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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.

Network166.64.0.0/11
Usable hosts2,097,150
Subnet mask255.224.0.0
Addresses2,097,152
Network address
166.64.0.0
Broadcast address
166.95.255.255
First usable
166.64.0.1
Last usable
166.95.255.254
Usable hosts
2,097,150 (2,097,152 less the network and broadcast addresses)
Subnet mask
255.224.0.0
Wildcard mask
0.31.255.255 (Cisco ACLs, OSPF)
Prefix length
/11
Type
Public public
Old class
B (default /16)
As numbers
Hex A6400000 · Integer 2789212160 to 2791309311
Reverse DNS zones
64.166.in-addr.arpa
65.166.in-addr.arpa
66.166.in-addr.arpa
67.166.in-addr.arpa
68.166.in-addr.arpa
69.166.in-addr.arpa
70.166.in-addr.arpa
71.166.in-addr.arpa
72.166.in-addr.arpa
73.166.in-addr.arpa
74.166.in-addr.arpa
75.166.in-addr.arpa
76.166.in-addr.arpa
77.166.in-addr.arpa
78.166.in-addr.arpa
79.166.in-addr.arpa
and 16 more
/11 is not on a 8-bit boundary, so it takes 32 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100110.01000000.00000000.00000000166.64.0.0
Subnet mask11111111.11100000.00000000.00000000255.224.0.0
Network10100110.01000000.00000000.00000000166.64.0.0
Broadcast10100110.01011111.11111111.11111111166.95.255.255
Split into smaller subnets/18
/12 (2)/13 (4)/14 (8)/15 (16)/16 (32)/17 (64)/18 (128)/19 (256)/20 (512)/21 (1,024)/22 (2,048)/23 (4,096)

166.64.0.0/11 makes 128 subnets of /18.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1166.64.0.0/18166.64.0.1 to 166.64.63.254166.64.63.25516,382
2166.64.64.0/18166.64.64.1 to 166.64.127.254166.64.127.25516,382
3166.64.128.0/18166.64.128.1 to 166.64.191.254166.64.191.25516,382
4166.64.192.0/18166.64.192.1 to 166.64.255.254166.64.255.25516,382
5166.65.0.0/18166.65.0.1 to 166.65.63.254166.65.63.25516,382
6166.65.64.0/18166.65.64.1 to 166.65.127.254166.65.127.25516,382
7166.65.128.0/18166.65.128.1 to 166.65.191.254166.65.191.25516,382
8166.65.192.0/18166.65.192.1 to 166.65.255.254166.65.255.25516,382
9166.66.0.0/18166.66.0.1 to 166.66.63.254166.66.63.25516,382
10166.66.64.0/18166.66.64.1 to 166.66.127.254166.66.127.25516,382
11166.66.128.0/18166.66.128.1 to 166.66.191.254166.66.191.25516,382
12166.66.192.0/18166.66.192.1 to 166.66.255.254166.66.255.25516,382
13166.67.0.0/18166.67.0.1 to 166.67.63.254166.67.63.25516,382
14166.67.64.0/18166.67.64.1 to 166.67.127.254166.67.127.25516,382
15166.67.128.0/18166.67.128.1 to 166.67.191.254166.67.191.25516,382
16166.67.192.0/18166.67.192.1 to 166.67.255.254166.67.255.25516,382
17166.68.0.0/18166.68.0.1 to 166.68.63.254166.68.63.25516,382
18166.68.64.0/18166.68.64.1 to 166.68.127.254166.68.127.25516,382
19166.68.128.0/18166.68.128.1 to 166.68.191.254166.68.191.25516,382
20166.68.192.0/18166.68.192.1 to 166.68.255.254166.68.255.25516,382
21166.69.0.0/18166.69.0.1 to 166.69.63.254166.69.63.25516,382
22166.69.64.0/18166.69.64.1 to 166.69.127.254166.69.127.25516,382
23166.69.128.0/18166.69.128.1 to 166.69.191.254166.69.191.25516,382
24166.69.192.0/18166.69.192.1 to 166.69.255.254166.69.255.25516,382
25166.70.0.0/18166.70.0.1 to 166.70.63.254166.70.63.25516,382
26166.70.64.0/18166.70.64.1 to 166.70.127.254166.70.127.25516,382
27166.70.128.0/18166.70.128.1 to 166.70.191.254166.70.191.25516,382
28166.70.192.0/18166.70.192.1 to 166.70.255.254166.70.255.25516,382
