Number Base Converter
Last updated: June 11, 2026Binary, octal, decimal and hex.
Number Base Converter is a free online tool to binary, octal, decimal and hex. It runs entirely in your browser, so your files never leave your device — nothing is uploaded. There's no sign-up, no watermark, and it works on any modern browser on desktop or mobile.
How to use Number Base Converter
The Number Base Converter instantly converts a number between binary, octal, decimal and hexadecimal. It uses arbitrary-precision integers, so even very large numbers convert exactly. Free and runs entirely in your browser.
Read the full guide: Number Base Converter: Binary, Hex, Decimal (Free)
- 1Enter your value.
- 2Choose the base you're converting from.
- 3Read the binary, octal, decimal and hex results.
All four bases
See binary, octal, decimal and hexadecimal at once.
Big-number safe
Uses BigInt, so large values don't lose precision.
Free & private
Runs on your device with no sign-up.
Convert a hex color or byte to decimal
Front-end and design work is full of hex: a CSS color like ff or a byte value. Drop in the hex (the 0x prefix is stripped for you) and read the decimal 0-255 channel value instantly, so you can plug it into an rgb() function, an alpha calculation or a sprite-sheet offset without doing the base-16 math in your head.
Read a hex memory address or register value
When you are debugging and the stack trace, hex dump or register window shows an address like 0x7ffee3b2, paste it here to get the exact decimal offset. Because conversion uses arbitrary-precision BigInt, full 64-bit pointers and large file offsets convert without rounding, which makes it easy to compute the gap between two addresses or line up a struct field.
Turn a decimal IP octet into binary for subnetting
Subnet masks and ACL bit-matching are easier to reason about in binary. Enter a decimal octet such as 192 or a mask value like 255, switch the from-base to decimal, and read the 8-bit binary pattern. Seeing the 1s and 0s makes it obvious where a /26 boundary falls or which host bits a wildcard mask leaves free.
Number Base Converter — frequently asked questions
How do I convert binary to decimal?
Select binary as the 'from' base and enter your 1s and 0s — the decimal value appears instantly, along with octal and hex.
Can it handle very large numbers?
Yes — it uses arbitrary-precision integers, so big values convert exactly without rounding.
Does it accept prefixes like 0x?
Yes, common prefixes (0x, 0b, 0o) are stripped automatically.
Is it free?
Yes, completely free.
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