Rounding Calculator
Round numbers using standard, banker's, floor, ceiling, or truncate methods. Supports decimal places and significant figures.
| Decimal Places | Standard | Floor | Ceiling |
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Round any number to a chosen number of decimal places or significant figures using standard, banker's, floor, ceiling, or truncate rules.
How Rounding Calculator Works
Standard ("half-up") rounding looks at the digit right after your chosen cutoff: if it is 5 or more, the last kept digit rounds up; otherwise it stays the same. Floor always rounds down toward negative infinity, ceiling always rounds up toward positive infinity, and truncate simply chops off the extra digits without rounding at all — each method can give a different answer for the same number.
Banker's rounding (also called "round-half-to-even") is a variant used to avoid statistical bias when rounding many numbers: when the digit being dropped is exactly 5, it rounds to whichever neighboring value is even, rather than always rounding up. This matters more for repeated rounding across large datasets than for a single calculation.
Switching to "significant figures" mode changes what is being preserved — instead of a fixed number of decimal places, it keeps a fixed number of meaningful digits regardless of where the decimal point falls, which matters for very large or very small numbers where decimal-place rounding would lose or add unwanted precision.
See It In Action
Who Uses Rounding Calculator and Why
- Rounding a financial total to the nearest cent before displaying it on an invoice.
- Reducing a long decimal measurement to a sensible number of significant figures for a lab report.
- Applying banker's rounding across a large batch of values to avoid the small upward bias standard rounding introduces over many numbers.
- Flooring or ceiling a calculated quantity when a real-world constraint requires a whole number that can't go over (ceiling) or under (floor) the true value.
Mistakes to Avoid
- Using truncate when rounding was actually intended — truncate simply deletes extra digits and always moves the value toward zero, which is never as accurate as proper rounding.
- Applying standard (half-up) rounding to a large repeated dataset where banker's rounding would be more appropriate, introducing a small systematic bias across many values.
- Confusing decimal places with significant figures — a number like 0.00456 has 5 decimal places but only 3 significant figures, and rounding to "2 decimal places" versus "2 significant figures" gives different results.
Tips for Best Results
- Switch to significant-figures mode for very large or very small numbers, where a fixed decimal-place cutoff would lose or add unwanted precision.
- Use floor or ceiling instead of standard rounding whenever the real-world situation can't tolerate going over or under the true value (like rounding up the number of boxes needed to fit an inventory).
Fixing Common Problems
Floor, ceiling, and standard rounding are all giving different answers for the same number. — That's expected — each method follows a different rule (nearest, always down, always up), so they only agree when the number is already at or very near the rounding cutoff.
I'm not sure which decimal place standard rounding rounded from. — Check the digit immediately after your chosen cutoff — 5 or higher rounds the last kept digit up, anything lower leaves it unchanged.
Terms Explained
Significant figures: All meaningful digits in a number regardless of where the decimal point falls, as opposed to decimal places, which count only digits after the point.
Banker's rounding: A round-half-to-even method that rounds an exact .5 to whichever neighboring value is even, used to reduce bias when rounding many numbers.