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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.

Network128.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
128.0.0.0
Broadcast address
131.255.255.255
First usable
128.0.0.1
Last usable
131.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Public public
Old class
B (default /16)
As numbers
Hex 80000000 · Integer 2147483648 to 2214592511
Reverse DNS zones
128.in-addr.arpa
129.in-addr.arpa
130.in-addr.arpa
131.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000000.00000000.00000000.00000000128.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network10000000.00000000.00000000.00000000128.0.0.0
Broadcast10000011.11111111.11111111.11111111131.255.255.255
Split into smaller subnets/13
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

128.0.0.0/6 makes 128 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1128.0.0.0/13128.0.0.1 to 128.7.255.254128.7.255.255524,286
2128.8.0.0/13128.8.0.1 to 128.15.255.254128.15.255.255524,286
3128.16.0.0/13128.16.0.1 to 128.23.255.254128.23.255.255524,286
4128.24.0.0/13128.24.0.1 to 128.31.255.254128.31.255.255524,286
5128.32.0.0/13128.32.0.1 to 128.39.255.254128.39.255.255524,286
6128.40.0.0/13128.40.0.1 to 128.47.255.254128.47.255.255524,286
7128.48.0.0/13128.48.0.1 to 128.55.255.254128.55.255.255524,286
8128.56.0.0/13128.56.0.1 to 128.63.255.254128.63.255.255524,286
9128.64.0.0/13128.64.0.1 to 128.71.255.254128.71.255.255524,286
10128.72.0.0/13128.72.0.1 to 128.79.255.254128.79.255.255524,286
11128.80.0.0/13128.80.0.1 to 128.87.255.254128.87.255.255524,286
12128.88.0.0/13128.88.0.1 to 128.95.255.254128.95.255.255524,286
13128.96.0.0/13128.96.0.1 to 128.103.255.254128.103.255.255524,286
14128.104.0.0/13128.104.0.1 to 128.111.255.254128.111.255.255524,286
15128.112.0.0/13128.112.0.1 to 128.119.255.254128.119.255.255524,286
16128.120.0.0/13128.120.0.1 to 128.127.255.254128.127.255.255524,286
17128.128.0.0/13128.128.0.1 to 128.135.255.254128.135.255.255524,286
18128.136.0.0/13128.136.0.1 to 128.143.255.254128.143.255.255524,286
19128.144.0.0/13128.144.0.1 to 128.151.255.254128.151.255.255524,286
20128.152.0.0/13128.152.0.1 to 128.159.255.254128.159.255.255524,286
21128.160.0.0/13128.160.0.1 to 128.167.255.254128.167.255.255524,286
22128.168.0.0/13128.168.0.1 to 128.175.255.254128.175.255.255524,286
23128.176.0.0/13128.176.0.1 to 128.183.255.254128.183.255.255524,286
24128.184.0.0/13128.184.0.1 to 128.191.255.254128.191.255.255524,286
25128.192.0.0/13128.192.0.1 to 128.199.255.254128.199.255.255524,286
26128.200.0.0/13128.200.0.1 to 128.207.255.254128.207.255.255524,286
27128.208.0.0/13128.208.0.1 to 128.215.255.254128.215.255.255524,286
28128.216.0.0/13128.216.0.1 to 128.223.255.254128.223.255.255524,286
29128.224.0.0/13128.224.0.1 to 128.231.255.254128.231.255.255524,286
30128.232.0.0/13128.232.0.1 to 128.239.255.254128.239.255.255524,286
31128.240.0.0/13128.240.0.1 to 128.247.255.254128.247.255.255524,286
32128.248.0.0/13128.248.0.1 to 128.255.255.254128.255.255.255524,286
33129.0.0.0/13129.0.0.1 to 129.7.255.254129.7.255.255524,286
34129.8.0.0/13129.8.0.1 to 129.15.255.254129.15.255.255524,286
