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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.

Network156.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
156.0.0.0
Broadcast address
159.255.255.255
First usable
156.0.0.1
Last usable
159.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Public public
Old class
B (default /16)
As numbers
Hex 9C000000 · Integer 2617245696 to 2684354559
Reverse DNS zones
156.in-addr.arpa
157.in-addr.arpa
158.in-addr.arpa
159.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10011100.00000000.00000000.00000000156.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network10011100.00000000.00000000.00000000156.0.0.0
Broadcast10011111.11111111.11111111.11111111159.255.255.255
Split into smaller subnets/13
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

156.0.0.0/6 makes 128 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1156.0.0.0/13156.0.0.1 to 156.7.255.254156.7.255.255524,286
2156.8.0.0/13156.8.0.1 to 156.15.255.254156.15.255.255524,286
3156.16.0.0/13156.16.0.1 to 156.23.255.254156.23.255.255524,286
4156.24.0.0/13156.24.0.1 to 156.31.255.254156.31.255.255524,286
5156.32.0.0/13156.32.0.1 to 156.39.255.254156.39.255.255524,286
6156.40.0.0/13156.40.0.1 to 156.47.255.254156.47.255.255524,286
7156.48.0.0/13156.48.0.1 to 156.55.255.254156.55.255.255524,286
8156.56.0.0/13156.56.0.1 to 156.63.255.254156.63.255.255524,286
9156.64.0.0/13156.64.0.1 to 156.71.255.254156.71.255.255524,286
10156.72.0.0/13156.72.0.1 to 156.79.255.254156.79.255.255524,286
11156.80.0.0/13156.80.0.1 to 156.87.255.254156.87.255.255524,286
12156.88.0.0/13156.88.0.1 to 156.95.255.254156.95.255.255524,286
13156.96.0.0/13156.96.0.1 to 156.103.255.254156.103.255.255524,286
14156.104.0.0/13156.104.0.1 to 156.111.255.254156.111.255.255524,286
15156.112.0.0/13156.112.0.1 to 156.119.255.254156.119.255.255524,286
16156.120.0.0/13156.120.0.1 to 156.127.255.254156.127.255.255524,286
17156.128.0.0/13156.128.0.1 to 156.135.255.254156.135.255.255524,286
18156.136.0.0/13156.136.0.1 to 156.143.255.254156.143.255.255524,286
19156.144.0.0/13156.144.0.1 to 156.151.255.254156.151.255.255524,286
20156.152.0.0/13156.152.0.1 to 156.159.255.254156.159.255.255524,286
21156.160.0.0/13156.160.0.1 to 156.167.255.254156.167.255.255524,286
22156.168.0.0/13156.168.0.1 to 156.175.255.254156.175.255.255524,286
23156.176.0.0/13156.176.0.1 to 156.183.255.254156.183.255.255524,286
24156.184.0.0/13156.184.0.1 to 156.191.255.254156.191.255.255524,286
25156.192.0.0/13156.192.0.1 to 156.199.255.254156.199.255.255524,286
26156.200.0.0/13156.200.0.1 to 156.207.255.254156.207.255.255524,286
27156.208.0.0/13156.208.0.1 to 156.215.255.254156.215.255.255524,286
28156.216.0.0/13156.216.0.1 to 156.223.255.254156.223.255.255524,286
29156.224.0.0/13156.224.0.1 to 156.231.255.254156.231.255.255524,286
30156.232.0.0/13156.232.0.1 to 156.239.255.254156.239.255.255524,286
31156.240.0.0/13156.240.0.1 to 156.247.255.254156.247.255.255524,286
32156.248.0.0/13156.248.0.1 to 156.255.255.254156.255.255.255524,286
33157.0.0.0/13157.0.0.1 to 157.7.255.254157.7.255.255524,286
34157.8.0.0/13157.8.0.1 to 157.15.255.254157.15.255.255524,286
