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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.

Network12.2.64.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
12.2.64.0
Broadcast address
12.2.127.255
First usable
12.2.64.1
Last usable
12.2.127.254
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 0C024000 · Integer 201474048 to 201490431
Reverse DNS zones
64.2.12.in-addr.arpa
65.2.12.in-addr.arpa
66.2.12.in-addr.arpa
67.2.12.in-addr.arpa
68.2.12.in-addr.arpa
69.2.12.in-addr.arpa
70.2.12.in-addr.arpa
71.2.12.in-addr.arpa
72.2.12.in-addr.arpa
73.2.12.in-addr.arpa
74.2.12.in-addr.arpa
75.2.12.in-addr.arpa
76.2.12.in-addr.arpa
77.2.12.in-addr.arpa
78.2.12.in-addr.arpa
79.2.12.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
Address00001100.00000010.01000000.0000000012.2.64.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network00001100.00000010.01000000.0000000012.2.64.0
Broadcast00001100.00000010.01111111.1111111112.2.127.255
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)

12.2.64.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
112.2.64.0/2512.2.64.1 to 12.2.64.12612.2.64.127126
212.2.64.128/2512.2.64.129 to 12.2.64.25412.2.64.255126
312.2.65.0/2512.2.65.1 to 12.2.65.12612.2.65.127126
412.2.65.128/2512.2.65.129 to 12.2.65.25412.2.65.255126
512.2.66.0/2512.2.66.1 to 12.2.66.12612.2.66.127126
612.2.66.128/2512.2.66.129 to 12.2.66.25412.2.66.255126
712.2.67.0/2512.2.67.1 to 12.2.67.12612.2.67.127126
812.2.67.128/2512.2.67.129 to 12.2.67.25412.2.67.255126
912.2.68.0/2512.2.68.1 to 12.2.68.12612.2.68.127126
1012.2.68.128/2512.2.68.129 to 12.2.68.25412.2.68.255126
1112.2.69.0/2512.2.69.1 to 12.2.69.12612.2.69.127126
1212.2.69.128/2512.2.69.129 to 12.2.69.25412.2.69.255126
1312.2.70.0/2512.2.70.1 to 12.2.70.12612.2.70.127126
1412.2.70.128/2512.2.70.129 to 12.2.70.25412.2.70.255126
1512.2.71.0/2512.2.71.1 to 12.2.71.12612.2.71.127126
1612.2.71.128/2512.2.71.129 to 12.2.71.25412.2.71.255126
1712.2.72.0/2512.2.72.1 to 12.2.72.12612.2.72.127126
1812.2.72.128/2512.2.72.129 to 12.2.72.25412.2.72.255126
1912.2.73.0/2512.2.73.1 to 12.2.73.12612.2.73.127126
2012.2.73.128/2512.2.73.129 to 12.2.73.25412.2.73.255126
2112.2.74.0/2512.2.74.1 to 12.2.74.12612.2.74.127126
2212.2.74.128/2512.2.74.129 to 12.2.74.25412.2.74.255126
2312.2.75.0/2512.2.75.1 to 12.2.75.12612.2.75.127126
2412.2.75.128/2512.2.75.129 to 12.2.75.25412.2.75.255126
2512.2.76.0/2512.2.76.1 to 12.2.76.12612.2.76.127126
2612.2.76.128/2512.2.76.129 to 12.2.76.25412.2.76.255126
2712.2.77.0/2512.2.77.1 to 12.2.77.12612.2.77.127126
2812.2.77.128/2512.2.77.129 to 12.2.77.25412.2.77.255126
2912.2.78.0/2512.2.78.1 to 12.2.78.12612.2.78.127126
3012.2.78.128/2512.2.78.129 to 12.2.78.25412.2.78.255126
3112.2.79.0/2512.2.79.1 to 12.2.79.12612.2.79.127126
