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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.

Network166.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
166.0.0.0
Broadcast address
166.255.255.255
First usable
166.0.0.1
Last usable
166.255.255.254
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 A6000000 · Integer 2785017856 to 2801795071
Reverse DNS zone
166.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100110..00000000.00000000.00000000166.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10100110..00000000.00000000.00000000166.0.0.0
Broadcast10100110..11111111.11111111.11111111166.255.255.255
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)

166.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1166.0.0.0/15166.0.0.1 to 166.1.255.254166.1.255.255131,070
2166.2.0.0/15166.2.0.1 to 166.3.255.254166.3.255.255131,070
3166.4.0.0/15166.4.0.1 to 166.5.255.254166.5.255.255131,070
4166.6.0.0/15166.6.0.1 to 166.7.255.254166.7.255.255131,070
5166.8.0.0/15166.8.0.1 to 166.9.255.254166.9.255.255131,070
6166.10.0.0/15166.10.0.1 to 166.11.255.254166.11.255.255131,070
7166.12.0.0/15166.12.0.1 to 166.13.255.254166.13.255.255131,070
8166.14.0.0/15166.14.0.1 to 166.15.255.254166.15.255.255131,070
9166.16.0.0/15166.16.0.1 to 166.17.255.254166.17.255.255131,070
10166.18.0.0/15166.18.0.1 to 166.19.255.254166.19.255.255131,070
11166.20.0.0/15166.20.0.1 to 166.21.255.254166.21.255.255131,070
12166.22.0.0/15166.22.0.1 to 166.23.255.254166.23.255.255131,070
13166.24.0.0/15166.24.0.1 to 166.25.255.254166.25.255.255131,070
14166.26.0.0/15166.26.0.1 to 166.27.255.254166.27.255.255131,070
15166.28.0.0/15166.28.0.1 to 166.29.255.254166.29.255.255131,070
16166.30.0.0/15166.30.0.1 to 166.31.255.254166.31.255.255131,070
17166.32.0.0/15166.32.0.1 to 166.33.255.254166.33.255.255131,070
18166.34.0.0/15166.34.0.1 to 166.35.255.254166.35.255.255131,070
19166.36.0.0/15166.36.0.1 to 166.37.255.254166.37.255.255131,070
20166.38.0.0/15166.38.0.1 to 166.39.255.254166.39.255.255131,070
21166.40.0.0/15166.40.0.1 to 166.41.255.254166.41.255.255131,070
22166.42.0.0/15166.42.0.1 to 166.43.255.254166.43.255.255131,070
23166.44.0.0/15166.44.0.1 to 166.45.255.254166.45.255.255131,070
24166.46.0.0/15166.46.0.1 to 166.47.255.254166.47.255.255131,070
25166.48.0.0/15166.48.0.1 to 166.49.255.254166.49.255.255131,070
26166.50.0.0/15166.50.0.1 to 166.51.255.254166.51.255.255131,070
27166.52.0.0/15166.52.0.1 to 166.53.255.254166.53.255.255131,070
28166.54.0.0/15166.54.0.1 to 166.55.255.254166.55.255.255131,070
29166.56.0.0/15166.56.0.1 to 166.57.255.254166.57.255.255131,070
30166.58.0.0/15166.58.0.1 to 166.59.255.254166.59.255.255131,070
31166.60.0.0/15166.60.0.1 to 166.61.255.254166.61.255.255131,070
32166.62.0.0/15166.62.0.1 to 166.63.255.254166.63.255.255131,070
33166.64.0.0/15166.64.0.1 to 166.65.255.254166.65.255.255131,070
34166.66.0.0/15166.66.0.1 to 166.67.255.254166.67.255.255131,070
35166.68.0.0/15166.68.0.1 to 166.69.255.254166.69.255.255131,070
36166.70.0.0/15166.70.0.1 to 166.71.255.254166.71.255.255131,070
37166.72.0.0/15166.72.0.1 to 166.73.255.254166.73.255.255131,070
