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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.

Network161.2.128.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
161.2.128.0
Broadcast address
161.2.159.255
First usable
161.2.128.1
Last usable
161.2.159.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Public public
Old class
B (default /16)
As numbers
Hex A1028000 · Integer 2701295616 to 2701303807
Reverse DNS zones
128.2.161.in-addr.arpa
129.2.161.in-addr.arpa
130.2.161.in-addr.arpa
131.2.161.in-addr.arpa
132.2.161.in-addr.arpa
133.2.161.in-addr.arpa
134.2.161.in-addr.arpa
135.2.161.in-addr.arpa
136.2.161.in-addr.arpa
137.2.161.in-addr.arpa
138.2.161.in-addr.arpa
139.2.161.in-addr.arpa
140.2.161.in-addr.arpa
141.2.161.in-addr.arpa
142.2.161.in-addr.arpa
143.2.161.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100001.00000010.10000000.00000000161.2.128.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network10100001.00000010.10000000.00000000161.2.128.0
Broadcast10100001.00000010.10011111.11111111161.2.159.255
Split into smaller subnets/26
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

161.2.128.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1161.2.128.0/26161.2.128.1 to 161.2.128.62161.2.128.6362
2161.2.128.64/26161.2.128.65 to 161.2.128.126161.2.128.12762
3161.2.128.128/26161.2.128.129 to 161.2.128.190161.2.128.19162
4161.2.128.192/26161.2.128.193 to 161.2.128.254161.2.128.25562
5161.2.129.0/26161.2.129.1 to 161.2.129.62161.2.129.6362
6161.2.129.64/26161.2.129.65 to 161.2.129.126161.2.129.12762
7161.2.129.128/26161.2.129.129 to 161.2.129.190161.2.129.19162
8161.2.129.192/26161.2.129.193 to 161.2.129.254161.2.129.25562
9161.2.130.0/26161.2.130.1 to 161.2.130.62161.2.130.6362
10161.2.130.64/26161.2.130.65 to 161.2.130.126161.2.130.12762
11161.2.130.128/26161.2.130.129 to 161.2.130.190161.2.130.19162
12161.2.130.192/26161.2.130.193 to 161.2.130.254161.2.130.25562
13161.2.131.0/26161.2.131.1 to 161.2.131.62161.2.131.6362
14161.2.131.64/26161.2.131.65 to 161.2.131.126161.2.131.12762
15161.2.131.128/26161.2.131.129 to 161.2.131.190161.2.131.19162
16161.2.131.192/26161.2.131.193 to 161.2.131.254161.2.131.25562
17161.2.132.0/26161.2.132.1 to 161.2.132.62161.2.132.6362
18161.2.132.64/26161.2.132.65 to 161.2.132.126161.2.132.12762
19161.2.132.128/26161.2.132.129 to 161.2.132.190161.2.132.19162
20161.2.132.192/26161.2.132.193 to 161.2.132.254161.2.132.25562
21161.2.133.0/26161.2.133.1 to 161.2.133.62161.2.133.6362
22161.2.133.64/26161.2.133.65 to 161.2.133.126161.2.133.12762
23161.2.133.128/26161.2.133.129 to 161.2.133.190161.2.133.19162
24161.2.133.192/26161.2.133.193 to 161.2.133.254161.2.133.25562
25161.2.134.0/26161.2.134.1 to 161.2.134.62161.2.134.6362
26161.2.134.64/26161.2.134.65 to 161.2.134.126161.2.134.12762
27161.2.134.128/26161.2.134.129 to 161.2.134.190161.2.134.19162
28161.2.134.192/26161.2.134.193 to 161.2.134.254161.2.134.25562
29161.2.135.0/26161.2.135.1 to 161.2.135.62161.2.135.6362
30161.2.135.64/26161.2.135.65 to 161.2.135.126161.2.135.12762
