Free Tool

CIDR / Subnet Calculator

Enter an IPv4 address and prefix length (e.g. 192.168.1.0/24), the calculator computes the subnet details locally in your browser.

IP address and prefix (CIDR)

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guest@404vpn:~$ cat subnet-faq.md

[01] $ What does /24 after an IP address mean? ▸

> It's the CIDR prefix length, the number of bits in the subnet mask. /24 means a 255.255.255.0 mask and 256 addresses in the network.

[02] $ Why are there fewer usable hosts than total addresses? ▸

> The first address in a subnet is reserved for the network address and the last for broadcast, so they're normally subtracted from the total.

[03] $ Does this calculator work with IPv6? ▸

> No, IPv4 only. IPv6 subnetting works differently because of its much larger address space.

[04] $ Is any data sent to a server? ▸

> No, the entire calculation runs locally in JavaScript in your browser.