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Subnet Calculator Validator🔒 100% local
Calculate subnet ranges. Privacy-first, no server uploads, no tracking.
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Turns a CIDR block such as 192.168.1.0/24 into the network address, netmask, broadcast address, wildcard mask, first and last usable host, usable host count, the RFC 1918 category and the binary netmask. Give it an address with no prefix and it assumes /24.
How to use it
- Enter a block as address/prefix, for example 192.168.1.10/24, or just an address.
- Press Process; the figures appear in the Output panel in labelled rows.
- Read the usable range rather than the total address count when the number of assignable hosts is what you need.
- Copy the block if you are documenting the subnet elsewhere.
Worked example
192.168.1.0/24becomesInput: 192.168.1.0/24
Network: 192.168.1.0/24
Netmask: 255.255.255.0 (/24)
Broadcast: 192.168.1.255
Wildcard: 0.0.0.255
Usable range: 192.168.1.1 – 192.168.1.254
Usable hosts: 254
Total addresses: 256
IP class: private (RFC 1918 192.168/16)
Binary netmask: 11111111.11111111.11111111.00000000
First address 192.168.1.0 belongs to the network address itself.10.0.0.5/30becomesInput: 10.0.0.5/30
Network: 10.0.0.4/30
Netmask: 255.255.255.252 (/30)
Broadcast: 10.0.0.7
Wildcard: 0.0.0.3
Usable range: 10.0.0.5 – 10.0.0.6
Usable hosts: 2
Total addresses: 4
IP class: private (RFC 1918 10.0.0.0/8)
Binary netmask: 11111111.11111111.11111111.11111100
First address 10.0.0.4 belongs to host range.Entering a host address makes the closing line wrong: 10.0.0.4 is the network address, yet it is reported as belonging to the host range.
When to use it
- Sizing a new VLAN and checking how many usable addresses a /26 leaves once the network and broadcast addresses are taken out.
- Turning a host address out of a log line into the network it sits in.
- Checking a netmask by eye against its binary form before typing it into a device.
What it does not do
- IPv4 only. An IPv6 prefix is rejected by the format check with an unrecognized-format error.
- Omit the prefix and it silently assumes /24, so 1.2.3.4 and 1.2.3.4/24 give identical output.
- The closing line compares the network address with the string you typed, so entering a host address makes it claim the network address belongs to the host range.
- The near-identical ipv4-subnet-calculator on this site reports the IPv4 class letter and the binary network address instead; this tool reports the RFC 1918 category and the usable host range.