Decimal to Binary Converter

Type a decimal number and get its binary form — 255 becomes 11111111 — with optional grouping into blocks of four bits.

This tool runs entirely in your browser.

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How to use the Decimal to Binary Converter

1Enter one or more numbers, one per line.
2Choose the base you are converting from (or Auto to detect 0x, 0b and 0o prefixes) and the base to convert to.
3Copy the result; turn on digit grouping for easier reading.

What is the Number Base Converter?

Each base uses a different number of digits: binary uses 0 and 1, octal 0–7, decimal 0–9 and hexadecimal 0–9 plus a–f. Hex is popular in programming because one hex digit is exactly four binary digits, so 0xFF is 1111 1111 — one byte.

Numbers are converted with arbitrary-precision integers, so even values larger than 2⁶⁴ convert exactly instead of being rounded, as they would be in a normal calculator. Negative numbers keep their minus sign; fractions are not supported.

Frequently asked questions

How do I convert binary to decimal by hand?

Multiply each digit by its place value (1, 2, 4, 8 … from the right) and add them up: 1011 = 8 + 0 + 2 + 1 = 11.

Does it show two’s complement for negative numbers?

No — negative numbers are shown with a minus sign. Two’s complement depends on the bit width (8, 16, 32 or 64 bits) chosen by a program.

Is the Number Base Converter free and private?

Yes. The Number Base Converter is free, needs no account, and runs entirely in your browser. What you type is never sent to a server or stored.

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