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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.

Network128.0.0.0/5
Usable hosts134,217,726
Subnet mask248.0.0.0
Addresses134,217,728
Network address
128.0.0.0
Broadcast address
135.255.255.255
First usable
128.0.0.1
Last usable
135.255.255.254
Usable hosts
134,217,726 (134,217,728 less the network and broadcast addresses)
Subnet mask
248.0.0.0
Wildcard mask
7.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/5
Type
Public public
Old class
B (default /16)
As numbers
Hex 80000000 · Integer 2147483648 to 2281701375
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
/5 is not on a 8-bit boundary, so it takes 8 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000000.00000000.00000000.00000000128.0.0.0
Subnet mask11111000.00000000.00000000.00000000248.0.0.0
Network10000000.00000000.00000000.00000000128.0.0.0
Broadcast10000111.11111111.11111111.11111111135.255.255.255
Split into smaller subnets/12
/6 (2)/7 (4)/8 (8)/9 (16)/10 (32)/11 (64)/12 (128)/13 (256)/14 (512)/15 (1,024)/16 (2,048)/17 (4,096)

128.0.0.0/5 makes 128 subnets of /12.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1128.0.0.0/12128.0.0.1 to 128.15.255.254128.15.255.2551,048,574
2128.16.0.0/12128.16.0.1 to 128.31.255.254128.31.255.2551,048,574
3128.32.0.0/12128.32.0.1 to 128.47.255.254128.47.255.2551,048,574
4128.48.0.0/12128.48.0.1 to 128.63.255.254128.63.255.2551,048,574
5128.64.0.0/12128.64.0.1 to 128.79.255.254128.79.255.2551,048,574
6128.80.0.0/12128.80.0.1 to 128.95.255.254128.95.255.2551,048,574
7128.96.0.0/12128.96.0.1 to 128.111.255.254128.111.255.2551,048,574
8128.112.0.0/12128.112.0.1 to 128.127.255.254128.127.255.2551,048,574
9128.128.0.0/12128.128.0.1 to 128.143.255.254128.143.255.2551,048,574
10128.144.0.0/12128.144.0.1 to 128.159.255.254128.159.255.2551,048,574
11128.160.0.0/12128.160.0.1 to 128.175.255.254128.175.255.2551,048,574
12128.176.0.0/12128.176.0.1 to 128.191.255.254128.191.255.2551,048,574
13128.192.0.0/12128.192.0.1 to 128.207.255.254128.207.255.2551,048,574
14128.208.0.0/12128.208.0.1 to 128.223.255.254128.223.255.2551,048,574
15128.224.0.0/12128.224.0.1 to 128.239.255.254128.239.255.2551,048,574
16128.240.0.0/12128.240.0.1 to 128.255.255.254128.255.255.2551,048,574
17129.0.0.0/12129.0.0.1 to 129.15.255.254129.15.255.2551,048,574
18129.16.0.0/12129.16.0.1 to 129.31.255.254129.31.255.2551,048,574
19129.32.0.0/12129.32.0.1 to 129.47.255.254129.47.255.2551,048,574
20129.48.0.0/12129.48.0.1 to 129.63.255.254129.63.255.2551,048,574
21129.64.0.0/12129.64.0.1 to 129.79.255.254129.79.255.2551,048,574
22129.80.0.0/12129.80.0.1 to 129.95.255.254129.95.255.2551,048,574
23129.96.0.0/12129.96.0.1 to 129.111.255.254129.111.255.2551,048,574
24129.112.0.0/12129.112.0.1 to 129.127.255.254129.127.255.2551,048,574
25129.128.0.0/12129.128.0.1 to 129.143.255.254129.143.255.2551,048,574
26129.144.0.0/12129.144.0.1 to 129.159.255.254129.159.255.2551,048,574
27129.160.0.0/12129.160.0.1 to 129.175.255.254129.175.255.2551,048,574
28129.176.0.0/12129.176.0.1 to 129.191.255.254129.191.255.2551,048,574
29129.192.0.0/12129.192.0.1 to 129.207.255.254129.207.255.2551,048,574
30129.208.0.0/12129.208.0.1 to 129.223.255.254129.223.255.2551,048,574
31129.224.0.0/12129.224.0.1 to 129.239.255.254129.239.255.2551,048,574
32129.240.0.0/12129.240.0.1 to 129.255.255.254129.255.255.2551,048,574
