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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.

Network129.112.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
129.112.0.0
Broadcast address
129.127.255.255
First usable
129.112.0.1
Last usable
129.127.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
B (default /16)
As numbers
Hex 81700000 · Integer 2171600896 to 2172649471
Reverse DNS zones
112.129.in-addr.arpa
113.129.in-addr.arpa
114.129.in-addr.arpa
115.129.in-addr.arpa
116.129.in-addr.arpa
117.129.in-addr.arpa
118.129.in-addr.arpa
119.129.in-addr.arpa
120.129.in-addr.arpa
121.129.in-addr.arpa
122.129.in-addr.arpa
123.129.in-addr.arpa
124.129.in-addr.arpa
125.129.in-addr.arpa
126.129.in-addr.arpa
127.129.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000001.01110000.00000000.00000000129.112.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network10000001.01110000.00000000.00000000129.112.0.0
Broadcast10000001.01111111.11111111.11111111129.127.255.255
Split into smaller subnets/19
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

129.112.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1129.112.0.0/19129.112.0.1 to 129.112.31.254129.112.31.2558,190
2129.112.32.0/19129.112.32.1 to 129.112.63.254129.112.63.2558,190
3129.112.64.0/19129.112.64.1 to 129.112.95.254129.112.95.2558,190
4129.112.96.0/19129.112.96.1 to 129.112.127.254129.112.127.2558,190
5129.112.128.0/19129.112.128.1 to 129.112.159.254129.112.159.2558,190
6129.112.160.0/19129.112.160.1 to 129.112.191.254129.112.191.2558,190
7129.112.192.0/19129.112.192.1 to 129.112.223.254129.112.223.2558,190
8129.112.224.0/19129.112.224.1 to 129.112.255.254129.112.255.2558,190
9129.113.0.0/19129.113.0.1 to 129.113.31.254129.113.31.2558,190
10129.113.32.0/19129.113.32.1 to 129.113.63.254129.113.63.2558,190
11129.113.64.0/19129.113.64.1 to 129.113.95.254129.113.95.2558,190
12129.113.96.0/19129.113.96.1 to 129.113.127.254129.113.127.2558,190
13129.113.128.0/19129.113.128.1 to 129.113.159.254129.113.159.2558,190
14129.113.160.0/19129.113.160.1 to 129.113.191.254129.113.191.2558,190
15129.113.192.0/19129.113.192.1 to 129.113.223.254129.113.223.2558,190
16129.113.224.0/19129.113.224.1 to 129.113.255.254129.113.255.2558,190
17129.114.0.0/19129.114.0.1 to 129.114.31.254129.114.31.2558,190
18129.114.32.0/19129.114.32.1 to 129.114.63.254129.114.63.2558,190
19129.114.64.0/19129.114.64.1 to 129.114.95.254129.114.95.2558,190
20129.114.96.0/19129.114.96.1 to 129.114.127.254129.114.127.2558,190
21129.114.128.0/19129.114.128.1 to 129.114.159.254129.114.159.2558,190
22129.114.160.0/19129.114.160.1 to 129.114.191.254129.114.191.2558,190
23129.114.192.0/19129.114.192.1 to 129.114.223.254129.114.223.2558,190
24129.114.224.0/19129.114.224.1 to 129.114.255.254129.114.255.2558,190
25129.115.0.0/19129.115.0.1 to 129.115.31.254129.115.31.2558,190
26129.115.32.0/19129.115.32.1 to 129.115.63.254129.115.63.2558,190
27129.115.64.0/19129.115.64.1 to 129.115.95.254129.115.95.2558,190
28129.115.96.0/19129.115.96.1 to 129.115.127.254129.115.127.2558,190
29129.115.128.0/19129.115.128.1 to 129.115.159.254129.115.159.2558,190
30129.115.160.0/19129.115.160.1 to 129.115.191.254129.115.191.2558,190
31129.115.192.0/19129.115.192.1 to 129.115.223.254129.115.223.2558,190
32129.115.224.0/19129.115.224.1 to 129.115.255.254129.115.255.2558,190
