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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.

Network43.44.64.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
43.44.64.0
Broadcast address
43.44.127.255
First usable
43.44.64.1
Last usable
43.44.127.254
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 2B2C4000 · Integer 724320256 to 724336639
Reverse DNS zones
64.44.43.in-addr.arpa
65.44.43.in-addr.arpa
66.44.43.in-addr.arpa
67.44.43.in-addr.arpa
68.44.43.in-addr.arpa
69.44.43.in-addr.arpa
70.44.43.in-addr.arpa
71.44.43.in-addr.arpa
72.44.43.in-addr.arpa
73.44.43.in-addr.arpa
74.44.43.in-addr.arpa
75.44.43.in-addr.arpa
76.44.43.in-addr.arpa
77.44.43.in-addr.arpa
78.44.43.in-addr.arpa
79.44.43.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
Address00101011.00101100.01000000.0000000043.44.64.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network00101011.00101100.01000000.0000000043.44.64.0
Broadcast00101011.00101100.01111111.1111111143.44.127.255
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)

43.44.64.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
143.44.64.0/2543.44.64.1 to 43.44.64.12643.44.64.127126
243.44.64.128/2543.44.64.129 to 43.44.64.25443.44.64.255126
343.44.65.0/2543.44.65.1 to 43.44.65.12643.44.65.127126
443.44.65.128/2543.44.65.129 to 43.44.65.25443.44.65.255126
543.44.66.0/2543.44.66.1 to 43.44.66.12643.44.66.127126
643.44.66.128/2543.44.66.129 to 43.44.66.25443.44.66.255126
743.44.67.0/2543.44.67.1 to 43.44.67.12643.44.67.127126
843.44.67.128/2543.44.67.129 to 43.44.67.25443.44.67.255126
943.44.68.0/2543.44.68.1 to 43.44.68.12643.44.68.127126
1043.44.68.128/2543.44.68.129 to 43.44.68.25443.44.68.255126
1143.44.69.0/2543.44.69.1 to 43.44.69.12643.44.69.127126
1243.44.69.128/2543.44.69.129 to 43.44.69.25443.44.69.255126
1343.44.70.0/2543.44.70.1 to 43.44.70.12643.44.70.127126
1443.44.70.128/2543.44.70.129 to 43.44.70.25443.44.70.255126
1543.44.71.0/2543.44.71.1 to 43.44.71.12643.44.71.127126
1643.44.71.128/2543.44.71.129 to 43.44.71.25443.44.71.255126
1743.44.72.0/2543.44.72.1 to 43.44.72.12643.44.72.127126
1843.44.72.128/2543.44.72.129 to 43.44.72.25443.44.72.255126
1943.44.73.0/2543.44.73.1 to 43.44.73.12643.44.73.127126
2043.44.73.128/2543.44.73.129 to 43.44.73.25443.44.73.255126
2143.44.74.0/2543.44.74.1 to 43.44.74.12643.44.74.127126
2243.44.74.128/2543.44.74.129 to 43.44.74.25443.44.74.255126
2343.44.75.0/2543.44.75.1 to 43.44.75.12643.44.75.127126
2443.44.75.128/2543.44.75.129 to 43.44.75.25443.44.75.255126
2543.44.76.0/2543.44.76.1 to 43.44.76.12643.44.76.127126
2643.44.76.128/2543.44.76.129 to 43.44.76.25443.44.76.255126
2743.44.77.0/2543.44.77.1 to 43.44.77.12643.44.77.127126
2843.44.77.128/2543.44.77.129 to 43.44.77.25443.44.77.255126
2943.44.78.0/2543.44.78.1 to 43.44.78.12643.44.78.127126
3043.44.78.128/2543.44.78.129 to 43.44.78.25443.44.78.255126
3143.44.79.0/2543.44.79.1 to 43.44.79.12643.44.79.127126
3243.44.79.128/2543.44.79.129 to 43.44.79.25443.44.79.255126
