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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.

Network3.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
3.128.0.0
Broadcast address
3.255.255.255
First usable
3.128.0.1
Last usable
3.255.255.254
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 03800000 · Integer 58720256 to 67108863
Reverse DNS zones
128.3.in-addr.arpa
129.3.in-addr.arpa
130.3.in-addr.arpa
131.3.in-addr.arpa
132.3.in-addr.arpa
133.3.in-addr.arpa
134.3.in-addr.arpa
135.3.in-addr.arpa
136.3.in-addr.arpa
137.3.in-addr.arpa
138.3.in-addr.arpa
139.3.in-addr.arpa
140.3.in-addr.arpa
141.3.in-addr.arpa
142.3.in-addr.arpa
143.3.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
Address00000011.10000000.00000000.000000003.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00000011.10000000.00000000.000000003.128.0.0
Broadcast00000011.11111111.11111111.111111113.255.255.255
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)

3.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
13.128.0.0/163.128.0.1 to 3.128.255.2543.128.255.25565,534
23.129.0.0/163.129.0.1 to 3.129.255.2543.129.255.25565,534
33.130.0.0/163.130.0.1 to 3.130.255.2543.130.255.25565,534
43.131.0.0/163.131.0.1 to 3.131.255.2543.131.255.25565,534
53.132.0.0/163.132.0.1 to 3.132.255.2543.132.255.25565,534
63.133.0.0/163.133.0.1 to 3.133.255.2543.133.255.25565,534
73.134.0.0/163.134.0.1 to 3.134.255.2543.134.255.25565,534
83.135.0.0/163.135.0.1 to 3.135.255.2543.135.255.25565,534
93.136.0.0/163.136.0.1 to 3.136.255.2543.136.255.25565,534
103.137.0.0/163.137.0.1 to 3.137.255.2543.137.255.25565,534
113.138.0.0/163.138.0.1 to 3.138.255.2543.138.255.25565,534
123.139.0.0/163.139.0.1 to 3.139.255.2543.139.255.25565,534
133.140.0.0/163.140.0.1 to 3.140.255.2543.140.255.25565,534
143.141.0.0/163.141.0.1 to 3.141.255.2543.141.255.25565,534
153.142.0.0/163.142.0.1 to 3.142.255.2543.142.255.25565,534
163.143.0.0/163.143.0.1 to 3.143.255.2543.143.255.25565,534
173.144.0.0/163.144.0.1 to 3.144.255.2543.144.255.25565,534
183.145.0.0/163.145.0.1 to 3.145.255.2543.145.255.25565,534
193.146.0.0/163.146.0.1 to 3.146.255.2543.146.255.25565,534
203.147.0.0/163.147.0.1 to 3.147.255.2543.147.255.25565,534
213.148.0.0/163.148.0.1 to 3.148.255.2543.148.255.25565,534
223.149.0.0/163.149.0.1 to 3.149.255.2543.149.255.25565,534
233.150.0.0/163.150.0.1 to 3.150.255.2543.150.255.25565,534
243.151.0.0/163.151.0.1 to 3.151.255.2543.151.255.25565,534
253.152.0.0/163.152.0.1 to 3.152.255.2543.152.255.25565,534
263.153.0.0/163.153.0.1 to 3.153.255.2543.153.255.25565,534
273.154.0.0/163.154.0.1 to 3.154.255.2543.154.255.25565,534
283.155.0.0/163.155.0.1 to 3.155.255.2543.155.255.25565,534
293.156.0.0/163.156.0.1 to 3.156.255.2543.156.255.25565,534
303.157.0.0/163.157.0.1 to 3.157.255.2543.157.255.25565,534
313.158.0.0/163.158.0.1 to 3.158.255.2543.158.255.25565,534
323.159.0.0/163.159.0.1 to 3.159.255.2543.159.255.25565,534
