IPv6 Subnet Calculator
Calculate any IPv6 prefix: network, first and last address, total addresses and /64 count, then split it into smaller subnets.
Got a /48 or /56 from your ISP or hosting provider and need to plan your IPv6 network? GoogieHost’s free IPv6 Subnet Calculator shows the full details of any IPv6 prefix and can split it into smaller subnets in one click.
Enter an IPv6 address and prefix length (or type it in CIDR form like 2001:db8:abcd::/48). You get the network address, first and last address, total number of addresses, how many /64 subnets fit inside, the address type, the compressed and expanded forms, and the ip6.arpa reverse DNS zone.
What Does the IPv6 Subnet Calculator Show?
| Result | What it means |
|---|---|
| Compressed & Expanded Address | The short form (RFC 5952, with :: and no leading zeros) and the full 32-digit form. |
| Network (CIDR) | The prefix your address belongs to, such as 2001:db8:abcd::/48. |
| First & Last Address | The start and end of the address range. |
| Prefix Mask | The IPv6 equivalent of a subnet mask, for example ffff:ffff:ffff:ffff:: for a /64. |
| Total Addresses | The exact number of addresses in the prefix, shown in full and as a power of 2. |
| Number of /64 Subnets | How many standard LAN subnets you can create from the prefix. |
| Address Type | Global unicast, unique local (ULA), link-local, multicast, documentation, 6to4, Teredo and more. |
| Reverse DNS Zone | The ip6.arpa zone to delegate for PTR records. |
| Subnet List | When you choose “Split Into”, every resulting subnet with its range (up to the first 64). |
How to Use the IPv6 Subnet Calculator
- Enter an IPv6 address: Use any valid format: compressed (2001:db8::1), full, with an embedded IPv4 address, or with a prefix like /48.
- Pick the prefix length: Choose from /1 to /128. The default is /64, the standard size for one network.
- Split it (optional): Choose a longer prefix in “Split Into”, for example split a /48 into /56 or /64 subnets.
- Click Calculate: Copy any value with the copy icon.
How IPv6 Subnetting Works
An IPv6 address has 128 bits, written as eight groups of four hex digits. Like IPv4 CIDR, the number after the slash says how many leading bits are the network prefix. The rest identifies the interface.
The big difference from IPv4 is that you don’t subnet to save addresses. A single /64 holds 18,446,744,073,709,551,616 addresses. Instead, you subnet to organise the network: one /64 per VLAN, building, customer or service.
IPv6 also has no broadcast address (it uses multicast instead), so you don’t subtract two addresses like you do with IPv4.
Why /64 Is the Standard IPv6 Subnet
An IPv6 address is normally split into a 64-bit network prefix and a 64-bit interface ID. Features like SLAAC (stateless address autoconfiguration), privacy addresses and many router defaults expect every LAN to be exactly a /64. Using a longer prefix such as /80 on a LAN breaks SLAAC, so keep end-user networks at /64.
The main exceptions are /127 for point-to-point links between routers (RFC 6164) and /128 for a single address, such as a loopback.
IPv6 Prefix Cheat Sheet
How big each common IPv6 prefix is, and where you will usually see it:
| Prefix | Number of /64 Subnets | Total Addresses | Typical Use |
|---|---|---|---|
| /32 | 4,294,967,296 | 296 | Minimum ISP / RIR allocation |
| /40 | 16,777,216 | 288 | Large organisation or regional ISP block |
| /48 | 65,536 | 280 | One site or business (recommended) |
| /52 | 4,096 | 276 | Part of a site (e.g. a building) |
| /56 | 256 | 272 | Home or small business customer |
| /60 | 16 | 268 | Smaller home allocation by some ISPs |
| /64 | 1 | 264 | One LAN / VLAN (standard subnet) |
| /127 | — | 21 | Point-to-point router link (RFC 6164) |
| /128 | — | 20 | One single address (host route) |
Each step of 4 bits (one hex digit) multiplies the number of subnets by 16. That’s why IPv6 plans usually use prefix lengths that are multiples of 4: /48, /52, /56, /60 and /64. They also line up with ip6.arpa reverse DNS zones.
