IPv6 Subnet Calculator
Enter an IPv6 network to see its range, size and number of /64 subnets, and optionally split it into smaller ones.
How to use this tool and read the results
Enter an IPv6 network with its prefix length, such as 2001:db8:abcd::/48. The calculator shows the network address, the first and last address, the total number of addresses and how many /64 networks fit inside. The math runs in your browser, so nothing you type is sent to us.
To plan a layout, fill in the optional split box with a longer prefix. A /48 split into /56 gives 256 networks, and the first sixteen are listed so you can copy them. Addresses are written in the short form from RFC 5952: lower case, no leading zeros and the longest run of zero groups replaced by a double colon.
For the IPv4 version of this tool use the subnet calculator. To check whether your own connection has IPv6, run the IPv6 test.
Frequently asked questions
How many addresses are in an IPv6 /64?
A /64 holds 2^64 addresses, about 18.4 quintillion. It is the standard size for a single network, so you do not count hosts in IPv6 the way you do in IPv4. Many features, including SLAAC address autoconfiguration, expect a /64.
How many /64 networks are in a /48?
A /48 holds 65,536 /64 networks, because the difference between the prefixes is 16 bits and 2^16 is 65,536. A /56 holds 256 and a /60 holds 16.
What size IPv6 block does an ISP give a home or business?
Common allocations are a /56 or /60 for homes and a /48 for businesses and sites, though it varies by provider. RFC 6177 recommends giving each site a /48 so there is room to grow.
Is there a broadcast address in IPv6?
No. IPv6 replaced broadcast with multicast, so the last address in a range is a normal usable address. That is why this calculator shows a first and last address, not a broadcast address.
How do I split an IPv6 network into smaller subnets?
Pick a longer prefix and the network divides into 2 to the power of the difference. Splitting a /48 into /52 gives 16 networks. Enter the new prefix in the split box and the calculator lists the first sixteen.