CIDR Calculator
Calculate IP range, subnet mask and host count from CIDR notation.
CIDR (Classless Inter-Domain Routing) describes a network range by appending a /prefix to an IP address, e.g. 192.168.0.0/24. This calculator parses your CIDR input and instantly shows the network address, broadcast address, subnet mask, wildcard mask, and the usable host range and count.
Use it as the first step in firewall rules, cloud VPC/subnet design, routing table checks and ACL setup. Everything runs in your browser, so it is fast and private.
/24 network details
| Network address | 192.168.1.0 |
|---|---|
| Broadcast | 192.168.1.255 |
| Subnet mask | 255.255.255.0 |
| Wildcard mask | 0.0.0.255 |
| IP range | 192.168.1.0 - 192.168.1.255 |
| Usable host range | 192.168.1.1 - 192.168.1.254 |
| Total addresses | 256 |
| Usable hosts | 254 |
What each field means
- Network address: the first address of the range, usually not assigned to a host.
- Broadcast address: the last address, reserved for sending to the whole subnet.
- Subnet mask: the bitmask splitting network and host parts (e.g. 255.255.255.0).
- Wildcard mask: the inverted subnet mask, used in Cisco ACLs and OSPF.
- Usable hosts: addresses left for devices after excluding network and broadcast.
Hosts per prefix
/24= 256 addresses (254 usable) — the typical small LAN block/16= 65,536 — large private networks/30= 4 (2 usable) — router point-to-point links/32= 1 — a single host (loopback, allowlist)
Frequently asked questions
Why are usable hosts two fewer than the total?
The network and broadcast addresses are reserved rather than assigned to devices. For example, a /24 has 256 addresses but only 254 usable hosts. /31 and /32 are special cases.
How do subnet mask and wildcard mask differ?
The subnet mask marks network bits as 1; the wildcard mask is its bit-by-bit inverse. OSPF and ACLs often use the wildcard mask.
Does it support IPv6 CIDR?
This tool is IPv4 only. For IPv6 notation, use the IPv6 Compress / Expand tool.
Is my input sent to a server?
No. All calculations run entirely in your browser and nothing is transmitted or stored.
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