System: Calculating Subnets

Subnet and Network masks (Netmasks) are used for all sorts of tasks from firewalls to networking. It can be a time-consuming process to work out the appropriate netmask and subnet mask for different IP addresses. The form below makes it simple.

Netmask and Subnet Calculator

Enter two valid (and different) IPv4 addresses in the form below. It will calculate the most specific netmask and subnet mask that cover both addresses. If you have a range of IP address that appear to be from the same subnet, enter the lowest and highest for best results:

References

• Netmasks Expanded (/24 through /32)

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