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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.

Network19.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
19.0.0.0
Broadcast address
19.255.255.255
First usable
19.0.0.1
Last usable
19.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
A (default /8)
As numbers
Hex 13000000 · Integer 318767104 to 335544319
Reverse DNS zone
19.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010011..00000000.00000000.0000000019.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network00010011..00000000.00000000.0000000019.0.0.0
Broadcast00010011..11111111.11111111.1111111119.255.255.255
Split into smaller subnets/15
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

19.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
119.0.0.0/1519.0.0.1 to 19.1.255.25419.1.255.255131,070
219.2.0.0/1519.2.0.1 to 19.3.255.25419.3.255.255131,070
319.4.0.0/1519.4.0.1 to 19.5.255.25419.5.255.255131,070
419.6.0.0/1519.6.0.1 to 19.7.255.25419.7.255.255131,070
519.8.0.0/1519.8.0.1 to 19.9.255.25419.9.255.255131,070
619.10.0.0/1519.10.0.1 to 19.11.255.25419.11.255.255131,070
719.12.0.0/1519.12.0.1 to 19.13.255.25419.13.255.255131,070
819.14.0.0/1519.14.0.1 to 19.15.255.25419.15.255.255131,070
919.16.0.0/1519.16.0.1 to 19.17.255.25419.17.255.255131,070
1019.18.0.0/1519.18.0.1 to 19.19.255.25419.19.255.255131,070
1119.20.0.0/1519.20.0.1 to 19.21.255.25419.21.255.255131,070
1219.22.0.0/1519.22.0.1 to 19.23.255.25419.23.255.255131,070
1319.24.0.0/1519.24.0.1 to 19.25.255.25419.25.255.255131,070
1419.26.0.0/1519.26.0.1 to 19.27.255.25419.27.255.255131,070
1519.28.0.0/1519.28.0.1 to 19.29.255.25419.29.255.255131,070
1619.30.0.0/1519.30.0.1 to 19.31.255.25419.31.255.255131,070
1719.32.0.0/1519.32.0.1 to 19.33.255.25419.33.255.255131,070
1819.34.0.0/1519.34.0.1 to 19.35.255.25419.35.255.255131,070
1919.36.0.0/1519.36.0.1 to 19.37.255.25419.37.255.255131,070
2019.38.0.0/1519.38.0.1 to 19.39.255.25419.39.255.255131,070
2119.40.0.0/1519.40.0.1 to 19.41.255.25419.41.255.255131,070
2219.42.0.0/1519.42.0.1 to 19.43.255.25419.43.255.255131,070
2319.44.0.0/1519.44.0.1 to 19.45.255.25419.45.255.255131,070
2419.46.0.0/1519.46.0.1 to 19.47.255.25419.47.255.255131,070
2519.48.0.0/1519.48.0.1 to 19.49.255.25419.49.255.255131,070
2619.50.0.0/1519.50.0.1 to 19.51.255.25419.51.255.255131,070
2719.52.0.0/1519.52.0.1 to 19.53.255.25419.53.255.255131,070
2819.54.0.0/1519.54.0.1 to 19.55.255.25419.55.255.255131,070
2919.56.0.0/1519.56.0.1 to 19.57.255.25419.57.255.255131,070
3019.58.0.0/1519.58.0.1 to 19.59.255.25419.59.255.255131,070
3119.60.0.0/1519.60.0.1 to 19.61.255.25419.61.255.255131,070
3219.62.0.0/1519.62.0.1 to 19.63.255.25419.63.255.255131,070
3319.64.0.0/1519.64.0.1 to 19.65.255.25419.65.255.255131,070
3419.66.0.0/1519.66.0.1 to 19.67.255.25419.67.255.255131,070
3519.68.0.0/1519.68.0.1 to 19.69.255.25419.69.255.255131,070
3619.70.0.0/1519.70.0.1 to 19.71.255.25419.71.255.255131,070
