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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.

Network73.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
73.128.0.0
Broadcast address
73.255.255.255
First usable
73.128.0.1
Last usable
73.255.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 49800000 · Integer 1233125376 to 1241513983
Reverse DNS zones
128.73.in-addr.arpa
129.73.in-addr.arpa
130.73.in-addr.arpa
131.73.in-addr.arpa
132.73.in-addr.arpa
133.73.in-addr.arpa
134.73.in-addr.arpa
135.73.in-addr.arpa
136.73.in-addr.arpa
137.73.in-addr.arpa
138.73.in-addr.arpa
139.73.in-addr.arpa
140.73.in-addr.arpa
141.73.in-addr.arpa
142.73.in-addr.arpa
143.73.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01001001.10000000.00000000.0000000073.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network01001001.10000000.00000000.0000000073.128.0.0
Broadcast01001001.11111111.11111111.1111111173.255.255.255
Split into smaller subnets/16
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

73.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
173.128.0.0/1673.128.0.1 to 73.128.255.25473.128.255.25565,534
273.129.0.0/1673.129.0.1 to 73.129.255.25473.129.255.25565,534
373.130.0.0/1673.130.0.1 to 73.130.255.25473.130.255.25565,534
473.131.0.0/1673.131.0.1 to 73.131.255.25473.131.255.25565,534
573.132.0.0/1673.132.0.1 to 73.132.255.25473.132.255.25565,534
673.133.0.0/1673.133.0.1 to 73.133.255.25473.133.255.25565,534
773.134.0.0/1673.134.0.1 to 73.134.255.25473.134.255.25565,534
873.135.0.0/1673.135.0.1 to 73.135.255.25473.135.255.25565,534
973.136.0.0/1673.136.0.1 to 73.136.255.25473.136.255.25565,534
1073.137.0.0/1673.137.0.1 to 73.137.255.25473.137.255.25565,534
1173.138.0.0/1673.138.0.1 to 73.138.255.25473.138.255.25565,534
1273.139.0.0/1673.139.0.1 to 73.139.255.25473.139.255.25565,534
1373.140.0.0/1673.140.0.1 to 73.140.255.25473.140.255.25565,534
1473.141.0.0/1673.141.0.1 to 73.141.255.25473.141.255.25565,534
1573.142.0.0/1673.142.0.1 to 73.142.255.25473.142.255.25565,534
1673.143.0.0/1673.143.0.1 to 73.143.255.25473.143.255.25565,534
1773.144.0.0/1673.144.0.1 to 73.144.255.25473.144.255.25565,534
1873.145.0.0/1673.145.0.1 to 73.145.255.25473.145.255.25565,534
1973.146.0.0/1673.146.0.1 to 73.146.255.25473.146.255.25565,534
2073.147.0.0/1673.147.0.1 to 73.147.255.25473.147.255.25565,534
2173.148.0.0/1673.148.0.1 to 73.148.255.25473.148.255.25565,534
2273.149.0.0/1673.149.0.1 to 73.149.255.25473.149.255.25565,534
2373.150.0.0/1673.150.0.1 to 73.150.255.25473.150.255.25565,534
2473.151.0.0/1673.151.0.1 to 73.151.255.25473.151.255.25565,534
2573.152.0.0/1673.152.0.1 to 73.152.255.25473.152.255.25565,534
2673.153.0.0/1673.153.0.1 to 73.153.255.25473.153.255.25565,534
2773.154.0.0/1673.154.0.1 to 73.154.255.25473.154.255.25565,534
2873.155.0.0/1673.155.0.1 to 73.155.255.25473.155.255.25565,534
2973.156.0.0/1673.156.0.1 to 73.156.255.25473.156.255.25565,534
3073.157.0.0/1673.157.0.1 to 73.157.255.25473.157.255.25565,534
3173.158.0.0/1673.158.0.1 to 73.158.255.25473.158.255.25565,534
3273.159.0.0/1673.159.0.1 to 73.159.255.25473.159.255.25565,534