3212.2.79.128/2512.2.79.129 to 12.2.79.25412.2.79.255126
3312.2.80.0/2512.2.80.1 to 12.2.80.12612.2.80.127126
3412.2.80.128/2512.2.80.129 to 12.2.80.25412.2.80.255126
3512.2.81.0/2512.2.81.1 to 12.2.81.12612.2.81.127126
3612.2.81.128/2512.2.81.129 to 12.2.81.25412.2.81.255126
3712.2.82.0/2512.2.82.1 to 12.2.82.12612.2.82.127126
3812.2.82.128/2512.2.82.129 to 12.2.82.25412.2.82.255126
3912.2.83.0/2512.2.83.1 to 12.2.83.12612.2.83.127126
4012.2.83.128/2512.2.83.129 to 12.2.83.25412.2.83.255126
4112.2.84.0/2512.2.84.1 to 12.2.84.12612.2.84.127126
4212.2.84.128/2512.2.84.129 to 12.2.84.25412.2.84.255126
4312.2.85.0/2512.2.85.1 to 12.2.85.12612.2.85.127126
4412.2.85.128/2512.2.85.129 to 12.2.85.25412.2.85.255126
4512.2.86.0/2512.2.86.1 to 12.2.86.12612.2.86.127126
4612.2.86.128/2512.2.86.129 to 12.2.86.25412.2.86.255126
4712.2.87.0/2512.2.87.1 to 12.2.87.12612.2.87.127126
4812.2.87.128/2512.2.87.129 to 12.2.87.25412.2.87.255126
4912.2.88.0/2512.2.88.1 to 12.2.88.12612.2.88.127126
5012.2.88.128/2512.2.88.129 to 12.2.88.25412.2.88.255126
5112.2.89.0/2512.2.89.1 to 12.2.89.12612.2.89.127126
5212.2.89.128/2512.2.89.129 to 12.2.89.25412.2.89.255126
5312.2.90.0/2512.2.90.1 to 12.2.90.12612.2.90.127126
5412.2.90.128/2512.2.90.129 to 12.2.90.25412.2.90.255126
5512.2.91.0/2512.2.91.1 to 12.2.91.12612.2.91.127126
5612.2.91.128/2512.2.91.129 to 12.2.91.25412.2.91.255126
5712.2.92.0/2512.2.92.1 to 12.2.92.12612.2.92.127126
5812.2.92.128/2512.2.92.129 to 12.2.92.25412.2.92.255126
5912.2.93.0/2512.2.93.1 to 12.2.93.12612.2.93.127126
6012.2.93.128/2512.2.93.129 to 12.2.93.25412.2.93.255126
6112.2.94.0/2512.2.94.1 to 12.2.94.12612.2.94.127126
6212.2.94.128/2512.2.94.129 to 12.2.94.25412.2.94.255126
6312.2.95.0/2512.2.95.1 to 12.2.95.12612.2.95.127126
6412.2.95.128/2512.2.95.129 to 12.2.95.25412.2.95.255126
6512.2.96.0/2512.2.96.1 to 12.2.96.12612.2.96.127126
6612.2.96.128/2512.2.96.129 to 12.2.96.25412.2.96.255126
6712.2.97.0/2512.2.97.1 to 12.2.97.12612.2.97.127126
6812.2.97.128/2512.2.97.129 to 12.2.97.25412.2.97.255126
6912.2.98.0/2512.2.98.1 to 12.2.98.12612.2.98.127126
7012.2.98.128/2512.2.98.129 to 12.2.98.25412.2.98.255126
7112.2.99.0/2512.2.99.1 to 12.2.99.12612.2.99.127126
7212.2.99.128/2512.2.99.129 to 12.2.99.25412.2.99.255126
7312.2.100.0/2512.2.100.1 to 12.2.100.12612.2.100.127126
7412.2.100.128/2512.2.100.129 to 12.2.100.25412.2.100.255126
7512.2.101.0/2512.2.101.1 to 12.2.101.12612.2.101.127126
7612.2.101.128/2512.2.101.129 to 12.2.101.25412.2.101.255126
7712.2.102.0/2512.2.102.1 to 12.2.102.12612.2.102.127126
7812.2.102.128/2512.2.102.129 to 12.2.102.25412.2.102.255126
7912.2.103.0/2512.2.103.1 to 12.2.103.12612.2.103.127126
8012.2.103.128/2512.2.103.129 to 12.2.103.25412.2.103.255126
8112.2.104.0/2512.2.104.1 to 12.2.104.12612.2.104.127126
8212.2.104.128/2512.2.104.129 to 12.2.104.25412.2.104.255126
