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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.

Network172.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
172.0.0.0
Broadcast address
172.255.255.255
First usable
172.0.0.1
Last usable
172.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
B (default /16)
As numbers
Hex AC000000 · Integer 2885681152 to 2902458367
Reverse DNS zone
172.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101100..00000000.00000000.00000000172.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10101100..00000000.00000000.00000000172.0.0.0
Broadcast10101100..11111111.11111111.11111111172.255.255.255
Split into smaller subnets/15
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

172.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1172.0.0.0/15172.0.0.1 to 172.1.255.254172.1.255.255131,070
2172.2.0.0/15172.2.0.1 to 172.3.255.254172.3.255.255131,070
3172.4.0.0/15172.4.0.1 to 172.5.255.254172.5.255.255131,070
4172.6.0.0/15172.6.0.1 to 172.7.255.254172.7.255.255131,070
5172.8.0.0/15172.8.0.1 to 172.9.255.254172.9.255.255131,070
6172.10.0.0/15172.10.0.1 to 172.11.255.254172.11.255.255131,070
7172.12.0.0/15172.12.0.1 to 172.13.255.254172.13.255.255131,070
8172.14.0.0/15172.14.0.1 to 172.15.255.254172.15.255.255131,070
9172.16.0.0/15172.16.0.1 to 172.17.255.254172.17.255.255131,070
10172.18.0.0/15172.18.0.1 to 172.19.255.254172.19.255.255131,070
11172.20.0.0/15172.20.0.1 to 172.21.255.254172.21.255.255131,070
12172.22.0.0/15172.22.0.1 to 172.23.255.254172.23.255.255131,070
13172.24.0.0/15172.24.0.1 to 172.25.255.254172.25.255.255131,070
14172.26.0.0/15172.26.0.1 to 172.27.255.254172.27.255.255131,070
15172.28.0.0/15172.28.0.1 to 172.29.255.254172.29.255.255131,070
16172.30.0.0/15172.30.0.1 to 172.31.255.254172.31.255.255131,070
17172.32.0.0/15172.32.0.1 to 172.33.255.254172.33.255.255131,070
18172.34.0.0/15172.34.0.1 to 172.35.255.254172.35.255.255131,070
19172.36.0.0/15172.36.0.1 to 172.37.255.254172.37.255.255131,070
20172.38.0.0/15172.38.0.1 to 172.39.255.254172.39.255.255131,070
21172.40.0.0/15172.40.0.1 to 172.41.255.254172.41.255.255131,070
22172.42.0.0/15172.42.0.1 to 172.43.255.254172.43.255.255131,070
23172.44.0.0/15172.44.0.1 to 172.45.255.254172.45.255.255131,070
24172.46.0.0/15172.46.0.1 to 172.47.255.254172.47.255.255131,070
25172.48.0.0/15172.48.0.1 to 172.49.255.254172.49.255.255131,070
26172.50.0.0/15172.50.0.1 to 172.51.255.254172.51.255.255131,070
27172.52.0.0/15172.52.0.1 to 172.53.255.254172.53.255.255131,070
28172.54.0.0/15172.54.0.1 to 172.55.255.254172.55.255.255131,070
29172.56.0.0/15172.56.0.1 to 172.57.255.254172.57.255.255131,070
30172.58.0.0/15172.58.0.1 to 172.59.255.254172.59.255.255131,070
31172.60.0.0/15172.60.0.1 to 172.61.255.254172.61.255.255131,070
32172.62.0.0/15172.62.0.1 to 172.63.255.254172.63.255.255131,070
33172.64.0.0/15172.64.0.1 to 172.65.255.254172.65.255.255131,070
34172.66.0.0/15172.66.0.1 to 172.67.255.254172.67.255.255131,070
35172.68.0.0/15172.68.0.1 to 172.69.255.254172.69.255.255131,070
36172.70.0.0/15172.70.0.1 to 172.71.255.254172.71.255.255131,070
37172.72.0.0/15172.72.0.1 to 172.73.255.254172.73.255.255131,070
