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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.

Network219.71.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
219.71.0.0
Broadcast address
219.71.255.255
First usable
219.71.0.1
Last usable
219.71.255.254
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
C (default /24)
As numbers
Hex DB470000 · Integer 3678863360 to 3678928895
Reverse DNS zone
71.219.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11011011.01000111..00000000.00000000219.71.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network11011011.01000111..00000000.00000000219.71.0.0
Broadcast11011011.01000111..11111111.11111111219.71.255.255
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)

219.71.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1219.71.0.0/23219.71.0.1 to 219.71.1.254219.71.1.255510
2219.71.2.0/23219.71.2.1 to 219.71.3.254219.71.3.255510
3219.71.4.0/23219.71.4.1 to 219.71.5.254219.71.5.255510
4219.71.6.0/23219.71.6.1 to 219.71.7.254219.71.7.255510
5219.71.8.0/23219.71.8.1 to 219.71.9.254219.71.9.255510
6219.71.10.0/23219.71.10.1 to 219.71.11.254219.71.11.255510
7219.71.12.0/23219.71.12.1 to 219.71.13.254219.71.13.255510
8219.71.14.0/23219.71.14.1 to 219.71.15.254219.71.15.255510
9219.71.16.0/23219.71.16.1 to 219.71.17.254219.71.17.255510
10219.71.18.0/23219.71.18.1 to 219.71.19.254219.71.19.255510
11219.71.20.0/23219.71.20.1 to 219.71.21.254219.71.21.255510
12219.71.22.0/23219.71.22.1 to 219.71.23.254219.71.23.255510
13219.71.24.0/23219.71.24.1 to 219.71.25.254219.71.25.255510
14219.71.26.0/23219.71.26.1 to 219.71.27.254219.71.27.255510
15219.71.28.0/23219.71.28.1 to 219.71.29.254219.71.29.255510
16219.71.30.0/23219.71.30.1 to 219.71.31.254219.71.31.255510
17219.71.32.0/23219.71.32.1 to 219.71.33.254219.71.33.255510
18219.71.34.0/23219.71.34.1 to 219.71.35.254219.71.35.255510
19219.71.36.0/23219.71.36.1 to 219.71.37.254219.71.37.255510
20219.71.38.0/23219.71.38.1 to 219.71.39.254219.71.39.255510
21219.71.40.0/23219.71.40.1 to 219.71.41.254219.71.41.255510
22219.71.42.0/23219.71.42.1 to 219.71.43.254219.71.43.255510
23219.71.44.0/23219.71.44.1 to 219.71.45.254219.71.45.255510
24219.71.46.0/23219.71.46.1 to 219.71.47.254219.71.47.255510
25219.71.48.0/23219.71.48.1 to 219.71.49.254219.71.49.255510
26219.71.50.0/23219.71.50.1 to 219.71.51.254219.71.51.255510
27219.71.52.0/23219.71.52.1 to 219.71.53.254219.71.53.255510
28219.71.54.0/23219.71.54.1 to 219.71.55.254219.71.55.255510
29219.71.56.0/23219.71.56.1 to 219.71.57.254219.71.57.255510
30219.71.58.0/23219.71.58.1 to 219.71.59.254219.71.59.255510
31219.71.60.0/23219.71.60.1 to 219.71.61.254219.71.61.255510
32219.71.62.0/23219.71.62.1 to 219.71.63.254219.71.63.255510
33219.71.64.0/23219.71.64.1 to 219.71.65.254219.71.65.255510
34219.71.66.0/23219.71.66.1 to 219.71.67.254219.71.67.255510
35219.71.68.0/23219.71.68.1 to 219.71.69.254219.71.69.255510
36219.71.70.0/23219.71.70.1 to 219.71.71.254219.71.71.255510
