THE SUBNET FIELD GUIDE

Read the Prefix. Understand the Plan.

Start with an address and a known prefix. Read the arithmetic, then check what your network can actually assign.

The Four Questions Behind Every Subnet

1. Which block contains this address? The normalized CIDR starts at the network boundary, even when you enter a host address.
2. How large is that block? The remaining host bits determine its exact address count.
3. Which addresses can this environment assign? Conventional host counts are a starting point, not your DHCP pool or cloud-provider policy.
4. What will splitting change? Adding prefix bits creates more, smaller, equal blocks. It does not configure routes or create VLANs.

What This Calculator Does—and Does Not Do

IPCALCULATOR calculates IPv4 and IPv6 bounds, masks, exact counts, binary and numeric representations, and up to 16 equal child blocks. It constructs reverse-DNS names without making a DNS query.

It cannot discover your local prefix, gateway, free addresses, ownership, routing, VLANs, or DHCP reservations. No ping, port scan, PTR query, or network configuration is performed. Your connection IP starts with an illustrative /24 or /64, clearly labeled as an example prefix.

Use the IANA IPv4 special-purpose registry and IPv6 registry when an address’s detailed assignment status matters. The displayed scope is a broad local classification, not a live registry verdict.