Subnet & CIDR Calculator

Enter an IPv4 address with a prefix (e.g. 192.168.10.0/24) to get the network, broadcast, host range and masks.

Planning multiple IPv4/IPv6 ranges? Use the Network Planner for overlap checks, free gaps, VLSM, cloud reservations and CSV export.

IPv4 address or CIDR

Prefix length

Split into smaller subnets

#	Network	Usable range	Broadcast

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) writes an IPv4 network as an address plus a prefix length, like 10.0.0.0/8. The prefix is the number of leading bits that identify the network; the remaining bits identify hosts. A /24 leaves 8 host bits, so 256 addresses (254 usable).

Usable hosts

Normally the first address is the network address and the last is the broadcast address, so usable hosts = 2^{(32 − prefix)} − 2. Special cases: /31 (point-to-point links, RFC 3021) has 2 usable addresses and /32 is a single host.

Private ranges

Common private IPv4 ranges are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. The calculator labels the address type when it recognises one.