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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.

Network128.0.0.0/2
Usable hosts1,073,741,822
Subnet mask192.0.0.0
Addresses1,073,741,824
Network address
128.0.0.0
Broadcast address
191.255.255.255
First usable
128.0.0.1
Last usable
191.255.255.254
Usable hosts
1,073,741,822 (1,073,741,824 less the network and broadcast addresses)
Subnet mask
192.0.0.0
Wildcard mask
63.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/2
Type
Public public
Old class
B (default /16)
As numbers
Hex 80000000 · Integer 2147483648 to 3221225471
Reverse DNS zones
128.in-addr.arpa
129.in-addr.arpa
130.in-addr.arpa
131.in-addr.arpa
132.in-addr.arpa
133.in-addr.arpa
134.in-addr.arpa
135.in-addr.arpa
136.in-addr.arpa
137.in-addr.arpa
138.in-addr.arpa
139.in-addr.arpa
140.in-addr.arpa
141.in-addr.arpa
142.in-addr.arpa
143.in-addr.arpa
and 48 more
/2 is not on a 8-bit boundary, so it takes 64 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000000.00000000.00000000.00000000128.0.0.0
Subnet mask11000000.00000000.00000000.00000000192.0.0.0
Network10000000.00000000.00000000.00000000128.0.0.0
Broadcast10111111.11111111.11111111.11111111191.255.255.255
Split into smaller subnets/9
/3 (2)/4 (4)/5 (8)/6 (16)/7 (32)/8 (64)/9 (128)/10 (256)/11 (512)/12 (1,024)/13 (2,048)/14 (4,096)

128.0.0.0/2 makes 128 subnets of /9.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1128.0.0.0/9128.0.0.1 to 128.127.255.254128.127.255.2558,388,606
2128.128.0.0/9128.128.0.1 to 128.255.255.254128.255.255.2558,388,606
3129.0.0.0/9129.0.0.1 to 129.127.255.254129.127.255.2558,388,606
4129.128.0.0/9129.128.0.1 to 129.255.255.254129.255.255.2558,388,606
5130.0.0.0/9130.0.0.1 to 130.127.255.254130.127.255.2558,388,606
6130.128.0.0/9130.128.0.1 to 130.255.255.254130.255.255.2558,388,606
7131.0.0.0/9131.0.0.1 to 131.127.255.254131.127.255.2558,388,606
8131.128.0.0/9131.128.0.1 to 131.255.255.254131.255.255.2558,388,606
9132.0.0.0/9132.0.0.1 to 132.127.255.254132.127.255.2558,388,606
10132.128.0.0/9132.128.0.1 to 132.255.255.254132.255.255.2558,388,606
11133.0.0.0/9133.0.0.1 to 133.127.255.254133.127.255.2558,388,606
12133.128.0.0/9133.128.0.1 to 133.255.255.254133.255.255.2558,388,606
13134.0.0.0/9134.0.0.1 to 134.127.255.254134.127.255.2558,388,606
14134.128.0.0/9134.128.0.1 to 134.255.255.254134.255.255.2558,388,606
15135.0.0.0/9135.0.0.1 to 135.127.255.254135.127.255.2558,388,606
16135.128.0.0/9135.128.0.1 to 135.255.255.254135.255.255.2558,388,606
17136.0.0.0/9136.0.0.1 to 136.127.255.254136.127.255.2558,388,606
18136.128.0.0/9136.128.0.1 to 136.255.255.254136.255.255.2558,388,606
19137.0.0.0/9137.0.0.1 to 137.127.255.254137.127.255.2558,388,606
20137.128.0.0/9137.128.0.1 to 137.255.255.254137.255.255.2558,388,606
21138.0.0.0/9138.0.0.1 to 138.127.255.254138.127.255.2558,388,606
22138.128.0.0/9138.128.0.1 to 138.255.255.254138.255.255.2558,388,606
23139.0.0.0/9139.0.0.1 to 139.127.255.254139.127.255.2558,388,606
24139.128.0.0/9139.128.0.1 to 139.255.255.254139.255.255.2558,388,606
25140.0.0.0/9140.0.0.1 to 140.127.255.254140.127.255.2558,388,606
26140.128.0.0/9140.128.0.1 to 140.255.255.254140.255.255.2558,388,606
27141.0.0.0/9141.0.0.1 to 141.127.255.254141.127.255.2558,388,606
28141.128.0.0/9141.128.0.1 to 141.255.255.254141.255.255.2558,388,606
29142.0.0.0/9142.0.0.1 to 142.127.255.254142.127.255.2558,388,606
