Number Converters · Browser · Free

Octal to Decimal Converter

Octal is base 8 and the numbers you count with every day are base 10. Type an octal value into the field, press Convert, and the decimal answer appears in a card under the button.

Turning an Octal Number into Decimal

Octal is base 8 and decimal is base 10, so the same amount gets written with different digits. This tool reads an octal number from one text field and prints the decimal number that stands for it, together with the binary and hexadecimal forms. Letters in those extra forms print uppercase.

A leading sign is accepted and so is a fractional point. If you type several numbers with spaces between them, each one is converted on its own. Nothing is worked out until you press Convert, and once it is pressed the result shows up in a card below the button. Copy writes that result and its unit to the clipboard, and Clear puts the form back to an empty state.

Octal to Decimal Formula

Every digit of an octal number holds a place, and each place is worth eight times the place on its right: units, then eights, then the place worth eight eights, and so on. The decimal value is what the digits add up to once each one is counted at its own place.

Take 377. The 7 on the right counts single units, the 7 next to it counts eights, and the 3 counts the larger place beyond that, and the whole thing comes to 255 in decimal — the same pair the table lists. The shorter 20 reads the same way: two eights and no units, which is 16.