IPv6 Subnet Calculator
Use this IPv6 subnet calculator to inspect a prefix, identify the first and last address in the range, and see the size of the address block for network planning.
Calculator
How to use this calculator
Enter the planning values that match your network, storage, or cloud scenario. Use realistic production assumptions when sizing anything that affects availability, performance, or cost.
Formula or calculation method
The calculator expands the IPv6 address to eight hexadecimal groups, converts it to a 128-bit integer, applies the prefix mask, then derives the first and last address from the host-bit range.
Worked example
For 2001:db8:abcd:12::1/64, the network prefix is 2001:db8:abcd:12:0:0:0:0/64 and the block contains 2^64 addresses.
Practical planning tips
- Document delegated IPv6 prefixes.
- Check interface addressing against the expected prefix.
- Plan routed /64, /56, or /48 allocations.
Common mistakes to avoid
- Using IPv4 host-count assumptions with IPv6.
- Forgetting that a /64 is the common LAN prefix size.
- Typing invalid hexadecimal groups.
Frequently asked questions
Does this compress IPv6 output?
No. It shows expanded groups so the network and last address are unambiguous.
Can I use a /128?
Yes. A /128 represents one exact IPv6 address.