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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.

Network166.185.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
166.185.0.0
Broadcast address
166.185.255.255
First usable
166.185.0.1
Last usable
166.185.255.254
Usable hosts
65,534 (65,536 less the network and broadcast addresses)
Subnet mask
255.255.0.0
Wildcard mask
0.0.255.255 (Cisco ACLs, OSPF)
Prefix length
/16
Type
Public public
Old class
B (default /16)
As numbers
Hex A6B90000 · Integer 2797142016 to 2797207551
Reverse DNS zone
185.166.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100110.10111001..00000000.00000000166.185.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10100110.10111001..00000000.00000000166.185.0.0
Broadcast10100110.10111001..11111111.11111111166.185.255.255
Split into smaller subnets/23
/17 (2)/18 (4)/19 (8)/20 (16)/21 (32)/22 (64)/23 (128)/24 (256)/25 (512)/26 (1,024)/27 (2,048)/28 (4,096)

166.185.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1166.185.0.0/23166.185.0.1 to 166.185.1.254166.185.1.255510
2166.185.2.0/23166.185.2.1 to 166.185.3.254166.185.3.255510
3166.185.4.0/23166.185.4.1 to 166.185.5.254166.185.5.255510
4166.185.6.0/23166.185.6.1 to 166.185.7.254166.185.7.255510
5166.185.8.0/23166.185.8.1 to 166.185.9.254166.185.9.255510
6166.185.10.0/23166.185.10.1 to 166.185.11.254166.185.11.255510
7166.185.12.0/23166.185.12.1 to 166.185.13.254166.185.13.255510
8166.185.14.0/23166.185.14.1 to 166.185.15.254166.185.15.255510
9166.185.16.0/23166.185.16.1 to 166.185.17.254166.185.17.255510
10166.185.18.0/23166.185.18.1 to 166.185.19.254166.185.19.255510
11166.185.20.0/23166.185.20.1 to 166.185.21.254166.185.21.255510
12166.185.22.0/23166.185.22.1 to 166.185.23.254166.185.23.255510
13166.185.24.0/23166.185.24.1 to 166.185.25.254166.185.25.255510
14166.185.26.0/23166.185.26.1 to 166.185.27.254166.185.27.255510
15166.185.28.0/23166.185.28.1 to 166.185.29.254166.185.29.255510
16166.185.30.0/23166.185.30.1 to 166.185.31.254166.185.31.255510
17166.185.32.0/23166.185.32.1 to 166.185.33.254166.185.33.255510
18166.185.34.0/23166.185.34.1 to 166.185.35.254166.185.35.255510
19166.185.36.0/23166.185.36.1 to 166.185.37.254166.185.37.255510
20166.185.38.0/23166.185.38.1 to 166.185.39.254166.185.39.255510
21166.185.40.0/23166.185.40.1 to 166.185.41.254166.185.41.255510
22166.185.42.0/23166.185.42.1 to 166.185.43.254166.185.43.255510
23166.185.44.0/23166.185.44.1 to 166.185.45.254166.185.45.255510
24166.185.46.0/23166.185.46.1 to 166.185.47.254166.185.47.255510
25166.185.48.0/23166.185.48.1 to 166.185.49.254166.185.49.255510
26166.185.50.0/23166.185.50.1 to 166.185.51.254166.185.51.255510
27166.185.52.0/23166.185.52.1 to 166.185.53.254166.185.53.255510
28166.185.54.0/23166.185.54.1 to 166.185.55.254166.185.55.255510
29166.185.56.0/23166.185.56.1 to 166.185.57.254166.185.57.255510
30166.185.58.0/23166.185.58.1 to 166.185.59.254166.185.59.255510
31166.185.60.0/23166.185.60.1 to 166.185.61.254166.185.61.255510
32166.185.62.0/23166.185.62.1 to 166.185.63.254166.185.63.255510
33166.185.64.0/23166.185.64.1 to 166.185.65.254166.185.65.255510
34166.185.66.0/23166.185.66.1 to 166.185.67.254166.185.67.255510
35166.185.68.0/23166.185.68.1 to 166.185.69.254166.185.69.255510