33130.0.0.0/12130.0.0.1 to 130.15.255.254130.15.255.2551,048,574
34130.16.0.0/12130.16.0.1 to 130.31.255.254130.31.255.2551,048,574
35130.32.0.0/12130.32.0.1 to 130.47.255.254130.47.255.2551,048,574
36130.48.0.0/12130.48.0.1 to 130.63.255.254130.63.255.2551,048,574
37130.64.0.0/12130.64.0.1 to 130.79.255.254130.79.255.2551,048,574
38130.80.0.0/12130.80.0.1 to 130.95.255.254130.95.255.2551,048,574
39130.96.0.0/12130.96.0.1 to 130.111.255.254130.111.255.2551,048,574
40130.112.0.0/12130.112.0.1 to 130.127.255.254130.127.255.2551,048,574
41130.128.0.0/12130.128.0.1 to 130.143.255.254130.143.255.2551,048,574
42130.144.0.0/12130.144.0.1 to 130.159.255.254130.159.255.2551,048,574
43130.160.0.0/12130.160.0.1 to 130.175.255.254130.175.255.2551,048,574
44130.176.0.0/12130.176.0.1 to 130.191.255.254130.191.255.2551,048,574
45130.192.0.0/12130.192.0.1 to 130.207.255.254130.207.255.2551,048,574
46130.208.0.0/12130.208.0.1 to 130.223.255.254130.223.255.2551,048,574
47130.224.0.0/12130.224.0.1 to 130.239.255.254130.239.255.2551,048,574
48130.240.0.0/12130.240.0.1 to 130.255.255.254130.255.255.2551,048,574
49131.0.0.0/12131.0.0.1 to 131.15.255.254131.15.255.2551,048,574
50131.16.0.0/12131.16.0.1 to 131.31.255.254131.31.255.2551,048,574
51131.32.0.0/12131.32.0.1 to 131.47.255.254131.47.255.2551,048,574
52131.48.0.0/12131.48.0.1 to 131.63.255.254131.63.255.2551,048,574
53131.64.0.0/12131.64.0.1 to 131.79.255.254131.79.255.2551,048,574
54131.80.0.0/12131.80.0.1 to 131.95.255.254131.95.255.2551,048,574
55131.96.0.0/12131.96.0.1 to 131.111.255.254131.111.255.2551,048,574
56131.112.0.0/12131.112.0.1 to 131.127.255.254131.127.255.2551,048,574
57131.128.0.0/12131.128.0.1 to 131.143.255.254131.143.255.2551,048,574
58131.144.0.0/12131.144.0.1 to 131.159.255.254131.159.255.2551,048,574
59131.160.0.0/12131.160.0.1 to 131.175.255.254131.175.255.2551,048,574
60131.176.0.0/12131.176.0.1 to 131.191.255.254131.191.255.2551,048,574
61131.192.0.0/12131.192.0.1 to 131.207.255.254131.207.255.2551,048,574
62131.208.0.0/12131.208.0.1 to 131.223.255.254131.223.255.2551,048,574
63131.224.0.0/12131.224.0.1 to 131.239.255.254131.239.255.2551,048,574
64131.240.0.0/12131.240.0.1 to 131.255.255.254131.255.255.2551,048,574
65132.0.0.0/12132.0.0.1 to 132.15.255.254132.15.255.2551,048,574
66132.16.0.0/12132.16.0.1 to 132.31.255.254132.31.255.2551,048,574
67132.32.0.0/12132.32.0.1 to 132.47.255.254132.47.255.2551,048,574
68132.48.0.0/12132.48.0.1 to 132.63.255.254132.63.255.2551,048,574
69132.64.0.0/12132.64.0.1 to 132.79.255.254132.79.255.2551,048,574
70132.80.0.0/12132.80.0.1 to 132.95.255.254132.95.255.2551,048,574
71132.96.0.0/12132.96.0.1 to 132.111.255.254132.111.255.2551,048,574
72132.112.0.0/12132.112.0.1 to 132.127.255.254132.127.255.2551,048,574
73132.128.0.0/12132.128.0.1 to 132.143.255.254132.143.255.2551,048,574
74132.144.0.0/12132.144.0.1 to 132.159.255.254132.159.255.2551,048,574
75132.160.0.0/12132.160.0.1 to 132.175.255.254132.175.255.2551,048,574
76132.176.0.0/12132.176.0.1 to 132.191.255.254132.191.255.2551,048,574
77132.192.0.0/12132.192.0.1 to 132.207.255.254132.207.255.2551,048,574
78132.208.0.0/12132.208.0.1 to 132.223.255.254132.223.255.2551,048,574
79132.224.0.0/12132.224.0.1 to 132.239.255.254132.239.255.2551,048,574
80132.240.0.0/12132.240.0.1 to 132.255.255.254132.255.255.2551,048,574
81133.0.0.0/12133.0.0.1 to 133.15.255.254133.15.255.2551,048,574