29166.71.0.0/18166.71.0.1 to 166.71.63.254166.71.63.25516,382
30166.71.64.0/18166.71.64.1 to 166.71.127.254166.71.127.25516,382
31166.71.128.0/18166.71.128.1 to 166.71.191.254166.71.191.25516,382
32166.71.192.0/18166.71.192.1 to 166.71.255.254166.71.255.25516,382
33166.72.0.0/18166.72.0.1 to 166.72.63.254166.72.63.25516,382
34166.72.64.0/18166.72.64.1 to 166.72.127.254166.72.127.25516,382
35166.72.128.0/18166.72.128.1 to 166.72.191.254166.72.191.25516,382
36166.72.192.0/18166.72.192.1 to 166.72.255.254166.72.255.25516,382
37166.73.0.0/18166.73.0.1 to 166.73.63.254166.73.63.25516,382
38166.73.64.0/18166.73.64.1 to 166.73.127.254166.73.127.25516,382
39166.73.128.0/18166.73.128.1 to 166.73.191.254166.73.191.25516,382
40166.73.192.0/18166.73.192.1 to 166.73.255.254166.73.255.25516,382
41166.74.0.0/18166.74.0.1 to 166.74.63.254166.74.63.25516,382
42166.74.64.0/18166.74.64.1 to 166.74.127.254166.74.127.25516,382
43166.74.128.0/18166.74.128.1 to 166.74.191.254166.74.191.25516,382
44166.74.192.0/18166.74.192.1 to 166.74.255.254166.74.255.25516,382
45166.75.0.0/18166.75.0.1 to 166.75.63.254166.75.63.25516,382
46166.75.64.0/18166.75.64.1 to 166.75.127.254166.75.127.25516,382
47166.75.128.0/18166.75.128.1 to 166.75.191.254166.75.191.25516,382
48166.75.192.0/18166.75.192.1 to 166.75.255.254166.75.255.25516,382
49166.76.0.0/18166.76.0.1 to 166.76.63.254166.76.63.25516,382
50166.76.64.0/18166.76.64.1 to 166.76.127.254166.76.127.25516,382
51166.76.128.0/18166.76.128.1 to 166.76.191.254166.76.191.25516,382
52166.76.192.0/18166.76.192.1 to 166.76.255.254166.76.255.25516,382
53166.77.0.0/18166.77.0.1 to 166.77.63.254166.77.63.25516,382
54166.77.64.0/18166.77.64.1 to 166.77.127.254166.77.127.25516,382
55166.77.128.0/18166.77.128.1 to 166.77.191.254166.77.191.25516,382
56166.77.192.0/18166.77.192.1 to 166.77.255.254166.77.255.25516,382
57166.78.0.0/18166.78.0.1 to 166.78.63.254166.78.63.25516,382
58166.78.64.0/18166.78.64.1 to 166.78.127.254166.78.127.25516,382
59166.78.128.0/18166.78.128.1 to 166.78.191.254166.78.191.25516,382
60166.78.192.0/18166.78.192.1 to 166.78.255.254166.78.255.25516,382
61166.79.0.0/18166.79.0.1 to 166.79.63.254166.79.63.25516,382
62166.79.64.0/18166.79.64.1 to 166.79.127.254166.79.127.25516,382
63166.79.128.0/18166.79.128.1 to 166.79.191.254166.79.191.25516,382
64166.79.192.0/18166.79.192.1 to 166.79.255.254166.79.255.25516,382
65166.80.0.0/18166.80.0.1 to 166.80.63.254166.80.63.25516,382
66166.80.64.0/18166.80.64.1 to 166.80.127.254166.80.127.25516,382
67166.80.128.0/18166.80.128.1 to 166.80.191.254166.80.191.25516,382
68166.80.192.0/18166.80.192.1 to 166.80.255.254166.80.255.25516,382
69166.81.0.0/18166.81.0.1 to 166.81.63.254166.81.63.25516,382
70166.81.64.0/18166.81.64.1 to 166.81.127.254166.81.127.25516,382
71166.81.128.0/18166.81.128.1 to 166.81.191.254166.81.191.25516,382
72166.81.192.0/18166.81.192.1 to 166.81.255.254166.81.255.25516,382
73166.82.0.0/18166.82.0.1 to 166.82.63.254166.82.63.25516,382
74166.82.64.0/18166.82.64.1 to 166.82.127.254166.82.127.25516,382
75166.82.128.0/18166.82.128.1 to 166.82.191.254166.82.191.25516,382
76166.82.192.0/18166.82.192.1 to 166.82.255.254166.82.255.25516,382
77166.83.0.0/18166.83.0.1 to 166.83.63.254166.83.63.25516,382
78166.83.64.0/18166.83.64.1 to 166.83.127.254166.83.127.25516,382
79166.83.128.0/18166.83.128.1 to 166.83.191.254166.83.191.25516,382