3343.44.80.0/2543.44.80.1 to 43.44.80.12643.44.80.127126
3443.44.80.128/2543.44.80.129 to 43.44.80.25443.44.80.255126
3543.44.81.0/2543.44.81.1 to 43.44.81.12643.44.81.127126
3643.44.81.128/2543.44.81.129 to 43.44.81.25443.44.81.255126
3743.44.82.0/2543.44.82.1 to 43.44.82.12643.44.82.127126
3843.44.82.128/2543.44.82.129 to 43.44.82.25443.44.82.255126
3943.44.83.0/2543.44.83.1 to 43.44.83.12643.44.83.127126
4043.44.83.128/2543.44.83.129 to 43.44.83.25443.44.83.255126
4143.44.84.0/2543.44.84.1 to 43.44.84.12643.44.84.127126
4243.44.84.128/2543.44.84.129 to 43.44.84.25443.44.84.255126
4343.44.85.0/2543.44.85.1 to 43.44.85.12643.44.85.127126
4443.44.85.128/2543.44.85.129 to 43.44.85.25443.44.85.255126
4543.44.86.0/2543.44.86.1 to 43.44.86.12643.44.86.127126
4643.44.86.128/2543.44.86.129 to 43.44.86.25443.44.86.255126
4743.44.87.0/2543.44.87.1 to 43.44.87.12643.44.87.127126
4843.44.87.128/2543.44.87.129 to 43.44.87.25443.44.87.255126
4943.44.88.0/2543.44.88.1 to 43.44.88.12643.44.88.127126
5043.44.88.128/2543.44.88.129 to 43.44.88.25443.44.88.255126
5143.44.89.0/2543.44.89.1 to 43.44.89.12643.44.89.127126
5243.44.89.128/2543.44.89.129 to 43.44.89.25443.44.89.255126
5343.44.90.0/2543.44.90.1 to 43.44.90.12643.44.90.127126
5443.44.90.128/2543.44.90.129 to 43.44.90.25443.44.90.255126
5543.44.91.0/2543.44.91.1 to 43.44.91.12643.44.91.127126
5643.44.91.128/2543.44.91.129 to 43.44.91.25443.44.91.255126
5743.44.92.0/2543.44.92.1 to 43.44.92.12643.44.92.127126
5843.44.92.128/2543.44.92.129 to 43.44.92.25443.44.92.255126
5943.44.93.0/2543.44.93.1 to 43.44.93.12643.44.93.127126
6043.44.93.128/2543.44.93.129 to 43.44.93.25443.44.93.255126
6143.44.94.0/2543.44.94.1 to 43.44.94.12643.44.94.127126
6243.44.94.128/2543.44.94.129 to 43.44.94.25443.44.94.255126
6343.44.95.0/2543.44.95.1 to 43.44.95.12643.44.95.127126
6443.44.95.128/2543.44.95.129 to 43.44.95.25443.44.95.255126
6543.44.96.0/2543.44.96.1 to 43.44.96.12643.44.96.127126
6643.44.96.128/2543.44.96.129 to 43.44.96.25443.44.96.255126
6743.44.97.0/2543.44.97.1 to 43.44.97.12643.44.97.127126
6843.44.97.128/2543.44.97.129 to 43.44.97.25443.44.97.255126
6943.44.98.0/2543.44.98.1 to 43.44.98.12643.44.98.127126
7043.44.98.128/2543.44.98.129 to 43.44.98.25443.44.98.255126
7143.44.99.0/2543.44.99.1 to 43.44.99.12643.44.99.127126
7243.44.99.128/2543.44.99.129 to 43.44.99.25443.44.99.255126
7343.44.100.0/2543.44.100.1 to 43.44.100.12643.44.100.127126
7443.44.100.128/2543.44.100.129 to 43.44.100.25443.44.100.255126
7543.44.101.0/2543.44.101.1 to 43.44.101.12643.44.101.127126
7643.44.101.128/2543.44.101.129 to 43.44.101.25443.44.101.255126
7743.44.102.0/2543.44.102.1 to 43.44.102.12643.44.102.127126
7843.44.102.128/2543.44.102.129 to 43.44.102.25443.44.102.255126
7943.44.103.0/2543.44.103.1 to 43.44.103.12643.44.103.127126
8043.44.103.128/2543.44.103.129 to 43.44.103.25443.44.103.255126
8143.44.104.0/2543.44.104.1 to 43.44.104.12643.44.104.127126
8243.44.104.128/2543.44.104.129 to 43.44.104.25443.44.104.255126
