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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.

Network19.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
19.128.0.0
Broadcast address
19.255.255.255
First usable
19.128.0.1
Last usable
19.255.255.254
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 13800000 · Integer 327155712 to 335544319
Reverse DNS zones
128.19.in-addr.arpa
129.19.in-addr.arpa
130.19.in-addr.arpa
131.19.in-addr.arpa
132.19.in-addr.arpa
133.19.in-addr.arpa
134.19.in-addr.arpa
135.19.in-addr.arpa
136.19.in-addr.arpa
137.19.in-addr.arpa
138.19.in-addr.arpa
139.19.in-addr.arpa
140.19.in-addr.arpa
141.19.in-addr.arpa
142.19.in-addr.arpa
143.19.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
Address00010011.10000000.00000000.0000000019.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00010011.10000000.00000000.0000000019.128.0.0
Broadcast00010011.11111111.11111111.1111111119.255.255.255
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)

19.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
119.128.0.0/1619.128.0.1 to 19.128.255.25419.128.255.25565,534
219.129.0.0/1619.129.0.1 to 19.129.255.25419.129.255.25565,534
319.130.0.0/1619.130.0.1 to 19.130.255.25419.130.255.25565,534
419.131.0.0/1619.131.0.1 to 19.131.255.25419.131.255.25565,534
519.132.0.0/1619.132.0.1 to 19.132.255.25419.132.255.25565,534
619.133.0.0/1619.133.0.1 to 19.133.255.25419.133.255.25565,534
719.134.0.0/1619.134.0.1 to 19.134.255.25419.134.255.25565,534
819.135.0.0/1619.135.0.1 to 19.135.255.25419.135.255.25565,534
919.136.0.0/1619.136.0.1 to 19.136.255.25419.136.255.25565,534
1019.137.0.0/1619.137.0.1 to 19.137.255.25419.137.255.25565,534
1119.138.0.0/1619.138.0.1 to 19.138.255.25419.138.255.25565,534
1219.139.0.0/1619.139.0.1 to 19.139.255.25419.139.255.25565,534
1319.140.0.0/1619.140.0.1 to 19.140.255.25419.140.255.25565,534
1419.141.0.0/1619.141.0.1 to 19.141.255.25419.141.255.25565,534
1519.142.0.0/1619.142.0.1 to 19.142.255.25419.142.255.25565,534
1619.143.0.0/1619.143.0.1 to 19.143.255.25419.143.255.25565,534
1719.144.0.0/1619.144.0.1 to 19.144.255.25419.144.255.25565,534
1819.145.0.0/1619.145.0.1 to 19.145.255.25419.145.255.25565,534
1919.146.0.0/1619.146.0.1 to 19.146.255.25419.146.255.25565,534
2019.147.0.0/1619.147.0.1 to 19.147.255.25419.147.255.25565,534
2119.148.0.0/1619.148.0.1 to 19.148.255.25419.148.255.25565,534
2219.149.0.0/1619.149.0.1 to 19.149.255.25419.149.255.25565,534
2319.150.0.0/1619.150.0.1 to 19.150.255.25419.150.255.25565,534
2419.151.0.0/1619.151.0.1 to 19.151.255.25419.151.255.25565,534
2519.152.0.0/1619.152.0.1 to 19.152.255.25419.152.255.25565,534
2619.153.0.0/1619.153.0.1 to 19.153.255.25419.153.255.25565,534
2719.154.0.0/1619.154.0.1 to 19.154.255.25419.154.255.25565,534
2819.155.0.0/1619.155.0.1 to 19.155.255.25419.155.255.25565,534
2919.156.0.0/1619.156.0.1 to 19.156.255.25419.156.255.25565,534
3019.157.0.0/1619.157.0.1 to 19.157.255.25419.157.255.25565,534
3119.158.0.0/1619.158.0.1 to 19.158.255.25419.158.255.25565,534
3219.159.0.0/1619.159.0.1 to 19.159.255.25419.159.255.25565,534
