Octal Calculator
Octal to decimal, binary and hexadecimal.
Work out Octal. Octal to decimal, binary and hexadecimal. Free, with no account and nothing to download.
Decimal
255
8 bits
Every base writes the same quantity differently — 255 is 11111111 in binary and FF in hex, and none is more correct than the others. Hexadecimal earns its place in computing because one hex digit is exactly four binary digits, so conversion between them needs no arithmetic at all.
How the Octal Calculator works
Octal uses digits 0 to 7, so each one carries exactly three bits. It survives mainly in Unix file permissions, where three bits map neatly onto read, write and execute — which is why chmod takes numbers like 755.
Also known as: octal to decimal · decimal to octal converter · base 8 calculator · octal converter
Frequently asked questions
How do I convert octal to decimal?
Each place is worth eight times the one to its right. 377 is 3 × 64 + 7 × 8 + 7 = 255.
Where is octal still used?
Chiefly Unix file permissions. Three bits — read, write, execute — fit one octal digit exactly, so 755 means full access for the owner and read-execute for everyone else.
Why did octal lose to hexadecimal?
Because bytes are eight bits, which divides evenly by four but not by three. Hex maps onto a byte as exactly two digits; octal does not.
What is the largest octal digit?
7. Base 8 uses only 0 through 7, so an 8 or 9 in an octal number is invalid — and this page rejects it rather than misreading it.
Put this calculator on your own site
Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.
<iframe src="https://www.thecalclibrary.com/embed/octal-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Octal Calculator"></iframe>The only condition is that the credit line stays visible. It sits inside the frame, so you do not have to do anything to keep it.