35129.16.0.0/13129.16.0.1 to 129.23.255.254129.23.255.255524,286
36129.24.0.0/13129.24.0.1 to 129.31.255.254129.31.255.255524,286
37129.32.0.0/13129.32.0.1 to 129.39.255.254129.39.255.255524,286
38129.40.0.0/13129.40.0.1 to 129.47.255.254129.47.255.255524,286
39129.48.0.0/13129.48.0.1 to 129.55.255.254129.55.255.255524,286
40129.56.0.0/13129.56.0.1 to 129.63.255.254129.63.255.255524,286
41129.64.0.0/13129.64.0.1 to 129.71.255.254129.71.255.255524,286
42129.72.0.0/13129.72.0.1 to 129.79.255.254129.79.255.255524,286
43129.80.0.0/13129.80.0.1 to 129.87.255.254129.87.255.255524,286
44129.88.0.0/13129.88.0.1 to 129.95.255.254129.95.255.255524,286
45129.96.0.0/13129.96.0.1 to 129.103.255.254129.103.255.255524,286
46129.104.0.0/13129.104.0.1 to 129.111.255.254129.111.255.255524,286
47129.112.0.0/13129.112.0.1 to 129.119.255.254129.119.255.255524,286
48129.120.0.0/13129.120.0.1 to 129.127.255.254129.127.255.255524,286
49129.128.0.0/13129.128.0.1 to 129.135.255.254129.135.255.255524,286
50129.136.0.0/13129.136.0.1 to 129.143.255.254129.143.255.255524,286
51129.144.0.0/13129.144.0.1 to 129.151.255.254129.151.255.255524,286
52129.152.0.0/13129.152.0.1 to 129.159.255.254129.159.255.255524,286
53129.160.0.0/13129.160.0.1 to 129.167.255.254129.167.255.255524,286
54129.168.0.0/13129.168.0.1 to 129.175.255.254129.175.255.255524,286
55129.176.0.0/13129.176.0.1 to 129.183.255.254129.183.255.255524,286
56129.184.0.0/13129.184.0.1 to 129.191.255.254129.191.255.255524,286
57129.192.0.0/13129.192.0.1 to 129.199.255.254129.199.255.255524,286
58129.200.0.0/13129.200.0.1 to 129.207.255.254129.207.255.255524,286
59129.208.0.0/13129.208.0.1 to 129.215.255.254129.215.255.255524,286
60129.216.0.0/13129.216.0.1 to 129.223.255.254129.223.255.255524,286
61129.224.0.0/13129.224.0.1 to 129.231.255.254129.231.255.255524,286
62129.232.0.0/13129.232.0.1 to 129.239.255.254129.239.255.255524,286
63129.240.0.0/13129.240.0.1 to 129.247.255.254129.247.255.255524,286
64129.248.0.0/13129.248.0.1 to 129.255.255.254129.255.255.255524,286
65130.0.0.0/13130.0.0.1 to 130.7.255.254130.7.255.255524,286
66130.8.0.0/13130.8.0.1 to 130.15.255.254130.15.255.255524,286
67130.16.0.0/13130.16.0.1 to 130.23.255.254130.23.255.255524,286
68130.24.0.0/13130.24.0.1 to 130.31.255.254130.31.255.255524,286
69130.32.0.0/13130.32.0.1 to 130.39.255.254130.39.255.255524,286
70130.40.0.0/13130.40.0.1 to 130.47.255.254130.47.255.255524,286
71130.48.0.0/13130.48.0.1 to 130.55.255.254130.55.255.255524,286
72130.56.0.0/13130.56.0.1 to 130.63.255.254130.63.255.255524,286
73130.64.0.0/13130.64.0.1 to 130.71.255.254130.71.255.255524,286
74130.72.0.0/13130.72.0.1 to 130.79.255.254130.79.255.255524,286
75130.80.0.0/13130.80.0.1 to 130.87.255.254130.87.255.255524,286
76130.88.0.0/13130.88.0.1 to 130.95.255.254130.95.255.255524,286
77130.96.0.0/13130.96.0.1 to 130.103.255.254130.103.255.255524,286
78130.104.0.0/13130.104.0.1 to 130.111.255.254130.111.255.255524,286
79130.112.0.0/13130.112.0.1 to 130.119.255.254130.119.255.255524,286
80130.120.0.0/13130.120.0.1 to 130.127.255.254130.127.255.255524,286
81130.128.0.0/13130.128.0.1 to 130.135.255.254130.135.255.255524,286
82130.136.0.0/13130.136.0.1 to 130.143.255.254130.143.255.255524,286
