Rounding Calculator
Round a number to decimal places or to significant figures.
Rounding Calculator
| Rounded value | 3.140000 |
| Difference (rounded − original) | -0.001590 |
π rounded to 2 decimal places is 3.14 — a difference of about −0.00159 from the full value. That is precise enough for most everyday calculations.
Rounding shortens a number to a chosen precision. Rounding to decimal places fixes how many digits sit after the decimal point; rounding to significant figures fixes how many meaningful digits the number has in total, whatever its size.
Choose a mode and a precision. The difference between the rounded and original values is shown as well, so you can see exactly how much the rounding moved the number — the rounding error.
The formula
Worked example
π rounded to 2 decimal places is 3.14 — a difference of about −0.00159 from the full value. That is precise enough for most everyday calculations.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Frequently asked questions
What is the difference between decimal places and significant figures?
Decimal places count digits after the point: 0.0045678 to 2 decimal places is 0.00 — useless. Significant figures count meaningful digits: the same number to 3 significant figures is 0.00457, which keeps the information. Scientists therefore prefer significant figures.
How are exact halves rounded?
This calculator rounds halves up (away from zero for positive numbers), the convention taught in schools: 2.5 to 0 decimal places becomes 3. Some statistical systems use 'round half to even' (banker's rounding) instead, which would give 2.
How many significant figures does 12,300 have?
Ambiguous without context: it could be 3, 4 or 5. Writing it as 1.23 × 10^4 makes clear it has 3 — one reason scientific notation pairs so well with rounding.
Category: Math calculators
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