3373.160.0.0/1673.160.0.1 to 73.160.255.25473.160.255.25565,534
3473.161.0.0/1673.161.0.1 to 73.161.255.25473.161.255.25565,534
3573.162.0.0/1673.162.0.1 to 73.162.255.25473.162.255.25565,534
3673.163.0.0/1673.163.0.1 to 73.163.255.25473.163.255.25565,534
3773.164.0.0/1673.164.0.1 to 73.164.255.25473.164.255.25565,534
3873.165.0.0/1673.165.0.1 to 73.165.255.25473.165.255.25565,534
3973.166.0.0/1673.166.0.1 to 73.166.255.25473.166.255.25565,534
4073.167.0.0/1673.167.0.1 to 73.167.255.25473.167.255.25565,534
4173.168.0.0/1673.168.0.1 to 73.168.255.25473.168.255.25565,534
4273.169.0.0/1673.169.0.1 to 73.169.255.25473.169.255.25565,534
4373.170.0.0/1673.170.0.1 to 73.170.255.25473.170.255.25565,534
4473.171.0.0/1673.171.0.1 to 73.171.255.25473.171.255.25565,534
4573.172.0.0/1673.172.0.1 to 73.172.255.25473.172.255.25565,534
4673.173.0.0/1673.173.0.1 to 73.173.255.25473.173.255.25565,534
4773.174.0.0/1673.174.0.1 to 73.174.255.25473.174.255.25565,534
4873.175.0.0/1673.175.0.1 to 73.175.255.25473.175.255.25565,534
4973.176.0.0/1673.176.0.1 to 73.176.255.25473.176.255.25565,534
5073.177.0.0/1673.177.0.1 to 73.177.255.25473.177.255.25565,534
5173.178.0.0/1673.178.0.1 to 73.178.255.25473.178.255.25565,534
5273.179.0.0/1673.179.0.1 to 73.179.255.25473.179.255.25565,534
5373.180.0.0/1673.180.0.1 to 73.180.255.25473.180.255.25565,534
5473.181.0.0/1673.181.0.1 to 73.181.255.25473.181.255.25565,534
5573.182.0.0/1673.182.0.1 to 73.182.255.25473.182.255.25565,534
5673.183.0.0/1673.183.0.1 to 73.183.255.25473.183.255.25565,534
5773.184.0.0/1673.184.0.1 to 73.184.255.25473.184.255.25565,534
5873.185.0.0/1673.185.0.1 to 73.185.255.25473.185.255.25565,534
5973.186.0.0/1673.186.0.1 to 73.186.255.25473.186.255.25565,534
6073.187.0.0/1673.187.0.1 to 73.187.255.25473.187.255.25565,534
6173.188.0.0/1673.188.0.1 to 73.188.255.25473.188.255.25565,534
6273.189.0.0/1673.189.0.1 to 73.189.255.25473.189.255.25565,534
6373.190.0.0/1673.190.0.1 to 73.190.255.25473.190.255.25565,534
6473.191.0.0/1673.191.0.1 to 73.191.255.25473.191.255.25565,534
6573.192.0.0/1673.192.0.1 to 73.192.255.25473.192.255.25565,534
6673.193.0.0/1673.193.0.1 to 73.193.255.25473.193.255.25565,534
6773.194.0.0/1673.194.0.1 to 73.194.255.25473.194.255.25565,534
6873.195.0.0/1673.195.0.1 to 73.195.255.25473.195.255.25565,534
6973.196.0.0/1673.196.0.1 to 73.196.255.25473.196.255.25565,534
7073.197.0.0/1673.197.0.1 to 73.197.255.25473.197.255.25565,534
7173.198.0.0/1673.198.0.1 to 73.198.255.25473.198.255.25565,534
7273.199.0.0/1673.199.0.1 to 73.199.255.25473.199.255.25565,534
7373.200.0.0/1673.200.0.1 to 73.200.255.25473.200.255.25565,534
7473.201.0.0/1673.201.0.1 to 73.201.255.25473.201.255.25565,534
7573.202.0.0/1673.202.0.1 to 73.202.255.25473.202.255.25565,534
7673.203.0.0/1673.203.0.1 to 73.203.255.25473.203.255.25565,534
7773.204.0.0/1673.204.0.1 to 73.204.255.25473.204.255.25565,534
7873.205.0.0/1673.205.0.1 to 73.205.255.25473.205.255.25565,534
7973.206.0.0/1673.206.0.1 to 73.206.255.25473.206.255.25565,534
8073.207.0.0/1673.207.0.1 to 73.207.255.25473.207.255.25565,534
8173.208.0.0/1673.208.0.1 to 73.208.255.25473.208.255.25565,534
