CIDR Calculator

IPv4 CIDR Calculator for subnet ranges and masks

Calculate the network address, broadcast address, subnet mask, wildcard mask, full address range, and usable host range for any IPv4 CIDR block. Enter an address such as 192.168.1.42 with /24, or paste 192.168.1.42/24 directly. All calculations run locally in your browser.

What is CIDR notation?

Classless Inter-Domain Routing (CIDR) writes an IP network as an address followed by a slash and prefix length. The prefix shows how many of the 32 IPv4 bits identify the network. For example, 192.168.1.0/24 reserves 24 bits for the network and leaves 8 bits for addresses inside that subnet.

How do I calculate an IPv4 subnet from CIDR?

Enter any IPv4 address within the subnet and its prefix. The calculator clears the host bits to find the network address, sets them to one to find the broadcast address, and derives the complete range between those values. You do not need to enter the network address itself.

How do I convert a CIDR prefix to a subnet mask?

Enter a prefix from /0 through /32. A /24 prefix becomes 255.255.255.0, while /16 becomes 255.255.0.0. You can also enter a dotted mask in the prefix field, and the calculator converts it back to CIDR notation. Only contiguous subnet masks are valid.

What is a wildcard mask?

A wildcard mask is the bitwise inverse of the subnet mask. Wherever the subnet mask contains a 255 octet, the wildcard contains 0, and vice versa. Network equipment and access-control lists often use wildcard masks to describe which address bits may vary.

What is the difference between total addresses and usable hosts?

For prefixes from /0 to /30, the network and broadcast addresses are normally reserved, so the usable host count is two fewer than the total. Following modern point-to-point behavior, a /31 has two usable addresses. A /32 represents one specific host route.

Which CIDR prefix should I use?

Choose the smallest subnet that still leaves room for the required devices and reasonable growth. A /24 contains 256 total addresses, a /28 contains 16, and a /30 contains 4. The common-prefix buttons let you compare these sizes quickly without doing binary math.

Is my IP address sent to a server?

No. The calculator performs IPv4 parsing and subnet calculations entirely in your browser. The address you enter is not uploaded, which makes the tool suitable for private and internal network planning.