, 4 or less stays. This calculator also shows floor (always down), ceiling (always up), and banker's rounding (exact halves to the nearest even digit) so you can match any convention.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: standard rounding rules and IEEE round-half-to-even, recomputed in code.
Four ways to round
For most work, round half up is what people mean by "rounding". Floor and ceiling are blunt — they ignore the discarded digit and always move one way, which is handy for things like fitting whole boxes (ceiling) or safe limits (floor). Banker's rounding only differs on exact halves, sending them to the even neighbour so that, across many numbers, the rounding doesn't drift upward. To round to the nearest 10 or 100, divide, round, and multiply back.
Worked example — 3.14159 and 2.5
Scenario: a decimal-places case and a tie case.
Rounding 3.14159 to 2 decimal places gives 3.14, because the next digit (1) is below 5. The tie 2.5 splits the methods: half up and ceiling give 3, floor gives 2, and banker's gives 2 (the even neighbour). For 7.5 the even neighbour is 8, so banker's agrees with half up there. Rounding 1234.56 to the nearest 100 yields 1200, and to the nearest 10 it's 1230.
Frequently Asked Questions
Check the digit after the last one you keep: ≥5 rounds up, ≤4 stays. 3.14159 to 2 dp = 3.14 (next digit 1).
Floor always goes lower, ceiling always higher, ignoring the next digit. 3.14159 at 2 dp: floor 3.14, ceiling 3.15.
Round half to even: exact halves go to the nearest even digit. 2.5 → 2, 7.5 → 8. It avoids upward bias when summing.
Divide by the multiple, round, multiply back. 1234.56 → nearest 100 = 1200; nearest 10 = 1230.
Half up → 3; banker's → 2 (nearest even). This tool shows both, plus floor (2) and ceiling (3).