IPv6 calculator

Subnet details, /127 and /128 planning, splitting, compress/expand, overlap check.

What it is for

Enter any IPv6/CIDR and see the aligned network, address range, size and expanded form.

Why it helps

Quick check before configuring interfaces, ACLs or BGP — no manual bit math.

Subnet

E.g. 2001:db8:1::/64 or 2001:db8::1/128

Results

/64 — typical SLAAC / LAN segment (2⁶⁴ addresses).

Network2001:db8:1::/64
Prefix length/64
Compressed2001:db8:1::
Expanded2001:0db8:0001:0000:0000:0000:0000:0000
First address2001:db8:1::
Last address2001:db8:1:0:ffff:ffff:ffff:ffff
Addresses18446744073709551616
ip6.arpa0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa