Subnet calculator
Enter an IPv4 address with a CIDR prefix (e.g. 192.168.1.10/24) or a subnet mask (e.g. 192.168.1.10 255.255.255.0). Everything is computed in your browser.
Results
- Network address
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- Broadcast address
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- First usable host
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- Last usable host
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- Subnet mask
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- Wildcard mask
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- CIDR notation
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- Total addresses
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- Usable hosts
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- Address type
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Subnets, CIDR and masks explained
A subnet is a slice of a larger network. An IPv4 address has 32 bits; a subnet mask marks how many leading bits are the network portion, leaving the rest for hosts. CIDR notation writes that count after a slash — /24 means the first 24 bits are the network, so 255.255.255.0 is the same thing.
In each subnet, the first address is the network address and the last is the broadcast address; the addresses in between are usable for hosts. That's why a /24 has 256 total addresses but only 254 usable hosts. The wildcard mask is the inverse of the subnet mask and is used in access-control lists.
Working with home or office networks? Most use the private IP ranges like 192.168.0.0/16. See also what an IP address is, reserved address ranges, and how to find your local IP.