Rounding Calculator

Look at the third digit after the decimal point. If it is 5 or more, increase the second digit by one; otherwise leave it as it is, and drop everything after it. For example, 3.14159 rounded to 2 decimal places is 3.14, and 2.675 becomes 2.68.

Half up (standard rounding) goes to the nearest value, and a value exactly halfway goes away from zero: 2.5 → 3 and −2.5 → −3. Rounding up (ceiling) always goes towards plus infinity: 2.1 → 3 and −2.9 → −2. Rounding down (floor) always goes towards minus infinity: 2.9 → 2 and −2.1 → −3.

Significant figures are the digits that carry meaning, counted from the first non-zero digit. 123,456 to 3 significant figures is 123,000, and 0.0012345 to 2 significant figures is 0.0012. They show how precise a measurement is.

Look at the digit just to the right of the place you are rounding to. For 1,234 to the nearest hundred the tens digit is 3, which is less than 5, so the result is 1,200; 1,250 becomes 1,300. You can also round to the nearest 5 or 0.5, which is handy for prices and grades.

Computers store most decimals as binary fractions, so 1.005 is really stored as 1.00499999… and rounds down. This calculator rounds the digits exactly as you typed them, so 1.005 to 2 decimal places gives 1.01.