Binary to Decimal Converter - Fast and Easy Conversion

How binary-to-decimal conversion works

Binary is base 2: every digit position is worth double the one to its right, starting at 2⁰ on the far right. To read a binary number as decimal, multiply each digit by its positional value and add the results. For 1010: 1×8 + 0×4 + 1×2 + 0×1 = 10. Enter 1010 in the box above and the tool returns 10 — that's the exact calculation it runs, via JavaScript's parseInt(input, 2).

Input rules

The field only accepts strings made up of the characters 0 and 1 — a regex check (/^[01]+$/) rejects anything else, including spaces, negative signs, or a leading "0b" prefix, and shows an error instead of a result. There's no support for two's-complement negative binary or binary fractions (e.g. 101.1); this converts unsigned whole numbers only.

Reference values

A few binary/decimal pairs worth knowing by heart if you work with bytes: 11111111 = 255 (the max value of a single byte), 10000000 = 128, and 100000000 = 256. Leading zeros don't change the result — 0010 and 10 both convert to 2.