IPv4 Subnet & CIDR Calculator
Design network subnets, calculate broadcast bounds and usable host IP ranges, and visualize binary bit allocations in real time.
192.168.1.0/24
Routing identifier for subnet
192.168.1.255
Reserved for subnet-wide broadcast
255.255.255.0
Wildcard: 0.0.0.255
192.168.1.1 — 192.168.1.254
Assign to network cards, VM interfaces, or DHCP pools
254 Usable
256 Total IP addresses (2^8)
RFC 1918 Private
192.168.0.0/16 (Class C Private)
Class C (/24 Default)
Supernetted via Classless Inter-Domain Routing (CIDR)
IPv4 Subnetting & CIDR Cheatsheet
1. Understanding CIDR Notation
Classless Inter-Domain Routing replaces rigid Class A/B/C address blocks with variable length subnet masks (/1 to /32). The prefix length (such as /24) denotes the exact count of fixed network bits, leaving the remaining bits for host addressing.
2. Why Subtract 2 Usable Hosts?
In standard IPv4 subnets, two host addresses are reserved by networking standards: the lowest address (all host bits 0) represents the Network ID, and the highest address (all host bits 1) serves as the Broadcast Address.
3. RFC 1918 Private Ranges
Private subnets intended for LANs, Docker bridges, and VPC clouds are never routed over the public internet: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.
Common CIDR Prefix Reference Table
| CIDR Prefix | Subnet Mask | Total IP Addresses | Usable Host Capacity |
|---|---|---|---|
| /16 | 255.255.0.0 | 65,536 | 65,534 hosts (AWS / GCP VPC size) |
| /24 | 255.255.255.0 | 256 | 254 hosts (Standard office / home LAN) |
| /28 | 255.255.255.240 | 16 | 14 hosts (Micro-service subnet) |
| /30 | 255.255.255.252 | 4 | 2 hosts (Legacy router point-to-point) |
| /32 | 255.255.255.255 | 1 | 1 host (Single static host route) |