3719.72.0.0/1519.72.0.1 to 19.73.255.25419.73.255.255131,070
3819.74.0.0/1519.74.0.1 to 19.75.255.25419.75.255.255131,070
3919.76.0.0/1519.76.0.1 to 19.77.255.25419.77.255.255131,070
4019.78.0.0/1519.78.0.1 to 19.79.255.25419.79.255.255131,070
4119.80.0.0/1519.80.0.1 to 19.81.255.25419.81.255.255131,070
4219.82.0.0/1519.82.0.1 to 19.83.255.25419.83.255.255131,070
4319.84.0.0/1519.84.0.1 to 19.85.255.25419.85.255.255131,070
4419.86.0.0/1519.86.0.1 to 19.87.255.25419.87.255.255131,070
4519.88.0.0/1519.88.0.1 to 19.89.255.25419.89.255.255131,070
4619.90.0.0/1519.90.0.1 to 19.91.255.25419.91.255.255131,070
4719.92.0.0/1519.92.0.1 to 19.93.255.25419.93.255.255131,070
4819.94.0.0/1519.94.0.1 to 19.95.255.25419.95.255.255131,070
4919.96.0.0/1519.96.0.1 to 19.97.255.25419.97.255.255131,070
5019.98.0.0/1519.98.0.1 to 19.99.255.25419.99.255.255131,070
5119.100.0.0/1519.100.0.1 to 19.101.255.25419.101.255.255131,070
5219.102.0.0/1519.102.0.1 to 19.103.255.25419.103.255.255131,070
5319.104.0.0/1519.104.0.1 to 19.105.255.25419.105.255.255131,070
5419.106.0.0/1519.106.0.1 to 19.107.255.25419.107.255.255131,070
5519.108.0.0/1519.108.0.1 to 19.109.255.25419.109.255.255131,070
5619.110.0.0/1519.110.0.1 to 19.111.255.25419.111.255.255131,070
5719.112.0.0/1519.112.0.1 to 19.113.255.25419.113.255.255131,070
5819.114.0.0/1519.114.0.1 to 19.115.255.25419.115.255.255131,070
5919.116.0.0/1519.116.0.1 to 19.117.255.25419.117.255.255131,070
6019.118.0.0/1519.118.0.1 to 19.119.255.25419.119.255.255131,070
6119.120.0.0/1519.120.0.1 to 19.121.255.25419.121.255.255131,070
6219.122.0.0/1519.122.0.1 to 19.123.255.25419.123.255.255131,070
6319.124.0.0/1519.124.0.1 to 19.125.255.25419.125.255.255131,070
6419.126.0.0/1519.126.0.1 to 19.127.255.25419.127.255.255131,070
6519.128.0.0/1519.128.0.1 to 19.129.255.25419.129.255.255131,070
6619.130.0.0/1519.130.0.1 to 19.131.255.25419.131.255.255131,070
6719.132.0.0/1519.132.0.1 to 19.133.255.25419.133.255.255131,070
6819.134.0.0/1519.134.0.1 to 19.135.255.25419.135.255.255131,070
6919.136.0.0/1519.136.0.1 to 19.137.255.25419.137.255.255131,070
7019.138.0.0/1519.138.0.1 to 19.139.255.25419.139.255.255131,070
7119.140.0.0/1519.140.0.1 to 19.141.255.25419.141.255.255131,070
7219.142.0.0/1519.142.0.1 to 19.143.255.25419.143.255.255131,070
7319.144.0.0/1519.144.0.1 to 19.145.255.25419.145.255.255131,070
7419.146.0.0/1519.146.0.1 to 19.147.255.25419.147.255.255131,070
7519.148.0.0/1519.148.0.1 to 19.149.255.25419.149.255.255131,070
7619.150.0.0/1519.150.0.1 to 19.151.255.25419.151.255.255131,070
7719.152.0.0/1519.152.0.1 to 19.153.255.25419.153.255.255131,070
7819.154.0.0/1519.154.0.1 to 19.155.255.25419.155.255.255131,070
7919.156.0.0/1519.156.0.1 to 19.157.255.25419.157.255.255131,070
8019.158.0.0/1519.158.0.1 to 19.159.255.25419.159.255.255131,070
8119.160.0.0/1519.160.0.1 to 19.161.255.25419.161.255.255131,070
8219.162.0.0/1519.162.0.1 to 19.163.255.25419.163.255.255131,070
8319.164.0.0/1519.164.0.1 to 19.165.255.25419.165.255.255131,070
