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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.

Network126.3.192.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
126.3.192.0
Broadcast address
126.3.255.255
First usable
126.3.192.1
Last usable
126.3.255.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
A (default /8)
As numbers
Hex 7E03C000 · Integer 2114174976 to 2114191359
Reverse DNS zones
192.3.126.in-addr.arpa
193.3.126.in-addr.arpa
194.3.126.in-addr.arpa
195.3.126.in-addr.arpa
196.3.126.in-addr.arpa
197.3.126.in-addr.arpa
198.3.126.in-addr.arpa
199.3.126.in-addr.arpa
200.3.126.in-addr.arpa
201.3.126.in-addr.arpa
202.3.126.in-addr.arpa
203.3.126.in-addr.arpa
204.3.126.in-addr.arpa
205.3.126.in-addr.arpa
206.3.126.in-addr.arpa
207.3.126.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01111110.00000011.11000000.00000000126.3.192.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network01111110.00000011.11000000.00000000126.3.192.0
Broadcast01111110.00000011.11111111.11111111126.3.255.255
Split into smaller subnets/25
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

126.3.192.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1126.3.192.0/25126.3.192.1 to 126.3.192.126126.3.192.127126
2126.3.192.128/25126.3.192.129 to 126.3.192.254126.3.192.255126
3126.3.193.0/25126.3.193.1 to 126.3.193.126126.3.193.127126
4126.3.193.128/25126.3.193.129 to 126.3.193.254126.3.193.255126
5126.3.194.0/25126.3.194.1 to 126.3.194.126126.3.194.127126
6126.3.194.128/25126.3.194.129 to 126.3.194.254126.3.194.255126
7126.3.195.0/25126.3.195.1 to 126.3.195.126126.3.195.127126
8126.3.195.128/25126.3.195.129 to 126.3.195.254126.3.195.255126
9126.3.196.0/25126.3.196.1 to 126.3.196.126126.3.196.127126
10126.3.196.128/25126.3.196.129 to 126.3.196.254126.3.196.255126
11126.3.197.0/25126.3.197.1 to 126.3.197.126126.3.197.127126
12126.3.197.128/25126.3.197.129 to 126.3.197.254126.3.197.255126
13126.3.198.0/25126.3.198.1 to 126.3.198.126126.3.198.127126
14126.3.198.128/25126.3.198.129 to 126.3.198.254126.3.198.255126
15126.3.199.0/25126.3.199.1 to 126.3.199.126126.3.199.127126
16126.3.199.128/25126.3.199.129 to 126.3.199.254126.3.199.255126
17126.3.200.0/25126.3.200.1 to 126.3.200.126126.3.200.127126
18126.3.200.128/25126.3.200.129 to 126.3.200.254126.3.200.255126
19126.3.201.0/25126.3.201.1 to 126.3.201.126126.3.201.127126
20126.3.201.128/25126.3.201.129 to 126.3.201.254126.3.201.255126
21126.3.202.0/25126.3.202.1 to 126.3.202.126126.3.202.127126
22126.3.202.128/25126.3.202.129 to 126.3.202.254126.3.202.255126
23126.3.203.0/25126.3.203.1 to 126.3.203.126126.3.203.127126
24126.3.203.128/25126.3.203.129 to 126.3.203.254126.3.203.255126
25126.3.204.0/25126.3.204.1 to 126.3.204.126126.3.204.127126
26126.3.204.128/25126.3.204.129 to 126.3.204.254126.3.204.255126
27126.3.205.0/25126.3.205.1 to 126.3.205.126126.3.205.127126
28126.3.205.128/25126.3.205.129 to 126.3.205.254126.3.205.255126
29126.3.206.0/25126.3.206.1 to 126.3.206.126126.3.206.127126
30126.3.206.128/25126.3.206.129 to 126.3.206.254126.3.206.255126
31126.3.207.0/25126.3.207.1 to 126.3.207.126126.3.207.127126
