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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.

Network64.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
64.0.0.0
Broadcast address
67.255.255.255
First usable
64.0.0.1
Last usable
67.255.255.254
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 40000000 · Integer 1073741824 to 1140850687
Reverse DNS zones
64.in-addr.arpa
65.in-addr.arpa
66.in-addr.arpa
67.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
Address01000000.00000000.00000000.0000000064.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network01000000.00000000.00000000.0000000064.0.0.0
Broadcast01000011.11111111.11111111.1111111167.255.255.255
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)

64.0.0.0/6 makes 128 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
164.0.0.0/1364.0.0.1 to 64.7.255.25464.7.255.255524,286
264.8.0.0/1364.8.0.1 to 64.15.255.25464.15.255.255524,286
364.16.0.0/1364.16.0.1 to 64.23.255.25464.23.255.255524,286
464.24.0.0/1364.24.0.1 to 64.31.255.25464.31.255.255524,286
564.32.0.0/1364.32.0.1 to 64.39.255.25464.39.255.255524,286
664.40.0.0/1364.40.0.1 to 64.47.255.25464.47.255.255524,286
764.48.0.0/1364.48.0.1 to 64.55.255.25464.55.255.255524,286
864.56.0.0/1364.56.0.1 to 64.63.255.25464.63.255.255524,286
964.64.0.0/1364.64.0.1 to 64.71.255.25464.71.255.255524,286
1064.72.0.0/1364.72.0.1 to 64.79.255.25464.79.255.255524,286
1164.80.0.0/1364.80.0.1 to 64.87.255.25464.87.255.255524,286
1264.88.0.0/1364.88.0.1 to 64.95.255.25464.95.255.255524,286
1364.96.0.0/1364.96.0.1 to 64.103.255.25464.103.255.255524,286
1464.104.0.0/1364.104.0.1 to 64.111.255.25464.111.255.255524,286
1564.112.0.0/1364.112.0.1 to 64.119.255.25464.119.255.255524,286
1664.120.0.0/1364.120.0.1 to 64.127.255.25464.127.255.255524,286
1764.128.0.0/1364.128.0.1 to 64.135.255.25464.135.255.255524,286
1864.136.0.0/1364.136.0.1 to 64.143.255.25464.143.255.255524,286
1964.144.0.0/1364.144.0.1 to 64.151.255.25464.151.255.255524,286
2064.152.0.0/1364.152.0.1 to 64.159.255.25464.159.255.255524,286
2164.160.0.0/1364.160.0.1 to 64.167.255.25464.167.255.255524,286
2264.168.0.0/1364.168.0.1 to 64.175.255.25464.175.255.255524,286
2364.176.0.0/1364.176.0.1 to 64.183.255.25464.183.255.255524,286
2464.184.0.0/1364.184.0.1 to 64.191.255.25464.191.255.255524,286
2564.192.0.0/1364.192.0.1 to 64.199.255.25464.199.255.255524,286
2664.200.0.0/1364.200.0.1 to 64.207.255.25464.207.255.255524,286
2764.208.0.0/1364.208.0.1 to 64.215.255.25464.215.255.255524,286
2864.216.0.0/1364.216.0.1 to 64.223.255.25464.223.255.255524,286
2964.224.0.0/1364.224.0.1 to 64.231.255.25464.231.255.255524,286
3064.232.0.0/1364.232.0.1 to 64.239.255.25464.239.255.255524,286
3164.240.0.0/1364.240.0.1 to 64.247.255.25464.247.255.255524,286
3264.248.0.0/1364.248.0.1 to 64.255.255.25464.255.255.255524,286
3365.0.0.0/1365.0.0.1 to 65.7.255.25465.7.255.255524,286
3465.8.0.0/1365.8.0.1 to 65.15.255.25465.15.255.255524,286
3565.16.0.0/1365.16.0.1 to 65.23.255.25465.23.255.255524,286
3665.24.0.0/1365.24.0.1 to 65.31.255.25465.31.255.255524,286
3765.32.0.0/1365.32.0.1 to 65.39.255.25465.39.255.255524,286
3865.40.0.0/1365.40.0.1 to 65.47.255.25465.47.255.255524,286
3965.48.0.0/1365.48.0.1 to 65.55.255.25465.55.255.255524,286
4065.56.0.0/1365.56.0.1 to 65.63.255.25465.63.255.255524,286
4165.64.0.0/1365.64.0.1 to 65.71.255.25465.71.255.255524,286
4265.72.0.0/1365.72.0.1 to 65.79.255.25465.79.255.255524,286
4365.80.0.0/1365.80.0.1 to 65.87.255.25465.87.255.255524,286
4465.88.0.0/1365.88.0.1 to 65.95.255.25465.95.255.255524,286
4565.96.0.0/1365.96.0.1 to 65.103.255.25465.103.255.255524,286
4665.104.0.0/1365.104.0.1 to 65.111.255.25465.111.255.255524,286
4765.112.0.0/1365.112.0.1 to 65.119.255.25465.119.255.255524,286
4865.120.0.0/1365.120.0.1 to 65.127.255.25465.127.255.255524,286
4965.128.0.0/1365.128.0.1 to 65.135.255.25465.135.255.255524,286
5065.136.0.0/1365.136.0.1 to 65.143.255.25465.143.255.255524,286
5165.144.0.0/1365.144.0.1 to 65.151.255.25465.151.255.255524,286
