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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.

Network131.138.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
131.138.0.0
Broadcast address
131.138.255.255
First usable
131.138.0.1
Last usable
131.138.255.254
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 838A0000 · Integer 2206859264 to 2206924799
Reverse DNS zone
138.131.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000011.10001010..00000000.00000000131.138.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10000011.10001010..00000000.00000000131.138.0.0
Broadcast10000011.10001010..11111111.11111111131.138.255.255
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)

131.138.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1131.138.0.0/23131.138.0.1 to 131.138.1.254131.138.1.255510
2131.138.2.0/23131.138.2.1 to 131.138.3.254131.138.3.255510
3131.138.4.0/23131.138.4.1 to 131.138.5.254131.138.5.255510
4131.138.6.0/23131.138.6.1 to 131.138.7.254131.138.7.255510
5131.138.8.0/23131.138.8.1 to 131.138.9.254131.138.9.255510
6131.138.10.0/23131.138.10.1 to 131.138.11.254131.138.11.255510
7131.138.12.0/23131.138.12.1 to 131.138.13.254131.138.13.255510
8131.138.14.0/23131.138.14.1 to 131.138.15.254131.138.15.255510
9131.138.16.0/23131.138.16.1 to 131.138.17.254131.138.17.255510
10131.138.18.0/23131.138.18.1 to 131.138.19.254131.138.19.255510
11131.138.20.0/23131.138.20.1 to 131.138.21.254131.138.21.255510
12131.138.22.0/23131.138.22.1 to 131.138.23.254131.138.23.255510
13131.138.24.0/23131.138.24.1 to 131.138.25.254131.138.25.255510
14131.138.26.0/23131.138.26.1 to 131.138.27.254131.138.27.255510
15131.138.28.0/23131.138.28.1 to 131.138.29.254131.138.29.255510
16131.138.30.0/23131.138.30.1 to 131.138.31.254131.138.31.255510
17131.138.32.0/23131.138.32.1 to 131.138.33.254131.138.33.255510
18131.138.34.0/23131.138.34.1 to 131.138.35.254131.138.35.255510
19131.138.36.0/23131.138.36.1 to 131.138.37.254131.138.37.255510
20131.138.38.0/23131.138.38.1 to 131.138.39.254131.138.39.255510
21131.138.40.0/23131.138.40.1 to 131.138.41.254131.138.41.255510
22131.138.42.0/23131.138.42.1 to 131.138.43.254131.138.43.255510
23131.138.44.0/23131.138.44.1 to 131.138.45.254131.138.45.255510
24131.138.46.0/23131.138.46.1 to 131.138.47.254131.138.47.255510
25131.138.48.0/23131.138.48.1 to 131.138.49.254131.138.49.255510
26131.138.50.0/23131.138.50.1 to 131.138.51.254131.138.51.255510
27131.138.52.0/23131.138.52.1 to 131.138.53.254131.138.53.255510
28131.138.54.0/23131.138.54.1 to 131.138.55.254131.138.55.255510
29131.138.56.0/23131.138.56.1 to 131.138.57.254131.138.57.255510
30131.138.58.0/23131.138.58.1 to 131.138.59.254131.138.59.255510
31131.138.60.0/23131.138.60.1 to 131.138.61.254131.138.61.255510
32131.138.62.0/23131.138.62.1 to 131.138.63.254131.138.63.255510
33131.138.64.0/23131.138.64.1 to 131.138.65.254131.138.65.255510
34131.138.66.0/23131.138.66.1 to 131.138.67.254131.138.67.255510
35131.138.68.0/23131.138.68.1 to 131.138.69.254131.138.69.255510
36131.138.70.0/23131.138.70.1 to 131.138.71.254131.138.71.255510
37131.138.72.0/23131.138.72.1 to 131.138.73.254131.138.73.255510
