Subnet Calculator
Calculate network range, netmask, and usable hosts from IP and CIDR.
Network Definition
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Networking Basics
Subnetting is the practice of dividing a network into two or more smaller networks. It increases routing efficiency, enhances security, and reduces broadcast domain size.
Understanding CIDR
CIDR (Classless Inter-Domain Routing) notation (e.g., /24) tells you how many bits are used for the Network portion of the address.
- /24 means the first 24 bits (3 octets) are the network. (e.g., 192.168.1.X)
- /16 means the first 16 bits (2 octets) are the network. (e.g., 192.168.X.X)
Reserved Private Ranges (RFC 1918)
You can assign these IP addresses within your local network (LAN) without conflict with the public internet:
- 10.0.0.0 – 10.255.255.255 (Large networks, often enterprise)
- 172.16.0.0 – 172.31.255.255 (Medium networks, AWS/Docker defaults)
- 192.168.0.0 – 192.168.255.255 (Small home routers)