35157.16.0.0/13157.16.0.1 to 157.23.255.254157.23.255.255524,286
36157.24.0.0/13157.24.0.1 to 157.31.255.254157.31.255.255524,286
37157.32.0.0/13157.32.0.1 to 157.39.255.254157.39.255.255524,286
38157.40.0.0/13157.40.0.1 to 157.47.255.254157.47.255.255524,286
39157.48.0.0/13157.48.0.1 to 157.55.255.254157.55.255.255524,286
40157.56.0.0/13157.56.0.1 to 157.63.255.254157.63.255.255524,286
41157.64.0.0/13157.64.0.1 to 157.71.255.254157.71.255.255524,286
42157.72.0.0/13157.72.0.1 to 157.79.255.254157.79.255.255524,286
43157.80.0.0/13157.80.0.1 to 157.87.255.254157.87.255.255524,286
44157.88.0.0/13157.88.0.1 to 157.95.255.254157.95.255.255524,286
45157.96.0.0/13157.96.0.1 to 157.103.255.254157.103.255.255524,286
46157.104.0.0/13157.104.0.1 to 157.111.255.254157.111.255.255524,286
47157.112.0.0/13157.112.0.1 to 157.119.255.254157.119.255.255524,286
48157.120.0.0/13157.120.0.1 to 157.127.255.254157.127.255.255524,286
49157.128.0.0/13157.128.0.1 to 157.135.255.254157.135.255.255524,286
50157.136.0.0/13157.136.0.1 to 157.143.255.254157.143.255.255524,286
51157.144.0.0/13157.144.0.1 to 157.151.255.254157.151.255.255524,286
52157.152.0.0/13157.152.0.1 to 157.159.255.254157.159.255.255524,286
53157.160.0.0/13157.160.0.1 to 157.167.255.254157.167.255.255524,286
54157.168.0.0/13157.168.0.1 to 157.175.255.254157.175.255.255524,286
55157.176.0.0/13157.176.0.1 to 157.183.255.254157.183.255.255524,286
56157.184.0.0/13157.184.0.1 to 157.191.255.254157.191.255.255524,286
57157.192.0.0/13157.192.0.1 to 157.199.255.254157.199.255.255524,286
58157.200.0.0/13157.200.0.1 to 157.207.255.254157.207.255.255524,286
59157.208.0.0/13157.208.0.1 to 157.215.255.254157.215.255.255524,286
60157.216.0.0/13157.216.0.1 to 157.223.255.254157.223.255.255524,286
61157.224.0.0/13157.224.0.1 to 157.231.255.254157.231.255.255524,286
62157.232.0.0/13157.232.0.1 to 157.239.255.254157.239.255.255524,286
63157.240.0.0/13157.240.0.1 to 157.247.255.254157.247.255.255524,286
64157.248.0.0/13157.248.0.1 to 157.255.255.254157.255.255.255524,286
65158.0.0.0/13158.0.0.1 to 158.7.255.254158.7.255.255524,286
66158.8.0.0/13158.8.0.1 to 158.15.255.254158.15.255.255524,286
67158.16.0.0/13158.16.0.1 to 158.23.255.254158.23.255.255524,286
68158.24.0.0/13158.24.0.1 to 158.31.255.254158.31.255.255524,286
69158.32.0.0/13158.32.0.1 to 158.39.255.254158.39.255.255524,286
70158.40.0.0/13158.40.0.1 to 158.47.255.254158.47.255.255524,286
71158.48.0.0/13158.48.0.1 to 158.55.255.254158.55.255.255524,286
72158.56.0.0/13158.56.0.1 to 158.63.255.254158.63.255.255524,286
73158.64.0.0/13158.64.0.1 to 158.71.255.254158.71.255.255524,286
74158.72.0.0/13158.72.0.1 to 158.79.255.254158.79.255.255524,286
75158.80.0.0/13158.80.0.1 to 158.87.255.254158.87.255.255524,286
76158.88.0.0/13158.88.0.1 to 158.95.255.254158.95.255.255524,286
77158.96.0.0/13158.96.0.1 to 158.103.255.254158.103.255.255524,286
78158.104.0.0/13158.104.0.1 to 158.111.255.254158.111.255.255524,286
79158.112.0.0/13158.112.0.1 to 158.119.255.254158.119.255.255524,286
80158.120.0.0/13158.120.0.1 to 158.127.255.254158.127.255.255524,286
81158.128.0.0/13158.128.0.1 to 158.135.255.254158.135.255.255524,286
82158.136.0.0/13158.136.0.1 to 158.143.255.254158.143.255.255524,286
