Rounding Calculator
Frequently Asked Questions
What is the difference between rounding to decimal places and rounding to significant figures?
Decimal places count positions after the decimal point, so 0.00456 to 2 decimal places is 0.00. Significant figures count from the first non-zero digit, so 0.00456 to 2 significant figures is 0.0046. Use decimal places for money; use significant figures for scientific measurements where precision matters.
How do I round a negative number correctly?
Standard half-up rounding rounds toward positive infinity when the digit is exactly 5. So -2.5 rounds to -2, not -3. If you need half-away-from-zero behavior where -2.5 rounds to -3, that is a different rounding mode called symmetric rounding. Make sure you know which convention your context requires.
Why does 2.675 rounded to 2 decimal places sometimes give 2.67 instead of 2.68?
This is a floating-point representation issue. The decimal 2.675 cannot be stored exactly in binary, so the computer stores a value slightly below 2.675, causing it to round down to 2.67. This is a well-known quirk of IEEE 754 arithmetic, not a calculator error. Use arbitrary-precision libraries for financial software.
Can I round to the nearest 10, 100, or 1000?
Yes. Enter a negative number for decimal places: -1 rounds to the nearest 10, -2 to the nearest 100, -3 to the nearest 1000. For example, 2,748 rounded to the nearest 100 (decimal places = -2) becomes 2,700. This is useful for financial estimates and population statistics.
What is banker's rounding and when should I use it?
Banker's rounding (round half to even) rounds a .5 value to the nearest even number: 2.5 → 2, and 3.5 → 4. This reduces statistical bias over many rounding operations. It is the default in Python's round() and Excel's even function. Use it in large financial datasets and statistical analyses to minimize cumulative rounding error.
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