What is a /24 subnet? 256 IPs, the home-network default, and when to use it

How this is calculated

The /24 is ubiquitous because it's simple and fits the vast majority of home and small-office networks. With 254 usable addresses, you can connect every phone, laptop, smart TV, IoT device, and printer in a typical household with room to spare. In CIDR notation, /24 means the first 24 bits of the IP address are the network portion, leaving 8 bits for hosts (2^8 = 256). Moving to a /23 doubles your address space to 510 usable hosts. Moving to a /25 halves it to 126.

Verdict

The /24 math is 256 total addresses minus the network and broadcast reservations, leaving 254 usable hosts, which is what every consumer router ships with by default. The host-side arithmetic (8 bits = 256) maps cleanly to the last octet, which is why the /24 is the mental model every network engineer reaches for first. Step up to a /23 when you cross roughly 200 active devices on the same segment, because the doubling to 510 usable hosts clears the headroom without forcing a second VLAN and the inter-VLAN routing that comes with it.