~/tools/calculators/subnet

IPv4 Subnet Calculator

subnet-calculator

Address192.168.1.130
Prefix length/26
Network192.168.1.128
Netmask255.255.255.192
Wildcard0.0.0.63
Broadcast192.168.1.191
First host192.168.1.129
Last host192.168.1.190
Total addresses64
Usable hosts62

How it works

Give it any address inside a block, in CIDR notation, and it computes the block: the mask collapses the host bits to find the network address, and the wildcard mask fills them back in for the broadcast. Everything updates as you type, and the address you supply does not need to be the network address.

Edge blocks

Results follow RFC 3021: a /31 has no network or broadcast reserved, both addresses are usable, which is normal for routed point-to-point links. A /32 is a single host route with no room for anything else. Blocks from /30 up reserve the first and last address, which is why a /24 has 254 usable hosts rather than 256.

Private ranges

RFC 1918 sets aside 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 for private networks, and RFC 4193 sets aside fd00::/8 for IPv6. Homelabs live almost entirely inside these blocks, so if a plan for your network needs addresses outside them, double-check before assigning anything.

IPv6

IPv6 addressing is deliberately out of scope here for now. The mental model differs enough (no broadcast, /64 boundary conventions, SLAAC) that it deserves its own treatment rather than a bolted-on afterthought.