Octal to Decimal Converter
Convert octal numbers to decimal, with binary and hexadecimal equivalents.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Enter only octal digits 0–7. Invalid characters are rejected instead of removed; values beyond JavaScript’s safe integer range are not converted.
Worked example
calculated with the default values below
Octal number 755 Decimal 493 · Binary 111101101 · Hexadecimal 1ED · Octal digits 3
General background references
Disclaimer
These calculators give general mathematical results. They suit study, planning and estimation — verify anything that feeds a graded submission, a published figure or a financial commitment.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
D = Σ_{i=0}^{k−1} d_i × 8^i
- D
- decimal value
- d_i
- octal digit 0–7
- i
- position from right
- k
- number of digits
Characters outside 0–7 are stripped before conversion; binary and hex are the base-2 and base-16 forms of D; empty input gives 0.
Frequently asked questions
Why does octal 755 become 493 in decimal on this converter?
Each octal digit is a group of three bits, so 755 means 7×64 + 5×8 + 5, which equals 493 in decimal. That is why Unix permissions read 755: the three digits map directly to owner, group and other rwx bits. The tool also shows the binary 111101101 and hex 1ED, and counts the three octal digits for you.