About this tool
Binary (base-2) represents numbers using only 0 and 1, where each position is a power of two. Decimal (base-10) is the notation people read. Converting from binary to decimal means summing the place values of every 1 bit: 1010 is 8 + 2 = 10.
Paste a binary string and the decimal value updates as you type. Choose unsigned to read the bits as a plain non-negative number, or signed to interpret them as two's complement at the selected width (8, 16, 32 or 64 bits) — where a leading 1 marks a negative value. The tool validates that the input contains only 0 and 1 and fits the chosen width.
Conversion runs locally — nothing you enter is uploaded.
Frequently asked questions
What is two's complement?
It's the standard way computers store signed integers. In an N-bit two's-complement number the most significant bit has negative weight, so 11111111 in 8 bits is −1 rather than 255. Pick the signed option and a width to read values this way.
How wide can the input be?
Unsigned conversion handles arbitrarily long binary strings exactly. For signed interpretation the input must fit the chosen bit width, since two's complement is defined relative to a fixed number of bits.
Can I convert decimal back to binary?
Yes — use the decimal to binary converter, which supports the same signed and fixed-width options.