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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.

Network161.71.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
161.71.0.0
Broadcast address
161.71.255.255
First usable
161.71.0.1
Last usable
161.71.255.254
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 A1470000 · Integer 2705784832 to 2705850367
Reverse DNS zone
71.161.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100001.01000111..00000000.00000000161.71.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10100001.01000111..00000000.00000000161.71.0.0
Broadcast10100001.01000111..11111111.11111111161.71.255.255
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)

161.71.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1161.71.0.0/23161.71.0.1 to 161.71.1.254161.71.1.255510
2161.71.2.0/23161.71.2.1 to 161.71.3.254161.71.3.255510
3161.71.4.0/23161.71.4.1 to 161.71.5.254161.71.5.255510
4161.71.6.0/23161.71.6.1 to 161.71.7.254161.71.7.255510
5161.71.8.0/23161.71.8.1 to 161.71.9.254161.71.9.255510
6161.71.10.0/23161.71.10.1 to 161.71.11.254161.71.11.255510
7161.71.12.0/23161.71.12.1 to 161.71.13.254161.71.13.255510
8161.71.14.0/23161.71.14.1 to 161.71.15.254161.71.15.255510
9161.71.16.0/23161.71.16.1 to 161.71.17.254161.71.17.255510
10161.71.18.0/23161.71.18.1 to 161.71.19.254161.71.19.255510
11161.71.20.0/23161.71.20.1 to 161.71.21.254161.71.21.255510
12161.71.22.0/23161.71.22.1 to 161.71.23.254161.71.23.255510
13161.71.24.0/23161.71.24.1 to 161.71.25.254161.71.25.255510
14161.71.26.0/23161.71.26.1 to 161.71.27.254161.71.27.255510
15161.71.28.0/23161.71.28.1 to 161.71.29.254161.71.29.255510
16161.71.30.0/23161.71.30.1 to 161.71.31.254161.71.31.255510
17161.71.32.0/23161.71.32.1 to 161.71.33.254161.71.33.255510
18161.71.34.0/23161.71.34.1 to 161.71.35.254161.71.35.255510
19161.71.36.0/23161.71.36.1 to 161.71.37.254161.71.37.255510
20161.71.38.0/23161.71.38.1 to 161.71.39.254161.71.39.255510
21161.71.40.0/23161.71.40.1 to 161.71.41.254161.71.41.255510
22161.71.42.0/23161.71.42.1 to 161.71.43.254161.71.43.255510
23161.71.44.0/23161.71.44.1 to 161.71.45.254161.71.45.255510
24161.71.46.0/23161.71.46.1 to 161.71.47.254161.71.47.255510
25161.71.48.0/23161.71.48.1 to 161.71.49.254161.71.49.255510
26161.71.50.0/23161.71.50.1 to 161.71.51.254161.71.51.255510
27161.71.52.0/23161.71.52.1 to 161.71.53.254161.71.53.255510
28161.71.54.0/23161.71.54.1 to 161.71.55.254161.71.55.255510
29161.71.56.0/23161.71.56.1 to 161.71.57.254161.71.57.255510
30161.71.58.0/23161.71.58.1 to 161.71.59.254161.71.59.255510
31161.71.60.0/23161.71.60.1 to 161.71.61.254161.71.61.255510
32161.71.62.0/23161.71.62.1 to 161.71.63.254161.71.63.255510
33161.71.64.0/23161.71.64.1 to 161.71.65.254161.71.65.255510
34161.71.66.0/23161.71.66.1 to 161.71.67.254161.71.67.255510
35161.71.68.0/23161.71.68.1 to 161.71.69.254161.71.69.255510
36161.71.70.0/23161.71.70.1 to 161.71.71.254161.71.71.255510
37161.71.72.0/23161.71.72.1 to 161.71.73.254161.71.73.255510
