IPv6 subnet calculator
Calculate an IPv6 address range with exact arithmetic.
IPv6 subnet calculator
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How to use IPv6 subnet calculator
The IPv6 subnet calculator takes an IPv6 address with or without a /prefix and returns the network, first address, last address, total address count and netmask. Calculations use exact BigInt arithmetic across all 128 bits, so even huge totals are printed in full. Without a prefix it uses the CIDR setting, which defaults to /64.
- Type or paste your source, or load an example.
- Change the basic settings or open Advanced mode to fine-tune the result.
- Review and copy or download your result. Pause Live results to run manually. Sources or individual settings above 20,000 characters require an explicit run.
What this tool supports
Calculate an IPv6 address range with exact arithmetic.
- CIDR prefix (used if address has no /prefix)
- Range: 0 to 128
Limits and processing
Text operations generally accept up to 2,000,000 characters. Individual parsers, generators and formulas apply additional limits shown by their controls.
Example source
2001:db8::1234/64
Frequently asked questions
How many addresses are in an IPv6 /64?
A /64 contains 2 to the power of 64, or 18446744073709551616 addresses. The calculator prints the exact figure rather than scientific notation; it describes the size of the address range, not a count of devices.
How are IPv6 addresses written in the results?
Results are written as eight colon-separated hexadecimal groups without :: compression, for example 2001:db8:0:0:0:0:0:0. That full form makes the first and last addresses of a range easy to compare.
Why is there no broadcast address in the IPv6 results?
IPv6 does not use broadcast, so the calculator lists only network, first address, last address, total and netmask. IPv4 input is rejected with a note to use the IPv4 subnet calculator instead.
Where is my input processed?
This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.
What are the input limits?
Text operations generally accept up to 2,000,000 characters. Individual parsers, generators and formulas apply additional limits shown by their controls.