Calculate subnet masks, IP ranges, network details, and usable hosts instantly for any CIDR notation. Perfect for network administrators, developers, and IT students.
Enter a CIDR notation and the number of usable IPs to display.
CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses and IP routing. It replaces the previous system based on Class A, Class B and Class C networks.
CIDR notation is a compact representation of an IP address and its associated network mask. It's written as the IP address, a slash ('/'), and a decimal number representing the number of leading 1 bits in the network mask.
For example, 192.168.1.0/24 represents the IP address 192.168.1.0 with a subnet mask of 255.255.255.0, which means the first 24 bits are the network address and the remaining 8 bits are for host addresses.
Pro Tip: For larger networks, you might want to increase the number of IPs to display to see more addresses in the list.
Plan and design network subnets efficiently. Calculate subnet masks, IP ranges, and allocate addresses for corporate networks, data centers, and cloud infrastructure.
Configure firewalls, routers, and network devices. Determine broadcast addresses, network addresses, and usable host ranges for proper network setup.
Work with cloud platforms like AWS, Azure, or GCP. Calculate VPC subnets, security group rules, and network segmentation for applications and microservices.
Learn networking concepts, practice subnetting calculations, and prepare for certifications like CCNA, CompTIA Network+, or AWS certifications.
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Set up office networks, configure routers, and understand basic network planning without deep technical knowledge of subnetting mathematics.
CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its associated network mask. It consists of an IP address followed by a slash and a number (e.g., 192.168.1.0/24). The number after the slash indicates how many bits are used for the network portion of the address.
For most networks (prefix less than 31), subtract 2 from the total addresses to get usable IPs (excluding network and broadcast addresses). For /31 networks, both addresses are usable (point-to-point links). For /32 networks, only one address exists (the host itself). Our calculator automatically handles these special cases.
The network address is the first address in a subnet and identifies the network itself. The broadcast address is the last address and is used to send data to all devices on the subnet. Neither address can be assigned to individual devices.
A subnet mask is a 32-bit number that separates an IP address into network and host portions (e.g., 255.255.255.0). CIDR notation is a more compact way to represent the same information (e.g., /24 equals subnet mask 255.255.255.0).
Currently, this calculator supports IPv4 addresses only. IPv6 uses a different addressing scheme and much larger address spaces. We're working on adding IPv6 support in a future update.
For performance reasons, we limit the number of displayed IP addresses. You can adjust the "IPs to show" count, but for very large subnets (like /8 or /16), showing all addresses would be impractical. The "Total Usable Hosts" field shows the complete count regardless of display limit.
Yes! Our CIDR calculator is completely free with no registration required. You can use it as much as you need for personal or professional network planning.