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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.

Network172.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
172.0.0.0
Broadcast address
175.255.255.255
First usable
172.0.0.1
Last usable
175.255.255.254
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 AC000000 · Integer 2885681152 to 2952790015
Reverse DNS zones
172.in-addr.arpa
173.in-addr.arpa
174.in-addr.arpa
175.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
Address10101100.00000000.00000000.00000000172.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network10101100.00000000.00000000.00000000172.0.0.0
Broadcast10101111.11111111.11111111.11111111175.255.255.255
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)

172.0.0.0/6 makes 128 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1172.0.0.0/13172.0.0.1 to 172.7.255.254172.7.255.255524,286
2172.8.0.0/13172.8.0.1 to 172.15.255.254172.15.255.255524,286
3172.16.0.0/13172.16.0.1 to 172.23.255.254172.23.255.255524,286
4172.24.0.0/13172.24.0.1 to 172.31.255.254172.31.255.255524,286
5172.32.0.0/13172.32.0.1 to 172.39.255.254172.39.255.255524,286
6172.40.0.0/13172.40.0.1 to 172.47.255.254172.47.255.255524,286
7172.48.0.0/13172.48.0.1 to 172.55.255.254172.55.255.255524,286
8172.56.0.0/13172.56.0.1 to 172.63.255.254172.63.255.255524,286
9172.64.0.0/13172.64.0.1 to 172.71.255.254172.71.255.255524,286
10172.72.0.0/13172.72.0.1 to 172.79.255.254172.79.255.255524,286
11172.80.0.0/13172.80.0.1 to 172.87.255.254172.87.255.255524,286
12172.88.0.0/13172.88.0.1 to 172.95.255.254172.95.255.255524,286
13172.96.0.0/13172.96.0.1 to 172.103.255.254172.103.255.255524,286
14172.104.0.0/13172.104.0.1 to 172.111.255.254172.111.255.255524,286
15172.112.0.0/13172.112.0.1 to 172.119.255.254172.119.255.255524,286
16172.120.0.0/13172.120.0.1 to 172.127.255.254172.127.255.255524,286
17172.128.0.0/13172.128.0.1 to 172.135.255.254172.135.255.255524,286
18172.136.0.0/13172.136.0.1 to 172.143.255.254172.143.255.255524,286
19172.144.0.0/13172.144.0.1 to 172.151.255.254172.151.255.255524,286
20172.152.0.0/13172.152.0.1 to 172.159.255.254172.159.255.255524,286
21172.160.0.0/13172.160.0.1 to 172.167.255.254172.167.255.255524,286
22172.168.0.0/13172.168.0.1 to 172.175.255.254172.175.255.255524,286
23172.176.0.0/13172.176.0.1 to 172.183.255.254172.183.255.255524,286
24172.184.0.0/13172.184.0.1 to 172.191.255.254172.191.255.255524,286
25172.192.0.0/13172.192.0.1 to 172.199.255.254172.199.255.255524,286
26172.200.0.0/13172.200.0.1 to 172.207.255.254172.207.255.255524,286
27172.208.0.0/13172.208.0.1 to 172.215.255.254172.215.255.255524,286
28172.216.0.0/13172.216.0.1 to 172.223.255.254172.223.255.255524,286
29172.224.0.0/13172.224.0.1 to 172.231.255.254172.231.255.255524,286
30172.232.0.0/13172.232.0.1 to 172.239.255.254172.239.255.255524,286
31172.240.0.0/13172.240.0.1 to 172.247.255.254172.247.255.255524,286
32172.248.0.0/13172.248.0.1 to 172.255.255.254172.255.255.255524,286
33173.0.0.0/13173.0.0.1 to 173.7.255.254173.7.255.255524,286
34173.8.0.0/13173.8.0.1 to 173.15.255.254173.15.255.255524,286
35173.16.0.0/13173.16.0.1 to 173.23.255.254173.23.255.255524,286
