Number Base Converter
Convert whole numbers between binary, octal, decimal, hexadecimal and any base from 2 to 36. Runs in your browser with native big integers, so even very long numbers stay exact.
What this tool does
Type a whole number and read it at once in binary, octal, decimal and hexadecimal, plus a custom base from 2 to 36. The converter detects the 0x, 0b and 0o prefixes, accepts upper and lower case hex, and ignores the spaces or underscores you use to group digits. It works with native big integers, so a 200 digit value converts with no rounding. Nothing is uploaded, everything happens on your device.
What you can use it for
- Read a hexadecimal color or memory address as a plain decimal number.
- Turn a decimal value into the binary or hex a register or bitmask expects.
- Check a permission mask by switching an octal value to binary.
- Convert an id stored in base 36 back to decimal and the other way around.
How to use it
- Paste or type the number you want to convert.
- Pick the input base, or leave it on auto to detect the 0x, 0b and 0o prefixes.
- For an unusual base, choose custom and set a radix from 2 to 36.
- Read the binary, octal, decimal and hexadecimal results, then copy the ones you need.
Everything runs inside your browser. No file is uploaded to any server. See more tools in this field.
Pairs well with
Other tools people reach for in the same flow.
- Base64 Encoder and Decoder
encode and decode Base64 text
Essential when debugging an API.
- JSON Formatter and Validator
format and validate JSON
Strong fit in developer workflows.
- UUID Generator and Validator
work with UUIDs
Strong fit in developer workflows.
- Unix Timestamp Converter
convert Unix timestamps and dates
Strong fit in developer workflows.
Related tools
DataBase64 Encoder and Decoder
Encode and decode Base64 text online, with an optional URL-safe alphabet. Runs in your browser, nothing is uploaded to a server.
JSON Formatter and Validator
Format, validate and minify JSON online. Beautify messy JSON or compact it in one click, free and entirely in your browser, no upload.
UUID Generator and Validator
Generate, validate and convert UUIDs online: v4, v5, v7, NIL and MAX. Instant and free, in your browser, no upload to any server.
Unix Timestamp Converter
Convert Unix epoch timestamps to readable dates and back online, in seconds or milliseconds. Free and in your browser, no upload.
Frequently asked questions
Which bases are supported?
Binary, octal, decimal and hexadecimal directly, plus any custom base from 2 to 36. Bases above 10 use the letters a to z as extra digits, so base 16 uses 0 to 9 and a to f, and base 36 uses 0 to 9 and a to z.
Does it handle very large numbers?
Yes. The converter uses native big integers, not floating point, so there is no 53 bit limit and no rounding. A number with hundreds of digits converts exactly in every base.
Can I paste values with the 0x, 0b or 0o prefix?
Yes. On auto the prefix sets the base for you: 0x for hexadecimal, 0b for binary and 0o for octal. You can also keep the prefix when you pick that base by hand. Spaces and underscores used to group digits are ignored.
Does it convert decimals or fractions?
No. This is a whole number converter, so a value with a decimal point or a scientific exponent is rejected with a clear message. Convert only the integer part when you need a quick reading.
Is my data sent anywhere?
No. The conversion runs entirely in your browser. Nothing you type is uploaded or stored on a server.