Subnet Calculator
IPv4 address and prefix length to network, broadcast, host range and count.
Network
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Subnet mask
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Usable hosts
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Broadcast
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Usable addresses
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Mask in binary
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Worked example
192.168.1.10/24 covers 192.168.1.0 to 192.168.1.255. The network address is .0, the broadcast is .255, and 254 addresses are usable — the two excluded ones exist but cannot be assigned to a host.
A subnet mask splits the 32-bit address into a network part and a host part. The prefix length is the number of leading network bits, so /24 means 24 network bits and 8 host bits, giving 256 addresses.
Why two addresses disappear
The all-zeros host part identifies the network itself and the all-ones host part is the broadcast address. Neither can be assigned to an interface. The exceptions are /31, used for point-to-point links where both addresses are usable, and /32, which is a single host.