How rounding works
Look at the digit after the one you are keeping. If it is 5 or more, round up; if it is 4 or less, round down.
A half rounds away from zero here, so 2.5 becomes 3 and -2.5 becomes -3. Some statistical software rounds halves to the nearest even number instead.
Worked example
1234.5678 to two decimal places is 1234.57, because the third decimal is 7.
To the nearest whole number it is 1235, to the nearest ten it is 1230, to the nearest hundred it is 1200 and to the nearest thousand it is 1000.
Why the change is shown
Rounding loses information. The calculator shows the difference so you can see how much was thrown away.
Rounding twice can drift: rounding 2.4449 to two places gives 2.44, but rounding it to one place first gives 2.4 and then 2.4 again. Round once, at the end.
Inputs for the rounding calculator
Number to round
The number you want to round. Negative numbers round away from zero at a half.
Round to
Choose decimal places, the nearest whole number, or the nearest ten, hundred or thousand.
Decimal places
Only shown for decimal places. 2 keeps two digits after the point; 0 rounds to the nearest whole number.
CALCULATOR QUESTIONS
Rounding calculator questions
How do I round to two decimal places?
Keep two digits after the point and look at the third. 1234.5678 becomes 1234.57 because the third digit is 7.
What happens to a 5?
This calculator rounds a half away from zero, so 2.5 becomes 3 and -2.5 becomes -3.
How do I round to the nearest ten?
Choose nearest ten. 1234.5678 becomes 1230, because 1234.5678 is closer to 1230 than to 1240.
Does rounding change the number?
Yes. The rounded value is usually slightly different, and the change row shows by how much.