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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.

Network40.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
40.0.0.0
Broadcast address
43.255.255.255
First usable
40.0.0.1
Last usable
43.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Public public
Old class
A (default /8)
As numbers
Hex 28000000 · Integer 671088640 to 738197503
Reverse DNS zones
40.in-addr.arpa
41.in-addr.arpa
42.in-addr.arpa
43.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00101000.00000000.00000000.0000000040.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network00101000.00000000.00000000.0000000040.0.0.0
Broadcast00101011.11111111.11111111.1111111143.255.255.255
Split into smaller subnets/13
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

40.0.0.0/6 makes 128 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
140.0.0.0/1340.0.0.1 to 40.7.255.25440.7.255.255524,286
240.8.0.0/1340.8.0.1 to 40.15.255.25440.15.255.255524,286
340.16.0.0/1340.16.0.1 to 40.23.255.25440.23.255.255524,286
440.24.0.0/1340.24.0.1 to 40.31.255.25440.31.255.255524,286
540.32.0.0/1340.32.0.1 to 40.39.255.25440.39.255.255524,286
640.40.0.0/1340.40.0.1 to 40.47.255.25440.47.255.255524,286
740.48.0.0/1340.48.0.1 to 40.55.255.25440.55.255.255524,286
840.56.0.0/1340.56.0.1 to 40.63.255.25440.63.255.255524,286
940.64.0.0/1340.64.0.1 to 40.71.255.25440.71.255.255524,286
1040.72.0.0/1340.72.0.1 to 40.79.255.25440.79.255.255524,286
1140.80.0.0/1340.80.0.1 to 40.87.255.25440.87.255.255524,286
1240.88.0.0/1340.88.0.1 to 40.95.255.25440.95.255.255524,286
1340.96.0.0/1340.96.0.1 to 40.103.255.25440.103.255.255524,286
1440.104.0.0/1340.104.0.1 to 40.111.255.25440.111.255.255524,286
1540.112.0.0/1340.112.0.1 to 40.119.255.25440.119.255.255524,286
1640.120.0.0/1340.120.0.1 to 40.127.255.25440.127.255.255524,286
1740.128.0.0/1340.128.0.1 to 40.135.255.25440.135.255.255524,286
1840.136.0.0/1340.136.0.1 to 40.143.255.25440.143.255.255524,286
1940.144.0.0/1340.144.0.1 to 40.151.255.25440.151.255.255524,286
2040.152.0.0/1340.152.0.1 to 40.159.255.25440.159.255.255524,286
2140.160.0.0/1340.160.0.1 to 40.167.255.25440.167.255.255524,286
2240.168.0.0/1340.168.0.1 to 40.175.255.25440.175.255.255524,286
2340.176.0.0/1340.176.0.1 to 40.183.255.25440.183.255.255524,286
2440.184.0.0/1340.184.0.1 to 40.191.255.25440.191.255.255524,286
2540.192.0.0/1340.192.0.1 to 40.199.255.25440.199.255.255524,286
2640.200.0.0/1340.200.0.1 to 40.207.255.25440.207.255.255524,286
2740.208.0.0/1340.208.0.1 to 40.215.255.25440.215.255.255524,286
2840.216.0.0/1340.216.0.1 to 40.223.255.25440.223.255.255524,286
2940.224.0.0/1340.224.0.1 to 40.231.255.25440.231.255.255524,286
3040.232.0.0/1340.232.0.1 to 40.239.255.25440.239.255.255524,286
3140.240.0.0/1340.240.0.1 to 40.247.255.25440.247.255.255524,286
3240.248.0.0/1340.248.0.1 to 40.255.255.25440.255.255.255524,286
3341.0.0.0/1341.0.0.1 to 41.7.255.25441.7.255.255524,286
3441.8.0.0/1341.8.0.1 to 41.15.255.25441.15.255.255524,286
