Number Base Converter
Convert any whole number from base 2 to 36, with binary, octal, decimal and hexadecimal visible together.
- Fewer clicks, keyboard friendly
- Features others lock behind paywalls
- More accurate results
Updates as you type
The standard four bases and your extra base appear together.
All representations
Spaces make groups easier to scan; Copy uses the unspaced value.
How to use
- Enter a whole number, then choose the base it is currently written in.
- Read the live binary, octal, decimal and hexadecimal representations together.
- Choose any base from 2 through 36 for one additional representation.
- Copy any ungrouped result for code, a worksheet or a spreadsheet.
What a base means
A positional number system uses powers of its base. Decimal uses digits 0–9 and powers of 10; binary uses 0 and 1 with powers of 2. For example, 101101₂ is 1×2⁵ + 0×2⁴ + 1×2³ + 1×2² + 0×2¹ + 1×2⁰ = 45₁₀. Hexadecimal uses 0–9 and A–F, so FF₁₆ is 15×16 + 15 = 255₁₀.
Exact integers, not floating-point approximations
This converter handles whole numbers with JavaScript BigInt rather than a JavaScript Number. A Number cannot represent every integer above 2⁵³−1 (9,007,199,254,740,991) exactly; BigInt keeps every digit exact. To keep the browser responsive, one entry is limited to 10,000 digits. Results use uppercase A–Z for digit values 10–35, which is the conventional notation for bases through 36.
Input rules
Spaces and underscores are accepted as visual separators, so 1111 1111 and 1111_1111 are both valid binary input. A leading minus sign is supported. Standard prefixes also work when they match the selected base: 0b for binary, 0o for octal and 0x for hexadecimal. The converter deliberately rejects non-ASCII lookalike digits and invalid characters instead of removing them, because silently changing a pasted value can hide an error.
Frequently asked questions
How do I convert binary to decimal?
Multiply each binary digit by its matching power of 2 and add the results. For example, 101101₂ = 1×2⁵ + 1×2³ + 1×2² + 1×2⁰ = 45₁₀; this converter performs that expansion exactly for up to 10,000 input digits.
What is 11111111 in decimal?
11111111₂ equals 255₁₀. Its eight set bits add 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1, and it is the largest unsigned value that fits in 8 bits.
Can I convert hexadecimal to binary?
Yes. Choose base 16 as the input base and enter the hexadecimal value. Each hexadecimal digit corresponds to exactly 4 binary digits, so FF₁₆ becomes 11111111₂.
What bases does this converter support?
This converter accepts whole-number bases from 2 through 36. Bases above 10 use A through Z for digit values 10 through 35, and it always shows bases 2, 8, 10 and 16 alongside your selected extra base.
Why is a very large number different in another calculator?
Some calculators use floating-point numbers, which cannot represent every integer above 9,007,199,254,740,991 exactly. This converter uses BigInt for whole-number input, so values up to 10,000 digits are converted without that rounding limit.
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Updated 2026-10-15