🌐 CIDR Subnet Calculator

IPv4 Subnetting · Network Address · Broadcast · Usable IP Range

192.168.1.0/24 10.0.0.0/8 172.16.0.0/12 10.0.0.0/16 192.168.0.0/16
Network Address
Broadcast Address
Subnet Mask
CIDR Prefix
Usable IP Range
Total / Usable IPs
IP Type
Wildcard Mask
Inverse mask

❓ Frequently Asked Questions

What is CIDR?

CIDR (Classless Inter-Domain Routing) is a method for IP address allocation and routing. It's expressed as IP/prefix length, e.g. 192.168.1.0/24. The prefix length (0-32) indicates how many bits are used for the network portion, with remaining bits for host addresses. /24 means 24 network bits and 8 host bits.

How do I calculate the number of usable IP addresses?

Usable IPs = 2^(32 - prefix) - 2. We subtract 2 because the network address (first IP, e.g. 192.168.1.0) and broadcast address (last IP, e.g. 192.168.1.255) cannot be assigned to devices. A /24 network has 2^8 - 2 = 254 usable IP addresses.

What are private IP addresses?

Private IP addresses are used within local networks and cannot be routed on the public internet. IPv4 private ranges: 10.0.0.0/8 (~16.7M addresses), 172.16.0.0/12 (~1M addresses), 192.168.0.0/16 (~65K addresses). These can be reused across different LANs.

How are subnet masks related to CIDR prefix length?

The CIDR prefix length is the number of consecutive 1s in the subnet mask. For example: /24 = 255.255.255.0 (24 ones + 8 zeros), /16 = 255.255.0.0, /8 = 255.0.0.0. Longer prefixes mean fewer host addresses available.