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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.

Network187.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
187.0.0.0
Broadcast address
187.255.255.255
First usable
187.0.0.1
Last usable
187.255.255.254
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 BB000000 · Integer 3137339392 to 3154116607
Reverse DNS zone
187.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10111011..00000000.00000000.00000000187.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10111011..00000000.00000000.00000000187.0.0.0
Broadcast10111011..11111111.11111111.11111111187.255.255.255
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)

187.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1187.0.0.0/15187.0.0.1 to 187.1.255.254187.1.255.255131,070
2187.2.0.0/15187.2.0.1 to 187.3.255.254187.3.255.255131,070
3187.4.0.0/15187.4.0.1 to 187.5.255.254187.5.255.255131,070
4187.6.0.0/15187.6.0.1 to 187.7.255.254187.7.255.255131,070
5187.8.0.0/15187.8.0.1 to 187.9.255.254187.9.255.255131,070
6187.10.0.0/15187.10.0.1 to 187.11.255.254187.11.255.255131,070
7187.12.0.0/15187.12.0.1 to 187.13.255.254187.13.255.255131,070
8187.14.0.0/15187.14.0.1 to 187.15.255.254187.15.255.255131,070
9187.16.0.0/15187.16.0.1 to 187.17.255.254187.17.255.255131,070
10187.18.0.0/15187.18.0.1 to 187.19.255.254187.19.255.255131,070
11187.20.0.0/15187.20.0.1 to 187.21.255.254187.21.255.255131,070
12187.22.0.0/15187.22.0.1 to 187.23.255.254187.23.255.255131,070
13187.24.0.0/15187.24.0.1 to 187.25.255.254187.25.255.255131,070
14187.26.0.0/15187.26.0.1 to 187.27.255.254187.27.255.255131,070
15187.28.0.0/15187.28.0.1 to 187.29.255.254187.29.255.255131,070
16187.30.0.0/15187.30.0.1 to 187.31.255.254187.31.255.255131,070
17187.32.0.0/15187.32.0.1 to 187.33.255.254187.33.255.255131,070
18187.34.0.0/15187.34.0.1 to 187.35.255.254187.35.255.255131,070
19187.36.0.0/15187.36.0.1 to 187.37.255.254187.37.255.255131,070
20187.38.0.0/15187.38.0.1 to 187.39.255.254187.39.255.255131,070
21187.40.0.0/15187.40.0.1 to 187.41.255.254187.41.255.255131,070
22187.42.0.0/15187.42.0.1 to 187.43.255.254187.43.255.255131,070
23187.44.0.0/15187.44.0.1 to 187.45.255.254187.45.255.255131,070
24187.46.0.0/15187.46.0.1 to 187.47.255.254187.47.255.255131,070
25187.48.0.0/15187.48.0.1 to 187.49.255.254187.49.255.255131,070
26187.50.0.0/15187.50.0.1 to 187.51.255.254187.51.255.255131,070
27187.52.0.0/15187.52.0.1 to 187.53.255.254187.53.255.255131,070
28187.54.0.0/15187.54.0.1 to 187.55.255.254187.55.255.255131,070
29187.56.0.0/15187.56.0.1 to 187.57.255.254187.57.255.255131,070
30187.58.0.0/15187.58.0.1 to 187.59.255.254187.59.255.255131,070
31187.60.0.0/15187.60.0.1 to 187.61.255.254187.61.255.255131,070
32187.62.0.0/15187.62.0.1 to 187.63.255.254187.63.255.255131,070
33187.64.0.0/15187.64.0.1 to 187.65.255.254187.65.255.255131,070
34187.66.0.0/15187.66.0.1 to 187.67.255.254187.67.255.255131,070
35187.68.0.0/15187.68.0.1 to 187.69.255.254187.69.255.255131,070
36187.70.0.0/15187.70.0.1 to 187.71.255.254187.71.255.255131,070
37187.72.0.0/15187.72.0.1 to 187.73.255.254187.73.255.255131,070