38161.71.74.0/23161.71.74.1 to 161.71.75.254161.71.75.255510
39161.71.76.0/23161.71.76.1 to 161.71.77.254161.71.77.255510
40161.71.78.0/23161.71.78.1 to 161.71.79.254161.71.79.255510
41161.71.80.0/23161.71.80.1 to 161.71.81.254161.71.81.255510
42161.71.82.0/23161.71.82.1 to 161.71.83.254161.71.83.255510
43161.71.84.0/23161.71.84.1 to 161.71.85.254161.71.85.255510
44161.71.86.0/23161.71.86.1 to 161.71.87.254161.71.87.255510
45161.71.88.0/23161.71.88.1 to 161.71.89.254161.71.89.255510
46161.71.90.0/23161.71.90.1 to 161.71.91.254161.71.91.255510
47161.71.92.0/23161.71.92.1 to 161.71.93.254161.71.93.255510
48161.71.94.0/23161.71.94.1 to 161.71.95.254161.71.95.255510
49161.71.96.0/23161.71.96.1 to 161.71.97.254161.71.97.255510
50161.71.98.0/23161.71.98.1 to 161.71.99.254161.71.99.255510
51161.71.100.0/23161.71.100.1 to 161.71.101.254161.71.101.255510
52161.71.102.0/23161.71.102.1 to 161.71.103.254161.71.103.255510
53161.71.104.0/23161.71.104.1 to 161.71.105.254161.71.105.255510
54161.71.106.0/23161.71.106.1 to 161.71.107.254161.71.107.255510
55161.71.108.0/23161.71.108.1 to 161.71.109.254161.71.109.255510
56161.71.110.0/23161.71.110.1 to 161.71.111.254161.71.111.255510
57161.71.112.0/23161.71.112.1 to 161.71.113.254161.71.113.255510
58161.71.114.0/23161.71.114.1 to 161.71.115.254161.71.115.255510
59161.71.116.0/23161.71.116.1 to 161.71.117.254161.71.117.255510
60161.71.118.0/23161.71.118.1 to 161.71.119.254161.71.119.255510
61161.71.120.0/23161.71.120.1 to 161.71.121.254161.71.121.255510
62161.71.122.0/23161.71.122.1 to 161.71.123.254161.71.123.255510
63161.71.124.0/23161.71.124.1 to 161.71.125.254161.71.125.255510
64161.71.126.0/23161.71.126.1 to 161.71.127.254161.71.127.255510
65161.71.128.0/23161.71.128.1 to 161.71.129.254161.71.129.255510
66161.71.130.0/23161.71.130.1 to 161.71.131.254161.71.131.255510
67161.71.132.0/23161.71.132.1 to 161.71.133.254161.71.133.255510
68161.71.134.0/23161.71.134.1 to 161.71.135.254161.71.135.255510
69161.71.136.0/23161.71.136.1 to 161.71.137.254161.71.137.255510
70161.71.138.0/23161.71.138.1 to 161.71.139.254161.71.139.255510
71161.71.140.0/23161.71.140.1 to 161.71.141.254161.71.141.255510
72161.71.142.0/23161.71.142.1 to 161.71.143.254161.71.143.255510
73161.71.144.0/23161.71.144.1 to 161.71.145.254161.71.145.255510
74161.71.146.0/23161.71.146.1 to 161.71.147.254161.71.147.255510
75161.71.148.0/23161.71.148.1 to 161.71.149.254161.71.149.255510
76161.71.150.0/23161.71.150.1 to 161.71.151.254161.71.151.255510
77161.71.152.0/23161.71.152.1 to 161.71.153.254161.71.153.255510
78161.71.154.0/23161.71.154.1 to 161.71.155.254161.71.155.255510
79161.71.156.0/23161.71.156.1 to 161.71.157.254161.71.157.255510
80161.71.158.0/23161.71.158.1 to 161.71.159.254161.71.159.255510
81161.71.160.0/23161.71.160.1 to 161.71.161.254161.71.161.255510
82161.71.162.0/23161.71.162.1 to 161.71.163.254161.71.163.255510
83161.71.164.0/23161.71.164.1 to 161.71.165.254161.71.165.255510
