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Subnet Calculator

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Network & IP

Subnet Calculator

Calculate subnet masks, network addresses, and host ranges.

Workspace

Run the tool here

Browser utility

IPv4 address

Prefix length (0-32)

Output

Run the workspace to see the response here.

How to use

Enter the IP address and prefix length.
Read the network, broadcast and host range.
Use the result to configure a device or firewall.

About this tool

Calculate network and broadcast addresses, usable host ranges and subnet masks from an IP and CIDR prefix.

Subnet Calculator is part of the TmpMailer Network & IP set — free browser utilities that open instantly, need no account, and pair well with a temporary-email workflow when you just need a quick result.

Common use cases

Planning a small office VLAN.
Checking whether two hosts are on the same subnet.
Documenting a firewall rule.

Common questions

How many usable hosts does a /24 have?

254, because the network and broadcast addresses cannot be assigned to hosts.

Why is the host count different for /31 and /32?

Point-to-point links use /31 without broadcast, and /32 represents a single address.

Does this support IPv6?

The classic calculator targets IPv4. IPv6 subnetting uses a different mental model and prefix sizes.

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