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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.

Network191.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
191.0.0.0
Broadcast address
191.255.255.255
First usable
191.0.0.1
Last usable
191.255.255.254
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 BF000000 · Integer 3204448256 to 3221225471
Reverse DNS zone
191.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10111111..00000000.00000000.00000000191.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10111111..00000000.00000000.00000000191.0.0.0
Broadcast10111111..11111111.11111111.11111111191.255.255.255
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)

191.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1191.0.0.0/15191.0.0.1 to 191.1.255.254191.1.255.255131,070
2191.2.0.0/15191.2.0.1 to 191.3.255.254191.3.255.255131,070
3191.4.0.0/15191.4.0.1 to 191.5.255.254191.5.255.255131,070
4191.6.0.0/15191.6.0.1 to 191.7.255.254191.7.255.255131,070
5191.8.0.0/15191.8.0.1 to 191.9.255.254191.9.255.255131,070
6191.10.0.0/15191.10.0.1 to 191.11.255.254191.11.255.255131,070
7191.12.0.0/15191.12.0.1 to 191.13.255.254191.13.255.255131,070
8191.14.0.0/15191.14.0.1 to 191.15.255.254191.15.255.255131,070
9191.16.0.0/15191.16.0.1 to 191.17.255.254191.17.255.255131,070
10191.18.0.0/15191.18.0.1 to 191.19.255.254191.19.255.255131,070
11191.20.0.0/15191.20.0.1 to 191.21.255.254191.21.255.255131,070
12191.22.0.0/15191.22.0.1 to 191.23.255.254191.23.255.255131,070
13191.24.0.0/15191.24.0.1 to 191.25.255.254191.25.255.255131,070
14191.26.0.0/15191.26.0.1 to 191.27.255.254191.27.255.255131,070
15191.28.0.0/15191.28.0.1 to 191.29.255.254191.29.255.255131,070
16191.30.0.0/15191.30.0.1 to 191.31.255.254191.31.255.255131,070
17191.32.0.0/15191.32.0.1 to 191.33.255.254191.33.255.255131,070
18191.34.0.0/15191.34.0.1 to 191.35.255.254191.35.255.255131,070
19191.36.0.0/15191.36.0.1 to 191.37.255.254191.37.255.255131,070
20191.38.0.0/15191.38.0.1 to 191.39.255.254191.39.255.255131,070
21191.40.0.0/15191.40.0.1 to 191.41.255.254191.41.255.255131,070
22191.42.0.0/15191.42.0.1 to 191.43.255.254191.43.255.255131,070
23191.44.0.0/15191.44.0.1 to 191.45.255.254191.45.255.255131,070
24191.46.0.0/15191.46.0.1 to 191.47.255.254191.47.255.255131,070
25191.48.0.0/15191.48.0.1 to 191.49.255.254191.49.255.255131,070
26191.50.0.0/15191.50.0.1 to 191.51.255.254191.51.255.255131,070
27191.52.0.0/15191.52.0.1 to 191.53.255.254191.53.255.255131,070
28191.54.0.0/15191.54.0.1 to 191.55.255.254191.55.255.255131,070
29191.56.0.0/15191.56.0.1 to 191.57.255.254191.57.255.255131,070
30191.58.0.0/15191.58.0.1 to 191.59.255.254191.59.255.255131,070
31191.60.0.0/15191.60.0.1 to 191.61.255.254191.61.255.255131,070
32191.62.0.0/15191.62.0.1 to 191.63.255.254191.63.255.255131,070
33191.64.0.0/15191.64.0.1 to 191.65.255.254191.65.255.255131,070
34191.66.0.0/15191.66.0.1 to 191.67.255.254191.67.255.255131,070
35191.68.0.0/15191.68.0.1 to 191.69.255.254191.69.255.255131,070
36191.70.0.0/15191.70.0.1 to 191.71.255.254191.71.255.255131,070
37191.72.0.0/15191.72.0.1 to 191.73.255.254191.73.255.255131,070