333.160.0.0/163.160.0.1 to 3.160.255.2543.160.255.25565,534
343.161.0.0/163.161.0.1 to 3.161.255.2543.161.255.25565,534
353.162.0.0/163.162.0.1 to 3.162.255.2543.162.255.25565,534
363.163.0.0/163.163.0.1 to 3.163.255.2543.163.255.25565,534
373.164.0.0/163.164.0.1 to 3.164.255.2543.164.255.25565,534
383.165.0.0/163.165.0.1 to 3.165.255.2543.165.255.25565,534
393.166.0.0/163.166.0.1 to 3.166.255.2543.166.255.25565,534
403.167.0.0/163.167.0.1 to 3.167.255.2543.167.255.25565,534
413.168.0.0/163.168.0.1 to 3.168.255.2543.168.255.25565,534
423.169.0.0/163.169.0.1 to 3.169.255.2543.169.255.25565,534
433.170.0.0/163.170.0.1 to 3.170.255.2543.170.255.25565,534
443.171.0.0/163.171.0.1 to 3.171.255.2543.171.255.25565,534
453.172.0.0/163.172.0.1 to 3.172.255.2543.172.255.25565,534
463.173.0.0/163.173.0.1 to 3.173.255.2543.173.255.25565,534
473.174.0.0/163.174.0.1 to 3.174.255.2543.174.255.25565,534
483.175.0.0/163.175.0.1 to 3.175.255.2543.175.255.25565,534
493.176.0.0/163.176.0.1 to 3.176.255.2543.176.255.25565,534
503.177.0.0/163.177.0.1 to 3.177.255.2543.177.255.25565,534
513.178.0.0/163.178.0.1 to 3.178.255.2543.178.255.25565,534
523.179.0.0/163.179.0.1 to 3.179.255.2543.179.255.25565,534
533.180.0.0/163.180.0.1 to 3.180.255.2543.180.255.25565,534
543.181.0.0/163.181.0.1 to 3.181.255.2543.181.255.25565,534
553.182.0.0/163.182.0.1 to 3.182.255.2543.182.255.25565,534
563.183.0.0/163.183.0.1 to 3.183.255.2543.183.255.25565,534
573.184.0.0/163.184.0.1 to 3.184.255.2543.184.255.25565,534
583.185.0.0/163.185.0.1 to 3.185.255.2543.185.255.25565,534
593.186.0.0/163.186.0.1 to 3.186.255.2543.186.255.25565,534
603.187.0.0/163.187.0.1 to 3.187.255.2543.187.255.25565,534
613.188.0.0/163.188.0.1 to 3.188.255.2543.188.255.25565,534
623.189.0.0/163.189.0.1 to 3.189.255.2543.189.255.25565,534
633.190.0.0/163.190.0.1 to 3.190.255.2543.190.255.25565,534
643.191.0.0/163.191.0.1 to 3.191.255.2543.191.255.25565,534
653.192.0.0/163.192.0.1 to 3.192.255.2543.192.255.25565,534
663.193.0.0/163.193.0.1 to 3.193.255.2543.193.255.25565,534
673.194.0.0/163.194.0.1 to 3.194.255.2543.194.255.25565,534
683.195.0.0/163.195.0.1 to 3.195.255.2543.195.255.25565,534
693.196.0.0/163.196.0.1 to 3.196.255.2543.196.255.25565,534
703.197.0.0/163.197.0.1 to 3.197.255.2543.197.255.25565,534
713.198.0.0/163.198.0.1 to 3.198.255.2543.198.255.25565,534
723.199.0.0/163.199.0.1 to 3.199.255.2543.199.255.25565,534
733.200.0.0/163.200.0.1 to 3.200.255.2543.200.255.25565,534
743.201.0.0/163.201.0.1 to 3.201.255.2543.201.255.25565,534
753.202.0.0/163.202.0.1 to 3.202.255.2543.202.255.25565,534
763.203.0.0/163.203.0.1 to 3.203.255.2543.203.255.25565,534
773.204.0.0/163.204.0.1 to 3.204.255.2543.204.255.25565,534
783.205.0.0/163.205.0.1 to 3.205.255.2543.205.255.25565,534
793.206.0.0/163.206.0.1 to 3.206.255.2543.206.255.25565,534
803.207.0.0/163.207.0.1 to 3.207.255.2543.207.255.25565,534
813.208.0.0/163.208.0.1 to 3.208.255.2543.208.255.25565,534
