IP Subnet Calculator
Enter an IPv4 address in CIDR notation to instantly calculate network address, broadcast address, first and last usable hosts, subnet mask, wildcard mask, and total host count.
| CIDR / Range | Subnet Mask | Usable Hosts | Common Use |
|---|---|---|---|
| /8 (Class A) | 255.0.0.0 | 16,777,214 | ISP / large enterprise |
| /16 (Class B) | 255.255.0.0 | 65,534 | Campus / data centre |
| /24 (Class C) | 255.255.255.0 | 254 | Home / small office |
| /25 | 255.255.255.128 | 126 | Medium department |
| /28 | 255.255.255.240 | 14 | Small team / VLAN |
| /30 | 255.255.255.252 | 2 | Point-to-point links |
Frequently Asked Questions
What are the RFC 1918 private IP ranges?
RFC 1918 (1996) defines three address blocks for private networks: 10.0.0.0/8 (16.7 million addresses, used by large enterprises and ISPs for carrier-grade NAT), 172.16.0.0/12 (1 million addresses, used in data centres), and 192.168.0.0/16 (65,536 addresses, used in home and small office networks). Home routers worldwide typically assign 192.168.1.x or 192.168.0.x addresses to devices.
What is the difference between a subnet mask and a wildcard mask?
A subnet mask uses 1s for network bits and 0s for host bits (e.g., 255.255.255.0 for /24). A wildcard mask is the inverse — 0s for network bits and 1s for host bits (e.g., 0.0.0.255 for /24). Wildcard masks are used in Cisco IOS ACLs (Access Control Lists) and OSPF configurations. They specify which bits to match and which to ignore. Subnet masks are used in IP configuration; wildcard masks are used in router/firewall rules.