32126.3.207.128/25126.3.207.129 to 126.3.207.254126.3.207.255126
33126.3.208.0/25126.3.208.1 to 126.3.208.126126.3.208.127126
34126.3.208.128/25126.3.208.129 to 126.3.208.254126.3.208.255126
35126.3.209.0/25126.3.209.1 to 126.3.209.126126.3.209.127126
36126.3.209.128/25126.3.209.129 to 126.3.209.254126.3.209.255126
37126.3.210.0/25126.3.210.1 to 126.3.210.126126.3.210.127126
38126.3.210.128/25126.3.210.129 to 126.3.210.254126.3.210.255126
39126.3.211.0/25126.3.211.1 to 126.3.211.126126.3.211.127126
40126.3.211.128/25126.3.211.129 to 126.3.211.254126.3.211.255126
41126.3.212.0/25126.3.212.1 to 126.3.212.126126.3.212.127126
42126.3.212.128/25126.3.212.129 to 126.3.212.254126.3.212.255126
43126.3.213.0/25126.3.213.1 to 126.3.213.126126.3.213.127126
44126.3.213.128/25126.3.213.129 to 126.3.213.254126.3.213.255126
45126.3.214.0/25126.3.214.1 to 126.3.214.126126.3.214.127126
46126.3.214.128/25126.3.214.129 to 126.3.214.254126.3.214.255126
47126.3.215.0/25126.3.215.1 to 126.3.215.126126.3.215.127126
48126.3.215.128/25126.3.215.129 to 126.3.215.254126.3.215.255126
49126.3.216.0/25126.3.216.1 to 126.3.216.126126.3.216.127126
50126.3.216.128/25126.3.216.129 to 126.3.216.254126.3.216.255126
51126.3.217.0/25126.3.217.1 to 126.3.217.126126.3.217.127126
52126.3.217.128/25126.3.217.129 to 126.3.217.254126.3.217.255126
53126.3.218.0/25126.3.218.1 to 126.3.218.126126.3.218.127126
54126.3.218.128/25126.3.218.129 to 126.3.218.254126.3.218.255126
55126.3.219.0/25126.3.219.1 to 126.3.219.126126.3.219.127126
56126.3.219.128/25126.3.219.129 to 126.3.219.254126.3.219.255126
57126.3.220.0/25126.3.220.1 to 126.3.220.126126.3.220.127126
58126.3.220.128/25126.3.220.129 to 126.3.220.254126.3.220.255126
59126.3.221.0/25126.3.221.1 to 126.3.221.126126.3.221.127126
60126.3.221.128/25126.3.221.129 to 126.3.221.254126.3.221.255126
61126.3.222.0/25126.3.222.1 to 126.3.222.126126.3.222.127126
62126.3.222.128/25126.3.222.129 to 126.3.222.254126.3.222.255126
63126.3.223.0/25126.3.223.1 to 126.3.223.126126.3.223.127126
64126.3.223.128/25126.3.223.129 to 126.3.223.254126.3.223.255126
65126.3.224.0/25126.3.224.1 to 126.3.224.126126.3.224.127126
66126.3.224.128/25126.3.224.129 to 126.3.224.254126.3.224.255126
67126.3.225.0/25126.3.225.1 to 126.3.225.126126.3.225.127126
68126.3.225.128/25126.3.225.129 to 126.3.225.254126.3.225.255126
69126.3.226.0/25126.3.226.1 to 126.3.226.126126.3.226.127126
70126.3.226.128/25126.3.226.129 to 126.3.226.254126.3.226.255126
71126.3.227.0/25126.3.227.1 to 126.3.227.126126.3.227.127126
72126.3.227.128/25126.3.227.129 to 126.3.227.254126.3.227.255126
73126.3.228.0/25126.3.228.1 to 126.3.228.126126.3.228.127126
74126.3.228.128/25126.3.228.129 to 126.3.228.254126.3.228.255126
75126.3.229.0/25126.3.229.1 to 126.3.229.126126.3.229.127126
76126.3.229.128/25126.3.229.129 to 126.3.229.254126.3.229.255126
77126.3.230.0/25126.3.230.1 to 126.3.230.126126.3.230.127126
78126.3.230.128/25126.3.230.129 to 126.3.230.254126.3.230.255126
79126.3.231.0/25126.3.231.1 to 126.3.231.126126.3.231.127126
80126.3.231.128/25126.3.231.129 to 126.3.231.254126.3.231.255126
