Number Base Converter
Convert whole numbers between any bases from 2 to 36, computed with BigInt so long hexadecimal values keep every digit.
Number Base Converter workspace
Converter Inputs
Spaces and underscores are ignored. 0b, 0o and 0x prefixes are accepted. Invalid digits are rejected, not stripped.
Values of any size are handled with BigInt, so 64 one-bits give 18446744073709551615 exactly.
Applies to numeric results. Conversions themselves are computed at full precision.
Conversion Output
Enter a value — everything is computed in your browser.
Using Number Base Converter
Type or paste the number you want converted.
Select the base it is written in and the base you want it in, anywhere from 2 to 36.
Read the converted value, plus the binary, octal, decimal and hexadecimal forms and the bit length.
Copy any single row, or copy the whole result at once.
Any base from 2 to 36 converts to any other, with the four common bases and the bit length filled in alongside. A digit that does not belong to the source base halts the conversion and is named by position, rather than being quietly discarded to produce a plausible wrong answer.
Whole numbers between any two bases from 2 to 36. Whatever pair you pick, the result panel also fills in binary, octal, decimal and hexadecimal, plus the bit length of the value, because those four are what you usually needed next anyway.
An invalid digit is an error, not a hint
The version this replaced silently deleted anything that was not a 0 or a 1 and converted whatever survived. Type 1012 and it answered 5. Paste hello101 and it answered 5. Both are confidently, silently wrong, and 5 is a perfectly reasonable-looking number to copy into a config file.
Now a digit that does not belong to the source base stops the conversion and the message names it:
"2" (position 4) is not a valid base-2 digit. Base 2 allows 0-1.A refusal with a position in it costs you five seconds. A wrong answer that looks right can cost considerably more.
Large values stay exact
Arithmetic runs on BigInt rather than on the double-precision floats JavaScript normally uses. Doubles hold integers exactly only up to 2^53; past that they start rounding, and a converter built on them quietly loses the low digits of long hexadecimal values — precisely the values people paste in, since hashes and 64-bit identifiers are the reason anyone opens a base converter.
Sixty-four one-bits convert to 18446744073709551615, every digit correct. There is no upper limit beyond your patience.
What the parser accepts
Spaces and underscores are treated as digit-group separators and discarded, so 1101_0110 and 1101 0110 both parse as 11010110. Group your bits in fours or eights and the result is unaffected.
The prefixes 0b, 0o and 0x are accepted when they match the base you selected — 0x with base 16, 0b with base 2, 0o with base 8. Letter digits are case-insensitive going in and come back uppercase for any base above 10, so deadbeef and DEADBEEF are the same input.
A leading minus sign is understood, and the sign is printed before any prefix: -0x1A, never 0x-1A.
Two conversions worked through
DEADBEEF from base 16 to base 10 gives 3735928559. The panel adds the binary form 11011110101011011011111011101111, the octal 0o33653337357, and a bit length of 32 — which is the quickest confirmation that the value fits a 32-bit register with nothing to spare.
Base 36 uses the digits 0-9 followed by A-Z, one symbol for every value from zero to thirty-five. ZZ in base 36 is 35 × 36 + 35 = 1295, and the same 3735928559 written in base 36 is only seven characters: 1PS9WXB. That compactness is why short-link services reach for it.
Where this is the wrong tool
Integers only. There is no fractional support. Type 1.5 and the full stop is rejected as an invalid digit rather than interpreted, because a binary fraction is a different problem with different rounding behaviour.
No two's complement. A negative number is shown with a minus sign in front of its magnitude. That is the mathematical answer, and it is not what a debugger shows you: −1 in a 32-bit register reads FFFFFFFF, and nothing on this page will produce that. Sign extension depends on a register width the tool is never told.
No byte-order or encoding work. Converting a hex value tells you its numeric size, not how it sits in memory or what text it might decode to.
Related developer utilities
- Colour Code Converter — the other place hexadecimal shows up daily.
- Hash Generator — produces the long hex digests this handles cleanly.
- Base64 Encoder — a text encoding, not a numeric base, despite the name.
Frequently asked
What happens if I type a digit the base does not allow?
The conversion stops and the message names the character and its position — a `2` at position 4 in a base-2 number, for instance. Nothing is silently stripped and no answer is invented.
Are very large numbers handled exactly?
Yes. Arithmetic runs on BigInt rather than floating point, so values past 2^53 keep every digit; sixty-four one-bits convert to 18446744073709551615.
Can I paste values with 0x prefixes or underscores in them?
Yes. Spaces and underscores are discarded as digit separators, and the 0b, 0o and 0x prefixes are accepted when they match the base you selected.
Does it show two's complement for negative numbers?
No. A negative value is printed as a minus sign in front of its magnitude, so you will not see the FFFFFFFF a 32-bit debugger shows for −1. Register width is never supplied to the tool.