How do I convert binary to decimal or hex?

Choose the Input base, such as Binary, type your number, and the Octal, Decimal, Hexadecimal and custom Base results appear at once. Each result has a Copy button.

Can the converter handle very large numbers or negative numbers?

It uses BigInt, so large integers convert without rounding. Negative numbers are accepted in decimal input only, and input is limited to 256 characters. Fractions are not supported.

Can I type prefixes like 0x, 0b or # in the input?

Yes. 0x or # work for hexadecimal, 0b for binary and 0o for octal, when the matching Input base is selected. Other characters show an Invalid number message.

What does the Bit representation panel show?

It checks whether your value fits in 4-bit, 8-bit, 16-bit and 32-bit sizes. It shows a fits mark or the max value, and negatives are checked against the signed range.

What custom bases can I convert to?

Besides binary, octal, decimal and hex, the custom Base field covers any base from 2 to 36, using digits 0-9 and letters a-z. Hex is also shown in lowercase.

Yes. Every tool is free to use, with no account and no credit card. The work runs on your device rather than on our servers, which is what keeps it free to run.

Does it work on mobile?

Yes. It runs in current mobile browsers on iOS and Android, with nothing to install.

🔢

Free Number Base Converter

Convert numbers between binary, octal, decimal, and hexadecimal. See bit-size fit and grouped binary output instantly.

Runs in your browserNo sign-up, no pop-upsNo login requiredFree forever

Works offline once loaded

Input base:

Decimal number

Quick values

Common uses

Convert Numbers for ProgrammingConvert between binary, octal, decimal, and hex while writing code — instant reference for any number.
Convert Numbers for NetworkingConvert subnet masks, port numbers, and IP address octets between binary and decimal.
Number Systems for Computer ScienceLearn and verify binary, octal, hex conversions — perfect for CS students and exam prep.
Inspect Bit Patterns and FlagsConvert numbers to binary to inspect individual bits, bitmasks, and flag combinations.
Decode Hex Dumps and Debug LogsDecode hexadecimal values from crash reports, memory dumps, and debug logs into readable decimal.

How It Works

Conversion runs entirely in your browser using JavaScript's built-in BigInt type — no library, no server. BigInt is used instead of the older parseInt/Number approach specifically to handle values larger than 2^53 without rounding errors.

1
Input parsing with BigInt
A custom parser strips optional prefixes (0x, 0b, 0o, #) and validates the character set for the chosen base, then passes the cleaned string to the BigInt() constructor, which handles arbitrarily large integers losslessly.
2
Simultaneous base conversion
Once the BigInt value is known, the tool calls BigInt.prototype.toString() with each radix (2, 8, 10, 16, and a user-chosen base from 2–36) to produce all output representations in a single pass — no intermediate decimal step required.
3
Binary grouping and bit-width check
Binary output is padded to a multiple of 4 and split into nibble groups for readability. The tool also checks whether the value fits inside 4-, 8-, 16-, or 32-bit signed/unsigned ranges using BigInt arithmetic, so overflow behavior is exact even for 32-bit boundaries.
4
Shareable URL state
After each valid conversion the tool writes the input and source base to the URL fragment (#v=&from=) via history.replaceState, so the current conversion can be bookmarked or shared — the fragment is never sent to any server.