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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.

Network165.136.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
165.136.0.0
Broadcast address
165.143.255.255
First usable
165.136.0.1
Last usable
165.143.255.254
Usable hosts
524,286 (524,288 less the network and broadcast addresses)
Subnet mask
255.248.0.0
Wildcard mask
0.7.255.255 (Cisco ACLs, OSPF)
Prefix length
/13
Type
Public public
Old class
B (default /16)
As numbers
Hex A5880000 · Integer 2777153536 to 2777677823
Reverse DNS zones
136.165.in-addr.arpa
137.165.in-addr.arpa
138.165.in-addr.arpa
139.165.in-addr.arpa
140.165.in-addr.arpa
141.165.in-addr.arpa
142.165.in-addr.arpa
143.165.in-addr.arpa
/13 is not on a 8-bit boundary, so it takes 8 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100101.10001000.00000000.00000000165.136.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network10100101.10001000.00000000.00000000165.136.0.0
Broadcast10100101.10001111.11111111.11111111165.143.255.255
Split into smaller subnets/20
/14 (2)/15 (4)/16 (8)/17 (16)/18 (32)/19 (64)/20 (128)/21 (256)/22 (512)/23 (1,024)/24 (2,048)/25 (4,096)

165.136.0.0/13 makes 128 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1165.136.0.0/20165.136.0.1 to 165.136.15.254165.136.15.2554,094
2165.136.16.0/20165.136.16.1 to 165.136.31.254165.136.31.2554,094
3165.136.32.0/20165.136.32.1 to 165.136.47.254165.136.47.2554,094
4165.136.48.0/20165.136.48.1 to 165.136.63.254165.136.63.2554,094
5165.136.64.0/20165.136.64.1 to 165.136.79.254165.136.79.2554,094
6165.136.80.0/20165.136.80.1 to 165.136.95.254165.136.95.2554,094
7165.136.96.0/20165.136.96.1 to 165.136.111.254165.136.111.2554,094
8165.136.112.0/20165.136.112.1 to 165.136.127.254165.136.127.2554,094
9165.136.128.0/20165.136.128.1 to 165.136.143.254165.136.143.2554,094
10165.136.144.0/20165.136.144.1 to 165.136.159.254165.136.159.2554,094
11165.136.160.0/20165.136.160.1 to 165.136.175.254165.136.175.2554,094
12165.136.176.0/20165.136.176.1 to 165.136.191.254165.136.191.2554,094
13165.136.192.0/20165.136.192.1 to 165.136.207.254165.136.207.2554,094
14165.136.208.0/20165.136.208.1 to 165.136.223.254165.136.223.2554,094
15165.136.224.0/20165.136.224.1 to 165.136.239.254165.136.239.2554,094
16165.136.240.0/20165.136.240.1 to 165.136.255.254165.136.255.2554,094
17165.137.0.0/20165.137.0.1 to 165.137.15.254165.137.15.2554,094
18165.137.16.0/20165.137.16.1 to 165.137.31.254165.137.31.2554,094
19165.137.32.0/20165.137.32.1 to 165.137.47.254165.137.47.2554,094
20165.137.48.0/20165.137.48.1 to 165.137.63.254165.137.63.2554,094
21165.137.64.0/20165.137.64.1 to 165.137.79.254165.137.79.2554,094
22165.137.80.0/20165.137.80.1 to 165.137.95.254165.137.95.2554,094
23165.137.96.0/20165.137.96.1 to 165.137.111.254165.137.111.2554,094
24165.137.112.0/20165.137.112.1 to 165.137.127.254165.137.127.2554,094
25165.137.128.0/20165.137.128.1 to 165.137.143.254165.137.143.2554,094
26165.137.144.0/20165.137.144.1 to 165.137.159.254165.137.159.2554,094
27165.137.160.0/20165.137.160.1 to 165.137.175.254165.137.175.2554,094
28165.137.176.0/20165.137.176.1 to 165.137.191.254165.137.191.2554,094
29165.137.192.0/20165.137.192.1 to 165.137.207.254165.137.207.2554,094
30165.137.208.0/20165.137.208.1 to 165.137.223.254165.137.223.2554,094
31165.137.224.0/20165.137.224.1 to 165.137.239.254165.137.239.2554,094
