CIDR / Subnet Calculator
Paste a network in CIDR notation (e.g. 192.168.1.0/24) — you get the network address, broadcast, usable host range, mask, wildcard, and address type. Below you can split the network into subnets. IPv6 is on a separate tab.
Result
Split into subnets
Pick a prefix longer than the current one — the network splits into equal subnets.
What CIDR is. CIDR (Classless Inter-Domain Routing) is the address/prefix notation, where the prefix is the number of one-bits in the mask. /24 means 24 bits for the network and 8 for hosts, i.e. 256 addresses and 254 usable hosts (minus the network and broadcast addresses). The calculator shows every boundary and splits a network into subnets — the math people usually scribble on paper when planning addressing.
FAQ
How many hosts are in a /24?
A /24 has 256 addresses, but two are reserved — the network address (.0) and broadcast (.255) — so 254 are usable. The general formula: 2^(32−prefix) addresses, minus 2 for hosts (/31 and /32 are special point-to-point cases).
What is a wildcard mask?
It is the inverted subnet mask: where the mask has 0, the wildcard has 1, and vice versa. For /24 the mask is 255.255.255.0 and the wildcard is 0.0.0.255. It is used in Cisco ACLs and rules that specify ranges of "any" bits.
Which ranges are private?
Per RFC 1918 they are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — not routed on the internet, used in local networks. Separately there are 100.64.0.0/10 (CGNAT) and 169.254.0.0/16 (link-local).
How do you split a network into subnets?
Pick a prefix longer than the current one: a /24 split at /26 becomes 4 subnets of 64 addresses each. The calculator shows each subnet's boundaries. The larger the prefix difference, the more subnets you get (2^difference).
Free online CIDR calculator for IPv4 and IPv6. Enter a network in CIDR notation (address/prefix) and the calculator computes the network address, broadcast, first and last usable host, subnet and wildcard masks, total address and host counts, class and address type.
The split mode divides a network into equal subnets of a chosen prefix and shows each one's boundaries — handy for planning addressing, VLANs, and routing. For IPv6 the calculator normalizes the address into compressed and expanded forms and computes the range and address count with big numbers.
Everything runs in the browser; nothing is sent to a server. Useful for network engineers, sysadmins, and developers — to compute a range from CIDR, check whether an address falls within a subnet, or quickly sketch an addressing scheme.