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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.

Network243.96.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
243.96.0.0
Broadcast address
243.111.255.255
First usable
243.96.0.1
Last usable
243.111.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F3600000 · Integer 4083154944 to 4084203519
Reverse DNS zones
96.243.in-addr.arpa
97.243.in-addr.arpa
98.243.in-addr.arpa
99.243.in-addr.arpa
100.243.in-addr.arpa
101.243.in-addr.arpa
102.243.in-addr.arpa
103.243.in-addr.arpa
104.243.in-addr.arpa
105.243.in-addr.arpa
106.243.in-addr.arpa
107.243.in-addr.arpa
108.243.in-addr.arpa
109.243.in-addr.arpa
110.243.in-addr.arpa
111.243.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110011.01100000.00000000.00000000243.96.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11110011.01100000.00000000.00000000243.96.0.0
Broadcast11110011.01101111.11111111.11111111243.111.255.255
Split into smaller subnets/19
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

243.96.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1243.96.0.0/19243.96.0.1 to 243.96.31.254243.96.31.2558,190
2243.96.32.0/19243.96.32.1 to 243.96.63.254243.96.63.2558,190
3243.96.64.0/19243.96.64.1 to 243.96.95.254243.96.95.2558,190
4243.96.96.0/19243.96.96.1 to 243.96.127.254243.96.127.2558,190
5243.96.128.0/19243.96.128.1 to 243.96.159.254243.96.159.2558,190
6243.96.160.0/19243.96.160.1 to 243.96.191.254243.96.191.2558,190
7243.96.192.0/19243.96.192.1 to 243.96.223.254243.96.223.2558,190
8243.96.224.0/19243.96.224.1 to 243.96.255.254243.96.255.2558,190
9243.97.0.0/19243.97.0.1 to 243.97.31.254243.97.31.2558,190
10243.97.32.0/19243.97.32.1 to 243.97.63.254243.97.63.2558,190
11243.97.64.0/19243.97.64.1 to 243.97.95.254243.97.95.2558,190
12243.97.96.0/19243.97.96.1 to 243.97.127.254243.97.127.2558,190
13243.97.128.0/19243.97.128.1 to 243.97.159.254243.97.159.2558,190
14243.97.160.0/19243.97.160.1 to 243.97.191.254243.97.191.2558,190
15243.97.192.0/19243.97.192.1 to 243.97.223.254243.97.223.2558,190
16243.97.224.0/19243.97.224.1 to 243.97.255.254243.97.255.2558,190
17243.98.0.0/19243.98.0.1 to 243.98.31.254243.98.31.2558,190
18243.98.32.0/19243.98.32.1 to 243.98.63.254243.98.63.2558,190
19243.98.64.0/19243.98.64.1 to 243.98.95.254243.98.95.2558,190
20243.98.96.0/19243.98.96.1 to 243.98.127.254243.98.127.2558,190
21243.98.128.0/19243.98.128.1 to 243.98.159.254243.98.159.2558,190
22243.98.160.0/19243.98.160.1 to 243.98.191.254243.98.191.2558,190
23243.98.192.0/19243.98.192.1 to 243.98.223.254243.98.223.2558,190
24243.98.224.0/19243.98.224.1 to 243.98.255.254243.98.255.2558,190
25243.99.0.0/19243.99.0.1 to 243.99.31.254243.99.31.2558,190
26243.99.32.0/19243.99.32.1 to 243.99.63.254243.99.63.2558,190
27243.99.64.0/19243.99.64.1 to 243.99.95.254243.99.95.2558,190
28243.99.96.0/19243.99.96.1 to 243.99.127.254243.99.127.2558,190
29243.99.128.0/19243.99.128.1 to 243.99.159.254243.99.159.2558,190
30243.99.160.0/19243.99.160.1 to 243.99.191.254243.99.191.2558,190
31243.99.192.0/19243.99.192.1 to 243.99.223.254243.99.223.2558,190
32243.99.224.0/19243.99.224.1 to 243.99.255.254243.99.255.2558,190
33243.100.0.0/19243.100.0.1 to 243.100.31.254243.100.31.2558,190
34243.100.32.0/19243.100.32.1 to 243.100.63.254243.100.63.2558,190
