Rounding Calculator
Round numbers multiple ways simultaneously — decimal places, significant figures, nearest integer, and banker's rounding (IEEE 754).
Standard (half-up): ≥ 0.5 rounds up. Banker's (IEEE 754): 0.5 rounds to nearest even (2.5→2, 3.5→4). Ceiling: always rounds up. Floor: always rounds down. Truncate: drops decimal digits.
Rounding Rules by Country & Context
| Country / Context | Rule used | 2.5 rounds to | Local name |
|---|---|---|---|
| 🇺🇸 USA (schools) | Round half up | 3 | Standard rounding |
| 🇬🇧 UK (GCSE) | Round half up | 3 | Round half up |
| 🇩🇪 Germany | Round half up | 3 | Kaufmännisches Runden |
| 🇯🇵 Japan | Round half up | 3 | 四捨五入 (shisha-goonyuu) |
| 🇫🇷 France | Round half up | 3 | Arrondi commercial |
| 💰 Finance / Banking | Banker's (round half to even) | 2 | IEEE 754 / Gaussian rounding |
| 💻 Python 3 / Excel | Banker's rounding | 2 | round() in Python 3 |
| 🔬 Science / IB | Round half up (mostly) | 3 | Standard significant figures |
Frequently Asked Questions
What is the difference between rounding and truncating?
Rounding looks at the next digit to decide direction. Truncating simply drops the unwanted digits without rounding. Example: 3.999 truncated to 2 decimal places = 3.99; rounded = 4.00. Truncation always rounds toward zero.
Why does Python's round() give unexpected results?
Python 3 uses banker's rounding (round half to even), so round(2.5) = 2, not 3. This surprises many programmers expecting standard rounding. To get standard: use round(x + 0.0001, 0) or the Decimal library with ROUND_HALF_UP.
What does rounding to the nearest 10, 100, or 1000 mean?
3,467 rounded to nearest 10 = 3,470; to nearest 100 = 3,500; to nearest 1,000 = 3,000. Used widely in estimation: a budget of €3,467 rounded to €3,500. Japan uses this for statistical reporting (端数処理, hasu shori).
How do you round to 3 significant figures?
Identify the first 3 significant (non-zero leading) digits and round based on the 4th. Example: 3,456.78 → 3,460 (3 s.f.). 0.004567 → 0.00457 (3 s.f.). See our Sig Figs Calculator for dedicated help.