Guide
Finding network and broadcast addresses for a list of hosts
Setting up a DHCP scope, writing a firewall rule or auditing an inventory often means working out the same three values for many hosts: the network a host belongs to, the broadcast address of that network and the range of addresses in between. This page does it for a whole list at once, one address per line, each with its own prefix or mask.
The two rules
Every IPv4 network is defined by an address and a mask. The network address is the lowest address in the block: AND the host address with the mask. The broadcast address is the highest: take the network address and set every host bit to one, which is the same as ORing it with the wildcard mask (the mask inverted). Every address between them, exclusive, is usable by hosts. The count of usable hosts is the block size minus two, so a /26 with 64 addresses has 62. Classless prefixes of this kind are described in RFC 4632.
Input format
Type each host as address/prefix or address/dotted-mask, for example 10.20.30.40/255.255.0.0, one per line, or use the sample. Mixed styles on different lines are fine. The result table repeats your input, then gives the network in CIDR form, the broadcast address, the number of usable hosts and the host range. A button copies the table as tab-separated values, which pastes cleanly into a spreadsheet. A line that is not an IPv4 address with a prefix or mask produces an error message that quotes it.
The special cases
A /32 is a single host: network and broadcast are the same address and nothing is reserved. A /31 has two addresses and, under RFC 3021, both are usable on a point-to-point link; the page shows “none” for the broadcast address. A /30 is the classic point-to-point size with two usable hosts and two reserved. For ordinary networks, remember that the first and last address are never assigned to hosts, so a DHCP pool must stay inside the host range column.
A worked example
The sample has five lines. 192.168.1.130/26 is in the network 192.168.1.128/26 with broadcast 192.168.1.191, 62 usable hosts, from 192.168.1.129 to 192.168.1.190. 10.20.30.40/255.255.0.0 gives 10.20.0.0/16, broadcast 10.20.255.255, 65,534 hosts. 172.16.5.9/20 gives 172.16.0.0/20, broadcast 172.16.15.255, 4,094 hosts. 203.0.113.77/30 gives 203.0.113.76/30 with broadcast 203.0.113.79 and the two hosts .77 and .78. 192.168.100.1/31 gives 192.168.100.0/31, no broadcast, and two usable addresses.
Limits
IPv4 only. The page calculates from the text you provide: it does not discover your real network, so a wrong mask on a line gives a wrong block without warning. It also cannot tell whether a router will forward directed broadcasts. If you need one network in detail, with wildcard mask and binary view, use the Subnet Calculator.
Using the result in practice
The host range column is what you need for a DHCP scope. For the sample network 192.168.1.128/26, the usable range is 192.168.1.129 to 192.168.1.190. A common layout gives the router the first address, 192.168.1.129, reserves a few addresses after it for printers and servers with fixed addresses, and hands the rest to DHCP. Firewall rules and routing statements need the network and prefix, while the broadcast address matters mainly for diagnostics and for tools such as Wake-on-LAN that send a directed broadcast.
Related tools
- Subnet Calculator shows a single network with all derived values.
- CIDR to IP Range lists the first and last address of blocks.
- Wildcard Mask Calculator produces the inverse mask used to find the broadcast.
- Private IP Checker tells you which of your addresses are private or reserved.
Checked against the current version of the Broadcast Address Calculator on .