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IP Addressing

IPv6 Calculator

Paste an IPv6 address with its prefix and get the network, the compressed and expanded forms, the range, how many /64s fit and the address type.

Accepts :: (compression) and embedded IPv4. E.g.: fe80::1/64.

2^80 addresses
redzilla.cl — ipv6 
 
 
 
 Network —  
 
 First —  
 
 Last —  
 
 
 
Address notation
 
 
Compressed
 
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Expanded
 
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Reverse DNS
 
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 IPv6 address types 
 
 
PrefixType
  
::/128Unspecified
::1/128Loopback
::ffff:0:0/96IPv4-mapped
2000::/3Global unicast
2001:db8::/32Documentation
fc00::/7Unique local (ULA)
fe80::/10Link-local
ff00::/8Multicast
  
 
 
 
 
 
Runs locally in your browser · no sign-up · nothing leaves your browser
  
 
 
How it works
 
The calculator takes an IPv6 address with its prefix (for example 2001:db8::/48) and breaks it down completely: compressed and expanded forms, network address, full block range, how many addresses it contains, how many /64 subnets fit, the address type (global unicast, ULA, link-local, multicast, documentation, etc.) and the reverse DNS record under ip6.arpa. It accepts :: compression and embedded IPv4 (::ffff:192.0.2.1).
Internally it works with the full 128 bits: it ANDs the prefix mask with the address to get the network and uses its inverse for the last address of the block, exactly like a router. The compressed form follows the canonical rules of RFC 5952 (lowercase, no leading zeros, :: on the longest zero run) and the type classification follows the IANA ranges: 2000::/3 global, fc00::/7 ULA, fe80::/10 link-local, ff00::/8 multicast and 2001:db8::/32 for documentation.
 
 
Example: what is inside 2001:db8::/48?
 
     
  1. The network is 2001:db8:: and the range runs from 2001:db8:: to 2001:db8:0:ffff:ffff:ffff:ffff:ffff.
  2. There are 128 − 48 = 80 host bits left: 2^80 ≈ 1.2 × 10^24 addresses.
  3. Between /48 and /64 there are 16 subnet bits: 2^16 = 65,536 available /64 subnets.
  4. The detected type is Documentation (2001:db8::/32): that block is reserved for examples and is not routed on the internet.
    5.  
 
 
 
 
Frequently asked questions
 
 
 How many /64 subnets fit in a /48 or a /56? 
A /48 holds 2^16 = 65,536 /64 subnets; a /56 holds 2^8 = 256. That is why ISPs typically delegate a /48 to businesses and a /56 to residential customers: every VLAN or segment gets its own /64 with room to spare.
 
 What is the difference between the compressed and expanded forms of an IPv6 address? 
They are the same address written differently. The expanded form shows all 8 groups of 4 full hexadecimal digits; the compressed form drops leading zeros and replaces the longest run of zeros with a double colon, following RFC 5952. For example, 2001:0db8:0000:0000:0000:0000:0000:0001 compresses to 2001:db8::1.
 
 Why do almost all IPv6 networks use /64 instead of longer prefixes? 
Because SLAAC (stateless address autoconfiguration, RFC 4862) requires exactly 64 bits of interface identifier. With prefixes longer than /64 autoconfiguration stops working and mechanisms such as privacy identifiers break; longer prefixes are reserved almost exclusively for point-to-point links (/127, RFC 6164) or loopbacks (/128).
 
 Can I paste addresses from my internal network safely? 
Yes. All the math runs in your browser using 128-bit arithmetic (BigInt): no address is ever sent to a server, so you can analyze internal or production prefixes without exposing them.
 
 
 
  
   
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 Disclaimer We take great care to keep every tool accurate and review it thoroughly; even so, we can't guarantee it is free of errors or take responsibility for how the results are used. We recommend double-checking anything critical. 
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