Number Systems

Decimal & Binary Converter

Convert either way as you type, see exactly how the answer is built, then test yourself in quiz mode.

Exact big-integer math Hex & octal too Built-in quiz

Decimal (base 10)

Binary (base 2)

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Hexadecimal

Octal

Bit length

Bytes (padded)

Big numbers are exact Conversion runs on BigInt, so a 200-digit value converts without the rounding errors parseInt would introduce past 2⁵³.

Fractions and negatives Both are supported. A fraction is expanded to 24 binary places (or until it terminates); a negative value keeps a leading minus rather than being encoded as two's complement.

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