CIDR Calc
Subnet calculator
CIDR Subnet Calculator
Calculate network details from an IP and prefix length.
How to use ▸▾
Enter an IP and prefix in 192.168.1.0/24 format, then click Calculate.
Examples:10.0.0.0/8 for a large network, 192.168.1.0/30 for only 2 hosts.
Results show network address, broadcast, subnet mask, usable hosts, and IP range.
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How to use the CIDR Calc tool
A CIDR (Classless Inter-Domain Routing) calculator converts an IP address and prefix length into the full set of network details you need to plan or troubleshoot a network: network address, broadcast address, subnet mask, wildcard mask, usable host count, and host range. It is the quickest way to answer questions like how many hosts fit in a /28 or whether two machines are on the same subnet.
- 1 Enter an IP address and prefix length in CIDR notation, for example 192.168.1.0/24.
- 2 Click Calculate or press Enter.
- 3 Read the results: network address, broadcast address, usable hosts, subnet mask, wildcard mask, and the first-to-last usable host range.
Example: 192.168.1.0/24
192.168.1.0/24
Network: 192.168.1.0 Broadcast: 192.168.1.255 Usable hosts: 254 Mask: 255.255.255.0 Wildcard: 0.0.0.255 Range: 192.168.1.1 — 192.168.1.254
CIDR Calc FAQ
What does /24 mean in CIDR notation?
The /24 is the prefix length: the number of bits used for the network portion of the address. A /24 leaves 8 bits for hosts, which gives 256 addresses, 254 of them usable.
How many usable hosts does a subnet have?
Usable hosts = 2^(32 - prefix) - 2. The network address and broadcast address are not usable. For example, /24 gives 254 usable hosts, /30 gives 2, and /31 gives 0 (point-to-point).
What is the wildcard mask used for?
The wildcard mask is the inverse of the subnet mask. It is used by routers and firewalls in access control lists (ACLs) to match ranges of addresses, for example 0.0.0.255 to match any host in a /24 network.
Why do I see the same network from two different IPs?
If two IPs share the same network address after applying the mask, they are on the same subnet and can communicate directly without a router. This calculator makes that check trivial.
