Calculate subnet masks, CIDR notation, network address, broadcast address, and host ranges for IPv4/IPv6.
Given an IPv4 or IPv6 address with a prefix length, IP Subnet Calculator identifies the containing subnet and expresses its mask, network address, and address span. For IPv4, it also determines the broadcast address and the conventional usable host range between the network and broadcast values. The common surprise is that the entered address need not be the network address. The calculator clears its host bits to find the subnet boundary. IPv6 has no broadcast address, so that IPv4 result does not apply to an IPv6 prefix.
A concrete input and expected output from the current implementation.
Input
192.168.1.130/26
Expected output
Subnet mask: 255.255.255.192 Network CIDR: 192.168.1.128/26 Network address: 192.168.1.128 Broadcast address: 192.168.1.191 Usable host range: 192.168.1.129 - 192.168.1.190
A /26 leaves 6 host bits, so each block contains 2^6, or 64, addresses. The block containing 130 runs from 128 through 191; excluding those two IPv4 boundary addresses leaves 129 through 190, which is 62 conventional host addresses.
An IPv4 /n prefix assigns the first n of 32 bits to the network. Its subnet mask therefore has n leading 1 bits followed by 0 bits. Clearing the address's host bits gives the lowest address in the block. Setting every host bit to 1 gives the highest address, conventionally treated as the subnet's directed broadcast address.
For IPv6, the prefix length divides a 128-bit address into prefix and remaining bits. Clearing or setting the remaining bits establishes the numerical endpoints covered by that prefix: the lowest and highest addresses whose leading bits match the prefix. These endpoints describe the prefix range. They must not be interpreted as IPv4-style network and broadcast reservations because IPv6 does not define broadcast addresses.
The entered IP may be any address inside the subnet. Its prefix determines which leading bits identify the network and which remaining bits vary within the block. Clearing the varying bits produces the network address. Consequently, 192.168.1.130/26 belongs to 192.168.1.128/26 even though the entered address itself ends in 130.
No. The IPv6 addressing architecture defines unicast, anycast, and multicast addresses, but no broadcast address. IPv6 uses multicast for purposes that would commonly involve broadcast in IPv4. Treat an IPv6 prefix's upper endpoint only as the greatest numerical address covered by the prefix, not as a broadcast address or an automatically reserved equivalent.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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