- How do I use this subnet calculator?
- Enter an IP address with a CIDR prefix (for example 192.168.1.10/24 for IPv4 or 2001:db8::/48 for IPv6) and the tool instantly shows the network and broadcast addresses, usable host range, subnet mask and total host count. All math runs in your browser, so nothing you type is sent to a server or stored.
- What is a subnet and CIDR notation?
- A subnet is a logical division of an IP network, and CIDR notation writes the mask as a slash and a number (like /24) telling you how many leading bits identify the network. The remaining bits define how many host addresses fit inside that subnet.
- Why does subnetting matter?
- Subnetting lets you split address space efficiently, isolate traffic and plan firewall or routing rules without wasting IPs. Getting the boundaries right prevents overlapping ranges and hosts that cannot reach their gateway.
- How do I read the results?
- The network address is the first address in the block and identifies the subnet, the broadcast address is the last, and the usable host range is everything in between. For IPv4 a /24 gives 256 total addresses with 254 usable, since the network and broadcast addresses are reserved.
- Does this work the same for IPv6?
- IPv6 CIDR is calculated too, but IPv6 has no broadcast address and does not reserve the first and last addresses the way IPv4 does. A /64 is the standard subnet size for a single LAN, so you rarely subnet smaller than that in practice.