IPv6 Subnet Calculator / Converter

About this tool

Calculate networks, reference address ranges, address counts, mask conversions, attribute checks (link-local/ULA/multicast, etc.), and notation conversions (compressed/expanded, reverse ip6.arpa, binary/hex) from an IPv6 address and prefix length (CIDR /n) entirely in your browser. Works offline; IPv6 has no broadcast.

IPv6 Subnet Calculator

Mask conversion (128-bit mask ⇄ CIDR)

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VLSM helper (suggest smallest prefix from required addresses)

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How to use

  1. Enter an IPv6 address.
  2. Set the prefix length (CIDR /n) and press Calculate.
  3. Press Copy to capture the results.

Key features

  • Mutual conversion between 128-bit masks and CIDR (masks must have contiguous ones/zeros).
  • Network, reference last address, and approximate address count 2^(128-n).
  • Notation conversions (compressed/expanded), binary view, 128-bit hex, and ip6.arpa (PTR).
  • Attribute detection: Unspecified / Loopback / Link-Local / Unique-Local / Multicast / Documentation / Global-Unicast / IPv4-mapped / 6to4 / Teredo, etc.