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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.

Network181.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
181.0.0.0
Broadcast address
181.255.255.255
First usable
181.0.0.1
Last usable
181.255.255.254
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 B5000000 · Integer 3036676096 to 3053453311
Reverse DNS zone
181.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10110101..00000000.00000000.00000000181.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10110101..00000000.00000000.00000000181.0.0.0
Broadcast10110101..11111111.11111111.11111111181.255.255.255
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)

181.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1181.0.0.0/15181.0.0.1 to 181.1.255.254181.1.255.255131,070
2181.2.0.0/15181.2.0.1 to 181.3.255.254181.3.255.255131,070
3181.4.0.0/15181.4.0.1 to 181.5.255.254181.5.255.255131,070
4181.6.0.0/15181.6.0.1 to 181.7.255.254181.7.255.255131,070
5181.8.0.0/15181.8.0.1 to 181.9.255.254181.9.255.255131,070
6181.10.0.0/15181.10.0.1 to 181.11.255.254181.11.255.255131,070
7181.12.0.0/15181.12.0.1 to 181.13.255.254181.13.255.255131,070
8181.14.0.0/15181.14.0.1 to 181.15.255.254181.15.255.255131,070
9181.16.0.0/15181.16.0.1 to 181.17.255.254181.17.255.255131,070
10181.18.0.0/15181.18.0.1 to 181.19.255.254181.19.255.255131,070
11181.20.0.0/15181.20.0.1 to 181.21.255.254181.21.255.255131,070
12181.22.0.0/15181.22.0.1 to 181.23.255.254181.23.255.255131,070
13181.24.0.0/15181.24.0.1 to 181.25.255.254181.25.255.255131,070
14181.26.0.0/15181.26.0.1 to 181.27.255.254181.27.255.255131,070
15181.28.0.0/15181.28.0.1 to 181.29.255.254181.29.255.255131,070
16181.30.0.0/15181.30.0.1 to 181.31.255.254181.31.255.255131,070
17181.32.0.0/15181.32.0.1 to 181.33.255.254181.33.255.255131,070
18181.34.0.0/15181.34.0.1 to 181.35.255.254181.35.255.255131,070
19181.36.0.0/15181.36.0.1 to 181.37.255.254181.37.255.255131,070
20181.38.0.0/15181.38.0.1 to 181.39.255.254181.39.255.255131,070
21181.40.0.0/15181.40.0.1 to 181.41.255.254181.41.255.255131,070
22181.42.0.0/15181.42.0.1 to 181.43.255.254181.43.255.255131,070
23181.44.0.0/15181.44.0.1 to 181.45.255.254181.45.255.255131,070
24181.46.0.0/15181.46.0.1 to 181.47.255.254181.47.255.255131,070
25181.48.0.0/15181.48.0.1 to 181.49.255.254181.49.255.255131,070
26181.50.0.0/15181.50.0.1 to 181.51.255.254181.51.255.255131,070
27181.52.0.0/15181.52.0.1 to 181.53.255.254181.53.255.255131,070
28181.54.0.0/15181.54.0.1 to 181.55.255.254181.55.255.255131,070
29181.56.0.0/15181.56.0.1 to 181.57.255.254181.57.255.255131,070
30181.58.0.0/15181.58.0.1 to 181.59.255.254181.59.255.255131,070
31181.60.0.0/15181.60.0.1 to 181.61.255.254181.61.255.255131,070
32181.62.0.0/15181.62.0.1 to 181.63.255.254181.63.255.255131,070
33181.64.0.0/15181.64.0.1 to 181.65.255.254181.65.255.255131,070
34181.66.0.0/15181.66.0.1 to 181.67.255.254181.67.255.255131,070
35181.68.0.0/15181.68.0.1 to 181.69.255.254181.69.255.255131,070
36181.70.0.0/15181.70.0.1 to 181.71.255.254181.71.255.255131,070
37181.72.0.0/15181.72.0.1 to 181.73.255.254181.73.255.255131,070
