The /27 subnet
A /27 subnet uses the mask 255.255.255.224 and holds 32 addresses, 30 of them usable.
A /27 splits a /24 into smaller pieces: 32 addresses and 30 usable hosts, with the mask 255.255.255.224. It is a tidy size for a small VLAN, a DMZ, or a rack of servers.
Right-sizing a subnet to a /27 avoids wasting a full /24 on a handful of hosts. The wildcard mask 0.0.0.31 is the form you use in access lists and firewall rules to match this range.
Below you can see the exact network, broadcast, and host range for any /27 you enter, calculated instantly in your browser.
Calculate a /27 network
Accepts CIDR (192.0.2.0/24), IP + mask (192.0.2.0 255.255.255.0), or a bare IP (defaults to /24).
11000000.00000000.00000010.0000000011111111.11111111.11111111.11100000Example: 192.0.2.0/27
Taking 192.0.2.0/27 as a worked example, the block breaks down like this:
| Network address | 192.0.2.0 |
|---|---|
| Usable range | 192.0.2.1 - 192.0.2.30 |
| Broadcast address | 192.0.2.31 |
| Total addresses | 32 |
| Usable hosts | 30 |
| Size | 1/8 of a class C block |
Frequently asked questions
What is the subnet mask for a /27?
A /27 uses the subnet mask 255.255.255.224. Its wildcard mask, used in access lists, is 0.0.0.31.
How many hosts are in a /27 subnet?
A /27 has 32 total addresses and 30 usable hosts (the total minus the network and broadcast addresses, except for /31 and /32).
What is a /27 used for?
Small subnet. It is equivalent to 1/8 of a class C block.
How do I calculate a /27 network?
Set the host bits to zero for the network address and to one for the broadcast address. The calculator on this page does it for any /27 block you enter.