SubnetCalc
Calculate subnet

Subnet sizing

Find CIDR from required hosts

Enter the number of usable hosts to find the smallest ordinary LAN subnet, or explicitly size a two-endpoint point-to-point /31.

Private browser calculation

Address, prefix, and host sizing

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Calculation mode

Required usable hosts

Ordinary LAN sizing reserves network and broadcast addresses. One requested host produces a /32 host route.

Ordinary mode returns /32 for one host; two hosts require /30 because network and broadcast are reserved.

Exact unsigned 32-bit arithmetic runs locally. This tool does not query, scan, locate, or test any address, and it does not configure a device.