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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.

Network33.128.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
33.128.0.0
Broadcast address
33.191.255.255
First usable
33.128.0.1
Last usable
33.191.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
A (default /8)
As numbers
Hex 21800000 · Integer 562036736 to 566231039
Reverse DNS zones
128.33.in-addr.arpa
129.33.in-addr.arpa
130.33.in-addr.arpa
131.33.in-addr.arpa
132.33.in-addr.arpa
133.33.in-addr.arpa
134.33.in-addr.arpa
135.33.in-addr.arpa
136.33.in-addr.arpa
137.33.in-addr.arpa
138.33.in-addr.arpa
139.33.in-addr.arpa
140.33.in-addr.arpa
141.33.in-addr.arpa
142.33.in-addr.arpa
143.33.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00100001.10000000.00000000.0000000033.128.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00100001.10000000.00000000.0000000033.128.0.0
Broadcast00100001.10111111.11111111.1111111133.191.255.255
Split into smaller subnets/17
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

33.128.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
133.128.0.0/1733.128.0.1 to 33.128.127.25433.128.127.25532,766
233.128.128.0/1733.128.128.1 to 33.128.255.25433.128.255.25532,766
333.129.0.0/1733.129.0.1 to 33.129.127.25433.129.127.25532,766
433.129.128.0/1733.129.128.1 to 33.129.255.25433.129.255.25532,766
533.130.0.0/1733.130.0.1 to 33.130.127.25433.130.127.25532,766
633.130.128.0/1733.130.128.1 to 33.130.255.25433.130.255.25532,766
733.131.0.0/1733.131.0.1 to 33.131.127.25433.131.127.25532,766
833.131.128.0/1733.131.128.1 to 33.131.255.25433.131.255.25532,766
933.132.0.0/1733.132.0.1 to 33.132.127.25433.132.127.25532,766
1033.132.128.0/1733.132.128.1 to 33.132.255.25433.132.255.25532,766
1133.133.0.0/1733.133.0.1 to 33.133.127.25433.133.127.25532,766
1233.133.128.0/1733.133.128.1 to 33.133.255.25433.133.255.25532,766
1333.134.0.0/1733.134.0.1 to 33.134.127.25433.134.127.25532,766
1433.134.128.0/1733.134.128.1 to 33.134.255.25433.134.255.25532,766
1533.135.0.0/1733.135.0.1 to 33.135.127.25433.135.127.25532,766
1633.135.128.0/1733.135.128.1 to 33.135.255.25433.135.255.25532,766
1733.136.0.0/1733.136.0.1 to 33.136.127.25433.136.127.25532,766
1833.136.128.0/1733.136.128.1 to 33.136.255.25433.136.255.25532,766
1933.137.0.0/1733.137.0.1 to 33.137.127.25433.137.127.25532,766
2033.137.128.0/1733.137.128.1 to 33.137.255.25433.137.255.25532,766
2133.138.0.0/1733.138.0.1 to 33.138.127.25433.138.127.25532,766
2233.138.128.0/1733.138.128.1 to 33.138.255.25433.138.255.25532,766
2333.139.0.0/1733.139.0.1 to 33.139.127.25433.139.127.25532,766
2433.139.128.0/1733.139.128.1 to 33.139.255.25433.139.255.25532,766
2533.140.0.0/1733.140.0.1 to 33.140.127.25433.140.127.25532,766
2633.140.128.0/1733.140.128.1 to 33.140.255.25433.140.255.25532,766
2733.141.0.0/1733.141.0.1 to 33.141.127.25433.141.127.25532,766
2833.141.128.0/1733.141.128.1 to 33.141.255.25433.141.255.25532,766
2933.142.0.0/1733.142.0.1 to 33.142.127.25433.142.127.25532,766
3033.142.128.0/1733.142.128.1 to 33.142.255.25433.142.255.25532,766
3133.143.0.0/1733.143.0.1 to 33.143.127.25433.143.127.25532,766
3233.143.128.0/1733.143.128.1 to 33.143.255.25433.143.255.25532,766
