IPv4 Calculator¶
Input¶
| Field | Accepted formats |
|---|---|
| IP Address | 192.168.1.0, 192.168.1.0/24, 192.168.1.1/255.255.255.0 |
| Netmask | /24, 255.255.255.0, 0.0.0.255 (wildcard) — optional when CIDR is in the IP field |
Result rows¶
| Row | Description |
|---|---|
| Subnet (CIDR) | Network address + prefix length |
| Netmask (CIDR) | Prefix length alone (e.g. /24) |
| Netmask (Octet) | Dotted-decimal subnet mask |
| Wildcard Mask | Inverse of the subnet mask; used in ACLs |
| First Usable IP | First host address (network + 1) |
| Last Usable IP | Last host address (broadcast − 1) |
| Broadcast IP | All-ones host part |
| Usable IPs | Total usable host addresses |
| Address Type | Private / Public / Loopback / Link-local / Multicast / … |
| Reverse DNS Zone | in-addr.arpa zone for the network |
Click any result row to copy its value to the clipboard.
Binary Representation¶
Expand the Binary Representation panel to see:
- Network address in binary (blue = network bits, grey = host bits)
- Subnet mask in binary
- Network address in hexadecimal and unsigned decimal
Subnet Splitter¶
Enter a longer prefix (e.g. /25 to split a /24 into two /25s) and click Split. Results are listed with individual copy buttons and a Copy All / Export ASCII option.
The maximum number of subnets returned is set by $split_max_subnets in config.php (default 256).
Supernet & Route Summarisation¶
Enter one CIDR per line, then choose:
- Find Supernet — the smallest single block enclosing all inputs.
- Summarise Routes — the minimal set of non-overlapping CIDRs covering exactly the listed networks.
IP Range → CIDR¶
Enter a start and end IPv4 address to obtain the minimal set of CIDR blocks covering that range exactly (greedy largest-aligned-block algorithm).
Subnet Allocation Tree¶
Enter a parent CIDR and one or more child CIDRs (one per line). The tool displays a hierarchical tree showing which parts of the parent space are allocated and which are free (gap blocks).