Rounding Calculator

Rounds a number to the place you choose, up or down, or to significant figures: for example to two decimal places, the nearest thousand or the nearest 0.5.

How to use

1. Enter the value in "Number". Negative numbers and scientific notation such as 6.02e23 work.
2. Under "Round to", choose a number of decimal places, the nearest ten, hundred or thousand, "Nearest multiple of …" or "Significant figures".
3. Choose a "Rounding mode", such as half away from zero, round up, round down or banker's rounding. The result comes with a number line and the matching Excel formula.
4. "All modes compared" shows every mode side by side, and "Round a list" rounds a pasted column of numbers.

How it works

• Rounding to 2 decimal places keeps two digits after the point and looks at the third: 5 or more rounds up, 4 or less rounds down.
• The digits you type are used as exact decimals, so 1.005 rounded to 2 decimal places gives 1.01. Many programs that store numbers in binary give 1.00.
• Numbers exactly halfway differ by mode. Rounded to a whole number, −2.5 becomes −3 with half away from zero, −2 with half up and −2 with banker's rounding.

Questions and answers

How do I round to two decimal places?

Look at the third decimal digit; if it is 5 or more, round up. 3.14159 becomes 3.14 and 2.675 becomes 2.68.

What is the difference between rounding, rounding up and rounding down?

Rounding goes to the nearer value, rounding up always to the larger and rounding down always to the smaller. To a whole number, 4.2 rounds to 4, up to 5 and down to 4.

What is banker's rounding?

A number exactly halfway goes to the neighbour whose last digit is even: 2.5 becomes 2 and 3.5 becomes 4. This keeps the total error small when many values are added.

How do I count significant figures?

Start counting at the first non-zero digit. 0.0045 has 2, 1002 has 4 and 2.50 has 3. Trailing zeros of a whole number such as 1500 are unclear.