823.209.0.0/163.209.0.1 to 3.209.255.2543.209.255.25565,534
833.210.0.0/163.210.0.1 to 3.210.255.2543.210.255.25565,534
843.211.0.0/163.211.0.1 to 3.211.255.2543.211.255.25565,534
853.212.0.0/163.212.0.1 to 3.212.255.2543.212.255.25565,534
863.213.0.0/163.213.0.1 to 3.213.255.2543.213.255.25565,534
873.214.0.0/163.214.0.1 to 3.214.255.2543.214.255.25565,534
883.215.0.0/163.215.0.1 to 3.215.255.2543.215.255.25565,534
893.216.0.0/163.216.0.1 to 3.216.255.2543.216.255.25565,534
903.217.0.0/163.217.0.1 to 3.217.255.2543.217.255.25565,534
913.218.0.0/163.218.0.1 to 3.218.255.2543.218.255.25565,534
923.219.0.0/163.219.0.1 to 3.219.255.2543.219.255.25565,534
933.220.0.0/163.220.0.1 to 3.220.255.2543.220.255.25565,534
943.221.0.0/163.221.0.1 to 3.221.255.2543.221.255.25565,534
953.222.0.0/163.222.0.1 to 3.222.255.2543.222.255.25565,534
963.223.0.0/163.223.0.1 to 3.223.255.2543.223.255.25565,534
973.224.0.0/163.224.0.1 to 3.224.255.2543.224.255.25565,534
983.225.0.0/163.225.0.1 to 3.225.255.2543.225.255.25565,534
993.226.0.0/163.226.0.1 to 3.226.255.2543.226.255.25565,534
1003.227.0.0/163.227.0.1 to 3.227.255.2543.227.255.25565,534
1013.228.0.0/163.228.0.1 to 3.228.255.2543.228.255.25565,534
1023.229.0.0/163.229.0.1 to 3.229.255.2543.229.255.25565,534
1033.230.0.0/163.230.0.1 to 3.230.255.2543.230.255.25565,534
1043.231.0.0/163.231.0.1 to 3.231.255.2543.231.255.25565,534
1053.232.0.0/163.232.0.1 to 3.232.255.2543.232.255.25565,534
1063.233.0.0/163.233.0.1 to 3.233.255.2543.233.255.25565,534
1073.234.0.0/163.234.0.1 to 3.234.255.2543.234.255.25565,534
1083.235.0.0/163.235.0.1 to 3.235.255.2543.235.255.25565,534
1093.236.0.0/163.236.0.1 to 3.236.255.2543.236.255.25565,534
1103.237.0.0/163.237.0.1 to 3.237.255.2543.237.255.25565,534
1113.238.0.0/163.238.0.1 to 3.238.255.2543.238.255.25565,534
1123.239.0.0/163.239.0.1 to 3.239.255.2543.239.255.25565,534
1133.240.0.0/163.240.0.1 to 3.240.255.2543.240.255.25565,534
1143.241.0.0/163.241.0.1 to 3.241.255.2543.241.255.25565,534
1153.242.0.0/163.242.0.1 to 3.242.255.2543.242.255.25565,534
1163.243.0.0/163.243.0.1 to 3.243.255.2543.243.255.25565,534
1173.244.0.0/163.244.0.1 to 3.244.255.2543.244.255.25565,534
1183.245.0.0/163.245.0.1 to 3.245.255.2543.245.255.25565,534
1193.246.0.0/163.246.0.1 to 3.246.255.2543.246.255.25565,534
1203.247.0.0/163.247.0.1 to 3.247.255.2543.247.255.25565,534
1213.248.0.0/163.248.0.1 to 3.248.255.2543.248.255.25565,534
1223.249.0.0/163.249.0.1 to 3.249.255.2543.249.255.25565,534
1233.250.0.0/163.250.0.1 to 3.250.255.2543.250.255.25565,534
1243.251.0.0/163.251.0.1 to 3.251.255.2543.251.255.25565,534
1253.252.0.0/163.252.0.1 to 3.252.255.2543.252.255.25565,534
1263.253.0.0/163.253.0.1 to 3.253.255.2543.253.255.25565,534
1273.254.0.0/163.254.0.1 to 3.254.255.2543.254.255.25565,534
1283.255.0.0/163.255.0.1 to 3.255.255.2543.255.255.25565,534

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.