84161.71.166.0/23161.71.166.1 to 161.71.167.254161.71.167.255510
85161.71.168.0/23161.71.168.1 to 161.71.169.254161.71.169.255510
86161.71.170.0/23161.71.170.1 to 161.71.171.254161.71.171.255510
87161.71.172.0/23161.71.172.1 to 161.71.173.254161.71.173.255510
88161.71.174.0/23161.71.174.1 to 161.71.175.254161.71.175.255510
89161.71.176.0/23161.71.176.1 to 161.71.177.254161.71.177.255510
90161.71.178.0/23161.71.178.1 to 161.71.179.254161.71.179.255510
91161.71.180.0/23161.71.180.1 to 161.71.181.254161.71.181.255510
92161.71.182.0/23161.71.182.1 to 161.71.183.254161.71.183.255510
93161.71.184.0/23161.71.184.1 to 161.71.185.254161.71.185.255510
94161.71.186.0/23161.71.186.1 to 161.71.187.254161.71.187.255510
95161.71.188.0/23161.71.188.1 to 161.71.189.254161.71.189.255510
96161.71.190.0/23161.71.190.1 to 161.71.191.254161.71.191.255510
97161.71.192.0/23161.71.192.1 to 161.71.193.254161.71.193.255510
98161.71.194.0/23161.71.194.1 to 161.71.195.254161.71.195.255510
99161.71.196.0/23161.71.196.1 to 161.71.197.254161.71.197.255510
100161.71.198.0/23161.71.198.1 to 161.71.199.254161.71.199.255510
101161.71.200.0/23161.71.200.1 to 161.71.201.254161.71.201.255510
102161.71.202.0/23161.71.202.1 to 161.71.203.254161.71.203.255510
103161.71.204.0/23161.71.204.1 to 161.71.205.254161.71.205.255510
104161.71.206.0/23161.71.206.1 to 161.71.207.254161.71.207.255510
105161.71.208.0/23161.71.208.1 to 161.71.209.254161.71.209.255510
106161.71.210.0/23161.71.210.1 to 161.71.211.254161.71.211.255510
107161.71.212.0/23161.71.212.1 to 161.71.213.254161.71.213.255510
108161.71.214.0/23161.71.214.1 to 161.71.215.254161.71.215.255510
109161.71.216.0/23161.71.216.1 to 161.71.217.254161.71.217.255510
110161.71.218.0/23161.71.218.1 to 161.71.219.254161.71.219.255510
111161.71.220.0/23161.71.220.1 to 161.71.221.254161.71.221.255510
112161.71.222.0/23161.71.222.1 to 161.71.223.254161.71.223.255510
113161.71.224.0/23161.71.224.1 to 161.71.225.254161.71.225.255510
114161.71.226.0/23161.71.226.1 to 161.71.227.254161.71.227.255510
115161.71.228.0/23161.71.228.1 to 161.71.229.254161.71.229.255510
116161.71.230.0/23161.71.230.1 to 161.71.231.254161.71.231.255510
117161.71.232.0/23161.71.232.1 to 161.71.233.254161.71.233.255510
118161.71.234.0/23161.71.234.1 to 161.71.235.254161.71.235.255510
119161.71.236.0/23161.71.236.1 to 161.71.237.254161.71.237.255510
120161.71.238.0/23161.71.238.1 to 161.71.239.254161.71.239.255510
121161.71.240.0/23161.71.240.1 to 161.71.241.254161.71.241.255510
122161.71.242.0/23161.71.242.1 to 161.71.243.254161.71.243.255510
123161.71.244.0/23161.71.244.1 to 161.71.245.254161.71.245.255510
124161.71.246.0/23161.71.246.1 to 161.71.247.254161.71.247.255510
125161.71.248.0/23161.71.248.1 to 161.71.249.254161.71.249.255510
126161.71.250.0/23161.71.250.1 to 161.71.251.254161.71.251.255510
127161.71.252.0/23161.71.252.1 to 161.71.253.254161.71.253.255510
128161.71.254.0/23161.71.254.1 to 161.71.255.254161.71.255.255510

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.