81126.3.232.0/25126.3.232.1 to 126.3.232.126126.3.232.127126
82126.3.232.128/25126.3.232.129 to 126.3.232.254126.3.232.255126
83126.3.233.0/25126.3.233.1 to 126.3.233.126126.3.233.127126
84126.3.233.128/25126.3.233.129 to 126.3.233.254126.3.233.255126
85126.3.234.0/25126.3.234.1 to 126.3.234.126126.3.234.127126
86126.3.234.128/25126.3.234.129 to 126.3.234.254126.3.234.255126
87126.3.235.0/25126.3.235.1 to 126.3.235.126126.3.235.127126
88126.3.235.128/25126.3.235.129 to 126.3.235.254126.3.235.255126
89126.3.236.0/25126.3.236.1 to 126.3.236.126126.3.236.127126
90126.3.236.128/25126.3.236.129 to 126.3.236.254126.3.236.255126
91126.3.237.0/25126.3.237.1 to 126.3.237.126126.3.237.127126
92126.3.237.128/25126.3.237.129 to 126.3.237.254126.3.237.255126
93126.3.238.0/25126.3.238.1 to 126.3.238.126126.3.238.127126
94126.3.238.128/25126.3.238.129 to 126.3.238.254126.3.238.255126
95126.3.239.0/25126.3.239.1 to 126.3.239.126126.3.239.127126
96126.3.239.128/25126.3.239.129 to 126.3.239.254126.3.239.255126
97126.3.240.0/25126.3.240.1 to 126.3.240.126126.3.240.127126
98126.3.240.128/25126.3.240.129 to 126.3.240.254126.3.240.255126
99126.3.241.0/25126.3.241.1 to 126.3.241.126126.3.241.127126
100126.3.241.128/25126.3.241.129 to 126.3.241.254126.3.241.255126
101126.3.242.0/25126.3.242.1 to 126.3.242.126126.3.242.127126
102126.3.242.128/25126.3.242.129 to 126.3.242.254126.3.242.255126
103126.3.243.0/25126.3.243.1 to 126.3.243.126126.3.243.127126
104126.3.243.128/25126.3.243.129 to 126.3.243.254126.3.243.255126
105126.3.244.0/25126.3.244.1 to 126.3.244.126126.3.244.127126
106126.3.244.128/25126.3.244.129 to 126.3.244.254126.3.244.255126
107126.3.245.0/25126.3.245.1 to 126.3.245.126126.3.245.127126
108126.3.245.128/25126.3.245.129 to 126.3.245.254126.3.245.255126
109126.3.246.0/25126.3.246.1 to 126.3.246.126126.3.246.127126
110126.3.246.128/25126.3.246.129 to 126.3.246.254126.3.246.255126
111126.3.247.0/25126.3.247.1 to 126.3.247.126126.3.247.127126
112126.3.247.128/25126.3.247.129 to 126.3.247.254126.3.247.255126
113126.3.248.0/25126.3.248.1 to 126.3.248.126126.3.248.127126
114126.3.248.128/25126.3.248.129 to 126.3.248.254126.3.248.255126
115126.3.249.0/25126.3.249.1 to 126.3.249.126126.3.249.127126
116126.3.249.128/25126.3.249.129 to 126.3.249.254126.3.249.255126
117126.3.250.0/25126.3.250.1 to 126.3.250.126126.3.250.127126
118126.3.250.128/25126.3.250.129 to 126.3.250.254126.3.250.255126
119126.3.251.0/25126.3.251.1 to 126.3.251.126126.3.251.127126
120126.3.251.128/25126.3.251.129 to 126.3.251.254126.3.251.255126
121126.3.252.0/25126.3.252.1 to 126.3.252.126126.3.252.127126
122126.3.252.128/25126.3.252.129 to 126.3.252.254126.3.252.255126
123126.3.253.0/25126.3.253.1 to 126.3.253.126126.3.253.127126
124126.3.253.128/25126.3.253.129 to 126.3.253.254126.3.253.255126
125126.3.254.0/25126.3.254.1 to 126.3.254.126126.3.254.127126
126126.3.254.128/25126.3.254.129 to 126.3.254.254126.3.254.255126
127126.3.255.0/25126.3.255.1 to 126.3.255.126126.3.255.127126
128126.3.255.128/25126.3.255.129 to 126.3.255.254126.3.255.255126

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.