IPv6 calculator

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

What it is for

Divide a larger prefix into equal smaller ones (e.g. /48 → /56 or /64, /64 → /127).

Why it helps

Know the exact subnet count and first rows — allocate your whole /48 without gaps or guessing.

Subnet splitter

From prefix

To length

From #

Count

E.g. /48 → /64 = 65536 × /64 · /64 → /127 = 2⁶³ pairs.

Quick templates

/48→/64 /48→/56 /64→/127 /64→/128

Split result

From2001:db8:1:ffff::/64

To/128

Subnets18446744073709551616

#	Prefix	Network
0	`2001:db8:1:ffff::/128`	`2001:db8:1:ffff::`
1	`2001:db8:1:ffff::1/128`	`2001:db8:1:ffff::1`
2	`2001:db8:1:ffff::2/128`	`2001:db8:1:ffff::2`
3	`2001:db8:1:ffff::3/128`	`2001:db8:1:ffff::3`
4	`2001:db8:1:ffff::4/128`	`2001:db8:1:ffff::4`
5	`2001:db8:1:ffff::5/128`	`2001:db8:1:ffff::5`
6	`2001:db8:1:ffff::6/128`	`2001:db8:1:ffff::6`
7	`2001:db8:1:ffff::7/128`	`2001:db8:1:ffff::7`
8	`2001:db8:1:ffff::8/128`	`2001:db8:1:ffff::8`
9	`2001:db8:1:ffff::9/128`	`2001:db8:1:ffff::9`
10	`2001:db8:1:ffff::a/128`	`2001:db8:1:ffff::a`
11	`2001:db8:1:ffff::b/128`	`2001:db8:1:ffff::b`
12	`2001:db8:1:ffff::c/128`	`2001:db8:1:ffff::c`
13	`2001:db8:1:ffff::d/128`	`2001:db8:1:ffff::d`
14	`2001:db8:1:ffff::e/128`	`2001:db8:1:ffff::e`
15	`2001:db8:1:ffff::f/128`	`2001:db8:1:ffff::f`