31161.2.135.128/26161.2.135.129 to 161.2.135.190161.2.135.19162
32161.2.135.192/26161.2.135.193 to 161.2.135.254161.2.135.25562
33161.2.136.0/26161.2.136.1 to 161.2.136.62161.2.136.6362
34161.2.136.64/26161.2.136.65 to 161.2.136.126161.2.136.12762
35161.2.136.128/26161.2.136.129 to 161.2.136.190161.2.136.19162
36161.2.136.192/26161.2.136.193 to 161.2.136.254161.2.136.25562
37161.2.137.0/26161.2.137.1 to 161.2.137.62161.2.137.6362
38161.2.137.64/26161.2.137.65 to 161.2.137.126161.2.137.12762
39161.2.137.128/26161.2.137.129 to 161.2.137.190161.2.137.19162
40161.2.137.192/26161.2.137.193 to 161.2.137.254161.2.137.25562
41161.2.138.0/26161.2.138.1 to 161.2.138.62161.2.138.6362
42161.2.138.64/26161.2.138.65 to 161.2.138.126161.2.138.12762
43161.2.138.128/26161.2.138.129 to 161.2.138.190161.2.138.19162
44161.2.138.192/26161.2.138.193 to 161.2.138.254161.2.138.25562
45161.2.139.0/26161.2.139.1 to 161.2.139.62161.2.139.6362
46161.2.139.64/26161.2.139.65 to 161.2.139.126161.2.139.12762
47161.2.139.128/26161.2.139.129 to 161.2.139.190161.2.139.19162
48161.2.139.192/26161.2.139.193 to 161.2.139.254161.2.139.25562
49161.2.140.0/26161.2.140.1 to 161.2.140.62161.2.140.6362
50161.2.140.64/26161.2.140.65 to 161.2.140.126161.2.140.12762
51161.2.140.128/26161.2.140.129 to 161.2.140.190161.2.140.19162
52161.2.140.192/26161.2.140.193 to 161.2.140.254161.2.140.25562
53161.2.141.0/26161.2.141.1 to 161.2.141.62161.2.141.6362
54161.2.141.64/26161.2.141.65 to 161.2.141.126161.2.141.12762
55161.2.141.128/26161.2.141.129 to 161.2.141.190161.2.141.19162
56161.2.141.192/26161.2.141.193 to 161.2.141.254161.2.141.25562
57161.2.142.0/26161.2.142.1 to 161.2.142.62161.2.142.6362
58161.2.142.64/26161.2.142.65 to 161.2.142.126161.2.142.12762
59161.2.142.128/26161.2.142.129 to 161.2.142.190161.2.142.19162
60161.2.142.192/26161.2.142.193 to 161.2.142.254161.2.142.25562
61161.2.143.0/26161.2.143.1 to 161.2.143.62161.2.143.6362
62161.2.143.64/26161.2.143.65 to 161.2.143.126161.2.143.12762
63161.2.143.128/26161.2.143.129 to 161.2.143.190161.2.143.19162
64161.2.143.192/26161.2.143.193 to 161.2.143.254161.2.143.25562
65161.2.144.0/26161.2.144.1 to 161.2.144.62161.2.144.6362
66161.2.144.64/26161.2.144.65 to 161.2.144.126161.2.144.12762
67161.2.144.128/26161.2.144.129 to 161.2.144.190161.2.144.19162
68161.2.144.192/26161.2.144.193 to 161.2.144.254161.2.144.25562
69161.2.145.0/26161.2.145.1 to 161.2.145.62161.2.145.6362
70161.2.145.64/26161.2.145.65 to 161.2.145.126161.2.145.12762
71161.2.145.128/26161.2.145.129 to 161.2.145.190161.2.145.19162
72161.2.145.192/26161.2.145.193 to 161.2.145.254161.2.145.25562
73161.2.146.0/26161.2.146.1 to 161.2.146.62161.2.146.6362
74161.2.146.64/26161.2.146.65 to 161.2.146.126161.2.146.12762
75161.2.146.128/26161.2.146.129 to 161.2.146.190161.2.146.19162
76161.2.146.192/26161.2.146.193 to 161.2.146.254161.2.146.25562
77161.2.147.0/26161.2.147.1 to 161.2.147.62161.2.147.6362
78161.2.147.64/26161.2.147.65 to 161.2.147.126161.2.147.12762
79161.2.147.128/26161.2.147.129 to 161.2.147.190161.2.147.19162
80161.2.147.192/26161.2.147.193 to 161.2.147.254161.2.147.25562
