IPv6 Subnet Calculator

Calculate IPv6 subnet details from any prefix. Enter an IPv6 address with prefix length to get the network range, first and last address, and total number of addresses in the subnet.

Understanding IPv6 Subnetting

IPv6 subnetting works differently from IPv4 subnetting. With 128-bit addresses (vs IPv4's 32-bit), there are far more addresses available — making subnetting about organization rather than conservation. ISPs typically assign /48 or /56 prefixes to customers, which are then subdivided into /64 subnets for individual network segments.

If you're transitioning from IPv4, understanding the IPv6 addressing hierarchy is essential. Use our IPv6 Converter to expand and compress addresses, and our IPv4 to IPv6 Converter for mapping between protocols.

Common IPv6 Prefix Lengths

Prefix	Assignment	/64 Subnets	Total Addresses
/32	ISP allocation from RIR	4.3 billion	2^96
/48	Site allocation (standard)	65,536	2^80
/56	Residential allocation	256	2^72
/64	Single subnet (standard LAN)	1	2^64 (~18.4 quintillion)
/128	Single host (loopback)	N/A	1

IPv6 Address Types

IPv6 has several address types, each identified by their prefix:

Type	Prefix	Scope	Purpose
Global Unicast	2000::/3	Internet	Publicly routable (like IPv4 public IPs)
Link-Local	fe80::/10	Single link	Auto-configured, never routed
Unique Local	fc00::/7	Organization	Like IPv4 private (RFC 1918)
Multicast	ff00::/8	Varies	One-to-many communication
Loopback	::1/128	Host	Equivalent to 127.0.0.1

Learn more about multicast addresses with our IPv6 Multicast Reference and generate link-local addresses with the Link-Local Generator.

Pro Tip: In IPv6, the standard subnet size is /64 for any LAN segment. Don't use smaller subnets (like /112 or /126) unless you have a specific reason — many IPv6 features including SLAAC (Stateless Address Autoconfiguration) require a /64 prefix to function. Use our Prefix Delegation Calculator to plan how to split your /48 or /56 allocation into /64 subnets.

Planning Your IPv6 Subnet Layout

With a typical /48 allocation giving you 65,536 /64 subnets, you can organize generously. Here's a recommended approach for a home network:

# Example: ISP assigned 2001:db8:abc0::/48

2001:db8:abc0:0001::/64  → Main LAN (PCs, phones)
2001:db8:abc0:0002::/64  → IoT VLAN
2001:db8:abc0:0003::/64  → Guest WiFi
2001:db8:abc0:0004::/64  → Cameras
2001:db8:abc0:0010::/64  → Server VLAN
2001:db8:abc0:0020::/64  → Management VLAN

# Still have 65,530 subnets available!

Note: Unlike IPv4 where you carefully conserve addresses, IPv6 gives you more subnets than you'll ever need. Even a residential /56 assignment provides 256 /64 subnets. Focus on logical organization rather than address conservation. Check if your ISP provides IPv6 by visiting What Is My IP — if you see an IPv6 address, you're already connected.

IPv6 vs IPv4 Subnetting Comparison

Aspect	IPv4	IPv6
Address size	32 bits	128 bits
Standard LAN subnet	/24 (254 hosts)	/64 (2^64 hosts)
Subnet masks	Dotted decimal or CIDR	Prefix length only (/nn)
Address conservation	Critical concern	Not needed
NAT required	Usually (learn more)	No — end-to-end
Auto-configuration	DHCP required	SLAAC built-in

Key Takeaways

IPv6 subnetting uses /64 as the standard LAN prefix — each subnet has 2^64 addresses.
ISPs typically assign /48 (65,536 subnets) or /56 (256 subnets) to customers.
Focus on logical organization rather than address conservation — you have plenty.
SLAAC requires /64 prefixes — don't use smaller subnets on LAN segments.
Use Prefix Delegation Calculator to plan your subnet hierarchy.
Verify your IPv6 connectivity at What Is My IP and check dual-stack with our Dual-Stack Checker.

Video: IPv6 Subnetting Explained

Related Tools

Frequently Asked Questions

Why is /64 the standard subnet size in IPv6?

The /64 prefix is required for SLAAC (Stateless Address Autoconfiguration) to work. The last 64 bits form the Interface Identifier, typically derived from the device's MAC address via EUI-64. Using a different prefix length breaks auto-configuration.

How many subnets do I get with a /48 prefix?

A /48 gives you 2^16 = 65,536 /64 subnets. That's enough for even the largest enterprise networks. Residential users typically receive /56 (256 subnets), which is still more than sufficient.

Do I still need NAT with IPv6?

No. IPv6 provides enough addresses for every device to have a globally unique address, eliminating the need for NAT. This restores true end-to-end connectivity. Firewalls still provide security without NAT.

How do I subnet IPv6 for my home network?

Take your ISP-assigned prefix (typically /48 or /56) and divide it into /64 subnets. Assign one /64 per VLAN or network segment. Use our Prefix Delegation Calculator to plan the split.

Can I use IPv6 subnets smaller than /64?

Technically yes, but it's not recommended. Subnets smaller than /64 break SLAAC and may cause compatibility issues. Point-to-point links sometimes use /126 or /127, but LAN segments should always be /64.

Is IPv6 subnetting harder than IPv4?

IPv6 subnetting is actually simpler because you always use /64 for LANs. The complexity is in the addressing notation (hex) rather than the subnetting math. Once you're comfortable with hex, it's straightforward.

About Tommy N.

Tommy is the founder of RouterHax and a network engineer with 10+ years of experience in home and enterprise networking. He specializes in router configuration, WiFi optimization, and network security. When not writing guides, he's testing the latest mesh WiFi systems and helping readers troubleshoot their home networks.