CIDR Calculator
Why Use Our CIDR Calculator?
Full Network Breakdown
Get network address, broadcast address, first and last usable host IPs all in one place.
Subnet & Wildcard Masks
Instantly derive the subnet mask and its wildcard inverse from the CIDR prefix length.
Usable Host Count
See exactly how many host addresses are available in your subnet — no mental math required.
IP Class Detection
Automatically identifies whether the address belongs to IP class A, B, C, D (Multicast), or E (Reserved).
How to Use the CIDR Calculator
- 1
Enter Your CIDR Notation
Type your CIDR block in the input field, for example
192.168.1.0/24or10.0.0.0/16. - 2
Click Calculate
Press the Calculate button to process the CIDR block and display all network details.
- 3
Review Basic Info
The Basic Info tab shows network address, broadcast address, first and last host IPs, subnet mask, and total usable hosts.
- 4
Check Advanced Info
Switch to Advanced Info for the wildcard mask, IP class (A, B, C, D, or E), and additional network details.
Common CIDR Blocks Reference
| CIDR | Subnet Mask | Total IPs | Usable Hosts | Common Use |
|---|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 | Class A large enterprise networks |
| /16 | 255.255.0.0 | 65,536 | 65,534 | Class B medium networks, cloud VPCs |
| /24 | 255.255.255.0 | 256 | 254 | Class C, home & small office networks |
| /25 | 255.255.255.128 | 128 | 126 | Half-subnet splits |
| /26 | 255.255.255.192 | 64 | 62 | Small office segments |
| /27 | 255.255.255.224 | 32 | 30 | Very small network segments |
| /28 | 255.255.255.240 | 16 | 14 | VLAN segments |
| /30 | 255.255.255.252 | 4 | 2 | Point-to-point WAN links |
| /32 | 255.255.255.255 | 1 | 1 (host) | Single host routes, loopback addresses |
Common Uses for a CIDR Calculator
Network Planning
Design IP address schemes for offices, data centers, and branch networks before deployment.
Cloud VPC Configuration
Size and split VPC subnets correctly for AWS, Google Cloud, and Azure infrastructure.
Firewall Rules & ACLs
Verify CIDR blocks and wildcard masks when writing access control lists for routers and firewalls.
IP Address Management
Audit existing subnets and plan new allocations to avoid IP conflicts across networks.
DevOps & Containers
Configure Kubernetes cluster CIDRs, Docker network ranges, and service mesh IP pools.
Troubleshooting
Quickly verify whether two IP addresses belong to the same subnet or identify network boundaries.
Frequently Asked Questions
What is CIDR notation?▼
CIDR (Classless Inter-Domain Routing) notation is a compact way to represent an IP address and its network mask. It is written as an IP address followed by a slash and a prefix length — for example 192.168.1.0/24. The prefix length (0–32) indicates how many bits are used for the network portion.
How do I find the subnet mask from a CIDR prefix?▼
The prefix length tells you how many leading bits are set to 1 in the subnet mask. /24 gives 255.255.255.0, /16 gives 255.255.0.0, and /8 gives 255.0.0.0. Our calculator derives this automatically.
What is the difference between network address and broadcast address?▼
The network address is the first address in a subnet (all host bits set to 0) and identifies the network itself. The broadcast address is the last address (all host bits set to 1) and sends packets to all hosts on that subnet. Neither can be assigned to a host.
How many usable hosts are in a /24 network?▼
A /24 network contains 256 total IP addresses (2^8). Subtracting the network address and broadcast address leaves 254 usable host addresses.
What is a wildcard mask?▼
A wildcard mask is the bitwise inverse of the subnet mask. For 255.255.255.0, the wildcard mask is 0.0.0.255. Wildcard masks are used in firewall ACLs and routing protocols like OSPF to match ranges of IP addresses.
What is the difference between a /24 and /16 network?▼
A /24 has 254 usable hosts (subnet mask 255.255.255.0). A /16 has 65,534 usable hosts (255.255.0.0). The smaller the prefix number, the larger the network and the more IP addresses it contains.