36166.185.70.0/23166.185.70.1 to 166.185.71.254166.185.71.255510
37166.185.72.0/23166.185.72.1 to 166.185.73.254166.185.73.255510
38166.185.74.0/23166.185.74.1 to 166.185.75.254166.185.75.255510
39166.185.76.0/23166.185.76.1 to 166.185.77.254166.185.77.255510
40166.185.78.0/23166.185.78.1 to 166.185.79.254166.185.79.255510
41166.185.80.0/23166.185.80.1 to 166.185.81.254166.185.81.255510
42166.185.82.0/23166.185.82.1 to 166.185.83.254166.185.83.255510
43166.185.84.0/23166.185.84.1 to 166.185.85.254166.185.85.255510
44166.185.86.0/23166.185.86.1 to 166.185.87.254166.185.87.255510
45166.185.88.0/23166.185.88.1 to 166.185.89.254166.185.89.255510
46166.185.90.0/23166.185.90.1 to 166.185.91.254166.185.91.255510
47166.185.92.0/23166.185.92.1 to 166.185.93.254166.185.93.255510
48166.185.94.0/23166.185.94.1 to 166.185.95.254166.185.95.255510
49166.185.96.0/23166.185.96.1 to 166.185.97.254166.185.97.255510
50166.185.98.0/23166.185.98.1 to 166.185.99.254166.185.99.255510
51166.185.100.0/23166.185.100.1 to 166.185.101.254166.185.101.255510
52166.185.102.0/23166.185.102.1 to 166.185.103.254166.185.103.255510
53166.185.104.0/23166.185.104.1 to 166.185.105.254166.185.105.255510
54166.185.106.0/23166.185.106.1 to 166.185.107.254166.185.107.255510
55166.185.108.0/23166.185.108.1 to 166.185.109.254166.185.109.255510
56166.185.110.0/23166.185.110.1 to 166.185.111.254166.185.111.255510
57166.185.112.0/23166.185.112.1 to 166.185.113.254166.185.113.255510
58166.185.114.0/23166.185.114.1 to 166.185.115.254166.185.115.255510
59166.185.116.0/23166.185.116.1 to 166.185.117.254166.185.117.255510
60166.185.118.0/23166.185.118.1 to 166.185.119.254166.185.119.255510
61166.185.120.0/23166.185.120.1 to 166.185.121.254166.185.121.255510
62166.185.122.0/23166.185.122.1 to 166.185.123.254166.185.123.255510
63166.185.124.0/23166.185.124.1 to 166.185.125.254166.185.125.255510
64166.185.126.0/23166.185.126.1 to 166.185.127.254166.185.127.255510
65166.185.128.0/23166.185.128.1 to 166.185.129.254166.185.129.255510
66166.185.130.0/23166.185.130.1 to 166.185.131.254166.185.131.255510
67166.185.132.0/23166.185.132.1 to 166.185.133.254166.185.133.255510
68166.185.134.0/23166.185.134.1 to 166.185.135.254166.185.135.255510
69166.185.136.0/23166.185.136.1 to 166.185.137.254166.185.137.255510
70166.185.138.0/23166.185.138.1 to 166.185.139.254166.185.139.255510
71166.185.140.0/23166.185.140.1 to 166.185.141.254166.185.141.255510
72166.185.142.0/23166.185.142.1 to 166.185.143.254166.185.143.255510
73166.185.144.0/23166.185.144.1 to 166.185.145.254166.185.145.255510
74166.185.146.0/23166.185.146.1 to 166.185.147.254166.185.147.255510
75166.185.148.0/23166.185.148.1 to 166.185.149.254166.185.149.255510
76166.185.150.0/23166.185.150.1 to 166.185.151.254166.185.151.255510
77166.185.152.0/23166.185.152.1 to 166.185.153.254166.185.153.255510
78166.185.154.0/23166.185.154.1 to 166.185.155.254166.185.155.255510
79166.185.156.0/23166.185.156.1 to 166.185.157.254166.185.157.255510
80166.185.158.0/23166.185.158.1 to 166.185.159.254166.185.159.255510
81166.185.160.0/23166.185.160.1 to 166.185.161.254166.185.161.255510
82166.185.162.0/23166.185.162.1 to 166.185.163.254166.185.163.255510
