CIDR Calculator: Subnet Calculator & IP Range Tool
The CIDR Calculator is an essential tool for network administrators, system engineers, and IT professionals. It calculates all subnet information from CIDR notation including IP ranges, subnet masks, usable hosts, and network boundaries.
What You Can Calculate
- IP Range: First and last usable IP addresses in the subnet
- Subnet Mask: Network mask in dotted decimal format
- Network Address: The base address of the subnet
- Broadcast Address: The address for broadcasting to all hosts
- Total & Usable Hosts: Number of available IP addresses
- Wildcard Mask: Inverse of subnet mask for ACLs
Common CIDR Notations
/32 = Single host (1 IP)
/31 = Point-to-point (2 IPs, 0 usable)
/30 = Small network (4 IPs, 2 usable)
/29 = 8 IPs (6 usable)
/28 = 16 IPs (14 usable)
/27 = 32 IPs (30 usable)
/26 = 64 IPs (62 usable)
/25 = 128 IPs (126 usable)
/24 = 256 IPs (254 usable) - Most common for LANs
How to Use This CIDR Calculator
- Enter CIDR notation (e.g., 192.168.1.0/24) in the input field
- Alternatively, enter IP address with subnet mask (192.168.1.0 255.255.255.0)
- Click "Calculate" to get detailed subnet information
- For multiple calculations, enter one CIDR per line in the textarea
- Use "Copy Results" to copy the calculation data
- Use "Fill Example" to load common CIDR examples
Real-World Examples
Home Network: 192.168.1.0/24 provides 254 usable IPs for devices
Office Network: 10.0.0.0/23 provides 510 usable IPs for larger offices
Point-to-Point: 192.168.1.0/31 for router links (2 IPs, 0 usable hosts)
DMZ Network: 172.16.0.0/28 for secure servers (14 usable IPs)
Frequently Asked Questions (FAQ)
What is CIDR Notation?
CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its associated routing prefix. It is expressed as an IP address, a slash ('/'), and a decimal number (e.g., 192.168.1.0/24).
What is the purpose of CIDR?
CIDR allows for more efficient allocation of IP addresses and reduces the size of routing tables. It replaced the old classful network design and enables variable-length subnet masking (VLSM).
What does the number after the slash mean?
The number after the slash represents the network prefix length in bits. For example, /24 means the first 24 bits are the network portion, and the remaining 8 bits are for hosts.
How many hosts can a /24 network have?
A /24 network has 256 total addresses: 254 usable hosts (subtracting network and broadcast addresses), 1 network address, and 1 broadcast address.
What is the difference between network address and broadcast address?
The network address is the first address in a subnet (all host bits 0). The broadcast address is the last address (all host bits 1), used to send data to all devices in the subnet.
