IP Subnet Calculator
Calculate IP subnet masks, network addresses, broadcast addresses, and available host ranges.
Frequently Asked Questions
What is a subnet mask?
A subnet mask is a 32-bit number that divides an IP address into a network portion and a host portion. Written in dotted decimal (e.g., 255.255.255.0) or CIDR notation (/24), it defines which part of the IP address identifies the network and which identifies individual devices. For a /24 subnet, the first 24 bits identify the network, leaving 8 bits for hosts — allowing up to 254 usable host addresses (256 minus network and broadcast addresses).
How many hosts can a /24 subnet support?
A /24 subnet (subnet mask 255.255.255.0) provides 2^8 = 256 total addresses. Subtract 2 for the network address and broadcast address, leaving 254 usable host addresses. Common subnets and their host counts: /30 = 2 hosts (point-to-point links), /29 = 6 hosts, /28 = 14 hosts, /27 = 30 hosts, /26 = 62 hosts, /25 = 126 hosts, /24 = 254 hosts, /23 = 510 hosts. Network engineers choose subnet sizes based on the number of devices in each network segment.
What is the difference between public and private IP addresses?
Private IP addresses are used within local networks (LANs) and are not routable on the public internet. Reserved ranges are: 10.0.0.0–10.255.255.255, 172.16.0.0–172.31.255.255, and 192.168.0.0–192.168.255.255. Your home router assigns private IPs to your devices via DHCP and uses NAT (Network Address Translation) to share one public IP with all of them. Public IPs are globally unique and assigned by ISPs. Understanding this distinction is fundamental for network configuration and troubleshooting connectivity issues.