8343.44.105.0/2543.44.105.1 to 43.44.105.12643.44.105.127126
8443.44.105.128/2543.44.105.129 to 43.44.105.25443.44.105.255126
8543.44.106.0/2543.44.106.1 to 43.44.106.12643.44.106.127126
8643.44.106.128/2543.44.106.129 to 43.44.106.25443.44.106.255126
8743.44.107.0/2543.44.107.1 to 43.44.107.12643.44.107.127126
8843.44.107.128/2543.44.107.129 to 43.44.107.25443.44.107.255126
8943.44.108.0/2543.44.108.1 to 43.44.108.12643.44.108.127126
9043.44.108.128/2543.44.108.129 to 43.44.108.25443.44.108.255126
9143.44.109.0/2543.44.109.1 to 43.44.109.12643.44.109.127126
9243.44.109.128/2543.44.109.129 to 43.44.109.25443.44.109.255126
9343.44.110.0/2543.44.110.1 to 43.44.110.12643.44.110.127126
9443.44.110.128/2543.44.110.129 to 43.44.110.25443.44.110.255126
9543.44.111.0/2543.44.111.1 to 43.44.111.12643.44.111.127126
9643.44.111.128/2543.44.111.129 to 43.44.111.25443.44.111.255126
9743.44.112.0/2543.44.112.1 to 43.44.112.12643.44.112.127126
9843.44.112.128/2543.44.112.129 to 43.44.112.25443.44.112.255126
9943.44.113.0/2543.44.113.1 to 43.44.113.12643.44.113.127126
10043.44.113.128/2543.44.113.129 to 43.44.113.25443.44.113.255126
10143.44.114.0/2543.44.114.1 to 43.44.114.12643.44.114.127126
10243.44.114.128/2543.44.114.129 to 43.44.114.25443.44.114.255126
10343.44.115.0/2543.44.115.1 to 43.44.115.12643.44.115.127126
10443.44.115.128/2543.44.115.129 to 43.44.115.25443.44.115.255126
10543.44.116.0/2543.44.116.1 to 43.44.116.12643.44.116.127126
10643.44.116.128/2543.44.116.129 to 43.44.116.25443.44.116.255126
10743.44.117.0/2543.44.117.1 to 43.44.117.12643.44.117.127126
10843.44.117.128/2543.44.117.129 to 43.44.117.25443.44.117.255126
10943.44.118.0/2543.44.118.1 to 43.44.118.12643.44.118.127126
11043.44.118.128/2543.44.118.129 to 43.44.118.25443.44.118.255126
11143.44.119.0/2543.44.119.1 to 43.44.119.12643.44.119.127126
11243.44.119.128/2543.44.119.129 to 43.44.119.25443.44.119.255126
11343.44.120.0/2543.44.120.1 to 43.44.120.12643.44.120.127126
11443.44.120.128/2543.44.120.129 to 43.44.120.25443.44.120.255126
11543.44.121.0/2543.44.121.1 to 43.44.121.12643.44.121.127126
11643.44.121.128/2543.44.121.129 to 43.44.121.25443.44.121.255126
11743.44.122.0/2543.44.122.1 to 43.44.122.12643.44.122.127126
11843.44.122.128/2543.44.122.129 to 43.44.122.25443.44.122.255126
11943.44.123.0/2543.44.123.1 to 43.44.123.12643.44.123.127126
12043.44.123.128/2543.44.123.129 to 43.44.123.25443.44.123.255126
12143.44.124.0/2543.44.124.1 to 43.44.124.12643.44.124.127126
12243.44.124.128/2543.44.124.129 to 43.44.124.25443.44.124.255126
12343.44.125.0/2543.44.125.1 to 43.44.125.12643.44.125.127126
12443.44.125.128/2543.44.125.129 to 43.44.125.25443.44.125.255126
12543.44.126.0/2543.44.126.1 to 43.44.126.12643.44.126.127126
12643.44.126.128/2543.44.126.129 to 43.44.126.25443.44.126.255126
12743.44.127.0/2543.44.127.1 to 43.44.127.12643.44.127.127126
12843.44.127.128/2543.44.127.129 to 43.44.127.25443.44.127.255126

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.