What Is a Subnet Calculator?
A subnet calculator takes an IP address and CIDR prefix length (like 192.168.1.0/24) and computes everything you need to know about that network: the network address, broadcast address, usable host range, subnet mask, wildcard mask, and total number of addresses.
Subnetting is fundamental to network administration. Whether you're carving up a /16 for VLANs in a corporate environment or assigning a /28 to a DMZ in your homelab, getting the math right matters. One wrong bit and traffic goes nowhere.
CIDR Notation Explained
CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length separated by a slash. The prefix length tells you how many of the 32 bits in an IPv4 address are used for the network portion. The remaining bits are for host addresses.
For example, /24 means 24 network bits and 8 host bits, giving you 256 total addresses (254 usable, minus the network and broadcast addresses). A /22 gives you 1,024 total addresses across four /24 blocks.
Common Subnet Sizes
| CIDR | Subnet Mask | Usable Hosts | Typical Use |
|---|---|---|---|
| /30 | 255.255.255.252 | 2 | Point-to-point links |
| /28 | 255.255.255.240 | 14 | Small DMZ or management VLAN |
| /24 | 255.255.255.0 | 254 | Standard LAN segment |
| /22 | 255.255.252.0 | 1,022 | Medium office or campus |
| /16 | 255.255.0.0 | 65,534 | Large enterprise network |
| /8 | 255.0.0.0 | 16,777,214 | Class A (10.x.x.x private) |
How to Use This Tool
Enter any valid IPv4 address with a CIDR prefix (e.g. 10.0.0.0/22) and click Calculate. You can also type just an IP with a subnet mask like 192.168.1.0 255.255.255.0. The tool computes everything instantly in your browser — no data is sent to any server.
Use the quick buttons to jump to common prefix lengths, or click any row in the CIDR cheat sheet at the bottom to calculate that subnet.