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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.

Network29.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
29.128.0.0
Broadcast address
29.255.255.255
First usable
29.128.0.1
Last usable
29.255.255.254
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 1D800000 · Integer 494927872 to 503316479
Reverse DNS zones
128.29.in-addr.arpa
129.29.in-addr.arpa
130.29.in-addr.arpa
131.29.in-addr.arpa
132.29.in-addr.arpa
133.29.in-addr.arpa
134.29.in-addr.arpa
135.29.in-addr.arpa
136.29.in-addr.arpa
137.29.in-addr.arpa
138.29.in-addr.arpa
139.29.in-addr.arpa
140.29.in-addr.arpa
141.29.in-addr.arpa
142.29.in-addr.arpa
143.29.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
Address00011101.10000000.00000000.0000000029.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00011101.10000000.00000000.0000000029.128.0.0
Broadcast00011101.11111111.11111111.1111111129.255.255.255
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)

29.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
129.128.0.0/1629.128.0.1 to 29.128.255.25429.128.255.25565,534
229.129.0.0/1629.129.0.1 to 29.129.255.25429.129.255.25565,534
329.130.0.0/1629.130.0.1 to 29.130.255.25429.130.255.25565,534
429.131.0.0/1629.131.0.1 to 29.131.255.25429.131.255.25565,534
529.132.0.0/1629.132.0.1 to 29.132.255.25429.132.255.25565,534
629.133.0.0/1629.133.0.1 to 29.133.255.25429.133.255.25565,534
729.134.0.0/1629.134.0.1 to 29.134.255.25429.134.255.25565,534
829.135.0.0/1629.135.0.1 to 29.135.255.25429.135.255.25565,534
929.136.0.0/1629.136.0.1 to 29.136.255.25429.136.255.25565,534
1029.137.0.0/1629.137.0.1 to 29.137.255.25429.137.255.25565,534
1129.138.0.0/1629.138.0.1 to 29.138.255.25429.138.255.25565,534
1229.139.0.0/1629.139.0.1 to 29.139.255.25429.139.255.25565,534
1329.140.0.0/1629.140.0.1 to 29.140.255.25429.140.255.25565,534
1429.141.0.0/1629.141.0.1 to 29.141.255.25429.141.255.25565,534
1529.142.0.0/1629.142.0.1 to 29.142.255.25429.142.255.25565,534
1629.143.0.0/1629.143.0.1 to 29.143.255.25429.143.255.25565,534
1729.144.0.0/1629.144.0.1 to 29.144.255.25429.144.255.25565,534
1829.145.0.0/1629.145.0.1 to 29.145.255.25429.145.255.25565,534
1929.146.0.0/1629.146.0.1 to 29.146.255.25429.146.255.25565,534
2029.147.0.0/1629.147.0.1 to 29.147.255.25429.147.255.25565,534
2129.148.0.0/1629.148.0.1 to 29.148.255.25429.148.255.25565,534
2229.149.0.0/1629.149.0.1 to 29.149.255.25429.149.255.25565,534
2329.150.0.0/1629.150.0.1 to 29.150.255.25429.150.255.25565,534
2429.151.0.0/1629.151.0.1 to 29.151.255.25429.151.255.25565,534
2529.152.0.0/1629.152.0.1 to 29.152.255.25429.152.255.25565,534
2629.153.0.0/1629.153.0.1 to 29.153.255.25429.153.255.25565,534
2729.154.0.0/1629.154.0.1 to 29.154.255.25429.154.255.25565,534
2829.155.0.0/1629.155.0.1 to 29.155.255.25429.155.255.25565,534
2929.156.0.0/1629.156.0.1 to 29.156.255.25429.156.255.25565,534
3029.157.0.0/1629.157.0.1 to 29.157.255.25429.157.255.25565,534
3129.158.0.0/1629.158.0.1 to 29.158.255.25429.158.255.25565,534
3229.159.0.0/1629.159.0.1 to 29.159.255.25429.159.255.25565,534