30142.128.0.0/9142.128.0.1 to 142.255.255.254142.255.255.2558,388,606
31143.0.0.0/9143.0.0.1 to 143.127.255.254143.127.255.2558,388,606
32143.128.0.0/9143.128.0.1 to 143.255.255.254143.255.255.2558,388,606
33144.0.0.0/9144.0.0.1 to 144.127.255.254144.127.255.2558,388,606
34144.128.0.0/9144.128.0.1 to 144.255.255.254144.255.255.2558,388,606
35145.0.0.0/9145.0.0.1 to 145.127.255.254145.127.255.2558,388,606
36145.128.0.0/9145.128.0.1 to 145.255.255.254145.255.255.2558,388,606
37146.0.0.0/9146.0.0.1 to 146.127.255.254146.127.255.2558,388,606
38146.128.0.0/9146.128.0.1 to 146.255.255.254146.255.255.2558,388,606
39147.0.0.0/9147.0.0.1 to 147.127.255.254147.127.255.2558,388,606
40147.128.0.0/9147.128.0.1 to 147.255.255.254147.255.255.2558,388,606
41148.0.0.0/9148.0.0.1 to 148.127.255.254148.127.255.2558,388,606
42148.128.0.0/9148.128.0.1 to 148.255.255.254148.255.255.2558,388,606
43149.0.0.0/9149.0.0.1 to 149.127.255.254149.127.255.2558,388,606
44149.128.0.0/9149.128.0.1 to 149.255.255.254149.255.255.2558,388,606
45150.0.0.0/9150.0.0.1 to 150.127.255.254150.127.255.2558,388,606
46150.128.0.0/9150.128.0.1 to 150.255.255.254150.255.255.2558,388,606
47151.0.0.0/9151.0.0.1 to 151.127.255.254151.127.255.2558,388,606
48151.128.0.0/9151.128.0.1 to 151.255.255.254151.255.255.2558,388,606
49152.0.0.0/9152.0.0.1 to 152.127.255.254152.127.255.2558,388,606
50152.128.0.0/9152.128.0.1 to 152.255.255.254152.255.255.2558,388,606
51153.0.0.0/9153.0.0.1 to 153.127.255.254153.127.255.2558,388,606
52153.128.0.0/9153.128.0.1 to 153.255.255.254153.255.255.2558,388,606
53154.0.0.0/9154.0.0.1 to 154.127.255.254154.127.255.2558,388,606
54154.128.0.0/9154.128.0.1 to 154.255.255.254154.255.255.2558,388,606
55155.0.0.0/9155.0.0.1 to 155.127.255.254155.127.255.2558,388,606
56155.128.0.0/9155.128.0.1 to 155.255.255.254155.255.255.2558,388,606
57156.0.0.0/9156.0.0.1 to 156.127.255.254156.127.255.2558,388,606
58156.128.0.0/9156.128.0.1 to 156.255.255.254156.255.255.2558,388,606
59157.0.0.0/9157.0.0.1 to 157.127.255.254157.127.255.2558,388,606
60157.128.0.0/9157.128.0.1 to 157.255.255.254157.255.255.2558,388,606
61158.0.0.0/9158.0.0.1 to 158.127.255.254158.127.255.2558,388,606
62158.128.0.0/9158.128.0.1 to 158.255.255.254158.255.255.2558,388,606
63159.0.0.0/9159.0.0.1 to 159.127.255.254159.127.255.2558,388,606
64159.128.0.0/9159.128.0.1 to 159.255.255.254159.255.255.2558,388,606
65160.0.0.0/9160.0.0.1 to 160.127.255.254160.127.255.2558,388,606
66160.128.0.0/9160.128.0.1 to 160.255.255.254160.255.255.2558,388,606
67161.0.0.0/9161.0.0.1 to 161.127.255.254161.127.255.2558,388,606
68161.128.0.0/9161.128.0.1 to 161.255.255.254161.255.255.2558,388,606
69162.0.0.0/9162.0.0.1 to 162.127.255.254162.127.255.2558,388,606
70162.128.0.0/9162.128.0.1 to 162.255.255.254162.255.255.2558,388,606
71163.0.0.0/9163.0.0.1 to 163.127.255.254163.127.255.2558,388,606
72163.128.0.0/9163.128.0.1 to 163.255.255.254163.255.255.2558,388,606
73164.0.0.0/9164.0.0.1 to 164.127.255.254164.127.255.2558,388,606
74164.128.0.0/9164.128.0.1 to 164.255.255.254164.255.255.2558,388,606
75165.0.0.0/9165.0.0.1 to 165.127.255.254165.127.255.2558,388,606
76165.128.0.0/9165.128.0.1 to 165.255.255.254165.255.255.2558,388,606
77166.0.0.0/9166.0.0.1 to 166.127.255.254166.127.255.2558,388,606
78166.128.0.0/9166.128.0.1 to 166.255.255.254166.255.255.2558,388,606
79167.0.0.0/9167.0.0.1 to 167.127.255.254167.127.255.2558,388,606
