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Network Host Count from CIDR Prefix Length Calculator

Usable hosts per subnet from /prefix notation.

Calculates the number of usable hosts per subnet = 2^(32−prefix) − 2, total addresses = 2^(32−prefix), and the subnet mask for IPv4 CIDR notation.

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

Inputs

Results

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Hosts = 2^(32−prefix) − 2

In depth

Calculates the number of usable hosts per subnet = 2^(32−prefix) − 2, total addresses = 2^(32−prefix), and the subnet mask for IPv4 CIDR notation.