Rounding Calculator
Round a number to decimal places or to the nearest 10, 100 or 1000 using your choice of rounding mode.
Example
Round 2.345 to 2 decimal places using half-up:
2.345 / 0.01 = 234.5
round half-up -> 235
235 x 0.01 = 2.35
Round 1250 to the nearest 100: half-up gives 1300, half-down gives 1200.
How it works
Enter a number, pick what to round to (decimal places or a nearest multiple), and choose a rounding mode. The result updates instantly.
Good to know
This Rounding Calculator takes any number you type and reduces its precision in a controlled way: either to a fixed count of decimal places (0 to 12) or to the nearest 10, 100, 1000, or whole integer. Beyond the rounded answer it also shows the original value, the rounding step you applied, and the signed difference between the two, so you can see exactly how much precision was traded away. It is handy for students checking homework, developers verifying how a language or spreadsheet will round a figure, and anyone preparing numbers for invoices, measurements, or reports.
The reason rounding needs four separate modes is that the rule for a tie (a value sitting exactly on a .5 boundary) is genuinely a choice, not a law of math. Half up pushes ties away from zero, half down pulls them toward zero, while ceil and floor ignore the tie entirely and always move toward positive or negative infinity. Picking the wrong mode is a common source of off-by-one mismatches between a calculator, a database, and a programming language, which is exactly when this tool is useful for confirming which behavior you actually have.
To read the result, look at the Difference field: a positive value means rounding nudged the number upward, negative means downward, and zero means the input was already at that precision. The Rounded to field confirms the step in plain terms, such as "2 dp" or "nearest 100", so you are never guessing what was applied.
- Note that the decimal-places box is only active when "Decimal places" is selected; choosing a nearest-multiple option disables it.
- Values are clamped internally to about 10 significant digits, so extremely long decimals or very large magnitudes may not behave like an arbitrary-precision tool.
Frequently asked questions
What is the difference between half-up and half-down?
Both keep digits unless the dropped part is exactly .5. Half-up then rounds that .5 away from zero (2.5 to 3), while half-down rounds it toward zero (2.5 to 2). For any non-exact .5 they behave identically.
How do ceil and floor handle negative numbers?
Ceil always rounds toward positive infinity, so -2.7 becomes -2. Floor always rounds toward negative infinity, so -2.7 becomes -3. Neither looks at the .5 boundary.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser; nothing is uploaded.
Is it free?
Yes, completely free with no sign-up and no limits.
People also ask
What rounding mode does Excel or Google Sheets use by default?
The ROUND function in Excel and Google Sheets uses half-away-from-zero, which matches this tool's Half up mode, so 2.5 becomes 3 and -2.5 becomes -3. Note that many programming languages instead use banker's rounding (round half to even), which this calculator does not offer.
Why does 2.345 round to 2.34 instead of 2.35 in some tools?
Many numbers like 2.345 cannot be stored exactly in binary floating point, so the value held in memory may be slightly below 2.345, causing it to round down. Different tools compensate for this differently, which is why results can disagree on borderline cases.
What is the difference between rounding and truncating a number?
Rounding chooses the nearest value at the target precision and can move a digit up, while truncating simply drops the extra digits without adjusting. Truncation toward zero behaves like floor for positive numbers and like ceil for negative numbers.
How do I round to the nearest 5 or nearest 25?
This calculator offers fixed multiples of 10, 100, 1000, and 1 rather than arbitrary multiples like 5 or 25. To round to the nearest 5 manually, divide the number by 5, round to the nearest integer, then multiply by 5.
Does rounding to 2 decimal places change the value stored in money calculations?
Rounding to 2 decimal places produces a value suitable for displaying currency, but the difference between the original and rounded amount is real and can accumulate across many transactions. The Difference field here shows the size of that single rounding adjustment.
What does it mean to round to a negative number of decimal places?
Rounding to a negative number of places means rounding to the left of the decimal point, such as the nearest ten or hundred. This calculator handles that through its 'Nearest 10', 'Nearest 100', and 'Nearest 1000' options rather than accepting negative place values.
Is half up the same as 'round half away from zero'?
Yes. In this tool Half up rounds a .5 tie away from zero in both directions, so 2.5 goes to 3 and -2.5 goes to -3. This differs from a strict 'always increase' rule, which would send -2.5 to -2.
Related calculators