IPv6 Range Calculator
Enter an IPv6 address and prefix length to calculate the subnet range, first and last address, and total address count.
What is an IPv6 range?
An IPv6 range is the set of all addresses that belong to a network prefix. In CIDR notation, this is written as
address/prefix-length, such as 2001:db8::/64. The prefix identifies the network bits,
while the remaining bits are available for interface IDs or subnetting.
Unlike IPv4, IPv6 has a huge 128-bit address space. That means range calculations can involve very large numbers. This calculator handles those values directly and shows both compressed and expanded forms so you can validate your plan quickly.
How prefix length controls the range
Quick rule
Total addresses in a subnet = 2^(128 - prefix).
If the prefix is /64, host bits are 64, so total addresses are 2^64.
Example
- Input:
2001:db8::1/64 - Network:
2001:db8:: - Last address:
2001:db8::ffff:ffff:ffff:ffff - Count:
18,446,744,073,709,551,616addresses
How to use this IPv6 range calculator
- Enter an IPv6 address in any valid form (full or compressed).
- Enter the prefix length, or include it directly in the address using
/notation. - Click Calculate Range.
- Review network ID, end of range, total addresses, and normalized formats.
Common IPv6 prefix sizes
- /32 – Typical allocation to large organizations or ISPs.
- /48 – Common site allocation for enterprises.
- /56 – Often delegated to customers by providers.
- /64 – Standard LAN subnet size in IPv6.
- /128 – A single host address.
Why range calculation matters
Accurate range boundaries help with firewall policies, routing, ACL design, and documentation. If your prefix is wrong by even one bit, routes can overlap or security rules can fail. A reliable subnet range calculator prevents manual mistakes during planning and operations.
Common mistakes to avoid
- Using invalid shorthand with more than one
::. - Forgetting that IPv6 has 128 bits (not 32).
- Treating IPv6 like IPv4 broadcast logic in every context.
- Mixing prefix from input address and separate prefix field without confirming intent.
Final thoughts
IPv6 looks complex at first, but subnet math becomes straightforward once you anchor on the prefix. Use this tool to validate ranges before deploying changes. It is especially useful for network design, troubleshooting route scope, and building clean address plans.