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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.

Network43.80.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
43.80.0.0
Broadcast address
43.81.255.255
First usable
43.80.0.1
Last usable
43.81.255.254
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
A (default /8)
As numbers
Hex 2B500000 · Integer 726663168 to 726794239
Reverse DNS zones
80.43.in-addr.arpa
81.43.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
Address00101011.01010000.00000000.0000000043.80.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network00101011.01010000.00000000.0000000043.80.0.0
Broadcast00101011.01010001.11111111.1111111143.81.255.255
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)

43.80.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
143.80.0.0/2243.80.0.1 to 43.80.3.25443.80.3.2551,022
243.80.4.0/2243.80.4.1 to 43.80.7.25443.80.7.2551,022
343.80.8.0/2243.80.8.1 to 43.80.11.25443.80.11.2551,022
443.80.12.0/2243.80.12.1 to 43.80.15.25443.80.15.2551,022
543.80.16.0/2243.80.16.1 to 43.80.19.25443.80.19.2551,022
643.80.20.0/2243.80.20.1 to 43.80.23.25443.80.23.2551,022
743.80.24.0/2243.80.24.1 to 43.80.27.25443.80.27.2551,022
843.80.28.0/2243.80.28.1 to 43.80.31.25443.80.31.2551,022
943.80.32.0/2243.80.32.1 to 43.80.35.25443.80.35.2551,022
1043.80.36.0/2243.80.36.1 to 43.80.39.25443.80.39.2551,022
1143.80.40.0/2243.80.40.1 to 43.80.43.25443.80.43.2551,022
1243.80.44.0/2243.80.44.1 to 43.80.47.25443.80.47.2551,022
1343.80.48.0/2243.80.48.1 to 43.80.51.25443.80.51.2551,022
1443.80.52.0/2243.80.52.1 to 43.80.55.25443.80.55.2551,022
1543.80.56.0/2243.80.56.1 to 43.80.59.25443.80.59.2551,022
1643.80.60.0/2243.80.60.1 to 43.80.63.25443.80.63.2551,022
1743.80.64.0/2243.80.64.1 to 43.80.67.25443.80.67.2551,022
1843.80.68.0/2243.80.68.1 to 43.80.71.25443.80.71.2551,022
1943.80.72.0/2243.80.72.1 to 43.80.75.25443.80.75.2551,022
2043.80.76.0/2243.80.76.1 to 43.80.79.25443.80.79.2551,022
2143.80.80.0/2243.80.80.1 to 43.80.83.25443.80.83.2551,022
2243.80.84.0/2243.80.84.1 to 43.80.87.25443.80.87.2551,022
2343.80.88.0/2243.80.88.1 to 43.80.91.25443.80.91.2551,022
2443.80.92.0/2243.80.92.1 to 43.80.95.25443.80.95.2551,022
2543.80.96.0/2243.80.96.1 to 43.80.99.25443.80.99.2551,022
2643.80.100.0/2243.80.100.1 to 43.80.103.25443.80.103.2551,022
2743.80.104.0/2243.80.104.1 to 43.80.107.25443.80.107.2551,022
2843.80.108.0/2243.80.108.1 to 43.80.111.25443.80.111.2551,022
2943.80.112.0/2243.80.112.1 to 43.80.115.25443.80.115.2551,022
3043.80.116.0/2243.80.116.1 to 43.80.119.25443.80.119.2551,022
3143.80.120.0/2243.80.120.1 to 43.80.123.25443.80.123.2551,022
3243.80.124.0/2243.80.124.1 to 43.80.127.25443.80.127.2551,022
3343.80.128.0/2243.80.128.1 to 43.80.131.25443.80.131.2551,022
3443.80.132.0/2243.80.132.1 to 43.80.135.25443.80.135.2551,022
3543.80.136.0/2243.80.136.1 to 43.80.139.25443.80.139.2551,022
