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IPv6 Subnet Calculator

Enter any IPv6 address plus prefix length. Instant network address, last address, and total count.

Network2001:db8::/64
Network (expanded)2001:0db8:0000:0000:0000:0000:0000:0000
Last address2001:db8::ffff:ffff:ffff:ffff
Last (expanded)2001:0db8:0000:0000:ffff:ffff:ffff:ffff
Total addresses18446744073709551616

How to read the result

Network = address with host bits zeroed. Last = network + 2^(128-prefix) − 1. A /64 holds 2^64 ≈ 1.8×10^19 addresses.

Example

2001:db8::1/64 → network 2001:db8::, last 2001:db8::ffff:ffff:ffff:ffff

FAQ

How many addresses in a /64?

2^64, about 18 quintillion. IPv6 subnets are vast.

What is the typical LAN prefix?

/64. It is the standard subnet size for SLAAC.

Is my input sent anywhere?

No. All math runs in your browser with BigInt.