IPIP Address Lookup
Subnetting Tool

CIDR Subnet Calculator

Calculate IPv4 network ranges, broadcast addresses, usable hosts, and binary masks.

Quick Presets:
Network Address192.168.1.0
Broadcast Address192.168.1.255
Subnet Mask255.255.255.0
Wildcard Mask0.0.0.255
First Usable Host192.168.1.1
Last Usable Host192.168.1.254
Total Addresses256
Usable Host Count254
Classification & RFC 1918 StatusClass C • RFC 1918 Private Enterprise Network
Binary Subnet Mask11111111.11111111.11111111.00000000

IPv4 Subnet Mask & Prefix Cheatsheet

PrefixSubnet MaskTotal IPsUsable HostsCommon Usage
/32255.255.255.25511Single host route
/30255.255.255.25242Legacy point-to-point link
/29255.255.255.24886Small public server cluster
/28255.255.255.2401614Branch office subnet
/27255.255.255.2243230Medium workgroup VLAN
/26255.255.255.1926462Departmental subnet
/25255.255.255.128128126Half Class C
/24255.255.255.0256254Standard Class C / Minimum BGP route
/23255.255.254.0512510Supernetting / Two Class C blocks
/22255.255.252.010241022Regional enterprise allocation
/20255.255.240.040964094Datacenter pod
/16255.255.0.06553665534Standard Class B network
/8255.0.0.016,777,21616,777,214Class A enterprise block

Frequently Asked Questions

What is CIDR notation?▼

Classless Inter-Domain Routing (CIDR) notation expresses an IP address and its subnet mask as an IP followed by a forward slash and a prefix number (e.g. 192.168.1.0/24). The number represents how many leading bits are static network identifiers.

Why do usable hosts equal total addresses minus 2?▼

In traditional IPv4 subnets, the first address is reserved as the Network Identifier, and the last address is reserved as the Subnet Broadcast address. Thus, a /24 has 256 total addresses, but 254 usable host addresses.

What is an RFC 3021 /31 subnet?▼

RFC 3021 defines /31 subnets for point-to-point links between routers. Because broadcast and network addresses are unnecessary on isolated point-to-point connections, both addresses (2 hosts) are usable.

What is a wildcard mask?▼

A wildcard mask is the exact inverse of a subnet mask (255.255.255.255 minus the subnet mask). For example, a /24 subnet mask of 255.255.255.0 has a wildcard mask of 0.0.0.255. Cisco routers and access control lists (ACLs) use wildcard masks.