IPv4 Subnet Calculator

Enter an IP address with a CIDR prefix or subnet mask to get the network address, broadcast address, usable host range, and total host count — calculated entirely in your browser.

Enter IP Address with CIDR or Subnet Mask

Examples: 192.168.1.10/24 10.0.0.5/8 172.16.5.20 /25

Subnet Details

How Subnetting Works, Briefly

An IPv4 address is 32 bits. A CIDR prefix (like /24) or subnet mask (like 255.255.255.0) tells you how many of those bits are reserved for the network portion versus the host portion. A /24 reserves 24 bits for the network, leaving 8 bits — 256 addresses — for hosts, minus the network and broadcast addresses, giving 254 usable host addresses.

This calculator accepts either notation and derives: the network address (all host bits set to 0), the broadcast address (all host bits set to 1), the usable host range (everything in between), and the total number of hosts the subnet can address.

Tip: For point-to-point WAN links, a /30 (2 usable hosts) or /31 (RFC 3021, 2 usable hosts with no network/broadcast reserved) is standard practice to avoid wasting address space.

Frequently Asked Questions

Does this work for IPv6?+

Not currently — this tool is IPv4-only. IPv6 subnetting uses a different addressing model (128-bit addresses, no broadcast address) that would need a dedicated calculator.

Is my IP address sent anywhere?+

No — like our Type 7 decoder, this calculation runs entirely in your browser using JavaScript. Nothing is transmitted to any server.

What's the difference between /31 and /30 for point-to-point links?+

A /30 gives 4 total addresses (2 usable, plus network and broadcast). A /31, per RFC 3021, is a special case for point-to-point links that treats both addresses as usable, since there's no meaningful broadcast on a link with only two devices.