ip-calculator.uptool.net · tools
IPv4 subnet calculator
CIDR and dotted masks, network class, host range, wildcard mask, and equal subnet splits with hosts-per-subnet picks.
Leave the second box empty when you use slash notation in the first line.
Enter a.b.c.d/prefix, a.b.c.d with a second line for prefix or mask, or two tokens a.b.c.d m.m.m.m. Then pick a longer child prefix (or the matching usable-host count) to list every equal subnet inside the parent block. A sample calculation loads by default so you can explore binary view, class, scope, and the subnet table before you change the inputs.
Teaching notes
This page is for:
- Lab write-ups that still ask for “class” and dotted-binary alongside CIDR
- Checking wildcard masks before pasting into ACLs
- Listing child subnets after you pick hosts-per-subnet or prefix length
Not a substitute for your NMS
Always confirm masks and ranges against your IP plan and router config. Class labels describe the old high-bit pattern only; routing today is CIDR-first.