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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.

Network203.166.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
203.166.0.0
Broadcast address
203.167.255.255
First usable
203.166.0.1
Last usable
203.167.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
C (default /24)
As numbers
Hex CBA60000 · Integer 3416653824 to 3416784895
Reverse DNS zones
166.203.in-addr.arpa
167.203.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001011.10100110.00000000.00000000203.166.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network11001011.10100110.00000000.00000000203.166.0.0
Broadcast11001011.10100111.11111111.11111111203.167.255.255
Split into smaller subnets/22
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

203.166.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1203.166.0.0/22203.166.0.1 to 203.166.3.254203.166.3.2551,022
2203.166.4.0/22203.166.4.1 to 203.166.7.254203.166.7.2551,022
3203.166.8.0/22203.166.8.1 to 203.166.11.254203.166.11.2551,022
4203.166.12.0/22203.166.12.1 to 203.166.15.254203.166.15.2551,022
5203.166.16.0/22203.166.16.1 to 203.166.19.254203.166.19.2551,022
6203.166.20.0/22203.166.20.1 to 203.166.23.254203.166.23.2551,022
7203.166.24.0/22203.166.24.1 to 203.166.27.254203.166.27.2551,022
8203.166.28.0/22203.166.28.1 to 203.166.31.254203.166.31.2551,022
9203.166.32.0/22203.166.32.1 to 203.166.35.254203.166.35.2551,022
10203.166.36.0/22203.166.36.1 to 203.166.39.254203.166.39.2551,022
11203.166.40.0/22203.166.40.1 to 203.166.43.254203.166.43.2551,022
12203.166.44.0/22203.166.44.1 to 203.166.47.254203.166.47.2551,022
13203.166.48.0/22203.166.48.1 to 203.166.51.254203.166.51.2551,022
14203.166.52.0/22203.166.52.1 to 203.166.55.254203.166.55.2551,022
15203.166.56.0/22203.166.56.1 to 203.166.59.254203.166.59.2551,022
16203.166.60.0/22203.166.60.1 to 203.166.63.254203.166.63.2551,022
17203.166.64.0/22203.166.64.1 to 203.166.67.254203.166.67.2551,022
18203.166.68.0/22203.166.68.1 to 203.166.71.254203.166.71.2551,022
19203.166.72.0/22203.166.72.1 to 203.166.75.254203.166.75.2551,022
20203.166.76.0/22203.166.76.1 to 203.166.79.254203.166.79.2551,022
21203.166.80.0/22203.166.80.1 to 203.166.83.254203.166.83.2551,022
22203.166.84.0/22203.166.84.1 to 203.166.87.254203.166.87.2551,022
23203.166.88.0/22203.166.88.1 to 203.166.91.254203.166.91.2551,022
24203.166.92.0/22203.166.92.1 to 203.166.95.254203.166.95.2551,022
25203.166.96.0/22203.166.96.1 to 203.166.99.254203.166.99.2551,022
26203.166.100.0/22203.166.100.1 to 203.166.103.254203.166.103.2551,022
27203.166.104.0/22203.166.104.1 to 203.166.107.254203.166.107.2551,022
28203.166.108.0/22203.166.108.1 to 203.166.111.254203.166.111.2551,022
29203.166.112.0/22203.166.112.1 to 203.166.115.254203.166.115.2551,022
30203.166.116.0/22203.166.116.1 to 203.166.119.254203.166.119.2551,022
31203.166.120.0/22203.166.120.1 to 203.166.123.254203.166.123.2551,022
32203.166.124.0/22203.166.124.1 to 203.166.127.254203.166.127.2551,022
33203.166.128.0/22203.166.128.1 to 203.166.131.254203.166.131.2551,022
34203.166.132.0/22203.166.132.1 to 203.166.135.254203.166.135.2551,022
35203.166.136.0/22203.166.136.1 to 203.166.139.254203.166.139.2551,022
36203.166.140.0/22203.166.140.1 to 203.166.143.254203.166.143.2551,022
