IPv6 Calculator
Expand, compress, subnet IPv6 addresses on nibble boundaries, and build a full hierarchical address plan across multiple levels.
Hierarchical Address Plan Builder
Take a provider assignment, such as a /48 site prefix, and partition it into logical sub-allocations, such as regional branches, data centers, or VLANs, at as many levels as needed.
Related Network Tools
Why nibble boundaries matter
IPv6's 128-bit address space makes address conservation less of a concern than in IPv4. Instead, subnetting focuses on maintaining a clear and hierarchical address plan. Nibble-aligned prefixes such as /48, /52, /56, /60, and /64 are easier to read, organize, and summarize, while prefixes like /59 are valid but less straightforward to interpret.
Building a hierarchical address plan
Unlike IPv4, where subnets are often sized around host counts, IPv6 block delegation is purely top-down. A provider typically assigns a single prefix, such as a /48 for a site, and it is up to the network team to partition that block into a logical structure: regions, then buildings or data centers, then individual VLANs. The Hierarchical Address Plan Builder above mirrors that process. Start from your assigned prefix, split it into the first level of your plan, name each allocation, and split any of them again to add the next level down. Because every allocation stays inside its parent block, routers only need to know about the parent prefix to reach everything underneath it, which keeps routing tables clean at network boundaries.
Frequently asked questions
- How is IPv6 subnetting different from IPv4 VLSM?
- IPv4 VLSM sizes subnets according to host requirements. IPv6 generally uses hierarchical prefix allocation instead, with /64 commonly used for end-user networks.
- Why is /64 the standard host subnet size?
- /64 is the standard size for IPv6 LANs and is required by SLAAC in typical deployments.
- What does compressed vs expanded mean?
- Expanded form shows all eight IPv6 groups. Compressed form removes unnecessary zeros and uses '::' for consecutive zero groups, following the preferred IPv6 notation.
- Are non-nibble prefixes like /59 valid?
- Yes. /59 is a valid IPv6 prefix, but it does not align with a 4-bit hexadecimal boundary and can be harder to read and organize.
- Is any of my data sent to a server?
- No. All calculations run locally in your browser. No IPv6 addresses or calculation results are sent to a server.
- What is the Hierarchical Address Plan Builder for?
- It lets you take a provider assignment, such as a /48 site prefix, and break it down into multiple levels of sub-allocations, such as regional branches, data centers, or VLANs, with each level named for your own network plan.
- How is the plan builder different from the subnet calculator?
- The subnet calculator splits one IPv6 prefix into subnets of a single prefix length. The plan builder lets you organize those allocations into multiple levels, such as regions, sites, and VLANs, with each level further subdivided as needed.