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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.

Network7.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
7.128.0.0
Broadcast address
7.255.255.255
First usable
7.128.0.1
Last usable
7.255.255.254
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 07800000 · Integer 125829120 to 134217727
Reverse DNS zones
128.7.in-addr.arpa
129.7.in-addr.arpa
130.7.in-addr.arpa
131.7.in-addr.arpa
132.7.in-addr.arpa
133.7.in-addr.arpa
134.7.in-addr.arpa
135.7.in-addr.arpa
136.7.in-addr.arpa
137.7.in-addr.arpa
138.7.in-addr.arpa
139.7.in-addr.arpa
140.7.in-addr.arpa
141.7.in-addr.arpa
142.7.in-addr.arpa
143.7.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
Address00000111.10000000.00000000.000000007.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00000111.10000000.00000000.000000007.128.0.0
Broadcast00000111.11111111.11111111.111111117.255.255.255
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)

7.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
17.128.0.0/167.128.0.1 to 7.128.255.2547.128.255.25565,534
27.129.0.0/167.129.0.1 to 7.129.255.2547.129.255.25565,534
37.130.0.0/167.130.0.1 to 7.130.255.2547.130.255.25565,534
47.131.0.0/167.131.0.1 to 7.131.255.2547.131.255.25565,534
57.132.0.0/167.132.0.1 to 7.132.255.2547.132.255.25565,534
67.133.0.0/167.133.0.1 to 7.133.255.2547.133.255.25565,534
77.134.0.0/167.134.0.1 to 7.134.255.2547.134.255.25565,534
87.135.0.0/167.135.0.1 to 7.135.255.2547.135.255.25565,534
97.136.0.0/167.136.0.1 to 7.136.255.2547.136.255.25565,534
107.137.0.0/167.137.0.1 to 7.137.255.2547.137.255.25565,534
117.138.0.0/167.138.0.1 to 7.138.255.2547.138.255.25565,534
127.139.0.0/167.139.0.1 to 7.139.255.2547.139.255.25565,534
137.140.0.0/167.140.0.1 to 7.140.255.2547.140.255.25565,534
147.141.0.0/167.141.0.1 to 7.141.255.2547.141.255.25565,534
157.142.0.0/167.142.0.1 to 7.142.255.2547.142.255.25565,534
167.143.0.0/167.143.0.1 to 7.143.255.2547.143.255.25565,534
177.144.0.0/167.144.0.1 to 7.144.255.2547.144.255.25565,534
187.145.0.0/167.145.0.1 to 7.145.255.2547.145.255.25565,534
197.146.0.0/167.146.0.1 to 7.146.255.2547.146.255.25565,534
207.147.0.0/167.147.0.1 to 7.147.255.2547.147.255.25565,534
217.148.0.0/167.148.0.1 to 7.148.255.2547.148.255.25565,534
227.149.0.0/167.149.0.1 to 7.149.255.2547.149.255.25565,534
237.150.0.0/167.150.0.1 to 7.150.255.2547.150.255.25565,534
247.151.0.0/167.151.0.1 to 7.151.255.2547.151.255.25565,534
257.152.0.0/167.152.0.1 to 7.152.255.2547.152.255.25565,534
267.153.0.0/167.153.0.1 to 7.153.255.2547.153.255.25565,534
277.154.0.0/167.154.0.1 to 7.154.255.2547.154.255.25565,534
287.155.0.0/167.155.0.1 to 7.155.255.2547.155.255.25565,534
297.156.0.0/167.156.0.1 to 7.156.255.2547.156.255.25565,534
307.157.0.0/167.157.0.1 to 7.157.255.2547.157.255.25565,534
317.158.0.0/167.158.0.1 to 7.158.255.2547.158.255.25565,534
327.159.0.0/167.159.0.1 to 7.159.255.2547.159.255.25565,534
