Subnet / CIDR / IP Calculator
Calculate network address, broadcast address, subnet mask, usable hosts, and full IP range for any CIDR block. Essential tool for network admins.
📋 Common Subnet Reference
| CIDR | Subnet Mask | Usable Hosts | Common Use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Large ISP/organization |
| /16 | 255.255.0.0 | 65,534 | Large corporate network |
| /24 | 255.255.255.0 | 254 | Standard office network |
| /25 | 255.255.255.128 | 126 | Split office segment |
| /26 | 255.255.255.192 | 62 | Small department |
| /27 | 255.255.255.224 | 30 | Small team/VLAN |
| /28 | 255.255.255.240 | 14 | Small group of devices |
| /29 | 255.255.255.248 | 6 | Small point-to-point |
| /30 | 255.255.255.252 | 2 | Router-to-router link |
| /32 | 255.255.255.255 | 1 (host) | Single host route |
Understanding Subnets and CIDR
Subnetting divides a large network into smaller, more manageable segments. Every device needs an IP address, and subnets define which addresses belong to the same local network. Proper subnetting is fundamental to network design — it affects security (segmenting traffic between departments), performance (reducing broadcast domains), and IP address efficiency.
CIDR notation is the modern standard for expressing IP address ranges. The slash number tells you how many bits are fixed as the network portion. A /24 leaves 8 bits for hosts (256 addresses). A /16 leaves 16 bits (65,536 addresses). Smaller prefix numbers mean larger networks; larger prefix numbers mean smaller subnets.
This calculator is useful for network engineers, system administrators, students studying for CCNA or CompTIA Network+ certifications, and anyone building or troubleshooting IP-based networks. Enter any IP and prefix for instant calculation of all the values you need.
Frequently Asked Questions
A /24 is a subnet with 256 addresses (254 usable for devices). In home and small business networks, this is the most common subnet — e.g., 192.168.1.0/24 with devices from 192.168.1.1 to 192.168.1.254.
A subnet mask defines which part of an IP is the network vs. host portion. For a /24, the mask is 255.255.255.0 — three octets of 255 mean those bits are the network; the last octet identifies individual hosts.
Private IPs (10.x, 172.16-31.x, 192.168.x) are used inside local networks and not routable on the internet. Public IPs are globally unique. NAT (Network Address Translation) connects private networks to the internet through a shared public IP.