Rounding Calculator

Look at the hundredths digit, the second digit after the decimal point. If it's 5 or more, add 1 to the tenths digit; if it's 4 or less, keep the tenths digit. Then drop everything after it. 3.46 rounds to 3.5 and 3.44 rounds to 3.4.

Look at the third digit after the decimal point. 3.14159 has 1 there, which is less than 5, so it rounds down to 3.14. 2.675 has 5 there, so it rounds up to 2.68.

In the standard school rule, 5 always rounds up: 2.5 becomes 3 and 0.125 becomes 0.13 to two places. Banker's rounding (round half to even) instead sends an exact half to the nearest even digit, so 2.5 becomes 2 and 3.5 becomes 4.

Banker's rounding rounds exact halves to the nearest even number. Over many values, half of the halves go up and half go down, so totals don't drift upward. It's the default in accounting, many statistics packages and IEEE floating point.

Round the size of the number and keep the sign: −2.5 rounds to −3 and −2.4 to −2 with the school rule. Round up (ceiling) and round down (floor) are different: the ceiling of −2.9 is −2, the floor of −2.1 is −3.

Computers store 1.005 in binary as about 1.00499999999999989, which is just under the half, so it rounds down. This calculator works with the exact decimal digits you type, so 1.005 correctly rounds to 1.01.