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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.

Network129.2.32.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
129.2.32.0
Broadcast address
129.2.63.255
First usable
129.2.32.1
Last usable
129.2.63.254
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 81022000 · Integer 2164400128 to 2164408319
Reverse DNS zones
32.2.129.in-addr.arpa
33.2.129.in-addr.arpa
34.2.129.in-addr.arpa
35.2.129.in-addr.arpa
36.2.129.in-addr.arpa
37.2.129.in-addr.arpa
38.2.129.in-addr.arpa
39.2.129.in-addr.arpa
40.2.129.in-addr.arpa
41.2.129.in-addr.arpa
42.2.129.in-addr.arpa
43.2.129.in-addr.arpa
44.2.129.in-addr.arpa
45.2.129.in-addr.arpa
46.2.129.in-addr.arpa
47.2.129.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
Address10000001.00000010.00100000.00000000129.2.32.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network10000001.00000010.00100000.00000000129.2.32.0
Broadcast10000001.00000010.00111111.11111111129.2.63.255
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)

129.2.32.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1129.2.32.0/26129.2.32.1 to 129.2.32.62129.2.32.6362
2129.2.32.64/26129.2.32.65 to 129.2.32.126129.2.32.12762
3129.2.32.128/26129.2.32.129 to 129.2.32.190129.2.32.19162
4129.2.32.192/26129.2.32.193 to 129.2.32.254129.2.32.25562
5129.2.33.0/26129.2.33.1 to 129.2.33.62129.2.33.6362
6129.2.33.64/26129.2.33.65 to 129.2.33.126129.2.33.12762
7129.2.33.128/26129.2.33.129 to 129.2.33.190129.2.33.19162
8129.2.33.192/26129.2.33.193 to 129.2.33.254129.2.33.25562
9129.2.34.0/26129.2.34.1 to 129.2.34.62129.2.34.6362
10129.2.34.64/26129.2.34.65 to 129.2.34.126129.2.34.12762
11129.2.34.128/26129.2.34.129 to 129.2.34.190129.2.34.19162
12129.2.34.192/26129.2.34.193 to 129.2.34.254129.2.34.25562
13129.2.35.0/26129.2.35.1 to 129.2.35.62129.2.35.6362
14129.2.35.64/26129.2.35.65 to 129.2.35.126129.2.35.12762
15129.2.35.128/26129.2.35.129 to 129.2.35.190129.2.35.19162
16129.2.35.192/26129.2.35.193 to 129.2.35.254129.2.35.25562
17129.2.36.0/26129.2.36.1 to 129.2.36.62129.2.36.6362
18129.2.36.64/26129.2.36.65 to 129.2.36.126129.2.36.12762
19129.2.36.128/26129.2.36.129 to 129.2.36.190129.2.36.19162
20129.2.36.192/26129.2.36.193 to 129.2.36.254129.2.36.25562
21129.2.37.0/26129.2.37.1 to 129.2.37.62129.2.37.6362
22129.2.37.64/26129.2.37.65 to 129.2.37.126129.2.37.12762
23129.2.37.128/26129.2.37.129 to 129.2.37.190129.2.37.19162
24129.2.37.192/26129.2.37.193 to 129.2.37.254129.2.37.25562
25129.2.38.0/26129.2.38.1 to 129.2.38.62129.2.38.6362
26129.2.38.64/26129.2.38.65 to 129.2.38.126129.2.38.12762
27129.2.38.128/26129.2.38.129 to 129.2.38.190129.2.38.19162
28129.2.38.192/26129.2.38.193 to 129.2.38.254129.2.38.25562
29129.2.39.0/26129.2.39.1 to 129.2.39.62129.2.39.6362
30129.2.39.64/26129.2.39.65 to 129.2.39.126129.2.39.12762
31129.2.39.128/26129.2.39.129 to 129.2.39.190129.2.39.19162