3329.160.0.0/1629.160.0.1 to 29.160.255.25429.160.255.25565,534
3429.161.0.0/1629.161.0.1 to 29.161.255.25429.161.255.25565,534
3529.162.0.0/1629.162.0.1 to 29.162.255.25429.162.255.25565,534
3629.163.0.0/1629.163.0.1 to 29.163.255.25429.163.255.25565,534
3729.164.0.0/1629.164.0.1 to 29.164.255.25429.164.255.25565,534
3829.165.0.0/1629.165.0.1 to 29.165.255.25429.165.255.25565,534
3929.166.0.0/1629.166.0.1 to 29.166.255.25429.166.255.25565,534
4029.167.0.0/1629.167.0.1 to 29.167.255.25429.167.255.25565,534
4129.168.0.0/1629.168.0.1 to 29.168.255.25429.168.255.25565,534
4229.169.0.0/1629.169.0.1 to 29.169.255.25429.169.255.25565,534
4329.170.0.0/1629.170.0.1 to 29.170.255.25429.170.255.25565,534
4429.171.0.0/1629.171.0.1 to 29.171.255.25429.171.255.25565,534
4529.172.0.0/1629.172.0.1 to 29.172.255.25429.172.255.25565,534
4629.173.0.0/1629.173.0.1 to 29.173.255.25429.173.255.25565,534
4729.174.0.0/1629.174.0.1 to 29.174.255.25429.174.255.25565,534
4829.175.0.0/1629.175.0.1 to 29.175.255.25429.175.255.25565,534
4929.176.0.0/1629.176.0.1 to 29.176.255.25429.176.255.25565,534
5029.177.0.0/1629.177.0.1 to 29.177.255.25429.177.255.25565,534
5129.178.0.0/1629.178.0.1 to 29.178.255.25429.178.255.25565,534
5229.179.0.0/1629.179.0.1 to 29.179.255.25429.179.255.25565,534
5329.180.0.0/1629.180.0.1 to 29.180.255.25429.180.255.25565,534
5429.181.0.0/1629.181.0.1 to 29.181.255.25429.181.255.25565,534
5529.182.0.0/1629.182.0.1 to 29.182.255.25429.182.255.25565,534
5629.183.0.0/1629.183.0.1 to 29.183.255.25429.183.255.25565,534
5729.184.0.0/1629.184.0.1 to 29.184.255.25429.184.255.25565,534
5829.185.0.0/1629.185.0.1 to 29.185.255.25429.185.255.25565,534
5929.186.0.0/1629.186.0.1 to 29.186.255.25429.186.255.25565,534
6029.187.0.0/1629.187.0.1 to 29.187.255.25429.187.255.25565,534
6129.188.0.0/1629.188.0.1 to 29.188.255.25429.188.255.25565,534
6229.189.0.0/1629.189.0.1 to 29.189.255.25429.189.255.25565,534
6329.190.0.0/1629.190.0.1 to 29.190.255.25429.190.255.25565,534
6429.191.0.0/1629.191.0.1 to 29.191.255.25429.191.255.25565,534
6529.192.0.0/1629.192.0.1 to 29.192.255.25429.192.255.25565,534
6629.193.0.0/1629.193.0.1 to 29.193.255.25429.193.255.25565,534
6729.194.0.0/1629.194.0.1 to 29.194.255.25429.194.255.25565,534
6829.195.0.0/1629.195.0.1 to 29.195.255.25429.195.255.25565,534
6929.196.0.0/1629.196.0.1 to 29.196.255.25429.196.255.25565,534
7029.197.0.0/1629.197.0.1 to 29.197.255.25429.197.255.25565,534
7129.198.0.0/1629.198.0.1 to 29.198.255.25429.198.255.25565,534
7229.199.0.0/1629.199.0.1 to 29.199.255.25429.199.255.25565,534
7329.200.0.0/1629.200.0.1 to 29.200.255.25429.200.255.25565,534
7429.201.0.0/1629.201.0.1 to 29.201.255.25429.201.255.25565,534
7529.202.0.0/1629.202.0.1 to 29.202.255.25429.202.255.25565,534
7629.203.0.0/1629.203.0.1 to 29.203.255.25429.203.255.25565,534
7729.204.0.0/1629.204.0.1 to 29.204.255.25429.204.255.25565,534
7829.205.0.0/1629.205.0.1 to 29.205.255.25429.205.255.25565,534
7929.206.0.0/1629.206.0.1 to 29.206.255.25429.206.255.25565,534
8029.207.0.0/1629.207.0.1 to 29.207.255.25429.207.255.25565,534
8129.208.0.0/1629.208.0.1 to 29.208.255.25429.208.255.25565,534
