SubnetKit › /27 Subnet Calculator
/27 Subnet Calculator: how it works
A /27 gives you 32 addresses and 30 usable hosts. It is the sweet spot for a small team's VLAN, a guest Wi-Fi segment or a rack of management interfaces, and it appears constantly in certification exams because its boundaries are easy to get wrong.
SubnetKit shows the correct network and broadcast for whatever address you type, in the browser and at no cost. The calculator is preloaded with 192.168.1.0/27 below.
Worked example: 192.168.1.0/27
- Subnet mask: 255.255.255.224 (binary last octet 11100000)
- Wildcard mask: 0.0.0.31
- Network: 192.168.1.0
- Usable hosts: 192.168.1.1 – 192.168.1.30
- Broadcast: 192.168.1.31
- Total / usable: 32 / 30
The block size is 32, so every /27 in a /24 starts at a multiple of 32: 192.168.1.0, .32, .64, .96, .128, .160, .192 and .224. That is 8 subnets × 30 hosts = 240 usable addresses, compared with 254 for the undivided /24.
Finding which /27 an address belongs to
Take the last octet and divide by 32, discarding the remainder. For 192.168.1.77: 77 ÷ 32 = 2 remainder 13, so the address sits in block number 2, which starts at 2 × 32 = 64. The subnet is therefore 192.168.1.64/27, hosts run from .65 to .94 and the broadcast is .95.
Try the same with 192.168.1.200: 200 ÷ 32 = 6, block start 192, so 192.168.1.192/27 with hosts .193–.222 and broadcast .223. Typing either address into SubnetKit with prefix /27 returns these values immediately, and the binary view highlights the three borrowed bits that make the /27 distinct from the /24.
Frequently asked questions
How many hosts does a /27 have?
30 usable hosts out of 32 addresses. The remaining two are the network and broadcast addresses.
What is the subnet mask for a /27?
255.255.255.224. The wildcard mask is 0.0.0.31.
How many /27 subnets are in a /24?
Eight, starting at .0, .32, .64, .96, .128, .160, .192 and .224.
When should I use a /27 instead of a /28?
Choose /27 when a segment needs between 15 and 30 devices. A /28 only offers 14 usable hosts, and growing past it later means re-addressing.
Looking for the full guide, tips and the complete FAQ? Read the main SubnetKit page.