32129.2.39.192/26129.2.39.193 to 129.2.39.254129.2.39.25562
33129.2.40.0/26129.2.40.1 to 129.2.40.62129.2.40.6362
34129.2.40.64/26129.2.40.65 to 129.2.40.126129.2.40.12762
35129.2.40.128/26129.2.40.129 to 129.2.40.190129.2.40.19162
36129.2.40.192/26129.2.40.193 to 129.2.40.254129.2.40.25562
37129.2.41.0/26129.2.41.1 to 129.2.41.62129.2.41.6362
38129.2.41.64/26129.2.41.65 to 129.2.41.126129.2.41.12762
39129.2.41.128/26129.2.41.129 to 129.2.41.190129.2.41.19162
40129.2.41.192/26129.2.41.193 to 129.2.41.254129.2.41.25562
41129.2.42.0/26129.2.42.1 to 129.2.42.62129.2.42.6362
42129.2.42.64/26129.2.42.65 to 129.2.42.126129.2.42.12762
43129.2.42.128/26129.2.42.129 to 129.2.42.190129.2.42.19162
44129.2.42.192/26129.2.42.193 to 129.2.42.254129.2.42.25562
45129.2.43.0/26129.2.43.1 to 129.2.43.62129.2.43.6362
46129.2.43.64/26129.2.43.65 to 129.2.43.126129.2.43.12762
47129.2.43.128/26129.2.43.129 to 129.2.43.190129.2.43.19162
48129.2.43.192/26129.2.43.193 to 129.2.43.254129.2.43.25562
49129.2.44.0/26129.2.44.1 to 129.2.44.62129.2.44.6362
50129.2.44.64/26129.2.44.65 to 129.2.44.126129.2.44.12762
51129.2.44.128/26129.2.44.129 to 129.2.44.190129.2.44.19162
52129.2.44.192/26129.2.44.193 to 129.2.44.254129.2.44.25562
53129.2.45.0/26129.2.45.1 to 129.2.45.62129.2.45.6362
54129.2.45.64/26129.2.45.65 to 129.2.45.126129.2.45.12762
55129.2.45.128/26129.2.45.129 to 129.2.45.190129.2.45.19162
56129.2.45.192/26129.2.45.193 to 129.2.45.254129.2.45.25562
57129.2.46.0/26129.2.46.1 to 129.2.46.62129.2.46.6362
58129.2.46.64/26129.2.46.65 to 129.2.46.126129.2.46.12762
59129.2.46.128/26129.2.46.129 to 129.2.46.190129.2.46.19162
60129.2.46.192/26129.2.46.193 to 129.2.46.254129.2.46.25562
61129.2.47.0/26129.2.47.1 to 129.2.47.62129.2.47.6362
62129.2.47.64/26129.2.47.65 to 129.2.47.126129.2.47.12762
63129.2.47.128/26129.2.47.129 to 129.2.47.190129.2.47.19162
64129.2.47.192/26129.2.47.193 to 129.2.47.254129.2.47.25562
65129.2.48.0/26129.2.48.1 to 129.2.48.62129.2.48.6362
66129.2.48.64/26129.2.48.65 to 129.2.48.126129.2.48.12762
67129.2.48.128/26129.2.48.129 to 129.2.48.190129.2.48.19162
68129.2.48.192/26129.2.48.193 to 129.2.48.254129.2.48.25562
69129.2.49.0/26129.2.49.1 to 129.2.49.62129.2.49.6362
70129.2.49.64/26129.2.49.65 to 129.2.49.126129.2.49.12762
71129.2.49.128/26129.2.49.129 to 129.2.49.190129.2.49.19162
72129.2.49.192/26129.2.49.193 to 129.2.49.254129.2.49.25562
73129.2.50.0/26129.2.50.1 to 129.2.50.62129.2.50.6362
74129.2.50.64/26129.2.50.65 to 129.2.50.126129.2.50.12762
75129.2.50.128/26129.2.50.129 to 129.2.50.190129.2.50.19162
76129.2.50.192/26129.2.50.193 to 129.2.50.254129.2.50.25562
77129.2.51.0/26129.2.51.1 to 129.2.51.62129.2.51.6362
78129.2.51.64/26129.2.51.65 to 129.2.51.126129.2.51.12762
79129.2.51.128/26129.2.51.129 to 129.2.51.190129.2.51.19162
80129.2.51.192/26129.2.51.193 to 129.2.51.254129.2.51.25562