3333.144.0.0/1733.144.0.1 to 33.144.127.25433.144.127.25532,766
3433.144.128.0/1733.144.128.1 to 33.144.255.25433.144.255.25532,766
3533.145.0.0/1733.145.0.1 to 33.145.127.25433.145.127.25532,766
3633.145.128.0/1733.145.128.1 to 33.145.255.25433.145.255.25532,766
3733.146.0.0/1733.146.0.1 to 33.146.127.25433.146.127.25532,766
3833.146.128.0/1733.146.128.1 to 33.146.255.25433.146.255.25532,766
3933.147.0.0/1733.147.0.1 to 33.147.127.25433.147.127.25532,766
4033.147.128.0/1733.147.128.1 to 33.147.255.25433.147.255.25532,766
4133.148.0.0/1733.148.0.1 to 33.148.127.25433.148.127.25532,766
4233.148.128.0/1733.148.128.1 to 33.148.255.25433.148.255.25532,766
4333.149.0.0/1733.149.0.1 to 33.149.127.25433.149.127.25532,766
4433.149.128.0/1733.149.128.1 to 33.149.255.25433.149.255.25532,766
4533.150.0.0/1733.150.0.1 to 33.150.127.25433.150.127.25532,766
4633.150.128.0/1733.150.128.1 to 33.150.255.25433.150.255.25532,766
4733.151.0.0/1733.151.0.1 to 33.151.127.25433.151.127.25532,766
4833.151.128.0/1733.151.128.1 to 33.151.255.25433.151.255.25532,766
4933.152.0.0/1733.152.0.1 to 33.152.127.25433.152.127.25532,766
5033.152.128.0/1733.152.128.1 to 33.152.255.25433.152.255.25532,766
5133.153.0.0/1733.153.0.1 to 33.153.127.25433.153.127.25532,766
5233.153.128.0/1733.153.128.1 to 33.153.255.25433.153.255.25532,766
5333.154.0.0/1733.154.0.1 to 33.154.127.25433.154.127.25532,766
5433.154.128.0/1733.154.128.1 to 33.154.255.25433.154.255.25532,766
5533.155.0.0/1733.155.0.1 to 33.155.127.25433.155.127.25532,766
5633.155.128.0/1733.155.128.1 to 33.155.255.25433.155.255.25532,766
5733.156.0.0/1733.156.0.1 to 33.156.127.25433.156.127.25532,766
5833.156.128.0/1733.156.128.1 to 33.156.255.25433.156.255.25532,766
5933.157.0.0/1733.157.0.1 to 33.157.127.25433.157.127.25532,766
6033.157.128.0/1733.157.128.1 to 33.157.255.25433.157.255.25532,766
6133.158.0.0/1733.158.0.1 to 33.158.127.25433.158.127.25532,766
6233.158.128.0/1733.158.128.1 to 33.158.255.25433.158.255.25532,766
6333.159.0.0/1733.159.0.1 to 33.159.127.25433.159.127.25532,766
6433.159.128.0/1733.159.128.1 to 33.159.255.25433.159.255.25532,766
6533.160.0.0/1733.160.0.1 to 33.160.127.25433.160.127.25532,766
6633.160.128.0/1733.160.128.1 to 33.160.255.25433.160.255.25532,766
6733.161.0.0/1733.161.0.1 to 33.161.127.25433.161.127.25532,766
6833.161.128.0/1733.161.128.1 to 33.161.255.25433.161.255.25532,766
6933.162.0.0/1733.162.0.1 to 33.162.127.25433.162.127.25532,766
7033.162.128.0/1733.162.128.1 to 33.162.255.25433.162.255.25532,766
7133.163.0.0/1733.163.0.1 to 33.163.127.25433.163.127.25532,766
7233.163.128.0/1733.163.128.1 to 33.163.255.25433.163.255.25532,766
7333.164.0.0/1733.164.0.1 to 33.164.127.25433.164.127.25532,766
7433.164.128.0/1733.164.128.1 to 33.164.255.25433.164.255.25532,766
7533.165.0.0/1733.165.0.1 to 33.165.127.25433.165.127.25532,766
7633.165.128.0/1733.165.128.1 to 33.165.255.25433.165.255.25532,766
7733.166.0.0/1733.166.0.1 to 33.166.127.25433.166.127.25532,766
7833.166.128.0/1733.166.128.1 to 33.166.255.25433.166.255.25532,766
7933.167.0.0/1733.167.0.1 to 33.167.127.25433.167.127.25532,766
8033.167.128.0/1733.167.128.1 to 33.167.255.25433.167.255.25532,766
8133.168.0.0/1733.168.0.1 to 33.168.127.25433.168.127.25532,766