38191.74.0.0/15191.74.0.1 to 191.75.255.254191.75.255.255131,070
39191.76.0.0/15191.76.0.1 to 191.77.255.254191.77.255.255131,070
40191.78.0.0/15191.78.0.1 to 191.79.255.254191.79.255.255131,070
41191.80.0.0/15191.80.0.1 to 191.81.255.254191.81.255.255131,070
42191.82.0.0/15191.82.0.1 to 191.83.255.254191.83.255.255131,070
43191.84.0.0/15191.84.0.1 to 191.85.255.254191.85.255.255131,070
44191.86.0.0/15191.86.0.1 to 191.87.255.254191.87.255.255131,070
45191.88.0.0/15191.88.0.1 to 191.89.255.254191.89.255.255131,070
46191.90.0.0/15191.90.0.1 to 191.91.255.254191.91.255.255131,070
47191.92.0.0/15191.92.0.1 to 191.93.255.254191.93.255.255131,070
48191.94.0.0/15191.94.0.1 to 191.95.255.254191.95.255.255131,070
49191.96.0.0/15191.96.0.1 to 191.97.255.254191.97.255.255131,070
50191.98.0.0/15191.98.0.1 to 191.99.255.254191.99.255.255131,070
51191.100.0.0/15191.100.0.1 to 191.101.255.254191.101.255.255131,070
52191.102.0.0/15191.102.0.1 to 191.103.255.254191.103.255.255131,070
53191.104.0.0/15191.104.0.1 to 191.105.255.254191.105.255.255131,070
54191.106.0.0/15191.106.0.1 to 191.107.255.254191.107.255.255131,070
55191.108.0.0/15191.108.0.1 to 191.109.255.254191.109.255.255131,070
56191.110.0.0/15191.110.0.1 to 191.111.255.254191.111.255.255131,070
57191.112.0.0/15191.112.0.1 to 191.113.255.254191.113.255.255131,070
58191.114.0.0/15191.114.0.1 to 191.115.255.254191.115.255.255131,070
59191.116.0.0/15191.116.0.1 to 191.117.255.254191.117.255.255131,070
60191.118.0.0/15191.118.0.1 to 191.119.255.254191.119.255.255131,070
61191.120.0.0/15191.120.0.1 to 191.121.255.254191.121.255.255131,070
62191.122.0.0/15191.122.0.1 to 191.123.255.254191.123.255.255131,070
63191.124.0.0/15191.124.0.1 to 191.125.255.254191.125.255.255131,070
64191.126.0.0/15191.126.0.1 to 191.127.255.254191.127.255.255131,070
65191.128.0.0/15191.128.0.1 to 191.129.255.254191.129.255.255131,070
66191.130.0.0/15191.130.0.1 to 191.131.255.254191.131.255.255131,070
67191.132.0.0/15191.132.0.1 to 191.133.255.254191.133.255.255131,070
68191.134.0.0/15191.134.0.1 to 191.135.255.254191.135.255.255131,070
69191.136.0.0/15191.136.0.1 to 191.137.255.254191.137.255.255131,070
70191.138.0.0/15191.138.0.1 to 191.139.255.254191.139.255.255131,070
71191.140.0.0/15191.140.0.1 to 191.141.255.254191.141.255.255131,070
72191.142.0.0/15191.142.0.1 to 191.143.255.254191.143.255.255131,070
73191.144.0.0/15191.144.0.1 to 191.145.255.254191.145.255.255131,070
74191.146.0.0/15191.146.0.1 to 191.147.255.254191.147.255.255131,070
75191.148.0.0/15191.148.0.1 to 191.149.255.254191.149.255.255131,070
76191.150.0.0/15191.150.0.1 to 191.151.255.254191.151.255.255131,070
77191.152.0.0/15191.152.0.1 to 191.153.255.254191.153.255.255131,070
78191.154.0.0/15191.154.0.1 to 191.155.255.254191.155.255.255131,070
79191.156.0.0/15191.156.0.1 to 191.157.255.254191.157.255.255131,070
80191.158.0.0/15191.158.0.1 to 191.159.255.254191.159.255.255131,070
81191.160.0.0/15191.160.0.1 to 191.161.255.254191.161.255.255131,070
82191.162.0.0/15191.162.0.1 to 191.163.255.254191.163.255.255131,070
83191.164.0.0/15191.164.0.1 to 191.165.255.254191.165.255.255131,070
84191.166.0.0/15191.166.0.1 to 191.167.255.254191.167.255.255131,070