36173.24.0.0/13173.24.0.1 to 173.31.255.254173.31.255.255524,286
37173.32.0.0/13173.32.0.1 to 173.39.255.254173.39.255.255524,286
38173.40.0.0/13173.40.0.1 to 173.47.255.254173.47.255.255524,286
39173.48.0.0/13173.48.0.1 to 173.55.255.254173.55.255.255524,286
40173.56.0.0/13173.56.0.1 to 173.63.255.254173.63.255.255524,286
41173.64.0.0/13173.64.0.1 to 173.71.255.254173.71.255.255524,286
42173.72.0.0/13173.72.0.1 to 173.79.255.254173.79.255.255524,286
43173.80.0.0/13173.80.0.1 to 173.87.255.254173.87.255.255524,286
44173.88.0.0/13173.88.0.1 to 173.95.255.254173.95.255.255524,286
45173.96.0.0/13173.96.0.1 to 173.103.255.254173.103.255.255524,286
46173.104.0.0/13173.104.0.1 to 173.111.255.254173.111.255.255524,286
47173.112.0.0/13173.112.0.1 to 173.119.255.254173.119.255.255524,286
48173.120.0.0/13173.120.0.1 to 173.127.255.254173.127.255.255524,286
49173.128.0.0/13173.128.0.1 to 173.135.255.254173.135.255.255524,286
50173.136.0.0/13173.136.0.1 to 173.143.255.254173.143.255.255524,286
51173.144.0.0/13173.144.0.1 to 173.151.255.254173.151.255.255524,286
52173.152.0.0/13173.152.0.1 to 173.159.255.254173.159.255.255524,286
53173.160.0.0/13173.160.0.1 to 173.167.255.254173.167.255.255524,286
54173.168.0.0/13173.168.0.1 to 173.175.255.254173.175.255.255524,286
55173.176.0.0/13173.176.0.1 to 173.183.255.254173.183.255.255524,286
56173.184.0.0/13173.184.0.1 to 173.191.255.254173.191.255.255524,286
57173.192.0.0/13173.192.0.1 to 173.199.255.254173.199.255.255524,286
58173.200.0.0/13173.200.0.1 to 173.207.255.254173.207.255.255524,286
59173.208.0.0/13173.208.0.1 to 173.215.255.254173.215.255.255524,286
60173.216.0.0/13173.216.0.1 to 173.223.255.254173.223.255.255524,286
61173.224.0.0/13173.224.0.1 to 173.231.255.254173.231.255.255524,286
62173.232.0.0/13173.232.0.1 to 173.239.255.254173.239.255.255524,286
63173.240.0.0/13173.240.0.1 to 173.247.255.254173.247.255.255524,286
64173.248.0.0/13173.248.0.1 to 173.255.255.254173.255.255.255524,286
65174.0.0.0/13174.0.0.1 to 174.7.255.254174.7.255.255524,286
66174.8.0.0/13174.8.0.1 to 174.15.255.254174.15.255.255524,286
67174.16.0.0/13174.16.0.1 to 174.23.255.254174.23.255.255524,286
68174.24.0.0/13174.24.0.1 to 174.31.255.254174.31.255.255524,286
69174.32.0.0/13174.32.0.1 to 174.39.255.254174.39.255.255524,286
70174.40.0.0/13174.40.0.1 to 174.47.255.254174.47.255.255524,286
71174.48.0.0/13174.48.0.1 to 174.55.255.254174.55.255.255524,286
72174.56.0.0/13174.56.0.1 to 174.63.255.254174.63.255.255524,286
73174.64.0.0/13174.64.0.1 to 174.71.255.254174.71.255.255524,286
74174.72.0.0/13174.72.0.1 to 174.79.255.254174.79.255.255524,286
75174.80.0.0/13174.80.0.1 to 174.87.255.254174.87.255.255524,286
76174.88.0.0/13174.88.0.1 to 174.95.255.254174.95.255.255524,286
77174.96.0.0/13174.96.0.1 to 174.103.255.254174.103.255.255524,286
78174.104.0.0/13174.104.0.1 to 174.111.255.254174.111.255.255524,286
79174.112.0.0/13174.112.0.1 to 174.119.255.254174.119.255.255524,286
80174.120.0.0/13174.120.0.1 to 174.127.255.254174.127.255.255524,286
81174.128.0.0/13174.128.0.1 to 174.135.255.254174.135.255.255524,286
82174.136.0.0/13174.136.0.1 to 174.143.255.254174.143.255.255524,286