32165.137.240.0/20165.137.240.1 to 165.137.255.254165.137.255.2554,094
33165.138.0.0/20165.138.0.1 to 165.138.15.254165.138.15.2554,094
34165.138.16.0/20165.138.16.1 to 165.138.31.254165.138.31.2554,094
35165.138.32.0/20165.138.32.1 to 165.138.47.254165.138.47.2554,094
36165.138.48.0/20165.138.48.1 to 165.138.63.254165.138.63.2554,094
37165.138.64.0/20165.138.64.1 to 165.138.79.254165.138.79.2554,094
38165.138.80.0/20165.138.80.1 to 165.138.95.254165.138.95.2554,094
39165.138.96.0/20165.138.96.1 to 165.138.111.254165.138.111.2554,094
40165.138.112.0/20165.138.112.1 to 165.138.127.254165.138.127.2554,094
41165.138.128.0/20165.138.128.1 to 165.138.143.254165.138.143.2554,094
42165.138.144.0/20165.138.144.1 to 165.138.159.254165.138.159.2554,094
43165.138.160.0/20165.138.160.1 to 165.138.175.254165.138.175.2554,094
44165.138.176.0/20165.138.176.1 to 165.138.191.254165.138.191.2554,094
45165.138.192.0/20165.138.192.1 to 165.138.207.254165.138.207.2554,094
46165.138.208.0/20165.138.208.1 to 165.138.223.254165.138.223.2554,094
47165.138.224.0/20165.138.224.1 to 165.138.239.254165.138.239.2554,094
48165.138.240.0/20165.138.240.1 to 165.138.255.254165.138.255.2554,094
49165.139.0.0/20165.139.0.1 to 165.139.15.254165.139.15.2554,094
50165.139.16.0/20165.139.16.1 to 165.139.31.254165.139.31.2554,094
51165.139.32.0/20165.139.32.1 to 165.139.47.254165.139.47.2554,094
52165.139.48.0/20165.139.48.1 to 165.139.63.254165.139.63.2554,094
53165.139.64.0/20165.139.64.1 to 165.139.79.254165.139.79.2554,094
54165.139.80.0/20165.139.80.1 to 165.139.95.254165.139.95.2554,094
55165.139.96.0/20165.139.96.1 to 165.139.111.254165.139.111.2554,094
56165.139.112.0/20165.139.112.1 to 165.139.127.254165.139.127.2554,094
57165.139.128.0/20165.139.128.1 to 165.139.143.254165.139.143.2554,094
58165.139.144.0/20165.139.144.1 to 165.139.159.254165.139.159.2554,094
59165.139.160.0/20165.139.160.1 to 165.139.175.254165.139.175.2554,094
60165.139.176.0/20165.139.176.1 to 165.139.191.254165.139.191.2554,094
61165.139.192.0/20165.139.192.1 to 165.139.207.254165.139.207.2554,094
62165.139.208.0/20165.139.208.1 to 165.139.223.254165.139.223.2554,094
63165.139.224.0/20165.139.224.1 to 165.139.239.254165.139.239.2554,094
64165.139.240.0/20165.139.240.1 to 165.139.255.254165.139.255.2554,094
65165.140.0.0/20165.140.0.1 to 165.140.15.254165.140.15.2554,094
66165.140.16.0/20165.140.16.1 to 165.140.31.254165.140.31.2554,094
67165.140.32.0/20165.140.32.1 to 165.140.47.254165.140.47.2554,094
68165.140.48.0/20165.140.48.1 to 165.140.63.254165.140.63.2554,094
69165.140.64.0/20165.140.64.1 to 165.140.79.254165.140.79.2554,094
70165.140.80.0/20165.140.80.1 to 165.140.95.254165.140.95.2554,094
71165.140.96.0/20165.140.96.1 to 165.140.111.254165.140.111.2554,094
72165.140.112.0/20165.140.112.1 to 165.140.127.254165.140.127.2554,094
73165.140.128.0/20165.140.128.1 to 165.140.143.254165.140.143.2554,094
74165.140.144.0/20165.140.144.1 to 165.140.159.254165.140.159.2554,094
75165.140.160.0/20165.140.160.1 to 165.140.175.254165.140.175.2554,094
76165.140.176.0/20165.140.176.1 to 165.140.191.254165.140.191.2554,094
77165.140.192.0/20165.140.192.1 to 165.140.207.254165.140.207.2554,094
78165.140.208.0/20165.140.208.1 to 165.140.223.254165.140.223.2554,094
79165.140.224.0/20165.140.224.1 to 165.140.239.254165.140.239.2554,094
80165.140.240.0/20165.140.240.1 to 165.140.255.254165.140.255.2554,094