82133.16.0.0/12133.16.0.1 to 133.31.255.254133.31.255.2551,048,574
83133.32.0.0/12133.32.0.1 to 133.47.255.254133.47.255.2551,048,574
84133.48.0.0/12133.48.0.1 to 133.63.255.254133.63.255.2551,048,574
85133.64.0.0/12133.64.0.1 to 133.79.255.254133.79.255.2551,048,574
86133.80.0.0/12133.80.0.1 to 133.95.255.254133.95.255.2551,048,574
87133.96.0.0/12133.96.0.1 to 133.111.255.254133.111.255.2551,048,574
88133.112.0.0/12133.112.0.1 to 133.127.255.254133.127.255.2551,048,574
89133.128.0.0/12133.128.0.1 to 133.143.255.254133.143.255.2551,048,574
90133.144.0.0/12133.144.0.1 to 133.159.255.254133.159.255.2551,048,574
91133.160.0.0/12133.160.0.1 to 133.175.255.254133.175.255.2551,048,574
92133.176.0.0/12133.176.0.1 to 133.191.255.254133.191.255.2551,048,574
93133.192.0.0/12133.192.0.1 to 133.207.255.254133.207.255.2551,048,574
94133.208.0.0/12133.208.0.1 to 133.223.255.254133.223.255.2551,048,574
95133.224.0.0/12133.224.0.1 to 133.239.255.254133.239.255.2551,048,574
96133.240.0.0/12133.240.0.1 to 133.255.255.254133.255.255.2551,048,574
97134.0.0.0/12134.0.0.1 to 134.15.255.254134.15.255.2551,048,574
98134.16.0.0/12134.16.0.1 to 134.31.255.254134.31.255.2551,048,574
99134.32.0.0/12134.32.0.1 to 134.47.255.254134.47.255.2551,048,574
100134.48.0.0/12134.48.0.1 to 134.63.255.254134.63.255.2551,048,574
101134.64.0.0/12134.64.0.1 to 134.79.255.254134.79.255.2551,048,574
102134.80.0.0/12134.80.0.1 to 134.95.255.254134.95.255.2551,048,574
103134.96.0.0/12134.96.0.1 to 134.111.255.254134.111.255.2551,048,574
104134.112.0.0/12134.112.0.1 to 134.127.255.254134.127.255.2551,048,574
105134.128.0.0/12134.128.0.1 to 134.143.255.254134.143.255.2551,048,574
106134.144.0.0/12134.144.0.1 to 134.159.255.254134.159.255.2551,048,574
107134.160.0.0/12134.160.0.1 to 134.175.255.254134.175.255.2551,048,574
108134.176.0.0/12134.176.0.1 to 134.191.255.254134.191.255.2551,048,574
109134.192.0.0/12134.192.0.1 to 134.207.255.254134.207.255.2551,048,574
110134.208.0.0/12134.208.0.1 to 134.223.255.254134.223.255.2551,048,574
111134.224.0.0/12134.224.0.1 to 134.239.255.254134.239.255.2551,048,574
112134.240.0.0/12134.240.0.1 to 134.255.255.254134.255.255.2551,048,574
113135.0.0.0/12135.0.0.1 to 135.15.255.254135.15.255.2551,048,574
114135.16.0.0/12135.16.0.1 to 135.31.255.254135.31.255.2551,048,574
115135.32.0.0/12135.32.0.1 to 135.47.255.254135.47.255.2551,048,574
116135.48.0.0/12135.48.0.1 to 135.63.255.254135.63.255.2551,048,574
117135.64.0.0/12135.64.0.1 to 135.79.255.254135.79.255.2551,048,574
118135.80.0.0/12135.80.0.1 to 135.95.255.254135.95.255.2551,048,574
119135.96.0.0/12135.96.0.1 to 135.111.255.254135.111.255.2551,048,574
120135.112.0.0/12135.112.0.1 to 135.127.255.254135.127.255.2551,048,574
121135.128.0.0/12135.128.0.1 to 135.143.255.254135.143.255.2551,048,574
122135.144.0.0/12135.144.0.1 to 135.159.255.254135.159.255.2551,048,574
123135.160.0.0/12135.160.0.1 to 135.175.255.254135.175.255.2551,048,574
124135.176.0.0/12135.176.0.1 to 135.191.255.254135.191.255.2551,048,574
125135.192.0.0/12135.192.0.1 to 135.207.255.254135.207.255.2551,048,574
126135.208.0.0/12135.208.0.1 to 135.223.255.254135.223.255.2551,048,574
127135.224.0.0/12135.224.0.1 to 135.239.255.254135.239.255.2551,048,574
128135.240.0.0/12135.240.0.1 to 135.255.255.254135.255.255.2551,048,574

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.