CIDR to IP Range Calculator
Enter an IPv4 CIDR block (for example, 192.168.10.0/24) to instantly calculate the subnet mask, usable host range, broadcast address, and more.
Format: IP/prefix where prefix is between 0 and 32.
What this CIDR calculator does
A CIDR to IP range calculator converts compact network notation (like 192.168.1.0/24) into values you can actually use in networking tasks: the network address, first and last usable host, broadcast address, total addresses, and usable host count.
This is useful for designing LANs, setting firewall rules, creating cloud security groups, planning DHCP scopes, and avoiding subnet overlap.
Quick CIDR refresher
What does “/24” mean?
In CIDR (Classless Inter-Domain Routing), the number after the slash is the prefix length. It tells you how many bits belong to the network portion of the address.
- /24 means 24 network bits and 8 host bits.
- /16 means 16 network bits and 16 host bits.
- /32 means all bits are network bits, so it describes one single IP.
Why CIDR is better than old classful addressing
CIDR allows subnet sizes that match real requirements. Instead of wasting thousands of IPs, you can allocate exactly what you need and summarize routes more efficiently.
How to use the calculator
- Type a valid IPv4 CIDR block in the input field.
- Click Calculate Range (or press Enter).
- Read the generated network details in the result panel.
If your input IP is not the actual network boundary, the calculator still works and shows the normalized network for that CIDR.
How CIDR converts to an IP range (manual method)
Step 1: Get subnet mask from prefix
Example: /26 equals subnet mask 255.255.255.192.
Step 2: Compute network address
Apply a bitwise AND between the IP and subnet mask. The result is the network address.
Step 3: Compute broadcast address
Set all host bits to 1. That gives the broadcast address for the subnet.
Step 4: Derive usable host range
For most subnets, the first usable host is network + 1, and the last usable host is broadcast - 1.
Common IPv4 CIDR blocks
| CIDR | Subnet Mask | Total Addresses | Typical Usable Hosts |
|---|---|---|---|
| /30 | 255.255.255.252 | 4 | 2 |
| /29 | 255.255.255.248 | 8 | 6 |
| /28 | 255.255.255.240 | 16 | 14 |
| /24 | 255.255.255.0 | 256 | 254 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
Special cases: /31 and /32
/31 networks
Modern point-to-point links often use /31. In that case, both addresses are considered usable (RFC 3021), so you get 2 usable addresses.
/32 networks
A /32 represents exactly one host route. It is frequently used in routing tables, loopback interfaces, and ACL rules.
Where this helps in real projects
- Firewall policies: Define precise source/destination ranges.
- Cloud networking: Validate VPC and subnet layouts before deployment.
- On-prem planning: Avoid overlap between office, VPN, and datacenter networks.
- Troubleshooting: Quickly confirm whether two hosts should communicate directly.
FAQ
Can I enter any host IP with a prefix?
Yes. The calculator will map it to the correct subnet and display the real network and range.
Does this tool support IPv6 CIDR?
This version is focused on IPv4 only. IPv6 uses the same CIDR idea, but address math and display formats are different.
How do I avoid subnet overlap?
Calculate each CIDR block, list their start/end ranges, and ensure no ranges intersect. This tool is ideal for that quick validation step.