37219.71.72.0/23219.71.72.1 to 219.71.73.254219.71.73.255510
38219.71.74.0/23219.71.74.1 to 219.71.75.254219.71.75.255510
39219.71.76.0/23219.71.76.1 to 219.71.77.254219.71.77.255510
40219.71.78.0/23219.71.78.1 to 219.71.79.254219.71.79.255510
41219.71.80.0/23219.71.80.1 to 219.71.81.254219.71.81.255510
42219.71.82.0/23219.71.82.1 to 219.71.83.254219.71.83.255510
43219.71.84.0/23219.71.84.1 to 219.71.85.254219.71.85.255510
44219.71.86.0/23219.71.86.1 to 219.71.87.254219.71.87.255510
45219.71.88.0/23219.71.88.1 to 219.71.89.254219.71.89.255510
46219.71.90.0/23219.71.90.1 to 219.71.91.254219.71.91.255510
47219.71.92.0/23219.71.92.1 to 219.71.93.254219.71.93.255510
48219.71.94.0/23219.71.94.1 to 219.71.95.254219.71.95.255510
49219.71.96.0/23219.71.96.1 to 219.71.97.254219.71.97.255510
50219.71.98.0/23219.71.98.1 to 219.71.99.254219.71.99.255510
51219.71.100.0/23219.71.100.1 to 219.71.101.254219.71.101.255510
52219.71.102.0/23219.71.102.1 to 219.71.103.254219.71.103.255510
53219.71.104.0/23219.71.104.1 to 219.71.105.254219.71.105.255510
54219.71.106.0/23219.71.106.1 to 219.71.107.254219.71.107.255510
55219.71.108.0/23219.71.108.1 to 219.71.109.254219.71.109.255510
56219.71.110.0/23219.71.110.1 to 219.71.111.254219.71.111.255510
57219.71.112.0/23219.71.112.1 to 219.71.113.254219.71.113.255510
58219.71.114.0/23219.71.114.1 to 219.71.115.254219.71.115.255510
59219.71.116.0/23219.71.116.1 to 219.71.117.254219.71.117.255510
60219.71.118.0/23219.71.118.1 to 219.71.119.254219.71.119.255510
61219.71.120.0/23219.71.120.1 to 219.71.121.254219.71.121.255510
62219.71.122.0/23219.71.122.1 to 219.71.123.254219.71.123.255510
63219.71.124.0/23219.71.124.1 to 219.71.125.254219.71.125.255510
64219.71.126.0/23219.71.126.1 to 219.71.127.254219.71.127.255510
65219.71.128.0/23219.71.128.1 to 219.71.129.254219.71.129.255510
66219.71.130.0/23219.71.130.1 to 219.71.131.254219.71.131.255510
67219.71.132.0/23219.71.132.1 to 219.71.133.254219.71.133.255510
68219.71.134.0/23219.71.134.1 to 219.71.135.254219.71.135.255510
69219.71.136.0/23219.71.136.1 to 219.71.137.254219.71.137.255510
70219.71.138.0/23219.71.138.1 to 219.71.139.254219.71.139.255510
71219.71.140.0/23219.71.140.1 to 219.71.141.254219.71.141.255510
72219.71.142.0/23219.71.142.1 to 219.71.143.254219.71.143.255510
73219.71.144.0/23219.71.144.1 to 219.71.145.254219.71.145.255510
74219.71.146.0/23219.71.146.1 to 219.71.147.254219.71.147.255510
75219.71.148.0/23219.71.148.1 to 219.71.149.254219.71.149.255510
76219.71.150.0/23219.71.150.1 to 219.71.151.254219.71.151.255510
77219.71.152.0/23219.71.152.1 to 219.71.153.254219.71.153.255510
78219.71.154.0/23219.71.154.1 to 219.71.155.254219.71.155.255510
79219.71.156.0/23219.71.156.1 to 219.71.157.254219.71.157.255510
80219.71.158.0/23219.71.158.1 to 219.71.159.254219.71.159.255510
81219.71.160.0/23219.71.160.1 to 219.71.161.254219.71.161.255510
82219.71.162.0/23219.71.162.1 to 219.71.163.254219.71.163.255510
83219.71.164.0/23219.71.164.1 to 219.71.165.254219.71.165.255510