8229.209.0.0/1629.209.0.1 to 29.209.255.25429.209.255.25565,534
8329.210.0.0/1629.210.0.1 to 29.210.255.25429.210.255.25565,534
8429.211.0.0/1629.211.0.1 to 29.211.255.25429.211.255.25565,534
8529.212.0.0/1629.212.0.1 to 29.212.255.25429.212.255.25565,534
8629.213.0.0/1629.213.0.1 to 29.213.255.25429.213.255.25565,534
8729.214.0.0/1629.214.0.1 to 29.214.255.25429.214.255.25565,534
8829.215.0.0/1629.215.0.1 to 29.215.255.25429.215.255.25565,534
8929.216.0.0/1629.216.0.1 to 29.216.255.25429.216.255.25565,534
9029.217.0.0/1629.217.0.1 to 29.217.255.25429.217.255.25565,534
9129.218.0.0/1629.218.0.1 to 29.218.255.25429.218.255.25565,534
9229.219.0.0/1629.219.0.1 to 29.219.255.25429.219.255.25565,534
9329.220.0.0/1629.220.0.1 to 29.220.255.25429.220.255.25565,534
9429.221.0.0/1629.221.0.1 to 29.221.255.25429.221.255.25565,534
9529.222.0.0/1629.222.0.1 to 29.222.255.25429.222.255.25565,534
9629.223.0.0/1629.223.0.1 to 29.223.255.25429.223.255.25565,534
9729.224.0.0/1629.224.0.1 to 29.224.255.25429.224.255.25565,534
9829.225.0.0/1629.225.0.1 to 29.225.255.25429.225.255.25565,534
9929.226.0.0/1629.226.0.1 to 29.226.255.25429.226.255.25565,534
10029.227.0.0/1629.227.0.1 to 29.227.255.25429.227.255.25565,534
10129.228.0.0/1629.228.0.1 to 29.228.255.25429.228.255.25565,534
10229.229.0.0/1629.229.0.1 to 29.229.255.25429.229.255.25565,534
10329.230.0.0/1629.230.0.1 to 29.230.255.25429.230.255.25565,534
10429.231.0.0/1629.231.0.1 to 29.231.255.25429.231.255.25565,534
10529.232.0.0/1629.232.0.1 to 29.232.255.25429.232.255.25565,534
10629.233.0.0/1629.233.0.1 to 29.233.255.25429.233.255.25565,534
10729.234.0.0/1629.234.0.1 to 29.234.255.25429.234.255.25565,534
10829.235.0.0/1629.235.0.1 to 29.235.255.25429.235.255.25565,534
10929.236.0.0/1629.236.0.1 to 29.236.255.25429.236.255.25565,534
11029.237.0.0/1629.237.0.1 to 29.237.255.25429.237.255.25565,534
11129.238.0.0/1629.238.0.1 to 29.238.255.25429.238.255.25565,534
11229.239.0.0/1629.239.0.1 to 29.239.255.25429.239.255.25565,534
11329.240.0.0/1629.240.0.1 to 29.240.255.25429.240.255.25565,534
11429.241.0.0/1629.241.0.1 to 29.241.255.25429.241.255.25565,534
11529.242.0.0/1629.242.0.1 to 29.242.255.25429.242.255.25565,534
11629.243.0.0/1629.243.0.1 to 29.243.255.25429.243.255.25565,534
11729.244.0.0/1629.244.0.1 to 29.244.255.25429.244.255.25565,534
11829.245.0.0/1629.245.0.1 to 29.245.255.25429.245.255.25565,534
11929.246.0.0/1629.246.0.1 to 29.246.255.25429.246.255.25565,534
12029.247.0.0/1629.247.0.1 to 29.247.255.25429.247.255.25565,534
12129.248.0.0/1629.248.0.1 to 29.248.255.25429.248.255.25565,534
12229.249.0.0/1629.249.0.1 to 29.249.255.25429.249.255.25565,534
12329.250.0.0/1629.250.0.1 to 29.250.255.25429.250.255.25565,534
12429.251.0.0/1629.251.0.1 to 29.251.255.25429.251.255.25565,534
12529.252.0.0/1629.252.0.1 to 29.252.255.25429.252.255.25565,534
12629.253.0.0/1629.253.0.1 to 29.253.255.25429.253.255.25565,534
12729.254.0.0/1629.254.0.1 to 29.254.255.25429.254.255.25565,534
12829.255.0.0/1629.255.0.1 to 29.255.255.25429.255.255.25565,534

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.