33129.116.0.0/19129.116.0.1 to 129.116.31.254129.116.31.2558,190
34129.116.32.0/19129.116.32.1 to 129.116.63.254129.116.63.2558,190
35129.116.64.0/19129.116.64.1 to 129.116.95.254129.116.95.2558,190
36129.116.96.0/19129.116.96.1 to 129.116.127.254129.116.127.2558,190
37129.116.128.0/19129.116.128.1 to 129.116.159.254129.116.159.2558,190
38129.116.160.0/19129.116.160.1 to 129.116.191.254129.116.191.2558,190
39129.116.192.0/19129.116.192.1 to 129.116.223.254129.116.223.2558,190
40129.116.224.0/19129.116.224.1 to 129.116.255.254129.116.255.2558,190
41129.117.0.0/19129.117.0.1 to 129.117.31.254129.117.31.2558,190
42129.117.32.0/19129.117.32.1 to 129.117.63.254129.117.63.2558,190
43129.117.64.0/19129.117.64.1 to 129.117.95.254129.117.95.2558,190
44129.117.96.0/19129.117.96.1 to 129.117.127.254129.117.127.2558,190
45129.117.128.0/19129.117.128.1 to 129.117.159.254129.117.159.2558,190
46129.117.160.0/19129.117.160.1 to 129.117.191.254129.117.191.2558,190
47129.117.192.0/19129.117.192.1 to 129.117.223.254129.117.223.2558,190
48129.117.224.0/19129.117.224.1 to 129.117.255.254129.117.255.2558,190
49129.118.0.0/19129.118.0.1 to 129.118.31.254129.118.31.2558,190
50129.118.32.0/19129.118.32.1 to 129.118.63.254129.118.63.2558,190
51129.118.64.0/19129.118.64.1 to 129.118.95.254129.118.95.2558,190
52129.118.96.0/19129.118.96.1 to 129.118.127.254129.118.127.2558,190
53129.118.128.0/19129.118.128.1 to 129.118.159.254129.118.159.2558,190
54129.118.160.0/19129.118.160.1 to 129.118.191.254129.118.191.2558,190
55129.118.192.0/19129.118.192.1 to 129.118.223.254129.118.223.2558,190
56129.118.224.0/19129.118.224.1 to 129.118.255.254129.118.255.2558,190
57129.119.0.0/19129.119.0.1 to 129.119.31.254129.119.31.2558,190
58129.119.32.0/19129.119.32.1 to 129.119.63.254129.119.63.2558,190
59129.119.64.0/19129.119.64.1 to 129.119.95.254129.119.95.2558,190
60129.119.96.0/19129.119.96.1 to 129.119.127.254129.119.127.2558,190
61129.119.128.0/19129.119.128.1 to 129.119.159.254129.119.159.2558,190
62129.119.160.0/19129.119.160.1 to 129.119.191.254129.119.191.2558,190
63129.119.192.0/19129.119.192.1 to 129.119.223.254129.119.223.2558,190
64129.119.224.0/19129.119.224.1 to 129.119.255.254129.119.255.2558,190
65129.120.0.0/19129.120.0.1 to 129.120.31.254129.120.31.2558,190
66129.120.32.0/19129.120.32.1 to 129.120.63.254129.120.63.2558,190
67129.120.64.0/19129.120.64.1 to 129.120.95.254129.120.95.2558,190
68129.120.96.0/19129.120.96.1 to 129.120.127.254129.120.127.2558,190
69129.120.128.0/19129.120.128.1 to 129.120.159.254129.120.159.2558,190
70129.120.160.0/19129.120.160.1 to 129.120.191.254129.120.191.2558,190
71129.120.192.0/19129.120.192.1 to 129.120.223.254129.120.223.2558,190
72129.120.224.0/19129.120.224.1 to 129.120.255.254129.120.255.2558,190
73129.121.0.0/19129.121.0.1 to 129.121.31.254129.121.31.2558,190
74129.121.32.0/19129.121.32.1 to 129.121.63.254129.121.63.2558,190
75129.121.64.0/19129.121.64.1 to 129.121.95.254129.121.95.2558,190
76129.121.96.0/19129.121.96.1 to 129.121.127.254129.121.127.2558,190
77129.121.128.0/19129.121.128.1 to 129.121.159.254129.121.159.2558,190
78129.121.160.0/19129.121.160.1 to 129.121.191.254129.121.191.2558,190
79129.121.192.0/19129.121.192.1 to 129.121.223.254129.121.223.2558,190
80129.121.224.0/19129.121.224.1 to 129.121.255.254129.121.255.2558,190
81129.122.0.0/19129.122.0.1 to 129.122.31.254129.122.31.2558,190