3643.80.140.0/2243.80.140.1 to 43.80.143.25443.80.143.2551,022
3743.80.144.0/2243.80.144.1 to 43.80.147.25443.80.147.2551,022
3843.80.148.0/2243.80.148.1 to 43.80.151.25443.80.151.2551,022
3943.80.152.0/2243.80.152.1 to 43.80.155.25443.80.155.2551,022
4043.80.156.0/2243.80.156.1 to 43.80.159.25443.80.159.2551,022
4143.80.160.0/2243.80.160.1 to 43.80.163.25443.80.163.2551,022
4243.80.164.0/2243.80.164.1 to 43.80.167.25443.80.167.2551,022
4343.80.168.0/2243.80.168.1 to 43.80.171.25443.80.171.2551,022
4443.80.172.0/2243.80.172.1 to 43.80.175.25443.80.175.2551,022
4543.80.176.0/2243.80.176.1 to 43.80.179.25443.80.179.2551,022
4643.80.180.0/2243.80.180.1 to 43.80.183.25443.80.183.2551,022
4743.80.184.0/2243.80.184.1 to 43.80.187.25443.80.187.2551,022
4843.80.188.0/2243.80.188.1 to 43.80.191.25443.80.191.2551,022
4943.80.192.0/2243.80.192.1 to 43.80.195.25443.80.195.2551,022
5043.80.196.0/2243.80.196.1 to 43.80.199.25443.80.199.2551,022
5143.80.200.0/2243.80.200.1 to 43.80.203.25443.80.203.2551,022
5243.80.204.0/2243.80.204.1 to 43.80.207.25443.80.207.2551,022
5343.80.208.0/2243.80.208.1 to 43.80.211.25443.80.211.2551,022
5443.80.212.0/2243.80.212.1 to 43.80.215.25443.80.215.2551,022
5543.80.216.0/2243.80.216.1 to 43.80.219.25443.80.219.2551,022
5643.80.220.0/2243.80.220.1 to 43.80.223.25443.80.223.2551,022
5743.80.224.0/2243.80.224.1 to 43.80.227.25443.80.227.2551,022
5843.80.228.0/2243.80.228.1 to 43.80.231.25443.80.231.2551,022
5943.80.232.0/2243.80.232.1 to 43.80.235.25443.80.235.2551,022
6043.80.236.0/2243.80.236.1 to 43.80.239.25443.80.239.2551,022
6143.80.240.0/2243.80.240.1 to 43.80.243.25443.80.243.2551,022
6243.80.244.0/2243.80.244.1 to 43.80.247.25443.80.247.2551,022
6343.80.248.0/2243.80.248.1 to 43.80.251.25443.80.251.2551,022
6443.80.252.0/2243.80.252.1 to 43.80.255.25443.80.255.2551,022
6543.81.0.0/2243.81.0.1 to 43.81.3.25443.81.3.2551,022
6643.81.4.0/2243.81.4.1 to 43.81.7.25443.81.7.2551,022
6743.81.8.0/2243.81.8.1 to 43.81.11.25443.81.11.2551,022
6843.81.12.0/2243.81.12.1 to 43.81.15.25443.81.15.2551,022
6943.81.16.0/2243.81.16.1 to 43.81.19.25443.81.19.2551,022
7043.81.20.0/2243.81.20.1 to 43.81.23.25443.81.23.2551,022
7143.81.24.0/2243.81.24.1 to 43.81.27.25443.81.27.2551,022
7243.81.28.0/2243.81.28.1 to 43.81.31.25443.81.31.2551,022
7343.81.32.0/2243.81.32.1 to 43.81.35.25443.81.35.2551,022
7443.81.36.0/2243.81.36.1 to 43.81.39.25443.81.39.2551,022
7543.81.40.0/2243.81.40.1 to 43.81.43.25443.81.43.2551,022
7643.81.44.0/2243.81.44.1 to 43.81.47.25443.81.47.2551,022
7743.81.48.0/2243.81.48.1 to 43.81.51.25443.81.51.2551,022
7843.81.52.0/2243.81.52.1 to 43.81.55.25443.81.55.2551,022
7943.81.56.0/2243.81.56.1 to 43.81.59.25443.81.59.2551,022
8043.81.60.0/2243.81.60.1 to 43.81.63.25443.81.63.2551,022
8143.81.64.0/2243.81.64.1 to 43.81.67.25443.81.67.2551,022
8243.81.68.0/2243.81.68.1 to 43.81.71.25443.81.71.2551,022
8343.81.72.0/2243.81.72.1 to 43.81.75.25443.81.75.2551,022