3541.16.0.0/1341.16.0.1 to 41.23.255.25441.23.255.255524,286
3641.24.0.0/1341.24.0.1 to 41.31.255.25441.31.255.255524,286
3741.32.0.0/1341.32.0.1 to 41.39.255.25441.39.255.255524,286
3841.40.0.0/1341.40.0.1 to 41.47.255.25441.47.255.255524,286
3941.48.0.0/1341.48.0.1 to 41.55.255.25441.55.255.255524,286
4041.56.0.0/1341.56.0.1 to 41.63.255.25441.63.255.255524,286
4141.64.0.0/1341.64.0.1 to 41.71.255.25441.71.255.255524,286
4241.72.0.0/1341.72.0.1 to 41.79.255.25441.79.255.255524,286
4341.80.0.0/1341.80.0.1 to 41.87.255.25441.87.255.255524,286
4441.88.0.0/1341.88.0.1 to 41.95.255.25441.95.255.255524,286
4541.96.0.0/1341.96.0.1 to 41.103.255.25441.103.255.255524,286
4641.104.0.0/1341.104.0.1 to 41.111.255.25441.111.255.255524,286
4741.112.0.0/1341.112.0.1 to 41.119.255.25441.119.255.255524,286
4841.120.0.0/1341.120.0.1 to 41.127.255.25441.127.255.255524,286
4941.128.0.0/1341.128.0.1 to 41.135.255.25441.135.255.255524,286
5041.136.0.0/1341.136.0.1 to 41.143.255.25441.143.255.255524,286
5141.144.0.0/1341.144.0.1 to 41.151.255.25441.151.255.255524,286
5241.152.0.0/1341.152.0.1 to 41.159.255.25441.159.255.255524,286
5341.160.0.0/1341.160.0.1 to 41.167.255.25441.167.255.255524,286
5441.168.0.0/1341.168.0.1 to 41.175.255.25441.175.255.255524,286
5541.176.0.0/1341.176.0.1 to 41.183.255.25441.183.255.255524,286
5641.184.0.0/1341.184.0.1 to 41.191.255.25441.191.255.255524,286
5741.192.0.0/1341.192.0.1 to 41.199.255.25441.199.255.255524,286
5841.200.0.0/1341.200.0.1 to 41.207.255.25441.207.255.255524,286
5941.208.0.0/1341.208.0.1 to 41.215.255.25441.215.255.255524,286
6041.216.0.0/1341.216.0.1 to 41.223.255.25441.223.255.255524,286
6141.224.0.0/1341.224.0.1 to 41.231.255.25441.231.255.255524,286
6241.232.0.0/1341.232.0.1 to 41.239.255.25441.239.255.255524,286
6341.240.0.0/1341.240.0.1 to 41.247.255.25441.247.255.255524,286
6441.248.0.0/1341.248.0.1 to 41.255.255.25441.255.255.255524,286
6542.0.0.0/1342.0.0.1 to 42.7.255.25442.7.255.255524,286
6642.8.0.0/1342.8.0.1 to 42.15.255.25442.15.255.255524,286
6742.16.0.0/1342.16.0.1 to 42.23.255.25442.23.255.255524,286
6842.24.0.0/1342.24.0.1 to 42.31.255.25442.31.255.255524,286
6942.32.0.0/1342.32.0.1 to 42.39.255.25442.39.255.255524,286
7042.40.0.0/1342.40.0.1 to 42.47.255.25442.47.255.255524,286
7142.48.0.0/1342.48.0.1 to 42.55.255.25442.55.255.255524,286
7242.56.0.0/1342.56.0.1 to 42.63.255.25442.63.255.255524,286
7342.64.0.0/1342.64.0.1 to 42.71.255.25442.71.255.255524,286
7442.72.0.0/1342.72.0.1 to 42.79.255.25442.79.255.255524,286
7542.80.0.0/1342.80.0.1 to 42.87.255.25442.87.255.255524,286
7642.88.0.0/1342.88.0.1 to 42.95.255.25442.95.255.255524,286
7742.96.0.0/1342.96.0.1 to 42.103.255.25442.103.255.255524,286
7842.104.0.0/1342.104.0.1 to 42.111.255.25442.111.255.255524,286
7942.112.0.0/1342.112.0.1 to 42.119.255.25442.119.255.255524,286
8042.120.0.0/1342.120.0.1 to 42.127.255.25442.127.255.255524,286
8142.128.0.0/1342.128.0.1 to 42.135.255.25442.135.255.255524,286
8242.136.0.0/1342.136.0.1 to 42.143.255.25442.143.255.255524,286