337.160.0.0/167.160.0.1 to 7.160.255.2547.160.255.25565,534
347.161.0.0/167.161.0.1 to 7.161.255.2547.161.255.25565,534
357.162.0.0/167.162.0.1 to 7.162.255.2547.162.255.25565,534
367.163.0.0/167.163.0.1 to 7.163.255.2547.163.255.25565,534
377.164.0.0/167.164.0.1 to 7.164.255.2547.164.255.25565,534
387.165.0.0/167.165.0.1 to 7.165.255.2547.165.255.25565,534
397.166.0.0/167.166.0.1 to 7.166.255.2547.166.255.25565,534
407.167.0.0/167.167.0.1 to 7.167.255.2547.167.255.25565,534
417.168.0.0/167.168.0.1 to 7.168.255.2547.168.255.25565,534
427.169.0.0/167.169.0.1 to 7.169.255.2547.169.255.25565,534
437.170.0.0/167.170.0.1 to 7.170.255.2547.170.255.25565,534
447.171.0.0/167.171.0.1 to 7.171.255.2547.171.255.25565,534
457.172.0.0/167.172.0.1 to 7.172.255.2547.172.255.25565,534
467.173.0.0/167.173.0.1 to 7.173.255.2547.173.255.25565,534
477.174.0.0/167.174.0.1 to 7.174.255.2547.174.255.25565,534
487.175.0.0/167.175.0.1 to 7.175.255.2547.175.255.25565,534
497.176.0.0/167.176.0.1 to 7.176.255.2547.176.255.25565,534
507.177.0.0/167.177.0.1 to 7.177.255.2547.177.255.25565,534
517.178.0.0/167.178.0.1 to 7.178.255.2547.178.255.25565,534
527.179.0.0/167.179.0.1 to 7.179.255.2547.179.255.25565,534
537.180.0.0/167.180.0.1 to 7.180.255.2547.180.255.25565,534
547.181.0.0/167.181.0.1 to 7.181.255.2547.181.255.25565,534
557.182.0.0/167.182.0.1 to 7.182.255.2547.182.255.25565,534
567.183.0.0/167.183.0.1 to 7.183.255.2547.183.255.25565,534
577.184.0.0/167.184.0.1 to 7.184.255.2547.184.255.25565,534
587.185.0.0/167.185.0.1 to 7.185.255.2547.185.255.25565,534
597.186.0.0/167.186.0.1 to 7.186.255.2547.186.255.25565,534
607.187.0.0/167.187.0.1 to 7.187.255.2547.187.255.25565,534
617.188.0.0/167.188.0.1 to 7.188.255.2547.188.255.25565,534
627.189.0.0/167.189.0.1 to 7.189.255.2547.189.255.25565,534
637.190.0.0/167.190.0.1 to 7.190.255.2547.190.255.25565,534
647.191.0.0/167.191.0.1 to 7.191.255.2547.191.255.25565,534
657.192.0.0/167.192.0.1 to 7.192.255.2547.192.255.25565,534
667.193.0.0/167.193.0.1 to 7.193.255.2547.193.255.25565,534
677.194.0.0/167.194.0.1 to 7.194.255.2547.194.255.25565,534
687.195.0.0/167.195.0.1 to 7.195.255.2547.195.255.25565,534
697.196.0.0/167.196.0.1 to 7.196.255.2547.196.255.25565,534
707.197.0.0/167.197.0.1 to 7.197.255.2547.197.255.25565,534
717.198.0.0/167.198.0.1 to 7.198.255.2547.198.255.25565,534
727.199.0.0/167.199.0.1 to 7.199.255.2547.199.255.25565,534
737.200.0.0/167.200.0.1 to 7.200.255.2547.200.255.25565,534
747.201.0.0/167.201.0.1 to 7.201.255.2547.201.255.25565,534
757.202.0.0/167.202.0.1 to 7.202.255.2547.202.255.25565,534
767.203.0.0/167.203.0.1 to 7.203.255.2547.203.255.25565,534
777.204.0.0/167.204.0.1 to 7.204.255.2547.204.255.25565,534
787.205.0.0/167.205.0.1 to 7.205.255.2547.205.255.25565,534
797.206.0.0/167.206.0.1 to 7.206.255.2547.206.255.25565,534
807.207.0.0/167.207.0.1 to 7.207.255.2547.207.255.25565,534
817.208.0.0/167.208.0.1 to 7.208.255.2547.208.255.25565,534