38166.74.0.0/15166.74.0.1 to 166.75.255.254166.75.255.255131,070
39166.76.0.0/15166.76.0.1 to 166.77.255.254166.77.255.255131,070
40166.78.0.0/15166.78.0.1 to 166.79.255.254166.79.255.255131,070
41166.80.0.0/15166.80.0.1 to 166.81.255.254166.81.255.255131,070
42166.82.0.0/15166.82.0.1 to 166.83.255.254166.83.255.255131,070
43166.84.0.0/15166.84.0.1 to 166.85.255.254166.85.255.255131,070
44166.86.0.0/15166.86.0.1 to 166.87.255.254166.87.255.255131,070
45166.88.0.0/15166.88.0.1 to 166.89.255.254166.89.255.255131,070
46166.90.0.0/15166.90.0.1 to 166.91.255.254166.91.255.255131,070
47166.92.0.0/15166.92.0.1 to 166.93.255.254166.93.255.255131,070
48166.94.0.0/15166.94.0.1 to 166.95.255.254166.95.255.255131,070
49166.96.0.0/15166.96.0.1 to 166.97.255.254166.97.255.255131,070
50166.98.0.0/15166.98.0.1 to 166.99.255.254166.99.255.255131,070
51166.100.0.0/15166.100.0.1 to 166.101.255.254166.101.255.255131,070
52166.102.0.0/15166.102.0.1 to 166.103.255.254166.103.255.255131,070
53166.104.0.0/15166.104.0.1 to 166.105.255.254166.105.255.255131,070
54166.106.0.0/15166.106.0.1 to 166.107.255.254166.107.255.255131,070
55166.108.0.0/15166.108.0.1 to 166.109.255.254166.109.255.255131,070
56166.110.0.0/15166.110.0.1 to 166.111.255.254166.111.255.255131,070
57166.112.0.0/15166.112.0.1 to 166.113.255.254166.113.255.255131,070
58166.114.0.0/15166.114.0.1 to 166.115.255.254166.115.255.255131,070
59166.116.0.0/15166.116.0.1 to 166.117.255.254166.117.255.255131,070
60166.118.0.0/15166.118.0.1 to 166.119.255.254166.119.255.255131,070
61166.120.0.0/15166.120.0.1 to 166.121.255.254166.121.255.255131,070
62166.122.0.0/15166.122.0.1 to 166.123.255.254166.123.255.255131,070
63166.124.0.0/15166.124.0.1 to 166.125.255.254166.125.255.255131,070
64166.126.0.0/15166.126.0.1 to 166.127.255.254166.127.255.255131,070
65166.128.0.0/15166.128.0.1 to 166.129.255.254166.129.255.255131,070
66166.130.0.0/15166.130.0.1 to 166.131.255.254166.131.255.255131,070
67166.132.0.0/15166.132.0.1 to 166.133.255.254166.133.255.255131,070
68166.134.0.0/15166.134.0.1 to 166.135.255.254166.135.255.255131,070
69166.136.0.0/15166.136.0.1 to 166.137.255.254166.137.255.255131,070
70166.138.0.0/15166.138.0.1 to 166.139.255.254166.139.255.255131,070
71166.140.0.0/15166.140.0.1 to 166.141.255.254166.141.255.255131,070
72166.142.0.0/15166.142.0.1 to 166.143.255.254166.143.255.255131,070
73166.144.0.0/15166.144.0.1 to 166.145.255.254166.145.255.255131,070
74166.146.0.0/15166.146.0.1 to 166.147.255.254166.147.255.255131,070
75166.148.0.0/15166.148.0.1 to 166.149.255.254166.149.255.255131,070
76166.150.0.0/15166.150.0.1 to 166.151.255.254166.151.255.255131,070
77166.152.0.0/15166.152.0.1 to 166.153.255.254166.153.255.255131,070
78166.154.0.0/15166.154.0.1 to 166.155.255.254166.155.255.255131,070
79166.156.0.0/15166.156.0.1 to 166.157.255.254166.157.255.255131,070
80166.158.0.0/15166.158.0.1 to 166.159.255.254166.159.255.255131,070
81166.160.0.0/15166.160.0.1 to 166.161.255.254166.161.255.255131,070
82166.162.0.0/15166.162.0.1 to 166.163.255.254166.163.255.255131,070
83166.164.0.0/15166.164.0.1 to 166.165.255.254166.165.255.255131,070
84166.166.0.0/15166.166.0.1 to 166.167.255.254166.167.255.255131,070
