Free tool
NetworkingBroadcast Address Calculator
Free broadcast address calculator for CCNA students and network admins. Find the IPv4 broadcast from an IP plus CIDR or subnet mask, and see why hosts cannot use it.
Runs in your browser — your data stays on your device
Free toolThe broadcast address is the last address in an IPv4 subnet. Frames sent there reach every host in that broadcast domain, which is why you must never assign it to a PC, printer, or server. This free broadcast address calculator finds that address from any IP in the subnet plus a CIDR prefix or mask, and it states clearly that the broadcast cannot be a host assignment. In our labs, that single reminder prevents a surprising number of “interface is up but nobody replies” tickets.
How to use the Broadcast Address Calculator
- 1
Enter an IPv4 address that sits somewhere in the subnet.
- 2
Enter the matching CIDR prefix or dotted subnet mask.
- 3
Read the broadcast address, then compare it with the network ID and usable host range.
Why broadcast addresses still trip people up
On paper the rule is simple: last address equals broadcast. Under exam time pressure, students swap network and broadcast, or they treat .255 as always correct even on a /26. Network engineers meet the same confusion when documenting DHCP exclusions. Practising broadcast calculation with CIDR notation builds the reflex you need for Cisco networking questions and for clean network administration on home or office LANs.
IPv4 broadcast example
For 192.168.10.20/26 the broadcast is 192.168.10.63, not 192.168.10.255. The network is 192.168.10.0 and usable hosts run 192.168.10.1-192.168.10.62. If you assigned .63 to a host, you would collide with traffic meant for the entire subnet.
Guides and next steps
Privacy note
Broadcast calculations run locally in your browser with no server upload.
Frequently asked questions
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