Decimal to octal converter

Type a decimal number, like 493, and the octal appears straight away, with the division by 8 underneath. Numbers of any length work, negative ones too. Press swap to go from octal back to decimal.

Divide by 8 and write down the remainder, then divide the answer by 8 again, until the answer is 0. Read the remainders from the last back up to the first.

For 493, 493 ÷ 8 = 61 remainder 5, then 61 ÷ 8 = 7 remainder 5, then 7 ÷ 8 = 0 remainder 7. Reading upwards gives 755, which is the chmod setting for a file everyone can read and run but only its owner can change.

Since 8 is 2³, each octal digit is exactly three bits. If you have the number in binary, split the bits into threes from the right and turn each group into a digit from 0 to 7. 111 101 101 is 7, 5 and 5, which is 755 again.