38187.74.0.0/15187.74.0.1 to 187.75.255.254187.75.255.255131,070
39187.76.0.0/15187.76.0.1 to 187.77.255.254187.77.255.255131,070
40187.78.0.0/15187.78.0.1 to 187.79.255.254187.79.255.255131,070
41187.80.0.0/15187.80.0.1 to 187.81.255.254187.81.255.255131,070
42187.82.0.0/15187.82.0.1 to 187.83.255.254187.83.255.255131,070
43187.84.0.0/15187.84.0.1 to 187.85.255.254187.85.255.255131,070
44187.86.0.0/15187.86.0.1 to 187.87.255.254187.87.255.255131,070
45187.88.0.0/15187.88.0.1 to 187.89.255.254187.89.255.255131,070
46187.90.0.0/15187.90.0.1 to 187.91.255.254187.91.255.255131,070
47187.92.0.0/15187.92.0.1 to 187.93.255.254187.93.255.255131,070
48187.94.0.0/15187.94.0.1 to 187.95.255.254187.95.255.255131,070
49187.96.0.0/15187.96.0.1 to 187.97.255.254187.97.255.255131,070
50187.98.0.0/15187.98.0.1 to 187.99.255.254187.99.255.255131,070
51187.100.0.0/15187.100.0.1 to 187.101.255.254187.101.255.255131,070
52187.102.0.0/15187.102.0.1 to 187.103.255.254187.103.255.255131,070
53187.104.0.0/15187.104.0.1 to 187.105.255.254187.105.255.255131,070
54187.106.0.0/15187.106.0.1 to 187.107.255.254187.107.255.255131,070
55187.108.0.0/15187.108.0.1 to 187.109.255.254187.109.255.255131,070
56187.110.0.0/15187.110.0.1 to 187.111.255.254187.111.255.255131,070
57187.112.0.0/15187.112.0.1 to 187.113.255.254187.113.255.255131,070
58187.114.0.0/15187.114.0.1 to 187.115.255.254187.115.255.255131,070
59187.116.0.0/15187.116.0.1 to 187.117.255.254187.117.255.255131,070
60187.118.0.0/15187.118.0.1 to 187.119.255.254187.119.255.255131,070
61187.120.0.0/15187.120.0.1 to 187.121.255.254187.121.255.255131,070
62187.122.0.0/15187.122.0.1 to 187.123.255.254187.123.255.255131,070
63187.124.0.0/15187.124.0.1 to 187.125.255.254187.125.255.255131,070
64187.126.0.0/15187.126.0.1 to 187.127.255.254187.127.255.255131,070
65187.128.0.0/15187.128.0.1 to 187.129.255.254187.129.255.255131,070
66187.130.0.0/15187.130.0.1 to 187.131.255.254187.131.255.255131,070
67187.132.0.0/15187.132.0.1 to 187.133.255.254187.133.255.255131,070
68187.134.0.0/15187.134.0.1 to 187.135.255.254187.135.255.255131,070
69187.136.0.0/15187.136.0.1 to 187.137.255.254187.137.255.255131,070
70187.138.0.0/15187.138.0.1 to 187.139.255.254187.139.255.255131,070
71187.140.0.0/15187.140.0.1 to 187.141.255.254187.141.255.255131,070
72187.142.0.0/15187.142.0.1 to 187.143.255.254187.143.255.255131,070
73187.144.0.0/15187.144.0.1 to 187.145.255.254187.145.255.255131,070
74187.146.0.0/15187.146.0.1 to 187.147.255.254187.147.255.255131,070
75187.148.0.0/15187.148.0.1 to 187.149.255.254187.149.255.255131,070
76187.150.0.0/15187.150.0.1 to 187.151.255.254187.151.255.255131,070
77187.152.0.0/15187.152.0.1 to 187.153.255.254187.153.255.255131,070
78187.154.0.0/15187.154.0.1 to 187.155.255.254187.155.255.255131,070
79187.156.0.0/15187.156.0.1 to 187.157.255.254187.157.255.255131,070
80187.158.0.0/15187.158.0.1 to 187.159.255.254187.159.255.255131,070
81187.160.0.0/15187.160.0.1 to 187.161.255.254187.161.255.255131,070
82187.162.0.0/15187.162.0.1 to 187.163.255.254187.163.255.255131,070
83187.164.0.0/15187.164.0.1 to 187.165.255.254187.165.255.255131,070
84187.166.0.0/15187.166.0.1 to 187.167.255.254187.167.255.255131,070
