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IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

Prefix/120
Addresses256
/64 networksPart of one
Network
2001:db8::c600/120
First address
2001:db8::c600
Last address
2001:db8::c6ff
Addresses
256
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2001:0db8:0000:0000:0000:0000:0000:c600
Type
Documentation 2001:db8::/32
For examples; never used on a network
Reverse DNS zone
6.c.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
Split into smaller subnets/127
/121 (2)/122 (4)/123 (8)/124 (16)/127 (128)/128 (256)

2001:db8::c600/120 makes 128 subnets of /127.

Subnets
#SubnetLast address
12001:db8::c600/1272001:db8::c601
22001:db8::c602/1272001:db8::c603
32001:db8::c604/1272001:db8::c605
42001:db8::c606/1272001:db8::c607
52001:db8::c608/1272001:db8::c609
62001:db8::c60a/1272001:db8::c60b
72001:db8::c60c/1272001:db8::c60d
82001:db8::c60e/1272001:db8::c60f
92001:db8::c610/1272001:db8::c611
102001:db8::c612/1272001:db8::c613
112001:db8::c614/1272001:db8::c615
122001:db8::c616/1272001:db8::c617
132001:db8::c618/1272001:db8::c619
142001:db8::c61a/1272001:db8::c61b
152001:db8::c61c/1272001:db8::c61d
162001:db8::c61e/1272001:db8::c61f
172001:db8::c620/1272001:db8::c621
182001:db8::c622/1272001:db8::c623
192001:db8::c624/1272001:db8::c625
202001:db8::c626/1272001:db8::c627
212001:db8::c628/1272001:db8::c629
222001:db8::c62a/1272001:db8::c62b
232001:db8::c62c/1272001:db8::c62d
242001:db8::c62e/1272001:db8::c62f
252001:db8::c630/1272001:db8::c631
262001:db8::c632/1272001:db8::c633
272001:db8::c634/1272001:db8::c635
282001:db8::c636/1272001:db8::c637
292001:db8::c638/1272001:db8::c639
302001:db8::c63a/1272001:db8::c63b
312001:db8::c63c/1272001:db8::c63d
322001:db8::c63e/1272001:db8::c63f
332001:db8::c640/1272001:db8::c641
342001:db8::c642/1272001:db8::c643
352001:db8::c644/1272001:db8::c645
362001:db8::c646/1272001:db8::c647
372001:db8::c648/1272001:db8::c649
382001:db8::c64a/1272001:db8::c64b
392001:db8::c64c/1272001:db8::c64d
402001:db8::c64e/1272001:db8::c64f
412001:db8::c650/1272001:db8::c651
422001:db8::c652/1272001:db8::c653
432001:db8::c654/1272001:db8::c655
442001:db8::c656/1272001:db8::c657
452001:db8::c658/1272001:db8::c659
462001:db8::c65a/1272001:db8::c65b
472001:db8::c65c/1272001:db8::c65d
482001:db8::c65e/1272001:db8::c65f
492001:db8::c660/1272001:db8::c661
502001:db8::c662/1272001:db8::c663
512001:db8::c664/1272001:db8::c665
522001:db8::c666/1272001:db8::c667
532001:db8::c668/1272001:db8::c669
542001:db8::c66a/1272001:db8::c66b
552001:db8::c66c/1272001:db8::c66d
562001:db8::c66e/1272001:db8::c66f
572001:db8::c670/1272001:db8::c671
582001:db8::c672/1272001:db8::c673
592001:db8::c674/1272001:db8::c675
602001:db8::c676/1272001:db8::c677
612001:db8::c678/1272001:db8::c679
622001:db8::c67a/1272001:db8::c67b
632001:db8::c67c/1272001:db8::c67d
642001:db8::c67e/1272001:db8::c67f
652001:db8::c680/1272001:db8::c681
662001:db8::c682/1272001:db8::c683
672001:db8::c684/1272001:db8::c685
682001:db8::c686/1272001:db8::c687
692001:db8::c688/1272001:db8::c689
702001:db8::c68a/1272001:db8::c68b
712001:db8::c68c/1272001:db8::c68d
722001:db8::c68e/1272001:db8::c68f
732001:db8::c690/1272001:db8::c691
742001:db8::c692/1272001:db8::c693
752001:db8::c694/1272001:db8::c695
762001:db8::c696/1272001:db8::c697
772001:db8::c698/1272001:db8::c699
782001:db8::c69a/1272001:db8::c69b
792001:db8::c69c/1272001:db8::c69d
802001:db8::c69e/1272001:db8::c69f
812001:db8::c6a0/1272001:db8::c6a1
822001:db8::c6a2/1272001:db8::c6a3
832001:db8::c6a4/1272001:db8::c6a5
842001:db8::c6a6/1272001:db8::c6a7
852001:db8::c6a8/1272001:db8::c6a9
862001:db8::c6aa/1272001:db8::c6ab
872001:db8::c6ac/1272001:db8::c6ad
882001:db8::c6ae/1272001:db8::c6af
892001:db8::c6b0/1272001:db8::c6b1
902001:db8::c6b2/1272001:db8::c6b3
912001:db8::c6b4/1272001:db8::c6b5
922001:db8::c6b6/1272001:db8::c6b7
932001:db8::c6b8/1272001:db8::c6b9
942001:db8::c6ba/1272001:db8::c6bb
952001:db8::c6bc/1272001:db8::c6bd
962001:db8::c6be/1272001:db8::c6bf
972001:db8::c6c0/1272001:db8::c6c1
982001:db8::c6c2/1272001:db8::c6c3
992001:db8::c6c4/1272001:db8::c6c5
1002001:db8::c6c6/1272001:db8::c6c7
1012001:db8::c6c8/1272001:db8::c6c9
1022001:db8::c6ca/1272001:db8::c6cb
1032001:db8::c6cc/1272001:db8::c6cd
1042001:db8::c6ce/1272001:db8::c6cf
1052001:db8::c6d0/1272001:db8::c6d1
1062001:db8::c6d2/1272001:db8::c6d3
1072001:db8::c6d4/1272001:db8::c6d5
1082001:db8::c6d6/1272001:db8::c6d7
1092001:db8::c6d8/1272001:db8::c6d9
1102001:db8::c6da/1272001:db8::c6db
1112001:db8::c6dc/1272001:db8::c6dd
1122001:db8::c6de/1272001:db8::c6df
1132001:db8::c6e0/1272001:db8::c6e1
1142001:db8::c6e2/1272001:db8::c6e3
1152001:db8::c6e4/1272001:db8::c6e5
1162001:db8::c6e6/1272001:db8::c6e7
1172001:db8::c6e8/1272001:db8::c6e9
1182001:db8::c6ea/1272001:db8::c6eb
1192001:db8::c6ec/1272001:db8::c6ed
1202001:db8::c6ee/1272001:db8::c6ef
1212001:db8::c6f0/1272001:db8::c6f1
1222001:db8::c6f2/1272001:db8::c6f3
1232001:db8::c6f4/1272001:db8::c6f5
1242001:db8::c6f6/1272001:db8::c6f7
1252001:db8::c6f8/1272001:db8::c6f9
1262001:db8::c6fa/1272001:db8::c6fb
1272001:db8::c6fc/1272001:db8::c6fd
1282001:db8::c6fe/1272001:db8::c6ff

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.