CIDR / Subnet Calculator
Enter a CIDR block to get the network, broadcast, netmask, wildcard and usable host range.
Network address
192.168.1.0/24
Netmask
255.255.255.0
Wildcard mask
0.0.0.255
Broadcast address
192.168.1.255
First host
192.168.1.1
Last host
192.168.1.254
Total addresses
256
Usable hosts
254
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A CIDR block like a slash-24 hides the details you actually need to plan a network: the first and last address, the mask, and how many hosts fit. Enter a CIDR and this works out the network and broadcast addresses, the netmask, and the usable host range in one go.
How to use: CIDR Calculator
- 1Enter inputType a CIDR such as 192.168.1.0/24.
- 2Set optionsRead the network and broadcast addresses.
- 3ProcessCheck the netmask and wildcard mask.
- 4Get resultSee the first/last host and host count.
Common use cases
Plan a subnetSee how many usable addresses a block gives you before you carve up a network.
Check an IP is in rangeConfirm whether an address falls inside a given CIDR block.
Write firewall rulesGet the exact address range a rule will cover so you do not allow more than you mean to.
Split a networkWork out the boundaries when dividing a block into smaller subnets.
Good to know
Smaller slash, bigger networkA smaller prefix number covers more addresses; a slash-24 holds far more than a slash-30. It is easy to read this backwards.
Network and broadcast are reservedThe first and last addresses of a block are usually the network and broadcast, so in IPv4 the usable host count is two fewer than the total.
IPv4 and IPv6 differIPv6 is vast and has no broadcast address the way IPv4 does, so host-count rules of thumb from IPv4 do not carry over.
Double-check before you applyA calculator gets the maths right, but confirm the block matches your actual routing and firewall intent before you commit it.