85166.168.0.0/15166.168.0.1 to 166.169.255.254166.169.255.255131,070
86166.170.0.0/15166.170.0.1 to 166.171.255.254166.171.255.255131,070
87166.172.0.0/15166.172.0.1 to 166.173.255.254166.173.255.255131,070
88166.174.0.0/15166.174.0.1 to 166.175.255.254166.175.255.255131,070
89166.176.0.0/15166.176.0.1 to 166.177.255.254166.177.255.255131,070
90166.178.0.0/15166.178.0.1 to 166.179.255.254166.179.255.255131,070
91166.180.0.0/15166.180.0.1 to 166.181.255.254166.181.255.255131,070
92166.182.0.0/15166.182.0.1 to 166.183.255.254166.183.255.255131,070
93166.184.0.0/15166.184.0.1 to 166.185.255.254166.185.255.255131,070
94166.186.0.0/15166.186.0.1 to 166.187.255.254166.187.255.255131,070
95166.188.0.0/15166.188.0.1 to 166.189.255.254166.189.255.255131,070
96166.190.0.0/15166.190.0.1 to 166.191.255.254166.191.255.255131,070
97166.192.0.0/15166.192.0.1 to 166.193.255.254166.193.255.255131,070
98166.194.0.0/15166.194.0.1 to 166.195.255.254166.195.255.255131,070
99166.196.0.0/15166.196.0.1 to 166.197.255.254166.197.255.255131,070
100166.198.0.0/15166.198.0.1 to 166.199.255.254166.199.255.255131,070
101166.200.0.0/15166.200.0.1 to 166.201.255.254166.201.255.255131,070
102166.202.0.0/15166.202.0.1 to 166.203.255.254166.203.255.255131,070
103166.204.0.0/15166.204.0.1 to 166.205.255.254166.205.255.255131,070
104166.206.0.0/15166.206.0.1 to 166.207.255.254166.207.255.255131,070
105166.208.0.0/15166.208.0.1 to 166.209.255.254166.209.255.255131,070
106166.210.0.0/15166.210.0.1 to 166.211.255.254166.211.255.255131,070
107166.212.0.0/15166.212.0.1 to 166.213.255.254166.213.255.255131,070
108166.214.0.0/15166.214.0.1 to 166.215.255.254166.215.255.255131,070
109166.216.0.0/15166.216.0.1 to 166.217.255.254166.217.255.255131,070
110166.218.0.0/15166.218.0.1 to 166.219.255.254166.219.255.255131,070
111166.220.0.0/15166.220.0.1 to 166.221.255.254166.221.255.255131,070
112166.222.0.0/15166.222.0.1 to 166.223.255.254166.223.255.255131,070
113166.224.0.0/15166.224.0.1 to 166.225.255.254166.225.255.255131,070
114166.226.0.0/15166.226.0.1 to 166.227.255.254166.227.255.255131,070
115166.228.0.0/15166.228.0.1 to 166.229.255.254166.229.255.255131,070
116166.230.0.0/15166.230.0.1 to 166.231.255.254166.231.255.255131,070
117166.232.0.0/15166.232.0.1 to 166.233.255.254166.233.255.255131,070
118166.234.0.0/15166.234.0.1 to 166.235.255.254166.235.255.255131,070
119166.236.0.0/15166.236.0.1 to 166.237.255.254166.237.255.255131,070
120166.238.0.0/15166.238.0.1 to 166.239.255.254166.239.255.255131,070
121166.240.0.0/15166.240.0.1 to 166.241.255.254166.241.255.255131,070
122166.242.0.0/15166.242.0.1 to 166.243.255.254166.243.255.255131,070
123166.244.0.0/15166.244.0.1 to 166.245.255.254166.245.255.255131,070
124166.246.0.0/15166.246.0.1 to 166.247.255.254166.247.255.255131,070
125166.248.0.0/15166.248.0.1 to 166.249.255.254166.249.255.255131,070
126166.250.0.0/15166.250.0.1 to 166.251.255.254166.251.255.255131,070
127166.252.0.0/15166.252.0.1 to 166.253.255.254166.253.255.255131,070
128166.254.0.0/15166.254.0.1 to 166.255.255.254166.255.255.255131,070

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.