CIDR / Subnet Calculator

Calculate network details including Subnet Mask, Network Address, Broadcast Address, and IP Range by entering an IP address and CIDR mask (e.g., /24).

常见问题

What is CIDR?

CIDR (Classless Inter-Domain Routing) is a way to allocate IP addresses and route traffic, expressing the network prefix length as a number after a slash, e.g. 192.168.1.0/24.

How does CIDR relate to subnet masks?

The number in CIDR notation directly corresponds to the count of 1 bits in the subnet mask. For example, /24 corresponds to 255.255.255.0, and /16 to 255.255.0.0.

How do I calculate the number of usable IPs in a subnet?

Usable IPs = 2^(32 - prefix bits) - 2. For example, a /24 subnet has 2^8 - 2 = 254 usable IPs (subtracting the network address and the broadcast address).

Does this calculator support IPv6?

It primarily supports IPv4 CIDR calculations, including subnet mask, network address, broadcast address and IP range.

What are CIDR calculators useful for in practice?

Commonly used in network planning, server configuration, routing setup, firewall rule configuration, VPC subnet allocation and other network management and ops scenarios.