8233.168.128.0/1733.168.128.1 to 33.168.255.25433.168.255.25532,766
8333.169.0.0/1733.169.0.1 to 33.169.127.25433.169.127.25532,766
8433.169.128.0/1733.169.128.1 to 33.169.255.25433.169.255.25532,766
8533.170.0.0/1733.170.0.1 to 33.170.127.25433.170.127.25532,766
8633.170.128.0/1733.170.128.1 to 33.170.255.25433.170.255.25532,766
8733.171.0.0/1733.171.0.1 to 33.171.127.25433.171.127.25532,766
8833.171.128.0/1733.171.128.1 to 33.171.255.25433.171.255.25532,766
8933.172.0.0/1733.172.0.1 to 33.172.127.25433.172.127.25532,766
9033.172.128.0/1733.172.128.1 to 33.172.255.25433.172.255.25532,766
9133.173.0.0/1733.173.0.1 to 33.173.127.25433.173.127.25532,766
9233.173.128.0/1733.173.128.1 to 33.173.255.25433.173.255.25532,766
9333.174.0.0/1733.174.0.1 to 33.174.127.25433.174.127.25532,766
9433.174.128.0/1733.174.128.1 to 33.174.255.25433.174.255.25532,766
9533.175.0.0/1733.175.0.1 to 33.175.127.25433.175.127.25532,766
9633.175.128.0/1733.175.128.1 to 33.175.255.25433.175.255.25532,766
9733.176.0.0/1733.176.0.1 to 33.176.127.25433.176.127.25532,766
9833.176.128.0/1733.176.128.1 to 33.176.255.25433.176.255.25532,766
9933.177.0.0/1733.177.0.1 to 33.177.127.25433.177.127.25532,766
10033.177.128.0/1733.177.128.1 to 33.177.255.25433.177.255.25532,766
10133.178.0.0/1733.178.0.1 to 33.178.127.25433.178.127.25532,766
10233.178.128.0/1733.178.128.1 to 33.178.255.25433.178.255.25532,766
10333.179.0.0/1733.179.0.1 to 33.179.127.25433.179.127.25532,766
10433.179.128.0/1733.179.128.1 to 33.179.255.25433.179.255.25532,766
10533.180.0.0/1733.180.0.1 to 33.180.127.25433.180.127.25532,766
10633.180.128.0/1733.180.128.1 to 33.180.255.25433.180.255.25532,766
10733.181.0.0/1733.181.0.1 to 33.181.127.25433.181.127.25532,766
10833.181.128.0/1733.181.128.1 to 33.181.255.25433.181.255.25532,766
10933.182.0.0/1733.182.0.1 to 33.182.127.25433.182.127.25532,766
11033.182.128.0/1733.182.128.1 to 33.182.255.25433.182.255.25532,766
11133.183.0.0/1733.183.0.1 to 33.183.127.25433.183.127.25532,766
11233.183.128.0/1733.183.128.1 to 33.183.255.25433.183.255.25532,766
11333.184.0.0/1733.184.0.1 to 33.184.127.25433.184.127.25532,766
11433.184.128.0/1733.184.128.1 to 33.184.255.25433.184.255.25532,766
11533.185.0.0/1733.185.0.1 to 33.185.127.25433.185.127.25532,766
11633.185.128.0/1733.185.128.1 to 33.185.255.25433.185.255.25532,766
11733.186.0.0/1733.186.0.1 to 33.186.127.25433.186.127.25532,766
11833.186.128.0/1733.186.128.1 to 33.186.255.25433.186.255.25532,766
11933.187.0.0/1733.187.0.1 to 33.187.127.25433.187.127.25532,766
12033.187.128.0/1733.187.128.1 to 33.187.255.25433.187.255.25532,766
12133.188.0.0/1733.188.0.1 to 33.188.127.25433.188.127.25532,766
12233.188.128.0/1733.188.128.1 to 33.188.255.25433.188.255.25532,766
12333.189.0.0/1733.189.0.1 to 33.189.127.25433.189.127.25532,766
12433.189.128.0/1733.189.128.1 to 33.189.255.25433.189.255.25532,766
12533.190.0.0/1733.190.0.1 to 33.190.127.25433.190.127.25532,766
12633.190.128.0/1733.190.128.1 to 33.190.255.25433.190.255.25532,766
12733.191.0.0/1733.191.0.1 to 33.191.127.25433.191.127.25532,766
12833.191.128.0/1733.191.128.1 to 33.191.255.25433.191.255.25532,766

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.