Subnet Calculator
Enter an address with its prefix (like 192.168.1.10/24) to see the network, usable range, broadcast and mask. Split a network into equal subnets, plan subnets by how many devices each needs (VLSM), summarise routes, or work with IPv6.
- IPv4 and IPv6
- Split, VLSM and summarise
- Works in your browser
Subnet mask cheat sheet
| Prefix | Mask | Wildcard | Addresses | Usable hosts | Typical use |
|---|
Quick guide
- /24 (255.255.255.0) is the classic office or home network: 254 devices.
- The first address is the network address and the last is the broadcast; neither can be given to a device. Routers usually take the first usable address.
- /31 point-to-point links use both addresses (RFC 3021), and /32 is a single host.
- Private ranges (RFC 1918): 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. 100.64.0.0/10 is carrier-grade NAT, used by many mobile and Starlink connections.
- VLSM gives each subnet only the size it needs, biggest first, so address space isn't wasted.
IPv6 in a nutshell
- Every normal LAN is a /64, whatever the number of devices; SLAAC and many features need it.
- Home connections usually get a /56 or /48 from the ISP, which is 256 or 65,536 /64 networks.
- fe80::/10 is link-local (every interface has one), fc00::/7 is private (ULA), and 2000::/3 is the public internet.
- Leading zeros in each group can be dropped, and one run of zero groups can be written as
::.