38172.74.0.0/15172.74.0.1 to 172.75.255.254172.75.255.255131,070
39172.76.0.0/15172.76.0.1 to 172.77.255.254172.77.255.255131,070
40172.78.0.0/15172.78.0.1 to 172.79.255.254172.79.255.255131,070
41172.80.0.0/15172.80.0.1 to 172.81.255.254172.81.255.255131,070
42172.82.0.0/15172.82.0.1 to 172.83.255.254172.83.255.255131,070
43172.84.0.0/15172.84.0.1 to 172.85.255.254172.85.255.255131,070
44172.86.0.0/15172.86.0.1 to 172.87.255.254172.87.255.255131,070
45172.88.0.0/15172.88.0.1 to 172.89.255.254172.89.255.255131,070
46172.90.0.0/15172.90.0.1 to 172.91.255.254172.91.255.255131,070
47172.92.0.0/15172.92.0.1 to 172.93.255.254172.93.255.255131,070
48172.94.0.0/15172.94.0.1 to 172.95.255.254172.95.255.255131,070
49172.96.0.0/15172.96.0.1 to 172.97.255.254172.97.255.255131,070
50172.98.0.0/15172.98.0.1 to 172.99.255.254172.99.255.255131,070
51172.100.0.0/15172.100.0.1 to 172.101.255.254172.101.255.255131,070
52172.102.0.0/15172.102.0.1 to 172.103.255.254172.103.255.255131,070
53172.104.0.0/15172.104.0.1 to 172.105.255.254172.105.255.255131,070
54172.106.0.0/15172.106.0.1 to 172.107.255.254172.107.255.255131,070
55172.108.0.0/15172.108.0.1 to 172.109.255.254172.109.255.255131,070
56172.110.0.0/15172.110.0.1 to 172.111.255.254172.111.255.255131,070
57172.112.0.0/15172.112.0.1 to 172.113.255.254172.113.255.255131,070
58172.114.0.0/15172.114.0.1 to 172.115.255.254172.115.255.255131,070
59172.116.0.0/15172.116.0.1 to 172.117.255.254172.117.255.255131,070
60172.118.0.0/15172.118.0.1 to 172.119.255.254172.119.255.255131,070
61172.120.0.0/15172.120.0.1 to 172.121.255.254172.121.255.255131,070
62172.122.0.0/15172.122.0.1 to 172.123.255.254172.123.255.255131,070
63172.124.0.0/15172.124.0.1 to 172.125.255.254172.125.255.255131,070
64172.126.0.0/15172.126.0.1 to 172.127.255.254172.127.255.255131,070
65172.128.0.0/15172.128.0.1 to 172.129.255.254172.129.255.255131,070
66172.130.0.0/15172.130.0.1 to 172.131.255.254172.131.255.255131,070
67172.132.0.0/15172.132.0.1 to 172.133.255.254172.133.255.255131,070
68172.134.0.0/15172.134.0.1 to 172.135.255.254172.135.255.255131,070
69172.136.0.0/15172.136.0.1 to 172.137.255.254172.137.255.255131,070
70172.138.0.0/15172.138.0.1 to 172.139.255.254172.139.255.255131,070
71172.140.0.0/15172.140.0.1 to 172.141.255.254172.141.255.255131,070
72172.142.0.0/15172.142.0.1 to 172.143.255.254172.143.255.255131,070
73172.144.0.0/15172.144.0.1 to 172.145.255.254172.145.255.255131,070
74172.146.0.0/15172.146.0.1 to 172.147.255.254172.147.255.255131,070
75172.148.0.0/15172.148.0.1 to 172.149.255.254172.149.255.255131,070
76172.150.0.0/15172.150.0.1 to 172.151.255.254172.151.255.255131,070
77172.152.0.0/15172.152.0.1 to 172.153.255.254172.153.255.255131,070
78172.154.0.0/15172.154.0.1 to 172.155.255.254172.155.255.255131,070
79172.156.0.0/15172.156.0.1 to 172.157.255.254172.157.255.255131,070
80172.158.0.0/15172.158.0.1 to 172.159.255.254172.159.255.255131,070
81172.160.0.0/15172.160.0.1 to 172.161.255.254172.161.255.255131,070
82172.162.0.0/15172.162.0.1 to 172.163.255.254172.163.255.255131,070
83172.164.0.0/15172.164.0.1 to 172.165.255.254172.165.255.255131,070
