Binary Calculator

Binary to decimal, hex and octal, with validation that works.

Binary to decimal, hex and octal, with validation that works. Binary to decimal, hexadecimal and octal.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Value in binary

Decimal

255

8 bits

Decimal255

Binary11111111

Octal377

HexadecimalFF

Bits required8

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 Binary Calculator works

Binary to decimal, hexadecimal and octal. The validation is stricter than it looks: the standard parsing routine silently stops at the first invalid character, so '1234' would read as valid binary. This verifies the whole string round-trips before accepting it.

Also known as: binary to decimal · decimal to binary converter · binary converter · binary to hex converter

Where to go next

The Binary question rarely arrives on its own. These are the ones that usually come with it:

Hex Calculator — Hexadecimal to decimal, binary and octal.
Octal Calculator — Octal to decimal, binary and hexadecimal.
Base Converter — Decimal into binary, octal and hexadecimal at once.
Percentage Calculator — Every common percentage question in one place.

Sources

NIST Digital Library of Mathematical Functions

Frequently asked questions

How do I convert binary to decimal?

Add the place values where a 1 appears — 1, 2, 4, 8 and so on. 11111111 is 255, which is every bit set in a byte.

How many values fit in 8 bits?

256, from 0 to 255. Each extra bit doubles the range.

Why does computing use hexadecimal?

Because one hex digit is exactly four binary digits, so conversion between them needs no arithmetic at all. You can read hex off binary in blocks of four.

What is the largest number here?

Whatever fits in an exact integer, about 9 quadrillion. Beyond that, values lose precision and would be displayed wrongly, so they are refused.

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.

The one-line version

<iframe src="https://www.thecalclibrary.com/embed/binary-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Binary Calculator"></iframe>
<p style="font:13px/1.5 system-ui,sans-serif;margin:6px 0 0;color:#64748b">Powered by <a href="https://www.thecalclibrary.com/binary-calculator" style="color:#64748b">Binary Calculator</a> from The Calc Library</p>

The only condition is that the credit line below the frame stays in place. That one line is what pays for the tool being free — it is how anyone else finds it.