How to Calculate the Number of Hosts Available

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To determine the number of hosts available in a subnet, use this formula: (2^Z)-2    (where "Z" equals the number of zeroes in the binary version of the subnet address) e.g. 255.224.0.0 = 11111111.11100000.00000000.00000000    - 21 zeroes -     (2^21)-2 = 2,097,150
e.g. 255.255.224.0 = 11111111.11111111.11100000.00000000    - 13 zeroes -     (2^13)-2 = 8,190
e.g. 255.255.255.0 = 11111111.11111111.11111111.00000000    - 8 zeroes -     (2^8)-2 = 254
e.g. 255.255.128.0 = 11111111.11111111.10000000.00000000    - 15 zeroes -     (2^15)-2 = 32,766