CIDR Calculator - Subnet & IP Range Calculator
Calculate IP ranges, subnet masks, network addresses, and usable hosts from CIDR notation online for free. Perfect for network planning, subnetting, and IP address management.
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CIDR Calculator
Common CIDR Prefixes
What is CIDR?
CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses and routing Internet Protocol packets. It replaced the old classful network addressing architecture and allows for more efficient allocation of IP addresses.
CIDR Notation Explained
CIDR notation consists of an IP address followed by a slash and a number (e.g., 192.168.1.0/24). The number after the slash represents the number of bits in the network prefix.
Example: 192.168.1.0/24
- • 192.168.1.0 is the network address
- • /24 means the first 24 bits are the network portion
- • This leaves 8 bits for hosts (2^8 = 256 addresses)
- • Usable hosts: 254 (excluding network and broadcast addresses)
Common CIDR Blocks
| CIDR | Subnet Mask | Total IPs | Usable Hosts |
|---|---|---|---|
| /24 | 255.255.255.0 | 256 | 254 |
| /25 | 255.255.255.128 | 128 | 126 |
| /26 | 255.255.255.192 | 64 | 62 |
| /27 | 255.255.255.224 | 32 | 30 |