35243.100.64.0/19243.100.64.1 to 243.100.95.254243.100.95.2558,190
36243.100.96.0/19243.100.96.1 to 243.100.127.254243.100.127.2558,190
37243.100.128.0/19243.100.128.1 to 243.100.159.254243.100.159.2558,190
38243.100.160.0/19243.100.160.1 to 243.100.191.254243.100.191.2558,190
39243.100.192.0/19243.100.192.1 to 243.100.223.254243.100.223.2558,190
40243.100.224.0/19243.100.224.1 to 243.100.255.254243.100.255.2558,190
41243.101.0.0/19243.101.0.1 to 243.101.31.254243.101.31.2558,190
42243.101.32.0/19243.101.32.1 to 243.101.63.254243.101.63.2558,190
43243.101.64.0/19243.101.64.1 to 243.101.95.254243.101.95.2558,190
44243.101.96.0/19243.101.96.1 to 243.101.127.254243.101.127.2558,190
45243.101.128.0/19243.101.128.1 to 243.101.159.254243.101.159.2558,190
46243.101.160.0/19243.101.160.1 to 243.101.191.254243.101.191.2558,190
47243.101.192.0/19243.101.192.1 to 243.101.223.254243.101.223.2558,190
48243.101.224.0/19243.101.224.1 to 243.101.255.254243.101.255.2558,190
49243.102.0.0/19243.102.0.1 to 243.102.31.254243.102.31.2558,190
50243.102.32.0/19243.102.32.1 to 243.102.63.254243.102.63.2558,190
51243.102.64.0/19243.102.64.1 to 243.102.95.254243.102.95.2558,190
52243.102.96.0/19243.102.96.1 to 243.102.127.254243.102.127.2558,190
53243.102.128.0/19243.102.128.1 to 243.102.159.254243.102.159.2558,190
54243.102.160.0/19243.102.160.1 to 243.102.191.254243.102.191.2558,190
55243.102.192.0/19243.102.192.1 to 243.102.223.254243.102.223.2558,190
56243.102.224.0/19243.102.224.1 to 243.102.255.254243.102.255.2558,190
57243.103.0.0/19243.103.0.1 to 243.103.31.254243.103.31.2558,190
58243.103.32.0/19243.103.32.1 to 243.103.63.254243.103.63.2558,190
59243.103.64.0/19243.103.64.1 to 243.103.95.254243.103.95.2558,190
60243.103.96.0/19243.103.96.1 to 243.103.127.254243.103.127.2558,190
61243.103.128.0/19243.103.128.1 to 243.103.159.254243.103.159.2558,190
62243.103.160.0/19243.103.160.1 to 243.103.191.254243.103.191.2558,190
63243.103.192.0/19243.103.192.1 to 243.103.223.254243.103.223.2558,190
64243.103.224.0/19243.103.224.1 to 243.103.255.254243.103.255.2558,190
65243.104.0.0/19243.104.0.1 to 243.104.31.254243.104.31.2558,190
66243.104.32.0/19243.104.32.1 to 243.104.63.254243.104.63.2558,190
67243.104.64.0/19243.104.64.1 to 243.104.95.254243.104.95.2558,190
68243.104.96.0/19243.104.96.1 to 243.104.127.254243.104.127.2558,190
69243.104.128.0/19243.104.128.1 to 243.104.159.254243.104.159.2558,190
70243.104.160.0/19243.104.160.1 to 243.104.191.254243.104.191.2558,190
71243.104.192.0/19243.104.192.1 to 243.104.223.254243.104.223.2558,190
72243.104.224.0/19243.104.224.1 to 243.104.255.254243.104.255.2558,190
73243.105.0.0/19243.105.0.1 to 243.105.31.254243.105.31.2558,190
74243.105.32.0/19243.105.32.1 to 243.105.63.254243.105.63.2558,190
75243.105.64.0/19243.105.64.1 to 243.105.95.254243.105.95.2558,190
76243.105.96.0/19243.105.96.1 to 243.105.127.254243.105.127.2558,190
77243.105.128.0/19243.105.128.1 to 243.105.159.254243.105.159.2558,190
78243.105.160.0/19243.105.160.1 to 243.105.191.254243.105.191.2558,190
79243.105.192.0/19243.105.192.1 to 243.105.223.254243.105.223.2558,190
80243.105.224.0/19243.105.224.1 to 243.105.255.254243.105.255.2558,190
81243.106.0.0/19243.106.0.1 to 243.106.31.254243.106.31.2558,190
82243.106.32.0/19243.106.32.1 to 243.106.63.254243.106.63.2558,190
