Broadcast Address Calculator
Find the highest address in a traditional IPv4 subnet instantly. The calculator also shows the matching network address, subnet mask and conventional usable host range.
How to calculate a broadcast address
A traditional IPv4 broadcast address is found by setting every host bit in the subnet to one. It is therefore the final address in that CIDR block.
For 192.168.1.0/24 the broadcast address is 192.168.1.255. For 192.168.1.0/26 it is 192.168.1.63.
Broadcast calculation example
For 10.0.5.70/27, /27 blocks contain 32 addresses. The address belongs to the 64–95 block, so the network is 10.0.5.64 and the broadcast address is 10.0.5.95.
Broadcast vs last usable IP
In a conventional IPv4 subnet, the broadcast address is the final address in the block and the last usable host address is one lower. For a /24 ending at .255, the conventional last usable host is .254.
Special cases: /31 and /32
A /31 is commonly used for point-to-point links under RFC 3021, where both addresses can be endpoints rather than network/broadcast identifiers. A /32 represents a single IPv4 address.
What this calculator shows
The result panel reports the canonical network address, broadcast address, first and last conventional usable addresses, dotted-decimal subnet mask, wildcard mask, total IPv4 address count and usable-host count. The live 32-bit boundary updates with the CIDR prefix, so the relationship between prefix length, block size and address capacity is visible instead of hidden behind a static table.
How to read the result correctly
The calculator normalizes the IP address you enter to the network block that contains it. That means an input such as 192.168.1.42/24 correctly resolves to network 192.168.1.0/24. For prefixes /0 through /30, conventional IPv4 subnetting reserves the first address as the network identifier and the final address as broadcast. /31 and /32 have different practical semantics, so their address counts should not be interpreted with the ordinary “subtract two” rule.
Related subnet tools
You can also use the subnetting cheat sheet for a complete IPv4 prefix reference, browse individual CIDR prefix pages, try the IPv6 subnet calculator, or return to the main visual subnet calculator.
Frequently asked questions
What is a broadcast address?
It is traditionally the final address of an IPv4 subnet, with all host bits set to 1.
How do I find the broadcast address?
Find the network address and set every host bit to 1, or take the bitwise OR of the network address with the wildcard mask.
Can I assign the broadcast address to a device?
In conventional IPv4 LAN subnetting, no. The broadcast address is reserved for subnet-wide broadcast traffic.