IPv4 CIDR Calculator (Range & Host Details)
Enter a CIDR block such as 192.168.10.25/24 or 10.0.0.0/8 to compute its full network range.
Format: IPv4 address + slash prefix (0 to 32).
What a CIDR range calculator does
A CIDR calculator tells you exactly how big a network is and what addresses it contains. If you work with routers, cloud VPCs, firewalls, VPNs, or even home labs, this saves time and prevents painful addressing mistakes.
Given one input like 192.168.1.10/24, a good calculator should return:
- Network address
- Broadcast address
- Subnet mask and wildcard mask
- First and last usable host
- Total addresses and usable hosts
Quick CIDR refresher
CIDR stands for Classless Inter-Domain Routing. The number after the slash is the prefix length, which tells you how many bits are fixed for the network portion.
- /24 means 24 network bits and 8 host bits
- /16 means 16 network bits and 16 host bits
- /30 means 30 network bits and 2 host bits
As the prefix increases, subnets become smaller. As the prefix decreases, subnets become larger.
Common prefix sizes
| Prefix | Subnet Mask | Total Addresses | Typical Use |
|---|---|---|---|
| /32 | 255.255.255.255 | 1 | Single host route |
| /30 | 255.255.255.252 | 4 | Legacy point-to-point links |
| /24 | 255.255.255.0 | 256 | Small LAN segment |
| /16 | 255.255.0.0 | 65,536 | Large private network area |
| /8 | 255.0.0.0 | 16,777,216 | Very large private allocation |
How to read the calculator output
Network address
This is the first address in the block and identifies the subnet itself, not a host.
Broadcast address
This is the last address in the block. In traditional IPv4 subnetting, this is reserved for broadcast traffic (except special handling in some cases like /31 links).
Usable host range
For most subnets, usable hosts exclude the network and broadcast addresses. Two exceptions are important:
- /31 networks are commonly used for point-to-point links and can use both addresses.
- /32 represents a single host address.
Practical examples
Example 1: 192.168.50.14/24
This belongs to network 192.168.50.0/24. Range is 192.168.50.0 to 192.168.50.255, with host IPs usually from 192.168.50.1 to 192.168.50.254.
Example 2: 10.20.30.40/20
A /20 mask groups addresses in blocks of 16 in the third octet. This address falls in 10.20.16.0/20, which spans to 10.20.31.255.
Example 3: 203.0.113.7/32
This is exactly one IP. Network, broadcast, first host, and last host are all the same address.
Why CIDR range planning matters
IP conflicts, route overlap, and accidental broad firewall rules are often caused by poor subnet planning. A CIDR range calculator helps you avoid these issues before deployment.
- Prevents overlapping subnets in hybrid cloud environments
- Improves firewall and ACL accuracy
- Makes DHCP and static addressing easier to manage
- Supports cleaner route summarization
Final thoughts
If you manage networks at any scale, being fluent in CIDR ranges pays off quickly. Use the calculator above to verify every block before implementing routing, VPN tunnels, NAT policies, or security groups. A 10-second check can save hours of troubleshooting later.