Subnet calculator

Make sense of your address space.

Calculate IPv4 and IPv6 subnets, split networks, check membership and overlap, convert address ranges, and aggregate CIDRs in your browser.

Subnet workbench

Runs in your browser

Inspect an address, its network, masks, usable IPv4 range, and reverse-DNS pointer.

All calculations stay on this page. No addresses are probed, uploaded, or saved to browser storage.

IPV4 result

192.168.1.0/24

Canonical input address: 192.168.1.42
Expanded input address: 192.168.1.42
Network mask: 255.255.255.0
Wildcard mask (inverse): 0.0.0.255
First address (inclusive): 192.168.1.0
Last address (inclusive): 192.168.1.255
Total addresses: 256
Input address classification: Private network
Usable IPv4 hosts: 254
Conventional usable range: 192.168.1.1 – 192.168.1.254
Broadcast address: 192.168.1.255
Reverse-DNS pointer for input address: 42.1.168.192.in-addr.arpa

For /0–/30, usable counts exclude network and broadcast addresses. /31 assumes a point-to-point link; /32 identifies one address. Gateways and provider reservations can reduce assignable addresses. The reverse pointer is calculated locally, not looked up in DNS.

Split a /24 into four /26s

A /24 contains 256 addresses. Moving to /26 uses two more network bits: 2² = four subnets of 64 addresses each. For 192.168.1.0/24, they start at .0, .64, .128, and .192.

Combining those four adjacent /26s returns the original /24. Leaving one out must preserve the gap rather than include its addresses.

Learn how subnetting works →

Large IPv6 spaces, exact answers

A /64 contains 18,446,744,073,709,551,616 addresses. All address arithmetic uses exact integers, including full IPv6 /0 ranges.

The splitter generates at most one page of rows. A huge count does not require a huge download or list in memory. Use Compare to check one address or Range → CIDRs to describe a specific allocation.