81161.2.148.0/26161.2.148.1 to 161.2.148.62161.2.148.6362
82161.2.148.64/26161.2.148.65 to 161.2.148.126161.2.148.12762
83161.2.148.128/26161.2.148.129 to 161.2.148.190161.2.148.19162
84161.2.148.192/26161.2.148.193 to 161.2.148.254161.2.148.25562
85161.2.149.0/26161.2.149.1 to 161.2.149.62161.2.149.6362
86161.2.149.64/26161.2.149.65 to 161.2.149.126161.2.149.12762
87161.2.149.128/26161.2.149.129 to 161.2.149.190161.2.149.19162
88161.2.149.192/26161.2.149.193 to 161.2.149.254161.2.149.25562
89161.2.150.0/26161.2.150.1 to 161.2.150.62161.2.150.6362
90161.2.150.64/26161.2.150.65 to 161.2.150.126161.2.150.12762
91161.2.150.128/26161.2.150.129 to 161.2.150.190161.2.150.19162
92161.2.150.192/26161.2.150.193 to 161.2.150.254161.2.150.25562
93161.2.151.0/26161.2.151.1 to 161.2.151.62161.2.151.6362
94161.2.151.64/26161.2.151.65 to 161.2.151.126161.2.151.12762
95161.2.151.128/26161.2.151.129 to 161.2.151.190161.2.151.19162
96161.2.151.192/26161.2.151.193 to 161.2.151.254161.2.151.25562
97161.2.152.0/26161.2.152.1 to 161.2.152.62161.2.152.6362
98161.2.152.64/26161.2.152.65 to 161.2.152.126161.2.152.12762
99161.2.152.128/26161.2.152.129 to 161.2.152.190161.2.152.19162
100161.2.152.192/26161.2.152.193 to 161.2.152.254161.2.152.25562
101161.2.153.0/26161.2.153.1 to 161.2.153.62161.2.153.6362
102161.2.153.64/26161.2.153.65 to 161.2.153.126161.2.153.12762
103161.2.153.128/26161.2.153.129 to 161.2.153.190161.2.153.19162
104161.2.153.192/26161.2.153.193 to 161.2.153.254161.2.153.25562
105161.2.154.0/26161.2.154.1 to 161.2.154.62161.2.154.6362
106161.2.154.64/26161.2.154.65 to 161.2.154.126161.2.154.12762
107161.2.154.128/26161.2.154.129 to 161.2.154.190161.2.154.19162
108161.2.154.192/26161.2.154.193 to 161.2.154.254161.2.154.25562
109161.2.155.0/26161.2.155.1 to 161.2.155.62161.2.155.6362
110161.2.155.64/26161.2.155.65 to 161.2.155.126161.2.155.12762
111161.2.155.128/26161.2.155.129 to 161.2.155.190161.2.155.19162
112161.2.155.192/26161.2.155.193 to 161.2.155.254161.2.155.25562
113161.2.156.0/26161.2.156.1 to 161.2.156.62161.2.156.6362
114161.2.156.64/26161.2.156.65 to 161.2.156.126161.2.156.12762
115161.2.156.128/26161.2.156.129 to 161.2.156.190161.2.156.19162
116161.2.156.192/26161.2.156.193 to 161.2.156.254161.2.156.25562
117161.2.157.0/26161.2.157.1 to 161.2.157.62161.2.157.6362
118161.2.157.64/26161.2.157.65 to 161.2.157.126161.2.157.12762
119161.2.157.128/26161.2.157.129 to 161.2.157.190161.2.157.19162
120161.2.157.192/26161.2.157.193 to 161.2.157.254161.2.157.25562
121161.2.158.0/26161.2.158.1 to 161.2.158.62161.2.158.6362
122161.2.158.64/26161.2.158.65 to 161.2.158.126161.2.158.12762
123161.2.158.128/26161.2.158.129 to 161.2.158.190161.2.158.19162
124161.2.158.192/26161.2.158.193 to 161.2.158.254161.2.158.25562
125161.2.159.0/26161.2.159.1 to 161.2.159.62161.2.159.6362
126161.2.159.64/26161.2.159.65 to 161.2.159.126161.2.159.12762
127161.2.159.128/26161.2.159.129 to 161.2.159.190161.2.159.19162
128161.2.159.192/26161.2.159.193 to 161.2.159.254161.2.159.25562

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.