IP address to binary

Type an IPv4 address, or several, one per line. Each comes out as four groups of 8 bits, and a /prefix on the end is kept. The working shows how each number splits into place values, and the rows give the same address as one 32-bit number, a decimal integer and hex, with the kind of range it's in.

Swap the boxes to go the other way: four groups of up to 8 bits with dots or spaces between, or 32 bits in a row.

An IPv4 address is 32 bits. Written the usual way, it's split into four bytes of 8 bits, and each byte is written as a decimal number from 0 to 255. Converting to binary undoes that, one byte at a time.

Each of the 8 bits has a place value: 128, 64, 32, 16, 8, 4, 2 and 1. To convert a number, go along from 128 and take each value that still fits, subtracting it as you go. Every value you take is a 1, every value you skip a 0.

Take 192.168.1.10. 192 is 128 + 64, so 11000000. 168 is 128 + 32 + 8, so 10101000. 1 is just the last place: 00000001. 10 is 8 + 2: 00001010.

Put together, 192.168.1.10 is 11000000.10101000.00000001.00001010. Each group keeps its leading zeros, so every group is exactly 8 bits and the whole address is 32.

Subnetting happens in binary. A /24 means the first 24 bits name the network, and 255.255.255.0 is that written as a mask: 24 ones, then 8 zeros. The network address is the address ANDed with the mask, bit by bit. The subnet calculator shows that AND for any address and prefix.