The most complete free IP subnet calculator online. Get network address, broadcast address, usable host range, subnet mask, wildcard mask, binary representation and more. Essential for network engineers and sysadmins.
IP Subnet Calculator — CIDR Notation, Subnet Masks, Host Ranges and More
Our free IP subnet calculator is the most complete online subnetting tool for network engineers and sysadmins. Enter any IPv4 address in CIDR notation (e.g. 192.168.1.0/24) and instantly get the network address, broadcast address, usable host range, subnet mask, wildcard mask, binary representation, IP class, total hosts and whether the address is private or public — all in one place.
How IP Subnetting Works
An IP address is a 32-bit number divided into four octets (e.g. 192.168.1.100). The subnet mask defines which portion of the IP identifies the network and which identifies the host. In CIDR notation, /24 means the first 24 bits are the network portion, leaving 8 bits for hosts — giving 2⁸ = 256 addresses (254 usable, as the first is the network address and the last is the broadcast address).
Common Subnet Reference
- /24 — 254 usable hosts — typical small office or LAN segment
- /23 — 510 usable hosts — medium office network
- /22 — 1,022 usable hosts — campus or large office
- /16 — 65,534 usable hosts — entire Class B network
- /30 — 2 usable hosts — point-to-point WAN links
- /32 — Single host — used for loopback and static routes
Private IP Address Ranges (RFC 1918)
- 10.0.0.0/8 — 16,777,216 addresses — large enterprise networks
- 172.16.0.0/12 — 1,048,576 addresses — medium networks
- 192.168.0.0/16 — 65,536 addresses — home and small office networks
Who Uses a Subnet Calculator?
This tool is essential for network engineers designing IP address schemes, sysadmins configuring firewall rules and VLANs, cloud architects planning VPC and subnet allocation in AWS, Azure and Google Cloud, and IT students studying for CCNA, CompTIA Network+ and other networking certifications. Subnetting is one of the most tested topics in networking exams.
Frequently Asked Questions
What is a wildcard mask? The wildcard mask is the inverse of the subnet mask and is used in access control lists (ACLs) on Cisco routers. For /24 (255.255.255.0) the wildcard is 0.0.0.255.
How many hosts does a /25 give me? A /25 provides 128 addresses, of which 126 are usable hosts.