83158.144.0.0/13158.144.0.1 to 158.151.255.254158.151.255.255524,286
84158.152.0.0/13158.152.0.1 to 158.159.255.254158.159.255.255524,286
85158.160.0.0/13158.160.0.1 to 158.167.255.254158.167.255.255524,286
86158.168.0.0/13158.168.0.1 to 158.175.255.254158.175.255.255524,286
87158.176.0.0/13158.176.0.1 to 158.183.255.254158.183.255.255524,286
88158.184.0.0/13158.184.0.1 to 158.191.255.254158.191.255.255524,286
89158.192.0.0/13158.192.0.1 to 158.199.255.254158.199.255.255524,286
90158.200.0.0/13158.200.0.1 to 158.207.255.254158.207.255.255524,286
91158.208.0.0/13158.208.0.1 to 158.215.255.254158.215.255.255524,286
92158.216.0.0/13158.216.0.1 to 158.223.255.254158.223.255.255524,286
93158.224.0.0/13158.224.0.1 to 158.231.255.254158.231.255.255524,286
94158.232.0.0/13158.232.0.1 to 158.239.255.254158.239.255.255524,286
95158.240.0.0/13158.240.0.1 to 158.247.255.254158.247.255.255524,286
96158.248.0.0/13158.248.0.1 to 158.255.255.254158.255.255.255524,286
97159.0.0.0/13159.0.0.1 to 159.7.255.254159.7.255.255524,286
98159.8.0.0/13159.8.0.1 to 159.15.255.254159.15.255.255524,286
99159.16.0.0/13159.16.0.1 to 159.23.255.254159.23.255.255524,286
100159.24.0.0/13159.24.0.1 to 159.31.255.254159.31.255.255524,286
101159.32.0.0/13159.32.0.1 to 159.39.255.254159.39.255.255524,286
102159.40.0.0/13159.40.0.1 to 159.47.255.254159.47.255.255524,286
103159.48.0.0/13159.48.0.1 to 159.55.255.254159.55.255.255524,286
104159.56.0.0/13159.56.0.1 to 159.63.255.254159.63.255.255524,286
105159.64.0.0/13159.64.0.1 to 159.71.255.254159.71.255.255524,286
106159.72.0.0/13159.72.0.1 to 159.79.255.254159.79.255.255524,286
107159.80.0.0/13159.80.0.1 to 159.87.255.254159.87.255.255524,286
108159.88.0.0/13159.88.0.1 to 159.95.255.254159.95.255.255524,286
109159.96.0.0/13159.96.0.1 to 159.103.255.254159.103.255.255524,286
110159.104.0.0/13159.104.0.1 to 159.111.255.254159.111.255.255524,286
111159.112.0.0/13159.112.0.1 to 159.119.255.254159.119.255.255524,286
112159.120.0.0/13159.120.0.1 to 159.127.255.254159.127.255.255524,286
113159.128.0.0/13159.128.0.1 to 159.135.255.254159.135.255.255524,286
114159.136.0.0/13159.136.0.1 to 159.143.255.254159.143.255.255524,286
115159.144.0.0/13159.144.0.1 to 159.151.255.254159.151.255.255524,286
116159.152.0.0/13159.152.0.1 to 159.159.255.254159.159.255.255524,286
117159.160.0.0/13159.160.0.1 to 159.167.255.254159.167.255.255524,286
118159.168.0.0/13159.168.0.1 to 159.175.255.254159.175.255.255524,286
119159.176.0.0/13159.176.0.1 to 159.183.255.254159.183.255.255524,286
120159.184.0.0/13159.184.0.1 to 159.191.255.254159.191.255.255524,286
121159.192.0.0/13159.192.0.1 to 159.199.255.254159.199.255.255524,286
122159.200.0.0/13159.200.0.1 to 159.207.255.254159.207.255.255524,286
123159.208.0.0/13159.208.0.1 to 159.215.255.254159.215.255.255524,286
124159.216.0.0/13159.216.0.1 to 159.223.255.254159.223.255.255524,286
125159.224.0.0/13159.224.0.1 to 159.231.255.254159.231.255.255524,286
126159.232.0.0/13159.232.0.1 to 159.239.255.254159.239.255.255524,286
127159.240.0.0/13159.240.0.1 to 159.247.255.254159.247.255.255524,286
128159.248.0.0/13159.248.0.1 to 159.255.255.254159.255.255.255524,286

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.