Calculator
CIDR Subnet Mask
Change the inputs; results update automatically.
Formula
Usable hosts = 2^(32 - Prefix) - 2 Worked example
A /24 prefix gives mask 255.255.255.0 and 256 total addresses.
Scope and interpretation
This shows mask and capacity, not the network or broadcast address of a specific IP. /31 and /32 have special host-use cases.