84219.71.166.0/23219.71.166.1 to 219.71.167.254219.71.167.255510
85219.71.168.0/23219.71.168.1 to 219.71.169.254219.71.169.255510
86219.71.170.0/23219.71.170.1 to 219.71.171.254219.71.171.255510
87219.71.172.0/23219.71.172.1 to 219.71.173.254219.71.173.255510
88219.71.174.0/23219.71.174.1 to 219.71.175.254219.71.175.255510
89219.71.176.0/23219.71.176.1 to 219.71.177.254219.71.177.255510
90219.71.178.0/23219.71.178.1 to 219.71.179.254219.71.179.255510
91219.71.180.0/23219.71.180.1 to 219.71.181.254219.71.181.255510
92219.71.182.0/23219.71.182.1 to 219.71.183.254219.71.183.255510
93219.71.184.0/23219.71.184.1 to 219.71.185.254219.71.185.255510
94219.71.186.0/23219.71.186.1 to 219.71.187.254219.71.187.255510
95219.71.188.0/23219.71.188.1 to 219.71.189.254219.71.189.255510
96219.71.190.0/23219.71.190.1 to 219.71.191.254219.71.191.255510
97219.71.192.0/23219.71.192.1 to 219.71.193.254219.71.193.255510
98219.71.194.0/23219.71.194.1 to 219.71.195.254219.71.195.255510
99219.71.196.0/23219.71.196.1 to 219.71.197.254219.71.197.255510
100219.71.198.0/23219.71.198.1 to 219.71.199.254219.71.199.255510
101219.71.200.0/23219.71.200.1 to 219.71.201.254219.71.201.255510
102219.71.202.0/23219.71.202.1 to 219.71.203.254219.71.203.255510
103219.71.204.0/23219.71.204.1 to 219.71.205.254219.71.205.255510
104219.71.206.0/23219.71.206.1 to 219.71.207.254219.71.207.255510
105219.71.208.0/23219.71.208.1 to 219.71.209.254219.71.209.255510
106219.71.210.0/23219.71.210.1 to 219.71.211.254219.71.211.255510
107219.71.212.0/23219.71.212.1 to 219.71.213.254219.71.213.255510
108219.71.214.0/23219.71.214.1 to 219.71.215.254219.71.215.255510
109219.71.216.0/23219.71.216.1 to 219.71.217.254219.71.217.255510
110219.71.218.0/23219.71.218.1 to 219.71.219.254219.71.219.255510
111219.71.220.0/23219.71.220.1 to 219.71.221.254219.71.221.255510
112219.71.222.0/23219.71.222.1 to 219.71.223.254219.71.223.255510
113219.71.224.0/23219.71.224.1 to 219.71.225.254219.71.225.255510
114219.71.226.0/23219.71.226.1 to 219.71.227.254219.71.227.255510
115219.71.228.0/23219.71.228.1 to 219.71.229.254219.71.229.255510
116219.71.230.0/23219.71.230.1 to 219.71.231.254219.71.231.255510
117219.71.232.0/23219.71.232.1 to 219.71.233.254219.71.233.255510
118219.71.234.0/23219.71.234.1 to 219.71.235.254219.71.235.255510
119219.71.236.0/23219.71.236.1 to 219.71.237.254219.71.237.255510
120219.71.238.0/23219.71.238.1 to 219.71.239.254219.71.239.255510
121219.71.240.0/23219.71.240.1 to 219.71.241.254219.71.241.255510
122219.71.242.0/23219.71.242.1 to 219.71.243.254219.71.243.255510
123219.71.244.0/23219.71.244.1 to 219.71.245.254219.71.245.255510
124219.71.246.0/23219.71.246.1 to 219.71.247.254219.71.247.255510
125219.71.248.0/23219.71.248.1 to 219.71.249.254219.71.249.255510
126219.71.250.0/23219.71.250.1 to 219.71.251.254219.71.251.255510
127219.71.252.0/23219.71.252.1 to 219.71.253.254219.71.253.255510
128219.71.254.0/23219.71.254.1 to 219.71.255.254219.71.255.255510

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.