Network Engineering Tool
IP Subnet & CIDR Calculator
Instantly calculate IPv4 subnet ranges, broadcast addresses, usable host counts, wildcard masks, and binary bitmasks.
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Invalid IPv4 Address entered. Please enter a valid IPv4 address (e.g. 192.168.1.1).
CIDR Subnet Reference Table
| CIDR | Subnet Mask | Usable Hosts | Common Use Case |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Class A Default |
| /16 | 255.255.0.0 | 65,534 | Class B Default |
| /24 | 255.255.255.0 | 254 | Class C / LAN Default |
| /25 | 255.255.255.128 | 126 | Small Subnet |
| /26 | 255.255.255.192 | 62 | Quarter Class C |
| /27 | 255.255.255.224 | 30 | Branch Office |
| /28 | 255.255.255.240 | 14 | Small Office |
| /29 | 255.255.255.248 | 6 | Public IP Block / Router |
| /30 | 255.255.255.252 | 2 | Point-to-Point Link |
| /31 | 255.255.255.254 | 2 (RFC 3021) | Point-to-Point (No Broadcast) |
| /32 | 255.255.255.255 | 1 | Single Host |
Understanding Subnetting & CIDR (Classless Inter-Domain Routing)
An IP Subnet (subnetwork) is a logical subdivision of an IP network. Subnetting partitions a large network into smaller, more efficient connected subnetworks, reducing broadcast congestion and enhancing security.
CIDR (Classless Inter-Domain Routing) replaces legacy Class A, B, and C allocation by allowing flexible bitmask lengths designated by a slash (e.g., /24). The prefix number indicates how many leading bits are dedicated to the Network ID, with the remaining bits allocated for Host IDs.