84172.166.0.0/15172.166.0.1 to 172.167.255.254172.167.255.255131,070
85172.168.0.0/15172.168.0.1 to 172.169.255.254172.169.255.255131,070
86172.170.0.0/15172.170.0.1 to 172.171.255.254172.171.255.255131,070
87172.172.0.0/15172.172.0.1 to 172.173.255.254172.173.255.255131,070
88172.174.0.0/15172.174.0.1 to 172.175.255.254172.175.255.255131,070
89172.176.0.0/15172.176.0.1 to 172.177.255.254172.177.255.255131,070
90172.178.0.0/15172.178.0.1 to 172.179.255.254172.179.255.255131,070
91172.180.0.0/15172.180.0.1 to 172.181.255.254172.181.255.255131,070
92172.182.0.0/15172.182.0.1 to 172.183.255.254172.183.255.255131,070
93172.184.0.0/15172.184.0.1 to 172.185.255.254172.185.255.255131,070
94172.186.0.0/15172.186.0.1 to 172.187.255.254172.187.255.255131,070
95172.188.0.0/15172.188.0.1 to 172.189.255.254172.189.255.255131,070
96172.190.0.0/15172.190.0.1 to 172.191.255.254172.191.255.255131,070
97172.192.0.0/15172.192.0.1 to 172.193.255.254172.193.255.255131,070
98172.194.0.0/15172.194.0.1 to 172.195.255.254172.195.255.255131,070
99172.196.0.0/15172.196.0.1 to 172.197.255.254172.197.255.255131,070
100172.198.0.0/15172.198.0.1 to 172.199.255.254172.199.255.255131,070
101172.200.0.0/15172.200.0.1 to 172.201.255.254172.201.255.255131,070
102172.202.0.0/15172.202.0.1 to 172.203.255.254172.203.255.255131,070
103172.204.0.0/15172.204.0.1 to 172.205.255.254172.205.255.255131,070
104172.206.0.0/15172.206.0.1 to 172.207.255.254172.207.255.255131,070
105172.208.0.0/15172.208.0.1 to 172.209.255.254172.209.255.255131,070
106172.210.0.0/15172.210.0.1 to 172.211.255.254172.211.255.255131,070
107172.212.0.0/15172.212.0.1 to 172.213.255.254172.213.255.255131,070
108172.214.0.0/15172.214.0.1 to 172.215.255.254172.215.255.255131,070
109172.216.0.0/15172.216.0.1 to 172.217.255.254172.217.255.255131,070
110172.218.0.0/15172.218.0.1 to 172.219.255.254172.219.255.255131,070
111172.220.0.0/15172.220.0.1 to 172.221.255.254172.221.255.255131,070
112172.222.0.0/15172.222.0.1 to 172.223.255.254172.223.255.255131,070
113172.224.0.0/15172.224.0.1 to 172.225.255.254172.225.255.255131,070
114172.226.0.0/15172.226.0.1 to 172.227.255.254172.227.255.255131,070
115172.228.0.0/15172.228.0.1 to 172.229.255.254172.229.255.255131,070
116172.230.0.0/15172.230.0.1 to 172.231.255.254172.231.255.255131,070
117172.232.0.0/15172.232.0.1 to 172.233.255.254172.233.255.255131,070
118172.234.0.0/15172.234.0.1 to 172.235.255.254172.235.255.255131,070
119172.236.0.0/15172.236.0.1 to 172.237.255.254172.237.255.255131,070
120172.238.0.0/15172.238.0.1 to 172.239.255.254172.239.255.255131,070
121172.240.0.0/15172.240.0.1 to 172.241.255.254172.241.255.255131,070
122172.242.0.0/15172.242.0.1 to 172.243.255.254172.243.255.255131,070
123172.244.0.0/15172.244.0.1 to 172.245.255.254172.245.255.255131,070
124172.246.0.0/15172.246.0.1 to 172.247.255.254172.247.255.255131,070
125172.248.0.0/15172.248.0.1 to 172.249.255.254172.249.255.255131,070
126172.250.0.0/15172.250.0.1 to 172.251.255.254172.251.255.255131,070
127172.252.0.0/15172.252.0.1 to 172.253.255.254172.253.255.255131,070
128172.254.0.0/15172.254.0.1 to 172.255.255.254172.255.255.255131,070

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.