Hosts Per Subnet Calculator – Usable IP Addresses
Calculate usable host addresses in any subnet from CIDR prefix.
About This Calculator
Calculate usable host addresses in any subnet from CIDR prefix. Use the calculator above for instant results.
Worked Examples
Example 1: /24
- 256 total | 254 usable
Answer: 254 hosts
Example 2: /22
- 1,024 total | 1,022 usable
Answer: 1,022 hosts
Example 3: /30
- 4 total | 2 usable (router link)
Answer: 2 hosts
Who Uses This Calculator?
Network Engineers
IP space planning.
IT Admins
Right-size subnets.
CCNA Students
Subnetting exam prep.
CS Students
Networking coursework.
Common Mistakes to Avoid
❌ Always -2 for network and broadcast
Network address and broadcast address are not usable. /24 has 256 addresses but 254 hosts.
❌ Plan for growth
Add 50-100% growth buffer. Renumbering a live network is painful.
Frequently Asked Questions
Hosts by prefix?
/30=2, /29=6, /28=14, /27=30, /26=62, /25=126, /24=254, /23=510, /22=1022.
Right-size subnets?
Start with hosts needed, find smallest prefix >= that count. Add buffer for growth.
IPv6?
IPv6 /64 has 2^64 addresses — practically unlimited. Different conventions apply.