3319.160.0.0/1619.160.0.1 to 19.160.255.25419.160.255.25565,534
3419.161.0.0/1619.161.0.1 to 19.161.255.25419.161.255.25565,534
3519.162.0.0/1619.162.0.1 to 19.162.255.25419.162.255.25565,534
3619.163.0.0/1619.163.0.1 to 19.163.255.25419.163.255.25565,534
3719.164.0.0/1619.164.0.1 to 19.164.255.25419.164.255.25565,534
3819.165.0.0/1619.165.0.1 to 19.165.255.25419.165.255.25565,534
3919.166.0.0/1619.166.0.1 to 19.166.255.25419.166.255.25565,534
4019.167.0.0/1619.167.0.1 to 19.167.255.25419.167.255.25565,534
4119.168.0.0/1619.168.0.1 to 19.168.255.25419.168.255.25565,534
4219.169.0.0/1619.169.0.1 to 19.169.255.25419.169.255.25565,534
4319.170.0.0/1619.170.0.1 to 19.170.255.25419.170.255.25565,534
4419.171.0.0/1619.171.0.1 to 19.171.255.25419.171.255.25565,534
4519.172.0.0/1619.172.0.1 to 19.172.255.25419.172.255.25565,534
4619.173.0.0/1619.173.0.1 to 19.173.255.25419.173.255.25565,534
4719.174.0.0/1619.174.0.1 to 19.174.255.25419.174.255.25565,534
4819.175.0.0/1619.175.0.1 to 19.175.255.25419.175.255.25565,534
4919.176.0.0/1619.176.0.1 to 19.176.255.25419.176.255.25565,534
5019.177.0.0/1619.177.0.1 to 19.177.255.25419.177.255.25565,534
5119.178.0.0/1619.178.0.1 to 19.178.255.25419.178.255.25565,534
5219.179.0.0/1619.179.0.1 to 19.179.255.25419.179.255.25565,534
5319.180.0.0/1619.180.0.1 to 19.180.255.25419.180.255.25565,534
5419.181.0.0/1619.181.0.1 to 19.181.255.25419.181.255.25565,534
5519.182.0.0/1619.182.0.1 to 19.182.255.25419.182.255.25565,534
5619.183.0.0/1619.183.0.1 to 19.183.255.25419.183.255.25565,534
5719.184.0.0/1619.184.0.1 to 19.184.255.25419.184.255.25565,534
5819.185.0.0/1619.185.0.1 to 19.185.255.25419.185.255.25565,534
5919.186.0.0/1619.186.0.1 to 19.186.255.25419.186.255.25565,534
6019.187.0.0/1619.187.0.1 to 19.187.255.25419.187.255.25565,534
6119.188.0.0/1619.188.0.1 to 19.188.255.25419.188.255.25565,534
6219.189.0.0/1619.189.0.1 to 19.189.255.25419.189.255.25565,534
6319.190.0.0/1619.190.0.1 to 19.190.255.25419.190.255.25565,534
6419.191.0.0/1619.191.0.1 to 19.191.255.25419.191.255.25565,534
6519.192.0.0/1619.192.0.1 to 19.192.255.25419.192.255.25565,534
6619.193.0.0/1619.193.0.1 to 19.193.255.25419.193.255.25565,534
6719.194.0.0/1619.194.0.1 to 19.194.255.25419.194.255.25565,534
6819.195.0.0/1619.195.0.1 to 19.195.255.25419.195.255.25565,534
6919.196.0.0/1619.196.0.1 to 19.196.255.25419.196.255.25565,534
7019.197.0.0/1619.197.0.1 to 19.197.255.25419.197.255.25565,534
7119.198.0.0/1619.198.0.1 to 19.198.255.25419.198.255.25565,534
7219.199.0.0/1619.199.0.1 to 19.199.255.25419.199.255.25565,534
7319.200.0.0/1619.200.0.1 to 19.200.255.25419.200.255.25565,534
7419.201.0.0/1619.201.0.1 to 19.201.255.25419.201.255.25565,534
7519.202.0.0/1619.202.0.1 to 19.202.255.25419.202.255.25565,534
7619.203.0.0/1619.203.0.1 to 19.203.255.25419.203.255.25565,534
7719.204.0.0/1619.204.0.1 to 19.204.255.25419.204.255.25565,534
7819.205.0.0/1619.205.0.1 to 19.205.255.25419.205.255.25565,534
7919.206.0.0/1619.206.0.1 to 19.206.255.25419.206.255.25565,534
8019.207.0.0/1619.207.0.1 to 19.207.255.25419.207.255.25565,534
8119.208.0.0/1619.208.0.1 to 19.208.255.25419.208.255.25565,534
