Type an IPv6 address with its prefix, like 2001:db8:abcd:12::1/48. You get the network, the first and last address, how many addresses and /64 LANs it holds, and you can split it into smaller subnets such as /56 or /64.
Last updated:
Compressed or full form. If you leave out /prefix, the prefix field below is used
Split into child subnets
Must be longer than the network prefix, e.g. /56 or /64
Up to 4,096 rows
Enter your values to see the result.
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How to use the IPv6 Subnet Calculator
Enter an IPv6 address with its prefix, for example 2001:db8:abcd::/48.
Read the results: network, range, address count, /64 count and address type.
To subnet, enter a longer prefix in New prefix length, such as 56 or 64.
Choose how many child subnets to list and where to start, then press Calculate IPv6 subnet.
Download the CSV to keep the subnet plan.
IPv6 prefix sizes at a glance
Prefix
/64 subnets
Addresses
Typical use
/32
4,294,967,296
296
Minimum allocation to an ISP or LIR
/40
16,777,216
288
Large organisation or region
/44
1,048,576
284
Regional block
/48
65,536
280
One site (business, campus)
/52
4,096
276
Building or zone within a site
/56
256
272
Home or small office delegation
/60
16
268
Small delegation (some ISPs)
/64
1
264
One LAN or VLAN (SLAAC)
/127
—
2
Point-to-point link (RFC 6164)
/128
—
1
Single interface or loopback
How IPv6 subnetting works
An IPv6 address is 128 bits written as eight groups of four hex digits. The prefix length says how many leading bits identify the network. Network = address with all host bits set to 0; last address = all host bits set to 1. Each hex digit is 4 bits, so prefixes that are multiples of 4 end exactly on a digit boundary.
Example: 2001:db8:abcd::/48 split into /52 gives 24 = 16 subnets that differ only in the 13th hex digit: 2001:db8:abcd::/52, 2001:db8:abcd:1000::/52, 2001:db8:abcd:2000::/52 … 2001:db8:abcd:f000::/52.
Tips
Plan on nibble boundaries (/48, /52, /56, /60, /64) to keep addresses readable and reverse DNS simple.
Do not use prefixes longer than /64 on LANs where devices use SLAAC.
Use the 2001:db8::/32 documentation prefix in examples and training so nothing real is affected.
Frequently asked questions
How many /64 subnets are in a /48?
65,536. The number of /64s in a prefix /n is 2^(64 − n), so a /48 has 2^16 = 65,536, a /56 has 256 and a /60 has 16.
Why is /64 the standard IPv6 subnet size?
SLAAC (stateless address autoconfiguration) and many IPv6 features expect a 64-bit interface identifier, so LAN segments should be /64. Smaller subnets like /127 are used for point-to-point links (RFC 6164).
What prefix does an ISP give a home or a site?
Common practice is a /48 for business sites and a /56 or /48 for homes, according to RIPE and ARIN guidance. Some providers give only a /60 or /64; check what your provider delegates.
How many addresses are in an IPv6 /64?
2^64, which is 18,446,744,073,709,551,616 addresses. IPv6 has no broadcast address, so in practice all of them can be used, although the all-zero interface ID is the subnet-router anycast address.
How do I split an IPv6 prefix?
Choose a longer prefix. Going from /n to /m creates 2^(m − n) subnets, and subnet number k starts at the network address plus (k − 1) × 2^(128 − m). Splitting on 4-bit boundaries (/48, /52, /56, /60, /64) keeps the hex digits readable.
What is the address type label?
It shows which special-purpose range the network is in: 2000::/3 global unicast, fc00::/7 unique local (private), fe80::/10 link-local, ff00::/8 multicast, 2001:db8::/32 documentation, and others such as 6to4, Teredo and IPv4-mapped.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.