83166.185.164.0/23166.185.164.1 to 166.185.165.254166.185.165.255510
84166.185.166.0/23166.185.166.1 to 166.185.167.254166.185.167.255510
85166.185.168.0/23166.185.168.1 to 166.185.169.254166.185.169.255510
86166.185.170.0/23166.185.170.1 to 166.185.171.254166.185.171.255510
87166.185.172.0/23166.185.172.1 to 166.185.173.254166.185.173.255510
88166.185.174.0/23166.185.174.1 to 166.185.175.254166.185.175.255510
89166.185.176.0/23166.185.176.1 to 166.185.177.254166.185.177.255510
90166.185.178.0/23166.185.178.1 to 166.185.179.254166.185.179.255510
91166.185.180.0/23166.185.180.1 to 166.185.181.254166.185.181.255510
92166.185.182.0/23166.185.182.1 to 166.185.183.254166.185.183.255510
93166.185.184.0/23166.185.184.1 to 166.185.185.254166.185.185.255510
94166.185.186.0/23166.185.186.1 to 166.185.187.254166.185.187.255510
95166.185.188.0/23166.185.188.1 to 166.185.189.254166.185.189.255510
96166.185.190.0/23166.185.190.1 to 166.185.191.254166.185.191.255510
97166.185.192.0/23166.185.192.1 to 166.185.193.254166.185.193.255510
98166.185.194.0/23166.185.194.1 to 166.185.195.254166.185.195.255510
99166.185.196.0/23166.185.196.1 to 166.185.197.254166.185.197.255510
100166.185.198.0/23166.185.198.1 to 166.185.199.254166.185.199.255510
101166.185.200.0/23166.185.200.1 to 166.185.201.254166.185.201.255510
102166.185.202.0/23166.185.202.1 to 166.185.203.254166.185.203.255510
103166.185.204.0/23166.185.204.1 to 166.185.205.254166.185.205.255510
104166.185.206.0/23166.185.206.1 to 166.185.207.254166.185.207.255510
105166.185.208.0/23166.185.208.1 to 166.185.209.254166.185.209.255510
106166.185.210.0/23166.185.210.1 to 166.185.211.254166.185.211.255510
107166.185.212.0/23166.185.212.1 to 166.185.213.254166.185.213.255510
108166.185.214.0/23166.185.214.1 to 166.185.215.254166.185.215.255510
109166.185.216.0/23166.185.216.1 to 166.185.217.254166.185.217.255510
110166.185.218.0/23166.185.218.1 to 166.185.219.254166.185.219.255510
111166.185.220.0/23166.185.220.1 to 166.185.221.254166.185.221.255510
112166.185.222.0/23166.185.222.1 to 166.185.223.254166.185.223.255510
113166.185.224.0/23166.185.224.1 to 166.185.225.254166.185.225.255510
114166.185.226.0/23166.185.226.1 to 166.185.227.254166.185.227.255510
115166.185.228.0/23166.185.228.1 to 166.185.229.254166.185.229.255510
116166.185.230.0/23166.185.230.1 to 166.185.231.254166.185.231.255510
117166.185.232.0/23166.185.232.1 to 166.185.233.254166.185.233.255510
118166.185.234.0/23166.185.234.1 to 166.185.235.254166.185.235.255510
119166.185.236.0/23166.185.236.1 to 166.185.237.254166.185.237.255510
120166.185.238.0/23166.185.238.1 to 166.185.239.254166.185.239.255510
121166.185.240.0/23166.185.240.1 to 166.185.241.254166.185.241.255510
122166.185.242.0/23166.185.242.1 to 166.185.243.254166.185.243.255510
123166.185.244.0/23166.185.244.1 to 166.185.245.254166.185.245.255510
124166.185.246.0/23166.185.246.1 to 166.185.247.254166.185.247.255510
125166.185.248.0/23166.185.248.1 to 166.185.249.254166.185.249.255510
126166.185.250.0/23166.185.250.1 to 166.185.251.254166.185.251.255510
127166.185.252.0/23166.185.252.1 to 166.185.253.254166.185.253.255510
128166.185.254.0/23166.185.254.1 to 166.185.255.254166.185.255.255510

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.