8273.209.0.0/1673.209.0.1 to 73.209.255.25473.209.255.25565,534
8373.210.0.0/1673.210.0.1 to 73.210.255.25473.210.255.25565,534
8473.211.0.0/1673.211.0.1 to 73.211.255.25473.211.255.25565,534
8573.212.0.0/1673.212.0.1 to 73.212.255.25473.212.255.25565,534
8673.213.0.0/1673.213.0.1 to 73.213.255.25473.213.255.25565,534
8773.214.0.0/1673.214.0.1 to 73.214.255.25473.214.255.25565,534
8873.215.0.0/1673.215.0.1 to 73.215.255.25473.215.255.25565,534
8973.216.0.0/1673.216.0.1 to 73.216.255.25473.216.255.25565,534
9073.217.0.0/1673.217.0.1 to 73.217.255.25473.217.255.25565,534
9173.218.0.0/1673.218.0.1 to 73.218.255.25473.218.255.25565,534
9273.219.0.0/1673.219.0.1 to 73.219.255.25473.219.255.25565,534
9373.220.0.0/1673.220.0.1 to 73.220.255.25473.220.255.25565,534
9473.221.0.0/1673.221.0.1 to 73.221.255.25473.221.255.25565,534
9573.222.0.0/1673.222.0.1 to 73.222.255.25473.222.255.25565,534
9673.223.0.0/1673.223.0.1 to 73.223.255.25473.223.255.25565,534
9773.224.0.0/1673.224.0.1 to 73.224.255.25473.224.255.25565,534
9873.225.0.0/1673.225.0.1 to 73.225.255.25473.225.255.25565,534
9973.226.0.0/1673.226.0.1 to 73.226.255.25473.226.255.25565,534
10073.227.0.0/1673.227.0.1 to 73.227.255.25473.227.255.25565,534
10173.228.0.0/1673.228.0.1 to 73.228.255.25473.228.255.25565,534
10273.229.0.0/1673.229.0.1 to 73.229.255.25473.229.255.25565,534
10373.230.0.0/1673.230.0.1 to 73.230.255.25473.230.255.25565,534
10473.231.0.0/1673.231.0.1 to 73.231.255.25473.231.255.25565,534
10573.232.0.0/1673.232.0.1 to 73.232.255.25473.232.255.25565,534
10673.233.0.0/1673.233.0.1 to 73.233.255.25473.233.255.25565,534
10773.234.0.0/1673.234.0.1 to 73.234.255.25473.234.255.25565,534
10873.235.0.0/1673.235.0.1 to 73.235.255.25473.235.255.25565,534
10973.236.0.0/1673.236.0.1 to 73.236.255.25473.236.255.25565,534
11073.237.0.0/1673.237.0.1 to 73.237.255.25473.237.255.25565,534
11173.238.0.0/1673.238.0.1 to 73.238.255.25473.238.255.25565,534
11273.239.0.0/1673.239.0.1 to 73.239.255.25473.239.255.25565,534
11373.240.0.0/1673.240.0.1 to 73.240.255.25473.240.255.25565,534
11473.241.0.0/1673.241.0.1 to 73.241.255.25473.241.255.25565,534
11573.242.0.0/1673.242.0.1 to 73.242.255.25473.242.255.25565,534
11673.243.0.0/1673.243.0.1 to 73.243.255.25473.243.255.25565,534
11773.244.0.0/1673.244.0.1 to 73.244.255.25473.244.255.25565,534
11873.245.0.0/1673.245.0.1 to 73.245.255.25473.245.255.25565,534
11973.246.0.0/1673.246.0.1 to 73.246.255.25473.246.255.25565,534
12073.247.0.0/1673.247.0.1 to 73.247.255.25473.247.255.25565,534
12173.248.0.0/1673.248.0.1 to 73.248.255.25473.248.255.25565,534
12273.249.0.0/1673.249.0.1 to 73.249.255.25473.249.255.25565,534
12373.250.0.0/1673.250.0.1 to 73.250.255.25473.250.255.25565,534
12473.251.0.0/1673.251.0.1 to 73.251.255.25473.251.255.25565,534
12573.252.0.0/1673.252.0.1 to 73.252.255.25473.252.255.25565,534
12673.253.0.0/1673.253.0.1 to 73.253.255.25473.253.255.25565,534
12773.254.0.0/1673.254.0.1 to 73.254.255.25473.254.255.25565,534
12873.255.0.0/1673.255.0.1 to 73.255.255.25473.255.255.25565,534

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.