83130.144.0.0/13130.144.0.1 to 130.151.255.254130.151.255.255524,286
84130.152.0.0/13130.152.0.1 to 130.159.255.254130.159.255.255524,286
85130.160.0.0/13130.160.0.1 to 130.167.255.254130.167.255.255524,286
86130.168.0.0/13130.168.0.1 to 130.175.255.254130.175.255.255524,286
87130.176.0.0/13130.176.0.1 to 130.183.255.254130.183.255.255524,286
88130.184.0.0/13130.184.0.1 to 130.191.255.254130.191.255.255524,286
89130.192.0.0/13130.192.0.1 to 130.199.255.254130.199.255.255524,286
90130.200.0.0/13130.200.0.1 to 130.207.255.254130.207.255.255524,286
91130.208.0.0/13130.208.0.1 to 130.215.255.254130.215.255.255524,286
92130.216.0.0/13130.216.0.1 to 130.223.255.254130.223.255.255524,286
93130.224.0.0/13130.224.0.1 to 130.231.255.254130.231.255.255524,286
94130.232.0.0/13130.232.0.1 to 130.239.255.254130.239.255.255524,286
95130.240.0.0/13130.240.0.1 to 130.247.255.254130.247.255.255524,286
96130.248.0.0/13130.248.0.1 to 130.255.255.254130.255.255.255524,286
97131.0.0.0/13131.0.0.1 to 131.7.255.254131.7.255.255524,286
98131.8.0.0/13131.8.0.1 to 131.15.255.254131.15.255.255524,286
99131.16.0.0/13131.16.0.1 to 131.23.255.254131.23.255.255524,286
100131.24.0.0/13131.24.0.1 to 131.31.255.254131.31.255.255524,286
101131.32.0.0/13131.32.0.1 to 131.39.255.254131.39.255.255524,286
102131.40.0.0/13131.40.0.1 to 131.47.255.254131.47.255.255524,286
103131.48.0.0/13131.48.0.1 to 131.55.255.254131.55.255.255524,286
104131.56.0.0/13131.56.0.1 to 131.63.255.254131.63.255.255524,286
105131.64.0.0/13131.64.0.1 to 131.71.255.254131.71.255.255524,286
106131.72.0.0/13131.72.0.1 to 131.79.255.254131.79.255.255524,286
107131.80.0.0/13131.80.0.1 to 131.87.255.254131.87.255.255524,286
108131.88.0.0/13131.88.0.1 to 131.95.255.254131.95.255.255524,286
109131.96.0.0/13131.96.0.1 to 131.103.255.254131.103.255.255524,286
110131.104.0.0/13131.104.0.1 to 131.111.255.254131.111.255.255524,286
111131.112.0.0/13131.112.0.1 to 131.119.255.254131.119.255.255524,286
112131.120.0.0/13131.120.0.1 to 131.127.255.254131.127.255.255524,286
113131.128.0.0/13131.128.0.1 to 131.135.255.254131.135.255.255524,286
114131.136.0.0/13131.136.0.1 to 131.143.255.254131.143.255.255524,286
115131.144.0.0/13131.144.0.1 to 131.151.255.254131.151.255.255524,286
116131.152.0.0/13131.152.0.1 to 131.159.255.254131.159.255.255524,286
117131.160.0.0/13131.160.0.1 to 131.167.255.254131.167.255.255524,286
118131.168.0.0/13131.168.0.1 to 131.175.255.254131.175.255.255524,286
119131.176.0.0/13131.176.0.1 to 131.183.255.254131.183.255.255524,286
120131.184.0.0/13131.184.0.1 to 131.191.255.254131.191.255.255524,286
121131.192.0.0/13131.192.0.1 to 131.199.255.254131.199.255.255524,286
122131.200.0.0/13131.200.0.1 to 131.207.255.254131.207.255.255524,286
123131.208.0.0/13131.208.0.1 to 131.215.255.254131.215.255.255524,286
124131.216.0.0/13131.216.0.1 to 131.223.255.254131.223.255.255524,286
125131.224.0.0/13131.224.0.1 to 131.231.255.254131.231.255.255524,286
126131.232.0.0/13131.232.0.1 to 131.239.255.254131.239.255.255524,286
127131.240.0.0/13131.240.0.1 to 131.247.255.254131.247.255.255524,286
128131.248.0.0/13131.248.0.1 to 131.255.255.254131.255.255.255524,286

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.