82129.122.32.0/19129.122.32.1 to 129.122.63.254129.122.63.2558,190
83129.122.64.0/19129.122.64.1 to 129.122.95.254129.122.95.2558,190
84129.122.96.0/19129.122.96.1 to 129.122.127.254129.122.127.2558,190
85129.122.128.0/19129.122.128.1 to 129.122.159.254129.122.159.2558,190
86129.122.160.0/19129.122.160.1 to 129.122.191.254129.122.191.2558,190
87129.122.192.0/19129.122.192.1 to 129.122.223.254129.122.223.2558,190
88129.122.224.0/19129.122.224.1 to 129.122.255.254129.122.255.2558,190
89129.123.0.0/19129.123.0.1 to 129.123.31.254129.123.31.2558,190
90129.123.32.0/19129.123.32.1 to 129.123.63.254129.123.63.2558,190
91129.123.64.0/19129.123.64.1 to 129.123.95.254129.123.95.2558,190
92129.123.96.0/19129.123.96.1 to 129.123.127.254129.123.127.2558,190
93129.123.128.0/19129.123.128.1 to 129.123.159.254129.123.159.2558,190
94129.123.160.0/19129.123.160.1 to 129.123.191.254129.123.191.2558,190
95129.123.192.0/19129.123.192.1 to 129.123.223.254129.123.223.2558,190
96129.123.224.0/19129.123.224.1 to 129.123.255.254129.123.255.2558,190
97129.124.0.0/19129.124.0.1 to 129.124.31.254129.124.31.2558,190
98129.124.32.0/19129.124.32.1 to 129.124.63.254129.124.63.2558,190
99129.124.64.0/19129.124.64.1 to 129.124.95.254129.124.95.2558,190
100129.124.96.0/19129.124.96.1 to 129.124.127.254129.124.127.2558,190
101129.124.128.0/19129.124.128.1 to 129.124.159.254129.124.159.2558,190
102129.124.160.0/19129.124.160.1 to 129.124.191.254129.124.191.2558,190
103129.124.192.0/19129.124.192.1 to 129.124.223.254129.124.223.2558,190
104129.124.224.0/19129.124.224.1 to 129.124.255.254129.124.255.2558,190
105129.125.0.0/19129.125.0.1 to 129.125.31.254129.125.31.2558,190
106129.125.32.0/19129.125.32.1 to 129.125.63.254129.125.63.2558,190
107129.125.64.0/19129.125.64.1 to 129.125.95.254129.125.95.2558,190
108129.125.96.0/19129.125.96.1 to 129.125.127.254129.125.127.2558,190
109129.125.128.0/19129.125.128.1 to 129.125.159.254129.125.159.2558,190
110129.125.160.0/19129.125.160.1 to 129.125.191.254129.125.191.2558,190
111129.125.192.0/19129.125.192.1 to 129.125.223.254129.125.223.2558,190
112129.125.224.0/19129.125.224.1 to 129.125.255.254129.125.255.2558,190
113129.126.0.0/19129.126.0.1 to 129.126.31.254129.126.31.2558,190
114129.126.32.0/19129.126.32.1 to 129.126.63.254129.126.63.2558,190
115129.126.64.0/19129.126.64.1 to 129.126.95.254129.126.95.2558,190
116129.126.96.0/19129.126.96.1 to 129.126.127.254129.126.127.2558,190
117129.126.128.0/19129.126.128.1 to 129.126.159.254129.126.159.2558,190
118129.126.160.0/19129.126.160.1 to 129.126.191.254129.126.191.2558,190
119129.126.192.0/19129.126.192.1 to 129.126.223.254129.126.223.2558,190
120129.126.224.0/19129.126.224.1 to 129.126.255.254129.126.255.2558,190
121129.127.0.0/19129.127.0.1 to 129.127.31.254129.127.31.2558,190
122129.127.32.0/19129.127.32.1 to 129.127.63.254129.127.63.2558,190
123129.127.64.0/19129.127.64.1 to 129.127.95.254129.127.95.2558,190
124129.127.96.0/19129.127.96.1 to 129.127.127.254129.127.127.2558,190
125129.127.128.0/19129.127.128.1 to 129.127.159.254129.127.159.2558,190
126129.127.160.0/19129.127.160.1 to 129.127.191.254129.127.191.2558,190
127129.127.192.0/19129.127.192.1 to 129.127.223.254129.127.223.2558,190
128129.127.224.0/19129.127.224.1 to 129.127.255.254129.127.255.2558,190

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.