38131.138.74.0/23131.138.74.1 to 131.138.75.254131.138.75.255510
39131.138.76.0/23131.138.76.1 to 131.138.77.254131.138.77.255510
40131.138.78.0/23131.138.78.1 to 131.138.79.254131.138.79.255510
41131.138.80.0/23131.138.80.1 to 131.138.81.254131.138.81.255510
42131.138.82.0/23131.138.82.1 to 131.138.83.254131.138.83.255510
43131.138.84.0/23131.138.84.1 to 131.138.85.254131.138.85.255510
44131.138.86.0/23131.138.86.1 to 131.138.87.254131.138.87.255510
45131.138.88.0/23131.138.88.1 to 131.138.89.254131.138.89.255510
46131.138.90.0/23131.138.90.1 to 131.138.91.254131.138.91.255510
47131.138.92.0/23131.138.92.1 to 131.138.93.254131.138.93.255510
48131.138.94.0/23131.138.94.1 to 131.138.95.254131.138.95.255510
49131.138.96.0/23131.138.96.1 to 131.138.97.254131.138.97.255510
50131.138.98.0/23131.138.98.1 to 131.138.99.254131.138.99.255510
51131.138.100.0/23131.138.100.1 to 131.138.101.254131.138.101.255510
52131.138.102.0/23131.138.102.1 to 131.138.103.254131.138.103.255510
53131.138.104.0/23131.138.104.1 to 131.138.105.254131.138.105.255510
54131.138.106.0/23131.138.106.1 to 131.138.107.254131.138.107.255510
55131.138.108.0/23131.138.108.1 to 131.138.109.254131.138.109.255510
56131.138.110.0/23131.138.110.1 to 131.138.111.254131.138.111.255510
57131.138.112.0/23131.138.112.1 to 131.138.113.254131.138.113.255510
58131.138.114.0/23131.138.114.1 to 131.138.115.254131.138.115.255510
59131.138.116.0/23131.138.116.1 to 131.138.117.254131.138.117.255510
60131.138.118.0/23131.138.118.1 to 131.138.119.254131.138.119.255510
61131.138.120.0/23131.138.120.1 to 131.138.121.254131.138.121.255510
62131.138.122.0/23131.138.122.1 to 131.138.123.254131.138.123.255510
63131.138.124.0/23131.138.124.1 to 131.138.125.254131.138.125.255510
64131.138.126.0/23131.138.126.1 to 131.138.127.254131.138.127.255510
65131.138.128.0/23131.138.128.1 to 131.138.129.254131.138.129.255510
66131.138.130.0/23131.138.130.1 to 131.138.131.254131.138.131.255510
67131.138.132.0/23131.138.132.1 to 131.138.133.254131.138.133.255510
68131.138.134.0/23131.138.134.1 to 131.138.135.254131.138.135.255510
69131.138.136.0/23131.138.136.1 to 131.138.137.254131.138.137.255510
70131.138.138.0/23131.138.138.1 to 131.138.139.254131.138.139.255510
71131.138.140.0/23131.138.140.1 to 131.138.141.254131.138.141.255510
72131.138.142.0/23131.138.142.1 to 131.138.143.254131.138.143.255510
73131.138.144.0/23131.138.144.1 to 131.138.145.254131.138.145.255510
74131.138.146.0/23131.138.146.1 to 131.138.147.254131.138.147.255510
75131.138.148.0/23131.138.148.1 to 131.138.149.254131.138.149.255510
76131.138.150.0/23131.138.150.1 to 131.138.151.254131.138.151.255510
77131.138.152.0/23131.138.152.1 to 131.138.153.254131.138.153.255510
78131.138.154.0/23131.138.154.1 to 131.138.155.254131.138.155.255510
79131.138.156.0/23131.138.156.1 to 131.138.157.254131.138.157.255510
80131.138.158.0/23131.138.158.1 to 131.138.159.254131.138.159.255510
81131.138.160.0/23131.138.160.1 to 131.138.161.254131.138.161.255510
82131.138.162.0/23131.138.162.1 to 131.138.163.254131.138.163.255510
83131.138.164.0/23131.138.164.1 to 131.138.165.254131.138.165.255510
84131.138.166.0/23131.138.166.1 to 131.138.167.254131.138.167.255510
