What's the difference between 'Canonical' and 'Expanded' forms?

Canonical (RFC 5952) is the shortest correct way to write an IPv6 address: leading zeros stripped, the longest run of zero groups compressed to `::`. Expanded form spells out every 16-bit group: `2001:0db8:0000:0000:0000:0000:0000:0001`. Same address, different style. Canonical is what you should publish. Expanded is useful for reading bit boundaries.

How do I read the `/64` (or other prefix)?

It is the number of leading bits that define the network. The remaining 128 − prefix bits are the host portion. /64 is the de-facto subnet size for end users. ISPs usually delegate /48 to /56 networks. A /64 contains 2^64 addresses, about 18 quintillion.

Why is 'Total Hosts' so huge?

IPv6 has 128 address bits versus IPv4's 32. The address space is 2^128 ≈ 3.4 × 10^38. Even a single /64 subnet contains more addresses than the entire IPv4 internet, by a wide margin. Practical impact: stop thinking in scarce-address terms and pre-allocate generous networks.

Where does the address parsing come from?

From the `ip-address` library, run entirely in your browser. It validates the IPv6 syntax (including embedded IPv4 in `::ffff:1.2.3.4`), computes start and end addresses of the subnet, and produces the canonical form. Nothing is sent to a server.

Free, no signup, no rate limit (everything runs client-side).

Utility

IPv6 Calculator

IPv6 subnet calculator

Input

IPv6 Address

Prefix Length (Optional)

Expand and compress IPv6 addresses. Calculate subnet ranges for the next generation internet protocol.

Terminal

Console ready. Execute a command to see output...

About IPv6 Calculator

The Future is Hexadecimal

IPv6 addresses are 128-bit; written as 8 groups of 4 hexadecimal digits. They are massive.

Features

Compression: Condensing zeros (e.g., ::).
Expansion: Showing the full address.
Range: Calculating the Start and End of a prefix.

Why transition?

We ran out of IPv4 addresses in 2011. IPv6 allows for 340 undecillion addresses; enough for every atom on Earth to have its own IP.

How to use IPv6 Calculator

Enter an IPv6 address
For example 2001:db8::1. Compressed (with ::) or expanded forms both work.
(Optional) Enter a prefix length
A number 1 to 128, no slash. Default is whatever was embedded in the address (or /128 if you only gave a single host).
Hit Calculate
Canonical and expanded forms, start and end of the subnet range, and total host count (a BigInt for the large /n cases) all appear.

Frequently Asked Questions

: Canonical (RFC 5952) is the shortest correct way to write an IPv6 address: leading zeros stripped, the longest run of zero groups compressed to ::. Expanded form spells out every 16-bit group: 2001:0db8:0000:0000:0000:0000:0000:0001. Same address, different style. Canonical is what you should publish. Expanded is useful for reading bit boundaries.