8443.81.76.0/2243.81.76.1 to 43.81.79.25443.81.79.2551,022
8543.81.80.0/2243.81.80.1 to 43.81.83.25443.81.83.2551,022
8643.81.84.0/2243.81.84.1 to 43.81.87.25443.81.87.2551,022
8743.81.88.0/2243.81.88.1 to 43.81.91.25443.81.91.2551,022
8843.81.92.0/2243.81.92.1 to 43.81.95.25443.81.95.2551,022
8943.81.96.0/2243.81.96.1 to 43.81.99.25443.81.99.2551,022
9043.81.100.0/2243.81.100.1 to 43.81.103.25443.81.103.2551,022
9143.81.104.0/2243.81.104.1 to 43.81.107.25443.81.107.2551,022
9243.81.108.0/2243.81.108.1 to 43.81.111.25443.81.111.2551,022
9343.81.112.0/2243.81.112.1 to 43.81.115.25443.81.115.2551,022
9443.81.116.0/2243.81.116.1 to 43.81.119.25443.81.119.2551,022
9543.81.120.0/2243.81.120.1 to 43.81.123.25443.81.123.2551,022
9643.81.124.0/2243.81.124.1 to 43.81.127.25443.81.127.2551,022
9743.81.128.0/2243.81.128.1 to 43.81.131.25443.81.131.2551,022
9843.81.132.0/2243.81.132.1 to 43.81.135.25443.81.135.2551,022
9943.81.136.0/2243.81.136.1 to 43.81.139.25443.81.139.2551,022
10043.81.140.0/2243.81.140.1 to 43.81.143.25443.81.143.2551,022
10143.81.144.0/2243.81.144.1 to 43.81.147.25443.81.147.2551,022
10243.81.148.0/2243.81.148.1 to 43.81.151.25443.81.151.2551,022
10343.81.152.0/2243.81.152.1 to 43.81.155.25443.81.155.2551,022
10443.81.156.0/2243.81.156.1 to 43.81.159.25443.81.159.2551,022
10543.81.160.0/2243.81.160.1 to 43.81.163.25443.81.163.2551,022
10643.81.164.0/2243.81.164.1 to 43.81.167.25443.81.167.2551,022
10743.81.168.0/2243.81.168.1 to 43.81.171.25443.81.171.2551,022
10843.81.172.0/2243.81.172.1 to 43.81.175.25443.81.175.2551,022
10943.81.176.0/2243.81.176.1 to 43.81.179.25443.81.179.2551,022
11043.81.180.0/2243.81.180.1 to 43.81.183.25443.81.183.2551,022
11143.81.184.0/2243.81.184.1 to 43.81.187.25443.81.187.2551,022
11243.81.188.0/2243.81.188.1 to 43.81.191.25443.81.191.2551,022
11343.81.192.0/2243.81.192.1 to 43.81.195.25443.81.195.2551,022
11443.81.196.0/2243.81.196.1 to 43.81.199.25443.81.199.2551,022
11543.81.200.0/2243.81.200.1 to 43.81.203.25443.81.203.2551,022
11643.81.204.0/2243.81.204.1 to 43.81.207.25443.81.207.2551,022
11743.81.208.0/2243.81.208.1 to 43.81.211.25443.81.211.2551,022
11843.81.212.0/2243.81.212.1 to 43.81.215.25443.81.215.2551,022
11943.81.216.0/2243.81.216.1 to 43.81.219.25443.81.219.2551,022
12043.81.220.0/2243.81.220.1 to 43.81.223.25443.81.223.2551,022
12143.81.224.0/2243.81.224.1 to 43.81.227.25443.81.227.2551,022
12243.81.228.0/2243.81.228.1 to 43.81.231.25443.81.231.2551,022
12343.81.232.0/2243.81.232.1 to 43.81.235.25443.81.235.2551,022
12443.81.236.0/2243.81.236.1 to 43.81.239.25443.81.239.2551,022
12543.81.240.0/2243.81.240.1 to 43.81.243.25443.81.243.2551,022
12643.81.244.0/2243.81.244.1 to 43.81.247.25443.81.247.2551,022
12743.81.248.0/2243.81.248.1 to 43.81.251.25443.81.251.2551,022
12843.81.252.0/2243.81.252.1 to 43.81.255.25443.81.255.2551,022

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.