8342.144.0.0/1342.144.0.1 to 42.151.255.25442.151.255.255524,286
8442.152.0.0/1342.152.0.1 to 42.159.255.25442.159.255.255524,286
8542.160.0.0/1342.160.0.1 to 42.167.255.25442.167.255.255524,286
8642.168.0.0/1342.168.0.1 to 42.175.255.25442.175.255.255524,286
8742.176.0.0/1342.176.0.1 to 42.183.255.25442.183.255.255524,286
8842.184.0.0/1342.184.0.1 to 42.191.255.25442.191.255.255524,286
8942.192.0.0/1342.192.0.1 to 42.199.255.25442.199.255.255524,286
9042.200.0.0/1342.200.0.1 to 42.207.255.25442.207.255.255524,286
9142.208.0.0/1342.208.0.1 to 42.215.255.25442.215.255.255524,286
9242.216.0.0/1342.216.0.1 to 42.223.255.25442.223.255.255524,286
9342.224.0.0/1342.224.0.1 to 42.231.255.25442.231.255.255524,286
9442.232.0.0/1342.232.0.1 to 42.239.255.25442.239.255.255524,286
9542.240.0.0/1342.240.0.1 to 42.247.255.25442.247.255.255524,286
9642.248.0.0/1342.248.0.1 to 42.255.255.25442.255.255.255524,286
9743.0.0.0/1343.0.0.1 to 43.7.255.25443.7.255.255524,286
9843.8.0.0/1343.8.0.1 to 43.15.255.25443.15.255.255524,286
9943.16.0.0/1343.16.0.1 to 43.23.255.25443.23.255.255524,286
10043.24.0.0/1343.24.0.1 to 43.31.255.25443.31.255.255524,286
10143.32.0.0/1343.32.0.1 to 43.39.255.25443.39.255.255524,286
10243.40.0.0/1343.40.0.1 to 43.47.255.25443.47.255.255524,286
10343.48.0.0/1343.48.0.1 to 43.55.255.25443.55.255.255524,286
10443.56.0.0/1343.56.0.1 to 43.63.255.25443.63.255.255524,286
10543.64.0.0/1343.64.0.1 to 43.71.255.25443.71.255.255524,286
10643.72.0.0/1343.72.0.1 to 43.79.255.25443.79.255.255524,286
10743.80.0.0/1343.80.0.1 to 43.87.255.25443.87.255.255524,286
10843.88.0.0/1343.88.0.1 to 43.95.255.25443.95.255.255524,286
10943.96.0.0/1343.96.0.1 to 43.103.255.25443.103.255.255524,286
11043.104.0.0/1343.104.0.1 to 43.111.255.25443.111.255.255524,286
11143.112.0.0/1343.112.0.1 to 43.119.255.25443.119.255.255524,286
11243.120.0.0/1343.120.0.1 to 43.127.255.25443.127.255.255524,286
11343.128.0.0/1343.128.0.1 to 43.135.255.25443.135.255.255524,286
11443.136.0.0/1343.136.0.1 to 43.143.255.25443.143.255.255524,286
11543.144.0.0/1343.144.0.1 to 43.151.255.25443.151.255.255524,286
11643.152.0.0/1343.152.0.1 to 43.159.255.25443.159.255.255524,286
11743.160.0.0/1343.160.0.1 to 43.167.255.25443.167.255.255524,286
11843.168.0.0/1343.168.0.1 to 43.175.255.25443.175.255.255524,286
11943.176.0.0/1343.176.0.1 to 43.183.255.25443.183.255.255524,286
12043.184.0.0/1343.184.0.1 to 43.191.255.25443.191.255.255524,286
12143.192.0.0/1343.192.0.1 to 43.199.255.25443.199.255.255524,286
12243.200.0.0/1343.200.0.1 to 43.207.255.25443.207.255.255524,286
12343.208.0.0/1343.208.0.1 to 43.215.255.25443.215.255.255524,286
12443.216.0.0/1343.216.0.1 to 43.223.255.25443.223.255.255524,286
12543.224.0.0/1343.224.0.1 to 43.231.255.25443.231.255.255524,286
12643.232.0.0/1343.232.0.1 to 43.239.255.25443.239.255.255524,286
12743.240.0.0/1343.240.0.1 to 43.247.255.25443.247.255.255524,286
12843.248.0.0/1343.248.0.1 to 43.255.255.25443.255.255.255524,286

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.