| IP Address | |
| Network Address | |
| Subnet Mask | |
| Wildcard Mask (Cisco ACL) | |
| Broadcast Address | |
| First Usable Host | |
| Last Usable Host | |
| Total Addresses | |
| Usable Host Addresses | |
| CIDR Notation | |
| IP Class | |
| Private Range |
| CIDR | Subnet Mask | Wildcard | Total IPs | Usable Hosts | Common Use |
|---|
Click any row to calculate that CIDR using your entered IP address.
Enter an IPv4 address and select the CIDR prefix that matches the network you want to analyse. The calculator returns the network address, subnet mask, wildcard mask, broadcast address, first usable host, last usable host, total addresses and usable host count.
Use the result when checking whether a device has the correct IP settings, preparing DHCP scopes, documenting VLANs or validating firewall rules. For example, 192.168.10.25/24 belongs to the 192.168.10.0 network, while 192.168.10.25/27 belongs to a smaller 32-address block.
The wildcard mask is included because Cisco ACLs and some routing configurations use wildcard notation instead of subnet mask notation. A /24 subnet mask of 255.255.255.0 becomes a wildcard mask of 0.0.0.255.
What is a CIDR prefix? CIDR is the slash number after an IP address, such as /24 or /30. It tells you how many bits are used for the network portion of the address.
Why are usable hosts fewer than total addresses? In most IPv4 subnets, the first address is the network address and the last address is the broadcast address. Those two addresses are not assigned to normal hosts.
When should I use /30 or /31? A /30 is common for point-to-point links with two usable addresses. A /31 can be used in supported point-to-point environments, but it should only be used when the network equipment supports it.
About the Subnet Calculator
Subnetting is the process of dividing a larger IP network into smaller, more manageable segments. Every IPv4 address consists of a network portion and a host portion. The CIDR prefix (the number after the slash) tells you how many bits belong to the network. A /24 means 24 bits are the network, leaving 8 bits for hosts, giving 256 addresses (254 usable after reserving the network and broadcast addresses).
This calculator takes any IPv4 address and CIDR prefix and instantly computes all the values you need: the network address (the first address in the subnet), broadcast address (the last), first and last usable host addresses, subnet mask in dotted decimal, wildcard mask for Cisco ACLs, total address count and usable host count. The binary subnet mask display shows exactly which bits are network bits (1s) and which are host bits (0s), which is essential for understanding subnetting rather than just copying numbers.
Worked Examples
Input: 192.168.1.0/24
Network: 192.168.1.0
Broadcast: 192.168.1.255
First host: 192.168.1.1
Last host: 192.168.1.254
Hosts: 254 usable
Input: 10.0.0.0/30
Network: 10.0.0.0
Broadcast: 10.0.0.3
Hosts: 2 usable (point-to-point)
Wildcard: 0.0.0.3
Common Use Cases
- Network design and planning. Calculate the right subnet size for each network segment before configuring routers and switches. Use the host count to pick the smallest subnet that fits your requirements.
- Cisco ACL configuration. Get the correct wildcard mask for any subnet to use in access-list statements without manual binary arithmetic under pressure.
- CCNA and CCNP study. Subnetting is tested extensively in Cisco certification exams. Use the binary mask display to understand the underlying bit operations, not just memorise the answers.
- Troubleshooting connectivity. Verify that two IP addresses are in the same subnet by calculating both network addresses and checking they match.
- Documentation. Generate complete subnet details for network documentation, IP address management (IPAM) records and change request forms.