Subnet Calculator
Enter an IPv4 address with a CIDR prefix to see the network details. Everything is computed in your browser.
| Network address | |
|---|---|
| Broadcast address | |
| Subnet mask | |
| Wildcard mask | |
| First usable host | |
| Last usable host | |
| Total addresses | |
| Usable hosts |
How to work out a subnet
- Type an IPv4 address with a CIDR prefix into the “IPv4 address / CIDR” field, for example 192.168.1.10/24.
- The results table fills in as you type: network and broadcast addresses, plus the subnet and wildcard masks.
- Read the first and last usable host, and the usable host count, to see the range you can assign.
- Check “Total addresses” for the full size of the block.
When to use it
Reach for it when planning or documenting a network: work out which addresses a /24 or a /26 covers, where the usable range starts and ends, and how many hosts fit, before you settle on a prefix.
It also helps when reading configuration written in CIDR. Paste a block from a firewall rule, a router config, or an ACL to see its exact boundaries. The wildcard mask is the form some tools expect, such as Cisco ACLs, which want it instead of a subnet mask.
Frequently asked questions
Is the IP address I enter sent anywhere?
No. The subnet math is plain 32-bit arithmetic done in your browser. The address never leaves the page, which matters when you’re working with internal network ranges.
What does the calculator show for a CIDR block?
The network and broadcast addresses, subnet mask, wildcard mask, first and last usable host, total address count, and usable host count.
Why do /31 and /32 show no usable hosts?
Those blocks have no room for a separate network and broadcast address plus hosts: /32 is a single host route and /31 is a point-to-point pair, so the tool reports no conventional host range for them.
Does it support IPv6?
No, this calculator is IPv4 only. It accepts any prefix from /0 to /32 in standard dotted-quad/prefix notation.
Why is the usable host count two less than the total?
In a conventional subnet, the lowest address is the network address and the highest is the broadcast address, leaving the rest assignable to hosts.