Subnet splitter
Split an IPv4 block into equal subnets: by prefix length, by how many subnets you need, or by hosts per subnet. IPv6 works too.
Subnets
Example: type your own block above.
| # | Subnet | First usable | Last usable | Broadcast |
|---|---|---|---|---|
| 1 | 192.0.2.0/26 | 192.0.2.1 | 192.0.2.62 | 192.0.2.63 |
| 2 | 192.0.2.64/26 | 192.0.2.65 | 192.0.2.126 | 192.0.2.127 |
| 3 | 192.0.2.128/26 | 192.0.2.129 | 192.0.2.190 | 192.0.2.191 |
| 4 | 192.0.2.192/26 | 192.0.2.193 | 192.0.2.254 | 192.0.2.255 |
- #
- 1
- Subnet
- 192.0.2.0/26
- First usable
- 192.0.2.1
- Last usable
- 192.0.2.62
- Broadcast
- 192.0.2.63
- #
- 2
- Subnet
- 192.0.2.64/26
- First usable
- 192.0.2.65
- Last usable
- 192.0.2.126
- Broadcast
- 192.0.2.127
- #
- 3
- Subnet
- 192.0.2.128/26
- First usable
- 192.0.2.129
- Last usable
- 192.0.2.190
- Broadcast
- 192.0.2.191
- #
- 4
- Subnet
- 192.0.2.192/26
- First usable
- 192.0.2.193
- Last usable
- 192.0.2.254
- Broadcast
- 192.0.2.255
How it works
Splitting a block means cutting it into equal, smaller blocks. Each extra prefix bit doubles the number of subnets and halves their size. For example, 192.0.2.0/24 splits into two /25s, four /26s or eight /27s.
Asking for a number of subnets rounds up to the next power of two, because subnets only come in those sizes: 5 subnets of a /24 become 8 /27s. Asking for hosts per subnet picks the smallest block that fits. On IPv4, that includes the network and broadcast addresses, so 50 hosts need a /26 (62 usable).
On IPv6, each LAN should be a /64, because SLAAC (how devices give themselves an address) needs 64 host bits. A site usually gets a /48 (65,536 LANs) and a home often a /56 (256 LANs). Prefixes that are a multiple of 4 keep subnet numbers on whole hex digits, which makes them easier to read.
When subnets need different sizes, use the VLSM calculator. To check one subnet in detail, use the subnet calculator.