38181.74.0.0/15181.74.0.1 to 181.75.255.254181.75.255.255131,070
39181.76.0.0/15181.76.0.1 to 181.77.255.254181.77.255.255131,070
40181.78.0.0/15181.78.0.1 to 181.79.255.254181.79.255.255131,070
41181.80.0.0/15181.80.0.1 to 181.81.255.254181.81.255.255131,070
42181.82.0.0/15181.82.0.1 to 181.83.255.254181.83.255.255131,070
43181.84.0.0/15181.84.0.1 to 181.85.255.254181.85.255.255131,070
44181.86.0.0/15181.86.0.1 to 181.87.255.254181.87.255.255131,070
45181.88.0.0/15181.88.0.1 to 181.89.255.254181.89.255.255131,070
46181.90.0.0/15181.90.0.1 to 181.91.255.254181.91.255.255131,070
47181.92.0.0/15181.92.0.1 to 181.93.255.254181.93.255.255131,070
48181.94.0.0/15181.94.0.1 to 181.95.255.254181.95.255.255131,070
49181.96.0.0/15181.96.0.1 to 181.97.255.254181.97.255.255131,070
50181.98.0.0/15181.98.0.1 to 181.99.255.254181.99.255.255131,070
51181.100.0.0/15181.100.0.1 to 181.101.255.254181.101.255.255131,070
52181.102.0.0/15181.102.0.1 to 181.103.255.254181.103.255.255131,070
53181.104.0.0/15181.104.0.1 to 181.105.255.254181.105.255.255131,070
54181.106.0.0/15181.106.0.1 to 181.107.255.254181.107.255.255131,070
55181.108.0.0/15181.108.0.1 to 181.109.255.254181.109.255.255131,070
56181.110.0.0/15181.110.0.1 to 181.111.255.254181.111.255.255131,070
57181.112.0.0/15181.112.0.1 to 181.113.255.254181.113.255.255131,070
58181.114.0.0/15181.114.0.1 to 181.115.255.254181.115.255.255131,070
59181.116.0.0/15181.116.0.1 to 181.117.255.254181.117.255.255131,070
60181.118.0.0/15181.118.0.1 to 181.119.255.254181.119.255.255131,070
61181.120.0.0/15181.120.0.1 to 181.121.255.254181.121.255.255131,070
62181.122.0.0/15181.122.0.1 to 181.123.255.254181.123.255.255131,070
63181.124.0.0/15181.124.0.1 to 181.125.255.254181.125.255.255131,070
64181.126.0.0/15181.126.0.1 to 181.127.255.254181.127.255.255131,070
65181.128.0.0/15181.128.0.1 to 181.129.255.254181.129.255.255131,070
66181.130.0.0/15181.130.0.1 to 181.131.255.254181.131.255.255131,070
67181.132.0.0/15181.132.0.1 to 181.133.255.254181.133.255.255131,070
68181.134.0.0/15181.134.0.1 to 181.135.255.254181.135.255.255131,070
69181.136.0.0/15181.136.0.1 to 181.137.255.254181.137.255.255131,070
70181.138.0.0/15181.138.0.1 to 181.139.255.254181.139.255.255131,070
71181.140.0.0/15181.140.0.1 to 181.141.255.254181.141.255.255131,070
72181.142.0.0/15181.142.0.1 to 181.143.255.254181.143.255.255131,070
73181.144.0.0/15181.144.0.1 to 181.145.255.254181.145.255.255131,070
74181.146.0.0/15181.146.0.1 to 181.147.255.254181.147.255.255131,070
75181.148.0.0/15181.148.0.1 to 181.149.255.254181.149.255.255131,070
76181.150.0.0/15181.150.0.1 to 181.151.255.254181.151.255.255131,070
77181.152.0.0/15181.152.0.1 to 181.153.255.254181.153.255.255131,070
78181.154.0.0/15181.154.0.1 to 181.155.255.254181.155.255.255131,070
79181.156.0.0/15181.156.0.1 to 181.157.255.254181.157.255.255131,070
80181.158.0.0/15181.158.0.1 to 181.159.255.254181.159.255.255131,070
81181.160.0.0/15181.160.0.1 to 181.161.255.254181.161.255.255131,070
82181.162.0.0/15181.162.0.1 to 181.163.255.254181.163.255.255131,070
83181.164.0.0/15181.164.0.1 to 181.165.255.254181.165.255.255131,070
84181.166.0.0/15181.166.0.1 to 181.167.255.254181.167.255.255131,070
