IPv6 Subnet Calculator
Calculate the subnet details for any IPv6 address and prefix length. Enter something like 2001:db8::/32 and this tool instantly returns the network address, the last address in the range, the total address count and the fully expanded form — all computed locally in your browser.
What Is an IPv6 Subnet Calculator?
An IPv6 subnet calculator takes an IPv6 address plus a prefix length and works out the boundaries of the network that address belongs to. IPv6 addresses are 128 bits long, and the prefix length after the slash — such as the /32 in 2001:db8::/32 — tells you how many of those bits are fixed as the network portion. The remaining bits are available for subnets and hosts inside that network.
From just those two values the calculator derives the network address (the first address of the range, with all host bits zero), the last address in the range (all host bits set to one), and the total number of addresses the prefix covers. Because IPv6 uses such a large address space, these numbers are enormous — a /64 alone contains 264 addresses, which is why IPv6 subnetting is usually planned in terms of prefix lengths rather than host counts.
How to Use This Tool
- Enter an IPv6 address followed by a prefix length, for example
2001:db8::/32,2001:db8:abcd::/48orfe80::/64. - Press Calculate (or hit Enter).
- Read the network address, last address, address count and expanded form in the results table.
- Use it to plan IPv6 allocations, route summarization or firewall prefix rules.
The calculation runs entirely on your device. Your IPv6 address is never transmitted anywhere, so you can safely work with internal and private ranges without any privacy concern. For the reverse operation — turning a compressed address into its full form — see the IPv6 Expander.
IPv6 Subnet Calculator — Frequently Asked Questions
How do I calculate an IPv6 network address?
Apply a 128-bit mask to the address: the first prefix bits are kept and all remaining host bits are set to zero. For 2001:db8:abcd::/48, the first 48 bits (three groups) are the network, so the network address is 2001:db8:abcd::. The last address in the range sets all remaining host bits to one.
How many addresses does an IPv6 prefix contain?
A prefix of length N contains 2(128−N) addresses. A /64 holds 264 addresses, a /48 holds 280, and a /32 holds 296. These numbers are so large that host-count planning, common in IPv4, is rarely needed in IPv6.
What is the difference between /64, /48 and /32?
A /32 is typically a provider allocation, a /48 is the standard allocation for a single site, and a /64 is the standard size for a single subnet or LAN. The /64 is important because IPv6 stateless address autoconfiguration (SLAAC) requires a /64 prefix.
Does IPv6 have broadcast addresses like IPv4?
No. IPv6 does not use broadcast addresses. Instead it uses multicast groups such as the all-nodes group ff02::1. This calculator reports the network and last address of a range, but there is no reserved broadcast address in the IPv4 sense.
Is this IPv6 subnet calculator free and private?
Yes. This tool is completely free and runs entirely in your browser. The calculation is done locally in JavaScript, so the IPv6 address and prefix you enter are never transmitted to any server, logged, or stored.