Tech
Subnet Calculator (IPv4 CIDR)
Calculate IPv4 subnets from any IP and CIDR prefix. Get network address, broadcast, subnet mask, usable host range, and total hosts instantly.
IPv4 address and CIDR
Quick CIDR presets
Network address
192.168.1.0
Class C . 254 usable hosts
Broadcast address
192.168.1.255
Subnet mask
255.255.255.0
Wildcard mask
0.0.0.255
IP class
C
First usable host
192.168.1.1
Last usable host
192.168.1.254
Total addresses
256
Usable hosts
254
Binary mask
11111111.11111111.11111111.00000000
Frequently Asked Questions about the Subnet Calculator (IPv4 CIDR)
What is a subnet mask and CIDR notation?
A subnet mask defines which part of an IP address is the network and which part identifies individual hosts. CIDR notation expresses this as a slash followed by the number of network bits, so /24 equals the mask 255.255.255.0 and covers 256 total addresses. The calculator also shows the wildcard mask, which is the bitwise inverse of the subnet mask and is used in firewall and ACL rules.
What is the most common subnet for a home network?
/24 (255.255.255.0). It gives 254 usable host addresses, which covers any home or small office. Consumer routers default to ranges like 192.168.1.0/24 or 192.168.0.0/24.
Why are 2 addresses subtracted from the total?
Every subnet reserves its first address as the network identifier and its last as the broadcast address. A /24 has 256 total addresses (2^8) but only 254 are assignable to devices. The exceptions are /31 and /32: a /31 treats both addresses as usable hosts (per RFC 3021), and a /32 represents a single host with 1 usable address.
What is the difference between IP class and CIDR?
Classful addressing divided the IPv4 space into fixed blocks (Class A used /8, Class B used /16, and Class C used /24), which wasted enormous amounts of address space. CIDR (Classless Inter-Domain Routing), adopted in 1993, allows any prefix length from /0 to /32 so network administrators can allocate exactly the number of addresses a network needs.
What are /31 and /32 subnets used for?
A /32 identifies a single host and appears in routing tables, loopback addresses, and firewall rules targeting one IP. The calculator shows 1 usable address for /32. A /31 (RFC 3021) is designed for point-to-point links between two routers, where both addresses are usable so no addresses are wasted on a network or broadcast identifier.