8312.2.105.0/2512.2.105.1 to 12.2.105.12612.2.105.127126
8412.2.105.128/2512.2.105.129 to 12.2.105.25412.2.105.255126
8512.2.106.0/2512.2.106.1 to 12.2.106.12612.2.106.127126
8612.2.106.128/2512.2.106.129 to 12.2.106.25412.2.106.255126
8712.2.107.0/2512.2.107.1 to 12.2.107.12612.2.107.127126
8812.2.107.128/2512.2.107.129 to 12.2.107.25412.2.107.255126
8912.2.108.0/2512.2.108.1 to 12.2.108.12612.2.108.127126
9012.2.108.128/2512.2.108.129 to 12.2.108.25412.2.108.255126
9112.2.109.0/2512.2.109.1 to 12.2.109.12612.2.109.127126
9212.2.109.128/2512.2.109.129 to 12.2.109.25412.2.109.255126
9312.2.110.0/2512.2.110.1 to 12.2.110.12612.2.110.127126
9412.2.110.128/2512.2.110.129 to 12.2.110.25412.2.110.255126
9512.2.111.0/2512.2.111.1 to 12.2.111.12612.2.111.127126
9612.2.111.128/2512.2.111.129 to 12.2.111.25412.2.111.255126
9712.2.112.0/2512.2.112.1 to 12.2.112.12612.2.112.127126
9812.2.112.128/2512.2.112.129 to 12.2.112.25412.2.112.255126
9912.2.113.0/2512.2.113.1 to 12.2.113.12612.2.113.127126
10012.2.113.128/2512.2.113.129 to 12.2.113.25412.2.113.255126
10112.2.114.0/2512.2.114.1 to 12.2.114.12612.2.114.127126
10212.2.114.128/2512.2.114.129 to 12.2.114.25412.2.114.255126
10312.2.115.0/2512.2.115.1 to 12.2.115.12612.2.115.127126
10412.2.115.128/2512.2.115.129 to 12.2.115.25412.2.115.255126
10512.2.116.0/2512.2.116.1 to 12.2.116.12612.2.116.127126
10612.2.116.128/2512.2.116.129 to 12.2.116.25412.2.116.255126
10712.2.117.0/2512.2.117.1 to 12.2.117.12612.2.117.127126
10812.2.117.128/2512.2.117.129 to 12.2.117.25412.2.117.255126
10912.2.118.0/2512.2.118.1 to 12.2.118.12612.2.118.127126
11012.2.118.128/2512.2.118.129 to 12.2.118.25412.2.118.255126
11112.2.119.0/2512.2.119.1 to 12.2.119.12612.2.119.127126
11212.2.119.128/2512.2.119.129 to 12.2.119.25412.2.119.255126
11312.2.120.0/2512.2.120.1 to 12.2.120.12612.2.120.127126
11412.2.120.128/2512.2.120.129 to 12.2.120.25412.2.120.255126
11512.2.121.0/2512.2.121.1 to 12.2.121.12612.2.121.127126
11612.2.121.128/2512.2.121.129 to 12.2.121.25412.2.121.255126
11712.2.122.0/2512.2.122.1 to 12.2.122.12612.2.122.127126
11812.2.122.128/2512.2.122.129 to 12.2.122.25412.2.122.255126
11912.2.123.0/2512.2.123.1 to 12.2.123.12612.2.123.127126
12012.2.123.128/2512.2.123.129 to 12.2.123.25412.2.123.255126
12112.2.124.0/2512.2.124.1 to 12.2.124.12612.2.124.127126
12212.2.124.128/2512.2.124.129 to 12.2.124.25412.2.124.255126
12312.2.125.0/2512.2.125.1 to 12.2.125.12612.2.125.127126
12412.2.125.128/2512.2.125.129 to 12.2.125.25412.2.125.255126
12512.2.126.0/2512.2.126.1 to 12.2.126.12612.2.126.127126
12612.2.126.128/2512.2.126.129 to 12.2.126.25412.2.126.255126
12712.2.127.0/2512.2.127.1 to 12.2.127.12612.2.127.127126
12812.2.127.128/2512.2.127.129 to 12.2.127.25412.2.127.255126

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.