8219.209.0.0/1619.209.0.1 to 19.209.255.25419.209.255.25565,534
8319.210.0.0/1619.210.0.1 to 19.210.255.25419.210.255.25565,534
8419.211.0.0/1619.211.0.1 to 19.211.255.25419.211.255.25565,534
8519.212.0.0/1619.212.0.1 to 19.212.255.25419.212.255.25565,534
8619.213.0.0/1619.213.0.1 to 19.213.255.25419.213.255.25565,534
8719.214.0.0/1619.214.0.1 to 19.214.255.25419.214.255.25565,534
8819.215.0.0/1619.215.0.1 to 19.215.255.25419.215.255.25565,534
8919.216.0.0/1619.216.0.1 to 19.216.255.25419.216.255.25565,534
9019.217.0.0/1619.217.0.1 to 19.217.255.25419.217.255.25565,534
9119.218.0.0/1619.218.0.1 to 19.218.255.25419.218.255.25565,534
9219.219.0.0/1619.219.0.1 to 19.219.255.25419.219.255.25565,534
9319.220.0.0/1619.220.0.1 to 19.220.255.25419.220.255.25565,534
9419.221.0.0/1619.221.0.1 to 19.221.255.25419.221.255.25565,534
9519.222.0.0/1619.222.0.1 to 19.222.255.25419.222.255.25565,534
9619.223.0.0/1619.223.0.1 to 19.223.255.25419.223.255.25565,534
9719.224.0.0/1619.224.0.1 to 19.224.255.25419.224.255.25565,534
9819.225.0.0/1619.225.0.1 to 19.225.255.25419.225.255.25565,534
9919.226.0.0/1619.226.0.1 to 19.226.255.25419.226.255.25565,534
10019.227.0.0/1619.227.0.1 to 19.227.255.25419.227.255.25565,534
10119.228.0.0/1619.228.0.1 to 19.228.255.25419.228.255.25565,534
10219.229.0.0/1619.229.0.1 to 19.229.255.25419.229.255.25565,534
10319.230.0.0/1619.230.0.1 to 19.230.255.25419.230.255.25565,534
10419.231.0.0/1619.231.0.1 to 19.231.255.25419.231.255.25565,534
10519.232.0.0/1619.232.0.1 to 19.232.255.25419.232.255.25565,534
10619.233.0.0/1619.233.0.1 to 19.233.255.25419.233.255.25565,534
10719.234.0.0/1619.234.0.1 to 19.234.255.25419.234.255.25565,534
10819.235.0.0/1619.235.0.1 to 19.235.255.25419.235.255.25565,534
10919.236.0.0/1619.236.0.1 to 19.236.255.25419.236.255.25565,534
11019.237.0.0/1619.237.0.1 to 19.237.255.25419.237.255.25565,534
11119.238.0.0/1619.238.0.1 to 19.238.255.25419.238.255.25565,534
11219.239.0.0/1619.239.0.1 to 19.239.255.25419.239.255.25565,534
11319.240.0.0/1619.240.0.1 to 19.240.255.25419.240.255.25565,534
11419.241.0.0/1619.241.0.1 to 19.241.255.25419.241.255.25565,534
11519.242.0.0/1619.242.0.1 to 19.242.255.25419.242.255.25565,534
11619.243.0.0/1619.243.0.1 to 19.243.255.25419.243.255.25565,534
11719.244.0.0/1619.244.0.1 to 19.244.255.25419.244.255.25565,534
11819.245.0.0/1619.245.0.1 to 19.245.255.25419.245.255.25565,534
11919.246.0.0/1619.246.0.1 to 19.246.255.25419.246.255.25565,534
12019.247.0.0/1619.247.0.1 to 19.247.255.25419.247.255.25565,534
12119.248.0.0/1619.248.0.1 to 19.248.255.25419.248.255.25565,534
12219.249.0.0/1619.249.0.1 to 19.249.255.25419.249.255.25565,534
12319.250.0.0/1619.250.0.1 to 19.250.255.25419.250.255.25565,534
12419.251.0.0/1619.251.0.1 to 19.251.255.25419.251.255.25565,534
12519.252.0.0/1619.252.0.1 to 19.252.255.25419.252.255.25565,534
12619.253.0.0/1619.253.0.1 to 19.253.255.25419.253.255.25565,534
12719.254.0.0/1619.254.0.1 to 19.254.255.25419.254.255.25565,534
12819.255.0.0/1619.255.0.1 to 19.255.255.25419.255.255.25565,534

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.