83243.106.64.0/19243.106.64.1 to 243.106.95.254243.106.95.2558,190
84243.106.96.0/19243.106.96.1 to 243.106.127.254243.106.127.2558,190
85243.106.128.0/19243.106.128.1 to 243.106.159.254243.106.159.2558,190
86243.106.160.0/19243.106.160.1 to 243.106.191.254243.106.191.2558,190
87243.106.192.0/19243.106.192.1 to 243.106.223.254243.106.223.2558,190
88243.106.224.0/19243.106.224.1 to 243.106.255.254243.106.255.2558,190
89243.107.0.0/19243.107.0.1 to 243.107.31.254243.107.31.2558,190
90243.107.32.0/19243.107.32.1 to 243.107.63.254243.107.63.2558,190
91243.107.64.0/19243.107.64.1 to 243.107.95.254243.107.95.2558,190
92243.107.96.0/19243.107.96.1 to 243.107.127.254243.107.127.2558,190
93243.107.128.0/19243.107.128.1 to 243.107.159.254243.107.159.2558,190
94243.107.160.0/19243.107.160.1 to 243.107.191.254243.107.191.2558,190
95243.107.192.0/19243.107.192.1 to 243.107.223.254243.107.223.2558,190
96243.107.224.0/19243.107.224.1 to 243.107.255.254243.107.255.2558,190
97243.108.0.0/19243.108.0.1 to 243.108.31.254243.108.31.2558,190
98243.108.32.0/19243.108.32.1 to 243.108.63.254243.108.63.2558,190
99243.108.64.0/19243.108.64.1 to 243.108.95.254243.108.95.2558,190
100243.108.96.0/19243.108.96.1 to 243.108.127.254243.108.127.2558,190
101243.108.128.0/19243.108.128.1 to 243.108.159.254243.108.159.2558,190
102243.108.160.0/19243.108.160.1 to 243.108.191.254243.108.191.2558,190
103243.108.192.0/19243.108.192.1 to 243.108.223.254243.108.223.2558,190
104243.108.224.0/19243.108.224.1 to 243.108.255.254243.108.255.2558,190
105243.109.0.0/19243.109.0.1 to 243.109.31.254243.109.31.2558,190
106243.109.32.0/19243.109.32.1 to 243.109.63.254243.109.63.2558,190
107243.109.64.0/19243.109.64.1 to 243.109.95.254243.109.95.2558,190
108243.109.96.0/19243.109.96.1 to 243.109.127.254243.109.127.2558,190
109243.109.128.0/19243.109.128.1 to 243.109.159.254243.109.159.2558,190
110243.109.160.0/19243.109.160.1 to 243.109.191.254243.109.191.2558,190
111243.109.192.0/19243.109.192.1 to 243.109.223.254243.109.223.2558,190
112243.109.224.0/19243.109.224.1 to 243.109.255.254243.109.255.2558,190
113243.110.0.0/19243.110.0.1 to 243.110.31.254243.110.31.2558,190
114243.110.32.0/19243.110.32.1 to 243.110.63.254243.110.63.2558,190
115243.110.64.0/19243.110.64.1 to 243.110.95.254243.110.95.2558,190
116243.110.96.0/19243.110.96.1 to 243.110.127.254243.110.127.2558,190
117243.110.128.0/19243.110.128.1 to 243.110.159.254243.110.159.2558,190
118243.110.160.0/19243.110.160.1 to 243.110.191.254243.110.191.2558,190
119243.110.192.0/19243.110.192.1 to 243.110.223.254243.110.223.2558,190
120243.110.224.0/19243.110.224.1 to 243.110.255.254243.110.255.2558,190
121243.111.0.0/19243.111.0.1 to 243.111.31.254243.111.31.2558,190
122243.111.32.0/19243.111.32.1 to 243.111.63.254243.111.63.2558,190
123243.111.64.0/19243.111.64.1 to 243.111.95.254243.111.95.2558,190
124243.111.96.0/19243.111.96.1 to 243.111.127.254243.111.127.2558,190
125243.111.128.0/19243.111.128.1 to 243.111.159.254243.111.159.2558,190
126243.111.160.0/19243.111.160.1 to 243.111.191.254243.111.191.2558,190
127243.111.192.0/19243.111.192.1 to 243.111.223.254243.111.223.2558,190
128243.111.224.0/19243.111.224.1 to 243.111.255.254243.111.255.2558,190

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.