🔢 Number Base Converter
Convert between binary, octal, decimal, hexadecimal — or any base from 2 to 36 — with big-integer support and batch mode.
Digits 0-9 and letters a-z represent values 10-35 (upper or lower case both work).
📦 Batch conversion
📖 Quick reference: 0-15 in four bases
| Decimal | Binary | Octal | Hex | Base 36 |
|---|
Handy shortcut: group binary digits in fours from the right and each group maps straight to one hex digit (1010 = A). Group in threes for octal. That is why hex and binary conversions never need rounding.
Frequently Asked Questions
How do I convert decimal to binary?
Repeatedly divide by 2 and record the remainders, then read them in reverse. For example, 13 ÷ 2 = 6 remainder 1, 6 ÷ 2 = 3 remainder 0, 3 ÷ 2 = 1 remainder 1, 1 ÷ 2 = 0 remainder 1 — reading the remainders bottom-up gives 1101. This tool does the same thing instantly for any base from 2 to 36.
Why are hexadecimal and binary so easy to convert?
Because 16 is a power of 2: each hex digit maps to exactly four binary bits. So 0xA3F becomes 1010 0011 1111 — just expand each hex digit to 4 bits and concatenate. Octal works the same way with 3 bits per digit, which is why the grouping is always exact with no rounding.
How large a number can this converter handle?
There is no practical limit. The conversion uses JavaScript BigInt rather than floating-point numbers, so it stays exact for numbers far beyond 2^53 — the point where ordinary JavaScript arithmetic starts losing precision. Any length of digit string is fine.
What is base 36 used for?
Base 36 (digits 0-9 plus a-z) is the densest base that stays readable with plain alphanumeric characters. It shows up in short URLs, shortened IDs, licence-plate style codes and JavaScript's own Number.prototype.toString(36). Base 32, 60 and 64 are common in encoding work, and base 2, 8, 10 and 16 dominate computer science.
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