Quick-reference math for a single CIDR block, or divide a block down into a VLSM plan and join it back together — everything below runs entirely in your browser, nothing is sent anywhere.
Every row shows that field’s IPv4 value in binary. Each group of eight squares is one octet, so the four groups line up with the four dotted-decimal numbers shown beside them.
Amber marks the bit positions reserved for the network prefix; cyan marks the remaining host positions. That color split stays in the same place on every row. Fill is separate: a filled square is a binary 1, while an outlined square is a binary 0. The netmask and wildcard rows make the split especially easy to see—one fills the network positions, the other fills the host positions.
| Subnet | Range | Usable IPs | Hosts | ||
|---|---|---|---|---|---|