# IPv6 Subnet Calculator – Expand & Compress

> Expand or compress any IPv6 address, see total addresses and /64 subnet counts per prefix, detect special ranges, and share by link.

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# IPv6 Subnet Calculator

Expand or compress any IPv6 address, inspect its prefix and type, count addresses and /64 subnets — instantly and server-side.

## Results for 2001:db8::/32

2001:db8::/32 is the network in CIDR notation · Documentation (RFC 3849)

- **Fully expanded form:** 2001:0db8:0000:0000:0000:0000:0000:0000
- **Compressed form (RFC 5952):** 2001:db8::
- **Prefix length:** /32
- **Type:** Documentation (RFC 3849)
- **Total addresses:** 79,228,162,514,264,337,593,543,950,336
- **/64 subnets inside:** 4,294,967,296
- **First address of prefix:** 2001:db8::
- **Last address of prefix:** 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff
- **Network in CIDR notation:** 2001:db8::/32

## Keep exploring IPv6

Reference pages for the most common allocations: [/32 reference](https://itinsighthub.com/ipv6/32/) [/48 reference](https://itinsighthub.com/ipv6/48/) [/56 reference](https://itinsighthub.com/ipv6/56/) [/64 reference](https://itinsighthub.com/ipv6/64/)

## Working with IPv6 prefixes

An IPv6 address is 128 bits long and written as eight hexadecimal groups. Any single run of all-zero groups can be squeezed into `::`, which is why `2001:0db8:0000:0000:0000:0000:0000:0001` and `2001:db8::1` are the same address. A prefix written with a slash (“/48”) fixes that many leading bits, leaving the rest for subnets and hosts.

The /64 boundary is special. Interface identifiers are 64 bits wide, so a /64 is the standard subnet size — the smallest prefix that supports SLAAC, the mechanism that lets hosts configure their own addresses from router advertisements. Networks are therefore planned hierarchically: an ISP holds a /32, hands each customer site a /48 or /56, and every LAN inside it becomes one /64 containing 18 quintillion addresses.

Special ranges to know: `2001:db8::/32` is reserved for documentation (RFC 3849), `fe80::/10` is link-local, `fc00::/7` holds unique-local addresses, and `::1` is loopback — this tool labels them automatically.

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