80167.128.0.0/9167.128.0.1 to 167.255.255.254167.255.255.2558,388,606
81168.0.0.0/9168.0.0.1 to 168.127.255.254168.127.255.2558,388,606
82168.128.0.0/9168.128.0.1 to 168.255.255.254168.255.255.2558,388,606
83169.0.0.0/9169.0.0.1 to 169.127.255.254169.127.255.2558,388,606
84169.128.0.0/9169.128.0.1 to 169.255.255.254169.255.255.2558,388,606
85170.0.0.0/9170.0.0.1 to 170.127.255.254170.127.255.2558,388,606
86170.128.0.0/9170.128.0.1 to 170.255.255.254170.255.255.2558,388,606
87171.0.0.0/9171.0.0.1 to 171.127.255.254171.127.255.2558,388,606
88171.128.0.0/9171.128.0.1 to 171.255.255.254171.255.255.2558,388,606
89172.0.0.0/9172.0.0.1 to 172.127.255.254172.127.255.2558,388,606
90172.128.0.0/9172.128.0.1 to 172.255.255.254172.255.255.2558,388,606
91173.0.0.0/9173.0.0.1 to 173.127.255.254173.127.255.2558,388,606
92173.128.0.0/9173.128.0.1 to 173.255.255.254173.255.255.2558,388,606
93174.0.0.0/9174.0.0.1 to 174.127.255.254174.127.255.2558,388,606
94174.128.0.0/9174.128.0.1 to 174.255.255.254174.255.255.2558,388,606
95175.0.0.0/9175.0.0.1 to 175.127.255.254175.127.255.2558,388,606
96175.128.0.0/9175.128.0.1 to 175.255.255.254175.255.255.2558,388,606
97176.0.0.0/9176.0.0.1 to 176.127.255.254176.127.255.2558,388,606
98176.128.0.0/9176.128.0.1 to 176.255.255.254176.255.255.2558,388,606
99177.0.0.0/9177.0.0.1 to 177.127.255.254177.127.255.2558,388,606
100177.128.0.0/9177.128.0.1 to 177.255.255.254177.255.255.2558,388,606
101178.0.0.0/9178.0.0.1 to 178.127.255.254178.127.255.2558,388,606
102178.128.0.0/9178.128.0.1 to 178.255.255.254178.255.255.2558,388,606
103179.0.0.0/9179.0.0.1 to 179.127.255.254179.127.255.2558,388,606
104179.128.0.0/9179.128.0.1 to 179.255.255.254179.255.255.2558,388,606
105180.0.0.0/9180.0.0.1 to 180.127.255.254180.127.255.2558,388,606
106180.128.0.0/9180.128.0.1 to 180.255.255.254180.255.255.2558,388,606
107181.0.0.0/9181.0.0.1 to 181.127.255.254181.127.255.2558,388,606
108181.128.0.0/9181.128.0.1 to 181.255.255.254181.255.255.2558,388,606
109182.0.0.0/9182.0.0.1 to 182.127.255.254182.127.255.2558,388,606
110182.128.0.0/9182.128.0.1 to 182.255.255.254182.255.255.2558,388,606
111183.0.0.0/9183.0.0.1 to 183.127.255.254183.127.255.2558,388,606
112183.128.0.0/9183.128.0.1 to 183.255.255.254183.255.255.2558,388,606
113184.0.0.0/9184.0.0.1 to 184.127.255.254184.127.255.2558,388,606
114184.128.0.0/9184.128.0.1 to 184.255.255.254184.255.255.2558,388,606
115185.0.0.0/9185.0.0.1 to 185.127.255.254185.127.255.2558,388,606
116185.128.0.0/9185.128.0.1 to 185.255.255.254185.255.255.2558,388,606
117186.0.0.0/9186.0.0.1 to 186.127.255.254186.127.255.2558,388,606
118186.128.0.0/9186.128.0.1 to 186.255.255.254186.255.255.2558,388,606
119187.0.0.0/9187.0.0.1 to 187.127.255.254187.127.255.2558,388,606
120187.128.0.0/9187.128.0.1 to 187.255.255.254187.255.255.2558,388,606
121188.0.0.0/9188.0.0.1 to 188.127.255.254188.127.255.2558,388,606
122188.128.0.0/9188.128.0.1 to 188.255.255.254188.255.255.2558,388,606
123189.0.0.0/9189.0.0.1 to 189.127.255.254189.127.255.2558,388,606
124189.128.0.0/9189.128.0.1 to 189.255.255.254189.255.255.2558,388,606
125190.0.0.0/9190.0.0.1 to 190.127.255.254190.127.255.2558,388,606
126190.128.0.0/9190.128.0.1 to 190.255.255.254190.255.255.2558,388,606
127191.0.0.0/9191.0.0.1 to 191.127.255.254191.127.255.2558,388,606
128191.128.0.0/9191.128.0.1 to 191.255.255.254191.255.255.2558,388,606

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.