827.209.0.0/167.209.0.1 to 7.209.255.2547.209.255.25565,534
837.210.0.0/167.210.0.1 to 7.210.255.2547.210.255.25565,534
847.211.0.0/167.211.0.1 to 7.211.255.2547.211.255.25565,534
857.212.0.0/167.212.0.1 to 7.212.255.2547.212.255.25565,534
867.213.0.0/167.213.0.1 to 7.213.255.2547.213.255.25565,534
877.214.0.0/167.214.0.1 to 7.214.255.2547.214.255.25565,534
887.215.0.0/167.215.0.1 to 7.215.255.2547.215.255.25565,534
897.216.0.0/167.216.0.1 to 7.216.255.2547.216.255.25565,534
907.217.0.0/167.217.0.1 to 7.217.255.2547.217.255.25565,534
917.218.0.0/167.218.0.1 to 7.218.255.2547.218.255.25565,534
927.219.0.0/167.219.0.1 to 7.219.255.2547.219.255.25565,534
937.220.0.0/167.220.0.1 to 7.220.255.2547.220.255.25565,534
947.221.0.0/167.221.0.1 to 7.221.255.2547.221.255.25565,534
957.222.0.0/167.222.0.1 to 7.222.255.2547.222.255.25565,534
967.223.0.0/167.223.0.1 to 7.223.255.2547.223.255.25565,534
977.224.0.0/167.224.0.1 to 7.224.255.2547.224.255.25565,534
987.225.0.0/167.225.0.1 to 7.225.255.2547.225.255.25565,534
997.226.0.0/167.226.0.1 to 7.226.255.2547.226.255.25565,534
1007.227.0.0/167.227.0.1 to 7.227.255.2547.227.255.25565,534
1017.228.0.0/167.228.0.1 to 7.228.255.2547.228.255.25565,534
1027.229.0.0/167.229.0.1 to 7.229.255.2547.229.255.25565,534
1037.230.0.0/167.230.0.1 to 7.230.255.2547.230.255.25565,534
1047.231.0.0/167.231.0.1 to 7.231.255.2547.231.255.25565,534
1057.232.0.0/167.232.0.1 to 7.232.255.2547.232.255.25565,534
1067.233.0.0/167.233.0.1 to 7.233.255.2547.233.255.25565,534
1077.234.0.0/167.234.0.1 to 7.234.255.2547.234.255.25565,534
1087.235.0.0/167.235.0.1 to 7.235.255.2547.235.255.25565,534
1097.236.0.0/167.236.0.1 to 7.236.255.2547.236.255.25565,534
1107.237.0.0/167.237.0.1 to 7.237.255.2547.237.255.25565,534
1117.238.0.0/167.238.0.1 to 7.238.255.2547.238.255.25565,534
1127.239.0.0/167.239.0.1 to 7.239.255.2547.239.255.25565,534
1137.240.0.0/167.240.0.1 to 7.240.255.2547.240.255.25565,534
1147.241.0.0/167.241.0.1 to 7.241.255.2547.241.255.25565,534
1157.242.0.0/167.242.0.1 to 7.242.255.2547.242.255.25565,534
1167.243.0.0/167.243.0.1 to 7.243.255.2547.243.255.25565,534
1177.244.0.0/167.244.0.1 to 7.244.255.2547.244.255.25565,534
1187.245.0.0/167.245.0.1 to 7.245.255.2547.245.255.25565,534
1197.246.0.0/167.246.0.1 to 7.246.255.2547.246.255.25565,534
1207.247.0.0/167.247.0.1 to 7.247.255.2547.247.255.25565,534
1217.248.0.0/167.248.0.1 to 7.248.255.2547.248.255.25565,534
1227.249.0.0/167.249.0.1 to 7.249.255.2547.249.255.25565,534
1237.250.0.0/167.250.0.1 to 7.250.255.2547.250.255.25565,534
1247.251.0.0/167.251.0.1 to 7.251.255.2547.251.255.25565,534
1257.252.0.0/167.252.0.1 to 7.252.255.2547.252.255.25565,534
1267.253.0.0/167.253.0.1 to 7.253.255.2547.253.255.25565,534
1277.254.0.0/167.254.0.1 to 7.254.255.2547.254.255.25565,534
1287.255.0.0/167.255.0.1 to 7.255.255.2547.255.255.25565,534

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.