81129.2.52.0/26129.2.52.1 to 129.2.52.62129.2.52.6362
82129.2.52.64/26129.2.52.65 to 129.2.52.126129.2.52.12762
83129.2.52.128/26129.2.52.129 to 129.2.52.190129.2.52.19162
84129.2.52.192/26129.2.52.193 to 129.2.52.254129.2.52.25562
85129.2.53.0/26129.2.53.1 to 129.2.53.62129.2.53.6362
86129.2.53.64/26129.2.53.65 to 129.2.53.126129.2.53.12762
87129.2.53.128/26129.2.53.129 to 129.2.53.190129.2.53.19162
88129.2.53.192/26129.2.53.193 to 129.2.53.254129.2.53.25562
89129.2.54.0/26129.2.54.1 to 129.2.54.62129.2.54.6362
90129.2.54.64/26129.2.54.65 to 129.2.54.126129.2.54.12762
91129.2.54.128/26129.2.54.129 to 129.2.54.190129.2.54.19162
92129.2.54.192/26129.2.54.193 to 129.2.54.254129.2.54.25562
93129.2.55.0/26129.2.55.1 to 129.2.55.62129.2.55.6362
94129.2.55.64/26129.2.55.65 to 129.2.55.126129.2.55.12762
95129.2.55.128/26129.2.55.129 to 129.2.55.190129.2.55.19162
96129.2.55.192/26129.2.55.193 to 129.2.55.254129.2.55.25562
97129.2.56.0/26129.2.56.1 to 129.2.56.62129.2.56.6362
98129.2.56.64/26129.2.56.65 to 129.2.56.126129.2.56.12762
99129.2.56.128/26129.2.56.129 to 129.2.56.190129.2.56.19162
100129.2.56.192/26129.2.56.193 to 129.2.56.254129.2.56.25562
101129.2.57.0/26129.2.57.1 to 129.2.57.62129.2.57.6362
102129.2.57.64/26129.2.57.65 to 129.2.57.126129.2.57.12762
103129.2.57.128/26129.2.57.129 to 129.2.57.190129.2.57.19162
104129.2.57.192/26129.2.57.193 to 129.2.57.254129.2.57.25562
105129.2.58.0/26129.2.58.1 to 129.2.58.62129.2.58.6362
106129.2.58.64/26129.2.58.65 to 129.2.58.126129.2.58.12762
107129.2.58.128/26129.2.58.129 to 129.2.58.190129.2.58.19162
108129.2.58.192/26129.2.58.193 to 129.2.58.254129.2.58.25562
109129.2.59.0/26129.2.59.1 to 129.2.59.62129.2.59.6362
110129.2.59.64/26129.2.59.65 to 129.2.59.126129.2.59.12762
111129.2.59.128/26129.2.59.129 to 129.2.59.190129.2.59.19162
112129.2.59.192/26129.2.59.193 to 129.2.59.254129.2.59.25562
113129.2.60.0/26129.2.60.1 to 129.2.60.62129.2.60.6362
114129.2.60.64/26129.2.60.65 to 129.2.60.126129.2.60.12762
115129.2.60.128/26129.2.60.129 to 129.2.60.190129.2.60.19162
116129.2.60.192/26129.2.60.193 to 129.2.60.254129.2.60.25562
117129.2.61.0/26129.2.61.1 to 129.2.61.62129.2.61.6362
118129.2.61.64/26129.2.61.65 to 129.2.61.126129.2.61.12762
119129.2.61.128/26129.2.61.129 to 129.2.61.190129.2.61.19162
120129.2.61.192/26129.2.61.193 to 129.2.61.254129.2.61.25562
121129.2.62.0/26129.2.62.1 to 129.2.62.62129.2.62.6362
122129.2.62.64/26129.2.62.65 to 129.2.62.126129.2.62.12762
123129.2.62.128/26129.2.62.129 to 129.2.62.190129.2.62.19162
124129.2.62.192/26129.2.62.193 to 129.2.62.254129.2.62.25562
125129.2.63.0/26129.2.63.1 to 129.2.63.62129.2.63.6362
126129.2.63.64/26129.2.63.65 to 129.2.63.126129.2.63.12762
127129.2.63.128/26129.2.63.129 to 129.2.63.190129.2.63.19162
128129.2.63.192/26129.2.63.193 to 129.2.63.254129.2.63.25562

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.