85187.168.0.0/15187.168.0.1 to 187.169.255.254187.169.255.255131,070
86187.170.0.0/15187.170.0.1 to 187.171.255.254187.171.255.255131,070
87187.172.0.0/15187.172.0.1 to 187.173.255.254187.173.255.255131,070
88187.174.0.0/15187.174.0.1 to 187.175.255.254187.175.255.255131,070
89187.176.0.0/15187.176.0.1 to 187.177.255.254187.177.255.255131,070
90187.178.0.0/15187.178.0.1 to 187.179.255.254187.179.255.255131,070
91187.180.0.0/15187.180.0.1 to 187.181.255.254187.181.255.255131,070
92187.182.0.0/15187.182.0.1 to 187.183.255.254187.183.255.255131,070
93187.184.0.0/15187.184.0.1 to 187.185.255.254187.185.255.255131,070
94187.186.0.0/15187.186.0.1 to 187.187.255.254187.187.255.255131,070
95187.188.0.0/15187.188.0.1 to 187.189.255.254187.189.255.255131,070
96187.190.0.0/15187.190.0.1 to 187.191.255.254187.191.255.255131,070
97187.192.0.0/15187.192.0.1 to 187.193.255.254187.193.255.255131,070
98187.194.0.0/15187.194.0.1 to 187.195.255.254187.195.255.255131,070
99187.196.0.0/15187.196.0.1 to 187.197.255.254187.197.255.255131,070
100187.198.0.0/15187.198.0.1 to 187.199.255.254187.199.255.255131,070
101187.200.0.0/15187.200.0.1 to 187.201.255.254187.201.255.255131,070
102187.202.0.0/15187.202.0.1 to 187.203.255.254187.203.255.255131,070
103187.204.0.0/15187.204.0.1 to 187.205.255.254187.205.255.255131,070
104187.206.0.0/15187.206.0.1 to 187.207.255.254187.207.255.255131,070
105187.208.0.0/15187.208.0.1 to 187.209.255.254187.209.255.255131,070
106187.210.0.0/15187.210.0.1 to 187.211.255.254187.211.255.255131,070
107187.212.0.0/15187.212.0.1 to 187.213.255.254187.213.255.255131,070
108187.214.0.0/15187.214.0.1 to 187.215.255.254187.215.255.255131,070
109187.216.0.0/15187.216.0.1 to 187.217.255.254187.217.255.255131,070
110187.218.0.0/15187.218.0.1 to 187.219.255.254187.219.255.255131,070
111187.220.0.0/15187.220.0.1 to 187.221.255.254187.221.255.255131,070
112187.222.0.0/15187.222.0.1 to 187.223.255.254187.223.255.255131,070
113187.224.0.0/15187.224.0.1 to 187.225.255.254187.225.255.255131,070
114187.226.0.0/15187.226.0.1 to 187.227.255.254187.227.255.255131,070
115187.228.0.0/15187.228.0.1 to 187.229.255.254187.229.255.255131,070
116187.230.0.0/15187.230.0.1 to 187.231.255.254187.231.255.255131,070
117187.232.0.0/15187.232.0.1 to 187.233.255.254187.233.255.255131,070
118187.234.0.0/15187.234.0.1 to 187.235.255.254187.235.255.255131,070
119187.236.0.0/15187.236.0.1 to 187.237.255.254187.237.255.255131,070
120187.238.0.0/15187.238.0.1 to 187.239.255.254187.239.255.255131,070
121187.240.0.0/15187.240.0.1 to 187.241.255.254187.241.255.255131,070
122187.242.0.0/15187.242.0.1 to 187.243.255.254187.243.255.255131,070
123187.244.0.0/15187.244.0.1 to 187.245.255.254187.245.255.255131,070
124187.246.0.0/15187.246.0.1 to 187.247.255.254187.247.255.255131,070
125187.248.0.0/15187.248.0.1 to 187.249.255.254187.249.255.255131,070
126187.250.0.0/15187.250.0.1 to 187.251.255.254187.251.255.255131,070
127187.252.0.0/15187.252.0.1 to 187.253.255.254187.253.255.255131,070
128187.254.0.0/15187.254.0.1 to 187.255.255.254187.255.255.255131,070

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.