tools / subnet calculator
Subnet calculator
Convert CIDR notation into everything you need for network planning. Calculated instantly in your browser — nothing is sent to a server.
CIDR in 30 seconds
An IPv4 address is 32 bits. CIDR notation like 192.168.1.0/24 says the first 24 bits identify the network and the remaining 8 bits identify hosts inside it. Fewer prefix bits mean a bigger network: a /16 holds 65,536 addresses, a /24 holds 256, a /30 holds just 4.
The calculator shows the derived values network engineers actually use: the netmask (for interface configuration), the wildcard mask (for ACLs on Cisco-style gear), the broadcast address, and the usable host range once the network and broadcast addresses are excluded.
Common questions
What does /24 actually mean?
The number after the slash is how many bits of the address are fixed as the network part. A /24 fixes the first 24 bits (three octets), leaving 8 bits — 256 addresses — for hosts, of which 254 are usable.
Why are two addresses not usable?
The first address of a subnet is the network address itself and the last is the broadcast address. Neither can be assigned to a device (except in /31 point-to-point links, which are a special case).
Which private ranges can I use at home?
Three ranges are reserved for private networks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Home routers typically use 192.168.0.0/24 or 192.168.1.0/24.