80166.83.192.0/18166.83.192.1 to 166.83.255.254166.83.255.25516,382
81166.84.0.0/18166.84.0.1 to 166.84.63.254166.84.63.25516,382
82166.84.64.0/18166.84.64.1 to 166.84.127.254166.84.127.25516,382
83166.84.128.0/18166.84.128.1 to 166.84.191.254166.84.191.25516,382
84166.84.192.0/18166.84.192.1 to 166.84.255.254166.84.255.25516,382
85166.85.0.0/18166.85.0.1 to 166.85.63.254166.85.63.25516,382
86166.85.64.0/18166.85.64.1 to 166.85.127.254166.85.127.25516,382
87166.85.128.0/18166.85.128.1 to 166.85.191.254166.85.191.25516,382
88166.85.192.0/18166.85.192.1 to 166.85.255.254166.85.255.25516,382
89166.86.0.0/18166.86.0.1 to 166.86.63.254166.86.63.25516,382
90166.86.64.0/18166.86.64.1 to 166.86.127.254166.86.127.25516,382
91166.86.128.0/18166.86.128.1 to 166.86.191.254166.86.191.25516,382
92166.86.192.0/18166.86.192.1 to 166.86.255.254166.86.255.25516,382
93166.87.0.0/18166.87.0.1 to 166.87.63.254166.87.63.25516,382
94166.87.64.0/18166.87.64.1 to 166.87.127.254166.87.127.25516,382
95166.87.128.0/18166.87.128.1 to 166.87.191.254166.87.191.25516,382
96166.87.192.0/18166.87.192.1 to 166.87.255.254166.87.255.25516,382
97166.88.0.0/18166.88.0.1 to 166.88.63.254166.88.63.25516,382
98166.88.64.0/18166.88.64.1 to 166.88.127.254166.88.127.25516,382
99166.88.128.0/18166.88.128.1 to 166.88.191.254166.88.191.25516,382
100166.88.192.0/18166.88.192.1 to 166.88.255.254166.88.255.25516,382
101166.89.0.0/18166.89.0.1 to 166.89.63.254166.89.63.25516,382
102166.89.64.0/18166.89.64.1 to 166.89.127.254166.89.127.25516,382
103166.89.128.0/18166.89.128.1 to 166.89.191.254166.89.191.25516,382
104166.89.192.0/18166.89.192.1 to 166.89.255.254166.89.255.25516,382
105166.90.0.0/18166.90.0.1 to 166.90.63.254166.90.63.25516,382
106166.90.64.0/18166.90.64.1 to 166.90.127.254166.90.127.25516,382
107166.90.128.0/18166.90.128.1 to 166.90.191.254166.90.191.25516,382
108166.90.192.0/18166.90.192.1 to 166.90.255.254166.90.255.25516,382
109166.91.0.0/18166.91.0.1 to 166.91.63.254166.91.63.25516,382
110166.91.64.0/18166.91.64.1 to 166.91.127.254166.91.127.25516,382
111166.91.128.0/18166.91.128.1 to 166.91.191.254166.91.191.25516,382
112166.91.192.0/18166.91.192.1 to 166.91.255.254166.91.255.25516,382
113166.92.0.0/18166.92.0.1 to 166.92.63.254166.92.63.25516,382
114166.92.64.0/18166.92.64.1 to 166.92.127.254166.92.127.25516,382
115166.92.128.0/18166.92.128.1 to 166.92.191.254166.92.191.25516,382
116166.92.192.0/18166.92.192.1 to 166.92.255.254166.92.255.25516,382
117166.93.0.0/18166.93.0.1 to 166.93.63.254166.93.63.25516,382
118166.93.64.0/18166.93.64.1 to 166.93.127.254166.93.127.25516,382
119166.93.128.0/18166.93.128.1 to 166.93.191.254166.93.191.25516,382
120166.93.192.0/18166.93.192.1 to 166.93.255.254166.93.255.25516,382
121166.94.0.0/18166.94.0.1 to 166.94.63.254166.94.63.25516,382
122166.94.64.0/18166.94.64.1 to 166.94.127.254166.94.127.25516,382
123166.94.128.0/18166.94.128.1 to 166.94.191.254166.94.191.25516,382
124166.94.192.0/18166.94.192.1 to 166.94.255.254166.94.255.25516,382
125166.95.0.0/18166.95.0.1 to 166.95.63.254166.95.63.25516,382
126166.95.64.0/18166.95.64.1 to 166.95.127.254166.95.127.25516,382
127166.95.128.0/18166.95.128.1 to 166.95.191.254166.95.191.25516,382
128166.95.192.0/18166.95.192.1 to 166.95.255.254166.95.255.25516,382

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.