37203.166.144.0/22203.166.144.1 to 203.166.147.254203.166.147.2551,022
38203.166.148.0/22203.166.148.1 to 203.166.151.254203.166.151.2551,022
39203.166.152.0/22203.166.152.1 to 203.166.155.254203.166.155.2551,022
40203.166.156.0/22203.166.156.1 to 203.166.159.254203.166.159.2551,022
41203.166.160.0/22203.166.160.1 to 203.166.163.254203.166.163.2551,022
42203.166.164.0/22203.166.164.1 to 203.166.167.254203.166.167.2551,022
43203.166.168.0/22203.166.168.1 to 203.166.171.254203.166.171.2551,022
44203.166.172.0/22203.166.172.1 to 203.166.175.254203.166.175.2551,022
45203.166.176.0/22203.166.176.1 to 203.166.179.254203.166.179.2551,022
46203.166.180.0/22203.166.180.1 to 203.166.183.254203.166.183.2551,022
47203.166.184.0/22203.166.184.1 to 203.166.187.254203.166.187.2551,022
48203.166.188.0/22203.166.188.1 to 203.166.191.254203.166.191.2551,022
49203.166.192.0/22203.166.192.1 to 203.166.195.254203.166.195.2551,022
50203.166.196.0/22203.166.196.1 to 203.166.199.254203.166.199.2551,022
51203.166.200.0/22203.166.200.1 to 203.166.203.254203.166.203.2551,022
52203.166.204.0/22203.166.204.1 to 203.166.207.254203.166.207.2551,022
53203.166.208.0/22203.166.208.1 to 203.166.211.254203.166.211.2551,022
54203.166.212.0/22203.166.212.1 to 203.166.215.254203.166.215.2551,022
55203.166.216.0/22203.166.216.1 to 203.166.219.254203.166.219.2551,022
56203.166.220.0/22203.166.220.1 to 203.166.223.254203.166.223.2551,022
57203.166.224.0/22203.166.224.1 to 203.166.227.254203.166.227.2551,022
58203.166.228.0/22203.166.228.1 to 203.166.231.254203.166.231.2551,022
59203.166.232.0/22203.166.232.1 to 203.166.235.254203.166.235.2551,022
60203.166.236.0/22203.166.236.1 to 203.166.239.254203.166.239.2551,022
61203.166.240.0/22203.166.240.1 to 203.166.243.254203.166.243.2551,022
62203.166.244.0/22203.166.244.1 to 203.166.247.254203.166.247.2551,022
63203.166.248.0/22203.166.248.1 to 203.166.251.254203.166.251.2551,022
64203.166.252.0/22203.166.252.1 to 203.166.255.254203.166.255.2551,022
65203.167.0.0/22203.167.0.1 to 203.167.3.254203.167.3.2551,022
66203.167.4.0/22203.167.4.1 to 203.167.7.254203.167.7.2551,022
67203.167.8.0/22203.167.8.1 to 203.167.11.254203.167.11.2551,022
68203.167.12.0/22203.167.12.1 to 203.167.15.254203.167.15.2551,022
69203.167.16.0/22203.167.16.1 to 203.167.19.254203.167.19.2551,022
70203.167.20.0/22203.167.20.1 to 203.167.23.254203.167.23.2551,022
71203.167.24.0/22203.167.24.1 to 203.167.27.254203.167.27.2551,022
72203.167.28.0/22203.167.28.1 to 203.167.31.254203.167.31.2551,022
73203.167.32.0/22203.167.32.1 to 203.167.35.254203.167.35.2551,022
74203.167.36.0/22203.167.36.1 to 203.167.39.254203.167.39.2551,022
75203.167.40.0/22203.167.40.1 to 203.167.43.254203.167.43.2551,022
76203.167.44.0/22203.167.44.1 to 203.167.47.254203.167.47.2551,022
77203.167.48.0/22203.167.48.1 to 203.167.51.254203.167.51.2551,022
78203.167.52.0/22203.167.52.1 to 203.167.55.254203.167.55.2551,022
79203.167.56.0/22203.167.56.1 to 203.167.59.254203.167.59.2551,022
80203.167.60.0/22203.167.60.1 to 203.167.63.254203.167.63.2551,022
81203.167.64.0/22203.167.64.1 to 203.167.67.254203.167.67.2551,022
82203.167.68.0/22203.167.68.1 to 203.167.71.254203.167.71.2551,022
83203.167.72.0/22203.167.72.1 to 203.167.75.254203.167.75.2551,022