85131.138.168.0/23131.138.168.1 to 131.138.169.254131.138.169.255510
86131.138.170.0/23131.138.170.1 to 131.138.171.254131.138.171.255510
87131.138.172.0/23131.138.172.1 to 131.138.173.254131.138.173.255510
88131.138.174.0/23131.138.174.1 to 131.138.175.254131.138.175.255510
89131.138.176.0/23131.138.176.1 to 131.138.177.254131.138.177.255510
90131.138.178.0/23131.138.178.1 to 131.138.179.254131.138.179.255510
91131.138.180.0/23131.138.180.1 to 131.138.181.254131.138.181.255510
92131.138.182.0/23131.138.182.1 to 131.138.183.254131.138.183.255510
93131.138.184.0/23131.138.184.1 to 131.138.185.254131.138.185.255510
94131.138.186.0/23131.138.186.1 to 131.138.187.254131.138.187.255510
95131.138.188.0/23131.138.188.1 to 131.138.189.254131.138.189.255510
96131.138.190.0/23131.138.190.1 to 131.138.191.254131.138.191.255510
97131.138.192.0/23131.138.192.1 to 131.138.193.254131.138.193.255510
98131.138.194.0/23131.138.194.1 to 131.138.195.254131.138.195.255510
99131.138.196.0/23131.138.196.1 to 131.138.197.254131.138.197.255510
100131.138.198.0/23131.138.198.1 to 131.138.199.254131.138.199.255510
101131.138.200.0/23131.138.200.1 to 131.138.201.254131.138.201.255510
102131.138.202.0/23131.138.202.1 to 131.138.203.254131.138.203.255510
103131.138.204.0/23131.138.204.1 to 131.138.205.254131.138.205.255510
104131.138.206.0/23131.138.206.1 to 131.138.207.254131.138.207.255510
105131.138.208.0/23131.138.208.1 to 131.138.209.254131.138.209.255510
106131.138.210.0/23131.138.210.1 to 131.138.211.254131.138.211.255510
107131.138.212.0/23131.138.212.1 to 131.138.213.254131.138.213.255510
108131.138.214.0/23131.138.214.1 to 131.138.215.254131.138.215.255510
109131.138.216.0/23131.138.216.1 to 131.138.217.254131.138.217.255510
110131.138.218.0/23131.138.218.1 to 131.138.219.254131.138.219.255510
111131.138.220.0/23131.138.220.1 to 131.138.221.254131.138.221.255510
112131.138.222.0/23131.138.222.1 to 131.138.223.254131.138.223.255510
113131.138.224.0/23131.138.224.1 to 131.138.225.254131.138.225.255510
114131.138.226.0/23131.138.226.1 to 131.138.227.254131.138.227.255510
115131.138.228.0/23131.138.228.1 to 131.138.229.254131.138.229.255510
116131.138.230.0/23131.138.230.1 to 131.138.231.254131.138.231.255510
117131.138.232.0/23131.138.232.1 to 131.138.233.254131.138.233.255510
118131.138.234.0/23131.138.234.1 to 131.138.235.254131.138.235.255510
119131.138.236.0/23131.138.236.1 to 131.138.237.254131.138.237.255510
120131.138.238.0/23131.138.238.1 to 131.138.239.254131.138.239.255510
121131.138.240.0/23131.138.240.1 to 131.138.241.254131.138.241.255510
122131.138.242.0/23131.138.242.1 to 131.138.243.254131.138.243.255510
123131.138.244.0/23131.138.244.1 to 131.138.245.254131.138.245.255510
124131.138.246.0/23131.138.246.1 to 131.138.247.254131.138.247.255510
125131.138.248.0/23131.138.248.1 to 131.138.249.254131.138.249.255510
126131.138.250.0/23131.138.250.1 to 131.138.251.254131.138.251.255510
127131.138.252.0/23131.138.252.1 to 131.138.253.254131.138.253.255510
128131.138.254.0/23131.138.254.1 to 131.138.255.254131.138.255.255510

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.