Example: Splitting a /48 Into Subnets
Say your provider assigns 2001:db8:abcd::/48. The fourth group (16 bits) is yours to use for subnets:
- Split into /52: 16 blocks, one per site or building (2001:db8:abcd::/52, 2001:db8:abcd:1000::/52 … 2001:db8:abcd:f000::/52).
- Split into /56: 256 blocks, for example one per customer or department.
- Split into /64: 65,536 LANs, from 2001:db8:abcd:0::/64 to 2001:db8:abcd:ffff::/64.
Enter the /48 in the calculator and choose the size in “Split Into” to see each block.
IPv6 Address Types
| Prefix | Type | Used for |
|---|---|---|
| 2000::/3 | Global unicast | Public internet addresses |
| fc00::/7 | Unique local (ULA) | Private networks, similar to 10.0.0.0/8 in IPv4 |
| fe80::/10 | Link-local | Communication on the local link only; every interface has one |
| ff00::/8 | Multicast | One-to-many traffic (replaces broadcast) |
| 2001:db8::/32 | Documentation | Examples in guides and books |
| ::1/128 | Loopback | The local machine, like 127.0.0.1 |
| ::ffff:0:0/96 | IPv4-mapped | IPv4 addresses inside IPv6 sockets |
To pull the IPv4 address out of an IPv4-mapped, NAT64, 6to4 or Teredo address, use our IPv6 to IPv4 Converter.
How to Shorten (Compress) an IPv6 Address
RFC 5952 sets two rules for the short form, and the calculator follows both:
- Drop leading zeros in each group: 0db8 becomes db8 and 0000 becomes 0.
- Replace the longest run of zero groups with :: (only once per address). For example, 2001:0db8:0000:0000:0000:ff00:0042:8329 becomes 2001:db8::ff00:42:8329.
IPv4 vs IPv6 Subnetting
In IPv4 you pick the smallest subnet that fits your hosts and subtract the network and broadcast addresses. In IPv6 every LAN is a /64 and you think about how many subnets you need, not how many hosts. For IPv4 networks, use the Subnet Calculator or the CIDR Calculator.
FAQs
What is an IPv6 subnet calculator?
It is a tool that takes an IPv6 address and prefix length and shows the network address, address range, total addresses, number of /64 subnets and address type. It can also split a prefix into smaller subnets.
How many /64 subnets are in a /48?
A /48 contains 65,536 /64 subnets, because 64 − 48 = 16 bits and 2 to the power of 16 is 65,536. A /56 contains 256 /64 subnets and a /60 contains 16.
How many addresses are in a /64?
A /64 contains 2 to the power of 64 addresses, which is 18,446,744,073,709,551,616. That is about 4 billion times the entire IPv4 internet.
What is the IPv6 equivalent of a subnet mask?
IPv6 uses a prefix length instead of a dotted mask, for example /64. Written out, a /64 prefix mask is ffff:ffff:ffff:ffff::, which the calculator shows as Prefix Mask.
Should I get a /48 or a /56?
Many guidelines, including RIPE-690, suggest a /48 for businesses and a /56 for home users. A /56 still gives 256 separate /64 networks, which is plenty for most homes.
Can I use a subnet smaller than /64?
You can, but SLAAC and some devices stop working on LANs smaller than a /64. Longer prefixes are mainly used for router links (/127) and single addresses (/128).
Does IPv6 have a broadcast address?
No. IPv6 has no broadcast. It uses multicast groups such as ff02::1 (all nodes on the link) instead, so every address in a subnet can be used.
Is this IPv6 subnet calculator free?
Yes. It is free with no signup or limits, and it runs in your browser, so the addresses you enter are not sent to our server.
