Which addresses belong to a network?
A network like 192.168.1.0/24 is a block of addresses. Enter one to see which addresses your devices can use, how many there are, and what the number after the slash means.
16,777,214 addresses for devices: 203.0.0.1 to 203.255.255.254.
203.0.0.0 names the network and 203.255.255.255 reaches every device at once. Reserved for examples in documentation, like this one.
An IPv4 address has 32 bits. The first 8 name the network and stay the same for every device in it; the last 24 number the devices.
203.0.0.0/8255.0.0.0The same size, written as an address.0.255.255.255The mask flipped, used in router and firewall rules.203.0.0.1203.255.255.254203.255.255.255Click a row to try it with your address.
| Size | Mask | Devices | Typical use |
|---|---|---|---|
| /32 | 255.255.255.255 | One address | a single device or server |
| /31 | 255.255.255.254 | Two addresses | a link between two routers |
| /30 | 255.255.255.252 | Two addresses | a small link with room to spare |
| /29 | 255.255.255.248 | 6 | a small office's public block |
| /28 | 255.255.255.240 | 14 | a small office |
| /27 | 255.255.255.224 | 30 | a floor of an office |
| /26 | 255.255.255.192 | 62 | a guest Wi-Fi |
| /25 | 255.255.255.128 | 126 | half a home network |
| /24 | 255.255.255.0 | 254 | a typical home network |
| /23 | 255.255.254.0 | 510 | a bigger home or school network |
| /22 | 255.255.252.0 | 1,022 | a company building |
| /16 | 255.255.0.0 | 65,534 | a large company or campus |
| /8 | 255.0.0.0 | 16,777,214 | a whole provider or very large company |
One address can be written many ways. Browsers and most programs accept all of them, which is why odd-looking links like http://3232235777/ still open a site.
203.0.113.834058037840xCB00710811001011.00000000.01110001.00001000::ffff:203.0.113.8::ffff:cb00:71088.113.0.203.in-addr.arpacurl ip5.io/subnet-calculator/192.168.1.0/24 curl "ip5.io/subnet-calculator/2001:db8::/48?format=json"
Worked out in your browser. Nothing you enter is stored.
An IPv4 address has 32 bits. The number after the slash says how many of them name the network; the rest number the devices in it. /24 leaves 8 bits for devices: 256 addresses, 254 of them usable.
The same thing written as an address. 255.255.255.0 is /24: the 255s cover the network part, the 0 the device part. Older settings screens ask for the mask, newer ones for the number after the slash.
The first one names the network itself, and the last one is the broadcast address, which reaches every device at once. The exceptions are /31, used for links between two routers, and /32, a single address. IPv6 has no broadcast, so it uses every address.
192.168.0.0/16, 10.0.0.0/8 and 172.16.0.0/12 are set aside for private networks. Every home can use them, because they never appear on the internet: your router shares one public address for all of them.
Only if their network parts match. With /24, 192.168.1.20 and 192.168.1.200 are on the same network; 192.168.1.20 and 192.168.2.20 are not, and need a router between them.