IPv6 Subnet Calculator — Free Online IPv6 CIDR & Subnet Tool

IPv6 Subnet Calculator — Free Online IPv6 CIDR & Subnet Tool. Free online IPv6 subnet calculator. Enter any IPv6 CIDR block to instantly get network address, IP range, total addresses, and prefix details — all computed in your browser.

Instantly compute IPv6 address spaces with our free online IPv6 subnet calculator. Enter any IPv6 CIDR block (e.g.

2001:db8::/32) to get the network address, full IP range, total addresses, and prefix length — all computed in your browser with no data sent to any server.

Perfect for network engineers, ISP architects, cloud admins configuring VPCs, and students learning IPv6 subnetting. Supports all standard prefix lengths from /1 to /128.

Our IPv6 CIDR calculator processes all subnet calculations entirely client-side, so your internal routing schemas and IP assignments are never uploaded to a remote server.

Use it alongside our IPv4 Subnet Calculator, IPv4 Range Expander, and IPv4 Address Converter for a complete IP network planning toolkit covering both IPv4 and IPv6 infrastructure.

Frequently asked questions

How do I calculate an IPv6 subnet with this tool?

Type or paste an IPv6 address followed by a slash and the prefix length into the Input IPv6 CIDR field, for example 2001:0db8:85a3::/64. The results show the IP Address, the Network Address with its prefix, the Network Range from first to last address and the Total IP Addresses, each with a copy button.

Which IPv6 prefix lengths are supported?

Any prefix from /0 to /128. Typical sizes are /32 or /48 for ISP and site allocations, /56 for customer delegations and /64 for a single LAN; a /128 is one address.

How many addresses are in a /64?

A /64 contains 2 to the power of 64 addresses, which is 18446744073709551616. The Total IP Addresses field shows the exact count for any prefix because the calculator uses big-integer arithmetic instead of rounding.

Why do I see Invalid IPv6 CIDR format?

The input needs exactly one slash followed by a number from 0 to 128, and the address must be written as hexadecimal groups with at most one :: abbreviation. An embedded IPv4 part, as in ::ffff:192.0.2.1, is accepted at the end only and needs exactly four numbers from 0 to 255; it counts as two groups and is shown in hex, for example ::ffff:c000:201.

Are the results shown in compressed notation?

Yes. Leading zeros are dropped and the longest run of two or more zero groups is replaced by ::, so 2001:0db8:85a3::/64 is shown as the network 2001:db8:85a3::/64. You can type addresses in either full or compressed form.

How to use this online tool

IPv6 Subnet Calculator — Free Online IPv6 CIDR & Subnet Tool is designed for fast browser workflows when you need to format, validate, convert, decode, encode, generate, or inspect data without opening a heavy desktop app. Start with the input field or visible options, review the result, then copy or download the output for the next step.

Private processing in your browser

IPv6 Subnet Calculator — Free Online IPv6 CIDR & Subnet Tool keeps the normal processing step local in your browser. That is useful for code snippets, tokens, documents, configuration values, text samples, and other material that should not be sent to a remote service unless you explicitly choose to share it.

When this tool is useful

Use IPv6 Subnet Calculator — Free Online IPv6 CIDR & Subnet Tool for repeatable developer tasks, technical documentation, QA checks, quick conversions, debugging, content cleanup, and internal team workflows. The page focuses on clear inputs, immediate feedback, and output that is easy to reuse in code, reports, tickets, emails, or notes.

Practical tips

Before copying the final result, check important details such as spacing, casing, filenames, encoding, token structure, line breaks, or output format. Small checks prevent mistakes when the result is reused in source code, API requests, documentation, spreadsheets, or shared files.