85191.168.0.0/15191.168.0.1 to 191.169.255.254191.169.255.255131,070
86191.170.0.0/15191.170.0.1 to 191.171.255.254191.171.255.255131,070
87191.172.0.0/15191.172.0.1 to 191.173.255.254191.173.255.255131,070
88191.174.0.0/15191.174.0.1 to 191.175.255.254191.175.255.255131,070
89191.176.0.0/15191.176.0.1 to 191.177.255.254191.177.255.255131,070
90191.178.0.0/15191.178.0.1 to 191.179.255.254191.179.255.255131,070
91191.180.0.0/15191.180.0.1 to 191.181.255.254191.181.255.255131,070
92191.182.0.0/15191.182.0.1 to 191.183.255.254191.183.255.255131,070
93191.184.0.0/15191.184.0.1 to 191.185.255.254191.185.255.255131,070
94191.186.0.0/15191.186.0.1 to 191.187.255.254191.187.255.255131,070
95191.188.0.0/15191.188.0.1 to 191.189.255.254191.189.255.255131,070
96191.190.0.0/15191.190.0.1 to 191.191.255.254191.191.255.255131,070
97191.192.0.0/15191.192.0.1 to 191.193.255.254191.193.255.255131,070
98191.194.0.0/15191.194.0.1 to 191.195.255.254191.195.255.255131,070
99191.196.0.0/15191.196.0.1 to 191.197.255.254191.197.255.255131,070
100191.198.0.0/15191.198.0.1 to 191.199.255.254191.199.255.255131,070
101191.200.0.0/15191.200.0.1 to 191.201.255.254191.201.255.255131,070
102191.202.0.0/15191.202.0.1 to 191.203.255.254191.203.255.255131,070
103191.204.0.0/15191.204.0.1 to 191.205.255.254191.205.255.255131,070
104191.206.0.0/15191.206.0.1 to 191.207.255.254191.207.255.255131,070
105191.208.0.0/15191.208.0.1 to 191.209.255.254191.209.255.255131,070
106191.210.0.0/15191.210.0.1 to 191.211.255.254191.211.255.255131,070
107191.212.0.0/15191.212.0.1 to 191.213.255.254191.213.255.255131,070
108191.214.0.0/15191.214.0.1 to 191.215.255.254191.215.255.255131,070
109191.216.0.0/15191.216.0.1 to 191.217.255.254191.217.255.255131,070
110191.218.0.0/15191.218.0.1 to 191.219.255.254191.219.255.255131,070
111191.220.0.0/15191.220.0.1 to 191.221.255.254191.221.255.255131,070
112191.222.0.0/15191.222.0.1 to 191.223.255.254191.223.255.255131,070
113191.224.0.0/15191.224.0.1 to 191.225.255.254191.225.255.255131,070
114191.226.0.0/15191.226.0.1 to 191.227.255.254191.227.255.255131,070
115191.228.0.0/15191.228.0.1 to 191.229.255.254191.229.255.255131,070
116191.230.0.0/15191.230.0.1 to 191.231.255.254191.231.255.255131,070
117191.232.0.0/15191.232.0.1 to 191.233.255.254191.233.255.255131,070
118191.234.0.0/15191.234.0.1 to 191.235.255.254191.235.255.255131,070
119191.236.0.0/15191.236.0.1 to 191.237.255.254191.237.255.255131,070
120191.238.0.0/15191.238.0.1 to 191.239.255.254191.239.255.255131,070
121191.240.0.0/15191.240.0.1 to 191.241.255.254191.241.255.255131,070
122191.242.0.0/15191.242.0.1 to 191.243.255.254191.243.255.255131,070
123191.244.0.0/15191.244.0.1 to 191.245.255.254191.245.255.255131,070
124191.246.0.0/15191.246.0.1 to 191.247.255.254191.247.255.255131,070
125191.248.0.0/15191.248.0.1 to 191.249.255.254191.249.255.255131,070
126191.250.0.0/15191.250.0.1 to 191.251.255.254191.251.255.255131,070
127191.252.0.0/15191.252.0.1 to 191.253.255.254191.253.255.255131,070
128191.254.0.0/15191.254.0.1 to 191.255.255.254191.255.255.255131,070

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.