8419.166.0.0/1519.166.0.1 to 19.167.255.25419.167.255.255131,070
8519.168.0.0/1519.168.0.1 to 19.169.255.25419.169.255.255131,070
8619.170.0.0/1519.170.0.1 to 19.171.255.25419.171.255.255131,070
8719.172.0.0/1519.172.0.1 to 19.173.255.25419.173.255.255131,070
8819.174.0.0/1519.174.0.1 to 19.175.255.25419.175.255.255131,070
8919.176.0.0/1519.176.0.1 to 19.177.255.25419.177.255.255131,070
9019.178.0.0/1519.178.0.1 to 19.179.255.25419.179.255.255131,070
9119.180.0.0/1519.180.0.1 to 19.181.255.25419.181.255.255131,070
9219.182.0.0/1519.182.0.1 to 19.183.255.25419.183.255.255131,070
9319.184.0.0/1519.184.0.1 to 19.185.255.25419.185.255.255131,070
9419.186.0.0/1519.186.0.1 to 19.187.255.25419.187.255.255131,070
9519.188.0.0/1519.188.0.1 to 19.189.255.25419.189.255.255131,070
9619.190.0.0/1519.190.0.1 to 19.191.255.25419.191.255.255131,070
9719.192.0.0/1519.192.0.1 to 19.193.255.25419.193.255.255131,070
9819.194.0.0/1519.194.0.1 to 19.195.255.25419.195.255.255131,070
9919.196.0.0/1519.196.0.1 to 19.197.255.25419.197.255.255131,070
10019.198.0.0/1519.198.0.1 to 19.199.255.25419.199.255.255131,070
10119.200.0.0/1519.200.0.1 to 19.201.255.25419.201.255.255131,070
10219.202.0.0/1519.202.0.1 to 19.203.255.25419.203.255.255131,070
10319.204.0.0/1519.204.0.1 to 19.205.255.25419.205.255.255131,070
10419.206.0.0/1519.206.0.1 to 19.207.255.25419.207.255.255131,070
10519.208.0.0/1519.208.0.1 to 19.209.255.25419.209.255.255131,070
10619.210.0.0/1519.210.0.1 to 19.211.255.25419.211.255.255131,070
10719.212.0.0/1519.212.0.1 to 19.213.255.25419.213.255.255131,070
10819.214.0.0/1519.214.0.1 to 19.215.255.25419.215.255.255131,070
10919.216.0.0/1519.216.0.1 to 19.217.255.25419.217.255.255131,070
11019.218.0.0/1519.218.0.1 to 19.219.255.25419.219.255.255131,070
11119.220.0.0/1519.220.0.1 to 19.221.255.25419.221.255.255131,070
11219.222.0.0/1519.222.0.1 to 19.223.255.25419.223.255.255131,070
11319.224.0.0/1519.224.0.1 to 19.225.255.25419.225.255.255131,070
11419.226.0.0/1519.226.0.1 to 19.227.255.25419.227.255.255131,070
11519.228.0.0/1519.228.0.1 to 19.229.255.25419.229.255.255131,070
11619.230.0.0/1519.230.0.1 to 19.231.255.25419.231.255.255131,070
11719.232.0.0/1519.232.0.1 to 19.233.255.25419.233.255.255131,070
11819.234.0.0/1519.234.0.1 to 19.235.255.25419.235.255.255131,070
11919.236.0.0/1519.236.0.1 to 19.237.255.25419.237.255.255131,070
12019.238.0.0/1519.238.0.1 to 19.239.255.25419.239.255.255131,070
12119.240.0.0/1519.240.0.1 to 19.241.255.25419.241.255.255131,070
12219.242.0.0/1519.242.0.1 to 19.243.255.25419.243.255.255131,070
12319.244.0.0/1519.244.0.1 to 19.245.255.25419.245.255.255131,070
12419.246.0.0/1519.246.0.1 to 19.247.255.25419.247.255.255131,070
12519.248.0.0/1519.248.0.1 to 19.249.255.25419.249.255.255131,070
12619.250.0.0/1519.250.0.1 to 19.251.255.25419.251.255.255131,070
12719.252.0.0/1519.252.0.1 to 19.253.255.25419.253.255.255131,070
12819.254.0.0/1519.254.0.1 to 19.255.255.25419.255.255.255131,070

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.