81165.141.0.0/20165.141.0.1 to 165.141.15.254165.141.15.2554,094
82165.141.16.0/20165.141.16.1 to 165.141.31.254165.141.31.2554,094
83165.141.32.0/20165.141.32.1 to 165.141.47.254165.141.47.2554,094
84165.141.48.0/20165.141.48.1 to 165.141.63.254165.141.63.2554,094
85165.141.64.0/20165.141.64.1 to 165.141.79.254165.141.79.2554,094
86165.141.80.0/20165.141.80.1 to 165.141.95.254165.141.95.2554,094
87165.141.96.0/20165.141.96.1 to 165.141.111.254165.141.111.2554,094
88165.141.112.0/20165.141.112.1 to 165.141.127.254165.141.127.2554,094
89165.141.128.0/20165.141.128.1 to 165.141.143.254165.141.143.2554,094
90165.141.144.0/20165.141.144.1 to 165.141.159.254165.141.159.2554,094
91165.141.160.0/20165.141.160.1 to 165.141.175.254165.141.175.2554,094
92165.141.176.0/20165.141.176.1 to 165.141.191.254165.141.191.2554,094
93165.141.192.0/20165.141.192.1 to 165.141.207.254165.141.207.2554,094
94165.141.208.0/20165.141.208.1 to 165.141.223.254165.141.223.2554,094
95165.141.224.0/20165.141.224.1 to 165.141.239.254165.141.239.2554,094
96165.141.240.0/20165.141.240.1 to 165.141.255.254165.141.255.2554,094
97165.142.0.0/20165.142.0.1 to 165.142.15.254165.142.15.2554,094
98165.142.16.0/20165.142.16.1 to 165.142.31.254165.142.31.2554,094
99165.142.32.0/20165.142.32.1 to 165.142.47.254165.142.47.2554,094
100165.142.48.0/20165.142.48.1 to 165.142.63.254165.142.63.2554,094
101165.142.64.0/20165.142.64.1 to 165.142.79.254165.142.79.2554,094
102165.142.80.0/20165.142.80.1 to 165.142.95.254165.142.95.2554,094
103165.142.96.0/20165.142.96.1 to 165.142.111.254165.142.111.2554,094
104165.142.112.0/20165.142.112.1 to 165.142.127.254165.142.127.2554,094
105165.142.128.0/20165.142.128.1 to 165.142.143.254165.142.143.2554,094
106165.142.144.0/20165.142.144.1 to 165.142.159.254165.142.159.2554,094
107165.142.160.0/20165.142.160.1 to 165.142.175.254165.142.175.2554,094
108165.142.176.0/20165.142.176.1 to 165.142.191.254165.142.191.2554,094
109165.142.192.0/20165.142.192.1 to 165.142.207.254165.142.207.2554,094
110165.142.208.0/20165.142.208.1 to 165.142.223.254165.142.223.2554,094
111165.142.224.0/20165.142.224.1 to 165.142.239.254165.142.239.2554,094
112165.142.240.0/20165.142.240.1 to 165.142.255.254165.142.255.2554,094
113165.143.0.0/20165.143.0.1 to 165.143.15.254165.143.15.2554,094
114165.143.16.0/20165.143.16.1 to 165.143.31.254165.143.31.2554,094
115165.143.32.0/20165.143.32.1 to 165.143.47.254165.143.47.2554,094
116165.143.48.0/20165.143.48.1 to 165.143.63.254165.143.63.2554,094
117165.143.64.0/20165.143.64.1 to 165.143.79.254165.143.79.2554,094
118165.143.80.0/20165.143.80.1 to 165.143.95.254165.143.95.2554,094
119165.143.96.0/20165.143.96.1 to 165.143.111.254165.143.111.2554,094
120165.143.112.0/20165.143.112.1 to 165.143.127.254165.143.127.2554,094
121165.143.128.0/20165.143.128.1 to 165.143.143.254165.143.143.2554,094
122165.143.144.0/20165.143.144.1 to 165.143.159.254165.143.159.2554,094
123165.143.160.0/20165.143.160.1 to 165.143.175.254165.143.175.2554,094
124165.143.176.0/20165.143.176.1 to 165.143.191.254165.143.191.2554,094
125165.143.192.0/20165.143.192.1 to 165.143.207.254165.143.207.2554,094
126165.143.208.0/20165.143.208.1 to 165.143.223.254165.143.223.2554,094
127165.143.224.0/20165.143.224.1 to 165.143.239.254165.143.239.2554,094
128165.143.240.0/20165.143.240.1 to 165.143.255.254165.143.255.2554,094

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.