83174.144.0.0/13174.144.0.1 to 174.151.255.254174.151.255.255524,286
84174.152.0.0/13174.152.0.1 to 174.159.255.254174.159.255.255524,286
85174.160.0.0/13174.160.0.1 to 174.167.255.254174.167.255.255524,286
86174.168.0.0/13174.168.0.1 to 174.175.255.254174.175.255.255524,286
87174.176.0.0/13174.176.0.1 to 174.183.255.254174.183.255.255524,286
88174.184.0.0/13174.184.0.1 to 174.191.255.254174.191.255.255524,286
89174.192.0.0/13174.192.0.1 to 174.199.255.254174.199.255.255524,286
90174.200.0.0/13174.200.0.1 to 174.207.255.254174.207.255.255524,286
91174.208.0.0/13174.208.0.1 to 174.215.255.254174.215.255.255524,286
92174.216.0.0/13174.216.0.1 to 174.223.255.254174.223.255.255524,286
93174.224.0.0/13174.224.0.1 to 174.231.255.254174.231.255.255524,286
94174.232.0.0/13174.232.0.1 to 174.239.255.254174.239.255.255524,286
95174.240.0.0/13174.240.0.1 to 174.247.255.254174.247.255.255524,286
96174.248.0.0/13174.248.0.1 to 174.255.255.254174.255.255.255524,286
97175.0.0.0/13175.0.0.1 to 175.7.255.254175.7.255.255524,286
98175.8.0.0/13175.8.0.1 to 175.15.255.254175.15.255.255524,286
99175.16.0.0/13175.16.0.1 to 175.23.255.254175.23.255.255524,286
100175.24.0.0/13175.24.0.1 to 175.31.255.254175.31.255.255524,286
101175.32.0.0/13175.32.0.1 to 175.39.255.254175.39.255.255524,286
102175.40.0.0/13175.40.0.1 to 175.47.255.254175.47.255.255524,286
103175.48.0.0/13175.48.0.1 to 175.55.255.254175.55.255.255524,286
104175.56.0.0/13175.56.0.1 to 175.63.255.254175.63.255.255524,286
105175.64.0.0/13175.64.0.1 to 175.71.255.254175.71.255.255524,286
106175.72.0.0/13175.72.0.1 to 175.79.255.254175.79.255.255524,286
107175.80.0.0/13175.80.0.1 to 175.87.255.254175.87.255.255524,286
108175.88.0.0/13175.88.0.1 to 175.95.255.254175.95.255.255524,286
109175.96.0.0/13175.96.0.1 to 175.103.255.254175.103.255.255524,286
110175.104.0.0/13175.104.0.1 to 175.111.255.254175.111.255.255524,286
111175.112.0.0/13175.112.0.1 to 175.119.255.254175.119.255.255524,286
112175.120.0.0/13175.120.0.1 to 175.127.255.254175.127.255.255524,286
113175.128.0.0/13175.128.0.1 to 175.135.255.254175.135.255.255524,286
114175.136.0.0/13175.136.0.1 to 175.143.255.254175.143.255.255524,286
115175.144.0.0/13175.144.0.1 to 175.151.255.254175.151.255.255524,286
116175.152.0.0/13175.152.0.1 to 175.159.255.254175.159.255.255524,286
117175.160.0.0/13175.160.0.1 to 175.167.255.254175.167.255.255524,286
118175.168.0.0/13175.168.0.1 to 175.175.255.254175.175.255.255524,286
119175.176.0.0/13175.176.0.1 to 175.183.255.254175.183.255.255524,286
120175.184.0.0/13175.184.0.1 to 175.191.255.254175.191.255.255524,286
121175.192.0.0/13175.192.0.1 to 175.199.255.254175.199.255.255524,286
122175.200.0.0/13175.200.0.1 to 175.207.255.254175.207.255.255524,286
123175.208.0.0/13175.208.0.1 to 175.215.255.254175.215.255.255524,286
124175.216.0.0/13175.216.0.1 to 175.223.255.254175.223.255.255524,286
125175.224.0.0/13175.224.0.1 to 175.231.255.254175.231.255.255524,286
126175.232.0.0/13175.232.0.1 to 175.239.255.254175.239.255.255524,286
127175.240.0.0/13175.240.0.1 to 175.247.255.254175.247.255.255524,286
128175.248.0.0/13175.248.0.1 to 175.255.255.254175.255.255.255524,286

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.