85181.168.0.0/15181.168.0.1 to 181.169.255.254181.169.255.255131,070
86181.170.0.0/15181.170.0.1 to 181.171.255.254181.171.255.255131,070
87181.172.0.0/15181.172.0.1 to 181.173.255.254181.173.255.255131,070
88181.174.0.0/15181.174.0.1 to 181.175.255.254181.175.255.255131,070
89181.176.0.0/15181.176.0.1 to 181.177.255.254181.177.255.255131,070
90181.178.0.0/15181.178.0.1 to 181.179.255.254181.179.255.255131,070
91181.180.0.0/15181.180.0.1 to 181.181.255.254181.181.255.255131,070
92181.182.0.0/15181.182.0.1 to 181.183.255.254181.183.255.255131,070
93181.184.0.0/15181.184.0.1 to 181.185.255.254181.185.255.255131,070
94181.186.0.0/15181.186.0.1 to 181.187.255.254181.187.255.255131,070
95181.188.0.0/15181.188.0.1 to 181.189.255.254181.189.255.255131,070
96181.190.0.0/15181.190.0.1 to 181.191.255.254181.191.255.255131,070
97181.192.0.0/15181.192.0.1 to 181.193.255.254181.193.255.255131,070
98181.194.0.0/15181.194.0.1 to 181.195.255.254181.195.255.255131,070
99181.196.0.0/15181.196.0.1 to 181.197.255.254181.197.255.255131,070
100181.198.0.0/15181.198.0.1 to 181.199.255.254181.199.255.255131,070
101181.200.0.0/15181.200.0.1 to 181.201.255.254181.201.255.255131,070
102181.202.0.0/15181.202.0.1 to 181.203.255.254181.203.255.255131,070
103181.204.0.0/15181.204.0.1 to 181.205.255.254181.205.255.255131,070
104181.206.0.0/15181.206.0.1 to 181.207.255.254181.207.255.255131,070
105181.208.0.0/15181.208.0.1 to 181.209.255.254181.209.255.255131,070
106181.210.0.0/15181.210.0.1 to 181.211.255.254181.211.255.255131,070
107181.212.0.0/15181.212.0.1 to 181.213.255.254181.213.255.255131,070
108181.214.0.0/15181.214.0.1 to 181.215.255.254181.215.255.255131,070
109181.216.0.0/15181.216.0.1 to 181.217.255.254181.217.255.255131,070
110181.218.0.0/15181.218.0.1 to 181.219.255.254181.219.255.255131,070
111181.220.0.0/15181.220.0.1 to 181.221.255.254181.221.255.255131,070
112181.222.0.0/15181.222.0.1 to 181.223.255.254181.223.255.255131,070
113181.224.0.0/15181.224.0.1 to 181.225.255.254181.225.255.255131,070
114181.226.0.0/15181.226.0.1 to 181.227.255.254181.227.255.255131,070
115181.228.0.0/15181.228.0.1 to 181.229.255.254181.229.255.255131,070
116181.230.0.0/15181.230.0.1 to 181.231.255.254181.231.255.255131,070
117181.232.0.0/15181.232.0.1 to 181.233.255.254181.233.255.255131,070
118181.234.0.0/15181.234.0.1 to 181.235.255.254181.235.255.255131,070
119181.236.0.0/15181.236.0.1 to 181.237.255.254181.237.255.255131,070
120181.238.0.0/15181.238.0.1 to 181.239.255.254181.239.255.255131,070
121181.240.0.0/15181.240.0.1 to 181.241.255.254181.241.255.255131,070
122181.242.0.0/15181.242.0.1 to 181.243.255.254181.243.255.255131,070
123181.244.0.0/15181.244.0.1 to 181.245.255.254181.245.255.255131,070
124181.246.0.0/15181.246.0.1 to 181.247.255.254181.247.255.255131,070
125181.248.0.0/15181.248.0.1 to 181.249.255.254181.249.255.255131,070
126181.250.0.0/15181.250.0.1 to 181.251.255.254181.251.255.255131,070
127181.252.0.0/15181.252.0.1 to 181.253.255.254181.253.255.255131,070
128181.254.0.0/15181.254.0.1 to 181.255.255.254181.255.255.255131,070

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.