Subnet Calculator
Calculates the network address, mask, and address range, splits a network by device count, and merges networks.
You can append the mask to the address: /26, 255.255.255.192, or an inverse mask like 0.0.0.63.
Comma-separated, or one subnet per line; you can put a name before the number.
| Subnet | Devices | Network | Mask | Addresses for devices | Broadcast | Spare |
|---|
One entry per line: a network 10.0.0.0/24, an address 10.0.0.5, or a range 10.0.0.1 - 10.0.0.20.
Enter an address with a mask in any notation: 192.168.1.130/26, 192.168.1.130 255.255.255.192, or with a wildcard mask 0.0.0.63. The calculator shows the network address, the address range for devices, the broadcast address, the mask, and the address type from the IANA special-purpose address registry.
A /31 network has two addresses, and by RFC 3021 both are usable: such networks serve point-to-point links, and there is no broadcast address. Octets with leading zeros, such as 192.168.01.010, are rejected, because programs read this notation inconsistently.
Splitting and merging networks
To split a network, enter it along with the number of devices per subnet. Each subnet gets two service addresses, and subnets are allocated from largest to smallest. If the space is not enough, the calculator names the network mask that would fit the layout.
Merging combines a list of networks, addresses, and ranges into the smallest set of CIDR blocks, for example for an access list or a routing table. The tool also shows the single covering network and how many extra addresses it includes.
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