84203.167.76.0/22203.167.76.1 to 203.167.79.254203.167.79.2551,022
85203.167.80.0/22203.167.80.1 to 203.167.83.254203.167.83.2551,022
86203.167.84.0/22203.167.84.1 to 203.167.87.254203.167.87.2551,022
87203.167.88.0/22203.167.88.1 to 203.167.91.254203.167.91.2551,022
88203.167.92.0/22203.167.92.1 to 203.167.95.254203.167.95.2551,022
89203.167.96.0/22203.167.96.1 to 203.167.99.254203.167.99.2551,022
90203.167.100.0/22203.167.100.1 to 203.167.103.254203.167.103.2551,022
91203.167.104.0/22203.167.104.1 to 203.167.107.254203.167.107.2551,022
92203.167.108.0/22203.167.108.1 to 203.167.111.254203.167.111.2551,022
93203.167.112.0/22203.167.112.1 to 203.167.115.254203.167.115.2551,022
94203.167.116.0/22203.167.116.1 to 203.167.119.254203.167.119.2551,022
95203.167.120.0/22203.167.120.1 to 203.167.123.254203.167.123.2551,022
96203.167.124.0/22203.167.124.1 to 203.167.127.254203.167.127.2551,022
97203.167.128.0/22203.167.128.1 to 203.167.131.254203.167.131.2551,022
98203.167.132.0/22203.167.132.1 to 203.167.135.254203.167.135.2551,022
99203.167.136.0/22203.167.136.1 to 203.167.139.254203.167.139.2551,022
100203.167.140.0/22203.167.140.1 to 203.167.143.254203.167.143.2551,022
101203.167.144.0/22203.167.144.1 to 203.167.147.254203.167.147.2551,022
102203.167.148.0/22203.167.148.1 to 203.167.151.254203.167.151.2551,022
103203.167.152.0/22203.167.152.1 to 203.167.155.254203.167.155.2551,022
104203.167.156.0/22203.167.156.1 to 203.167.159.254203.167.159.2551,022
105203.167.160.0/22203.167.160.1 to 203.167.163.254203.167.163.2551,022
106203.167.164.0/22203.167.164.1 to 203.167.167.254203.167.167.2551,022
107203.167.168.0/22203.167.168.1 to 203.167.171.254203.167.171.2551,022
108203.167.172.0/22203.167.172.1 to 203.167.175.254203.167.175.2551,022
109203.167.176.0/22203.167.176.1 to 203.167.179.254203.167.179.2551,022
110203.167.180.0/22203.167.180.1 to 203.167.183.254203.167.183.2551,022
111203.167.184.0/22203.167.184.1 to 203.167.187.254203.167.187.2551,022
112203.167.188.0/22203.167.188.1 to 203.167.191.254203.167.191.2551,022
113203.167.192.0/22203.167.192.1 to 203.167.195.254203.167.195.2551,022
114203.167.196.0/22203.167.196.1 to 203.167.199.254203.167.199.2551,022
115203.167.200.0/22203.167.200.1 to 203.167.203.254203.167.203.2551,022
116203.167.204.0/22203.167.204.1 to 203.167.207.254203.167.207.2551,022
117203.167.208.0/22203.167.208.1 to 203.167.211.254203.167.211.2551,022
118203.167.212.0/22203.167.212.1 to 203.167.215.254203.167.215.2551,022
119203.167.216.0/22203.167.216.1 to 203.167.219.254203.167.219.2551,022
120203.167.220.0/22203.167.220.1 to 203.167.223.254203.167.223.2551,022
121203.167.224.0/22203.167.224.1 to 203.167.227.254203.167.227.2551,022
122203.167.228.0/22203.167.228.1 to 203.167.231.254203.167.231.2551,022
123203.167.232.0/22203.167.232.1 to 203.167.235.254203.167.235.2551,022
124203.167.236.0/22203.167.236.1 to 203.167.239.254203.167.239.2551,022
125203.167.240.0/22203.167.240.1 to 203.167.243.254203.167.243.2551,022
126203.167.244.0/22203.167.244.1 to 203.167.247.254203.167.247.2551,022
127203.167.248.0/22203.167.248.1 to 203.167.251.254203.167.251.2551,022
128203.167.252.0/22203.167.252.1 to 203.167.255.254203.167.255.2551,022

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.