How to use the Rounding Calculator
- Enter the number you want to round.
- Set the number of decimal places — use 0 for whole numbers, or a negative-style approach by scaling for tens and hundreds.
- Compare the four methods.
- Pick the rule your context requires: financial reporting, engineering tolerance or statistics.
How the calculation works
Rounding half up — the school rule — sends exact halves upward. It is simple but biased: across many values, a systematic upward drift accumulates. Banker's rounding (round half to even) fixes this by sending halves to the nearest even digit, so 2.5 becomes 2 and 3.5 becomes 4. It is the IEEE 754 default and what most financial and statistical software uses.
Rounding up (ceiling) and down (floor) are directional, not nearest-value, rules. Ceiling is right when a shortfall is unacceptable — ordering materials, sizing a cable, provisioning capacity. Floor is right when overshoot is unacceptable, such as counting how many complete units fit in a space. Truncation simply discards digits and behaves like floor for positive numbers but like ceiling for negatives, which is a frequent source of off-by-one bugs.
The overriding rule in any multi-step calculation: round once, at the end. Rounding intermediate values compounds error, and in long chains such as tax schedules or engineering stack-ups the drift can exceed the precision you were trying to protect.
Round to n places: round(x × 10ⁿ) / 10ⁿ ; ceiling and floor substitute ceil() and floor()Source: IEEE 754 rounding modes; ISO 80000-1 guidance on rounding of numerical values.
Worked example
A calculated unit cost of 7.125 needs presenting to two decimal places.
- Half up: 7.13.
- Down (floor): 7.12.
- Up (ceiling): 7.13.
- Banker's rounding: 7.12, because 2 is already even.
A one-cent difference per unit — trivial once, material across a million units.
Frequently asked questions
Which rounding method should I use for money?+
Follow the rule your jurisdiction or accounting standard specifies. Many financial systems use banker's rounding to avoid upward bias.
Why does 2.675 round to 2.67 in some software?+
Because 2.675 is stored in binary as very slightly below 2.675. It is a floating-point representation issue, not a rounding bug.
Is truncation the same as rounding down?+
Only for positive numbers. For negatives, truncation moves toward zero while floor moves away from it.
Should I round at each step?+
No. Carry full precision through the calculation and round once at the end.
Last reviewed September 1, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.