Subnet Calculator
CIDR / Subnet Mask
Calculate subnet details from a CIDR prefix length (e.g., /24)
Formula
Usable Hosts = 2^(32-CIDR) - 2 | Network = IP AND Mask | Broadcast = Network OR NOT Mask
Frequently Asked Questions
What is a subnet mask?
A subnet mask divides an IP address into network and host portions. For example, 255.255.255.0 (/24) means the first 24 bits are the network address, and the last 8 bits identify hosts. This allows 254 usable host addresses.
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation like /24 indicates how many bits of the IP address are used for the network portion. /24 = 255.255.255.0, /16 = 255.255.0.0, /8 = 255.0.0.0.
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