5265.152.0.0/1365.152.0.1 to 65.159.255.25465.159.255.255524,286
5365.160.0.0/1365.160.0.1 to 65.167.255.25465.167.255.255524,286
5465.168.0.0/1365.168.0.1 to 65.175.255.25465.175.255.255524,286
5565.176.0.0/1365.176.0.1 to 65.183.255.25465.183.255.255524,286
5665.184.0.0/1365.184.0.1 to 65.191.255.25465.191.255.255524,286
5765.192.0.0/1365.192.0.1 to 65.199.255.25465.199.255.255524,286
5865.200.0.0/1365.200.0.1 to 65.207.255.25465.207.255.255524,286
5965.208.0.0/1365.208.0.1 to 65.215.255.25465.215.255.255524,286
6065.216.0.0/1365.216.0.1 to 65.223.255.25465.223.255.255524,286
6165.224.0.0/1365.224.0.1 to 65.231.255.25465.231.255.255524,286
6265.232.0.0/1365.232.0.1 to 65.239.255.25465.239.255.255524,286
6365.240.0.0/1365.240.0.1 to 65.247.255.25465.247.255.255524,286
6465.248.0.0/1365.248.0.1 to 65.255.255.25465.255.255.255524,286
6566.0.0.0/1366.0.0.1 to 66.7.255.25466.7.255.255524,286
6666.8.0.0/1366.8.0.1 to 66.15.255.25466.15.255.255524,286
6766.16.0.0/1366.16.0.1 to 66.23.255.25466.23.255.255524,286
6866.24.0.0/1366.24.0.1 to 66.31.255.25466.31.255.255524,286
6966.32.0.0/1366.32.0.1 to 66.39.255.25466.39.255.255524,286
7066.40.0.0/1366.40.0.1 to 66.47.255.25466.47.255.255524,286
7166.48.0.0/1366.48.0.1 to 66.55.255.25466.55.255.255524,286
7266.56.0.0/1366.56.0.1 to 66.63.255.25466.63.255.255524,286
7366.64.0.0/1366.64.0.1 to 66.71.255.25466.71.255.255524,286
7466.72.0.0/1366.72.0.1 to 66.79.255.25466.79.255.255524,286
7566.80.0.0/1366.80.0.1 to 66.87.255.25466.87.255.255524,286
7666.88.0.0/1366.88.0.1 to 66.95.255.25466.95.255.255524,286
7766.96.0.0/1366.96.0.1 to 66.103.255.25466.103.255.255524,286
7866.104.0.0/1366.104.0.1 to 66.111.255.25466.111.255.255524,286
7966.112.0.0/1366.112.0.1 to 66.119.255.25466.119.255.255524,286
8066.120.0.0/1366.120.0.1 to 66.127.255.25466.127.255.255524,286
8166.128.0.0/1366.128.0.1 to 66.135.255.25466.135.255.255524,286
8266.136.0.0/1366.136.0.1 to 66.143.255.25466.143.255.255524,286
8366.144.0.0/1366.144.0.1 to 66.151.255.25466.151.255.255524,286
8466.152.0.0/1366.152.0.1 to 66.159.255.25466.159.255.255524,286
8566.160.0.0/1366.160.0.1 to 66.167.255.25466.167.255.255524,286
8666.168.0.0/1366.168.0.1 to 66.175.255.25466.175.255.255524,286
8766.176.0.0/1366.176.0.1 to 66.183.255.25466.183.255.255524,286
8866.184.0.0/1366.184.0.1 to 66.191.255.25466.191.255.255524,286
8966.192.0.0/1366.192.0.1 to 66.199.255.25466.199.255.255524,286
9066.200.0.0/1366.200.0.1 to 66.207.255.25466.207.255.255524,286
9166.208.0.0/1366.208.0.1 to 66.215.255.25466.215.255.255524,286
9266.216.0.0/1366.216.0.1 to 66.223.255.25466.223.255.255524,286
9366.224.0.0/1366.224.0.1 to 66.231.255.25466.231.255.255524,286
9466.232.0.0/1366.232.0.1 to 66.239.255.25466.239.255.255524,286
9566.240.0.0/1366.240.0.1 to 66.247.255.25466.247.255.255524,286
9666.248.0.0/1366.248.0.1 to 66.255.255.25466.255.255.255524,286
9767.0.0.0/1367.0.0.1 to 67.7.255.25467.7.255.255524,286
9867.8.0.0/1367.8.0.1 to 67.15.255.25467.15.255.255524,286
9967.16.0.0/1367.16.0.1 to 67.23.255.25467.23.255.255524,286
10067.24.0.0/1367.24.0.1 to 67.31.255.25467.31.255.255524,286
10167.32.0.0/1367.32.0.1 to 67.39.255.25467.39.255.255524,286
10267.40.0.0/1367.40.0.1 to 67.47.255.25467.47.255.255524,286
10367.48.0.0/1367.48.0.1 to 67.55.255.25467.55.255.255524,286
10467.56.0.0/1367.56.0.1 to 67.63.255.25467.63.255.255524,286
10567.64.0.0/1367.64.0.1 to 67.71.255.25467.71.255.255524,286
10667.72.0.0/1367.72.0.1 to 67.79.255.25467.79.255.255524,286
10767.80.0.0/1367.80.0.1 to 67.87.255.25467.87.255.255524,286
10867.88.0.0/1367.88.0.1 to 67.95.255.25467.95.255.255524,286
10967.96.0.0/1367.96.0.1 to 67.103.255.25467.103.255.255524,286
11067.104.0.0/1367.104.0.1 to 67.111.255.25467.111.255.255524,286
11167.112.0.0/1367.112.0.1 to 67.119.255.25467.119.255.255524,286
11267.120.0.0/1367.120.0.1 to 67.127.255.25467.127.255.255524,286
11367.128.0.0/1367.128.0.1 to 67.135.255.25467.135.255.255524,286
11467.136.0.0/1367.136.0.1 to 67.143.255.25467.143.255.255524,286
11567.144.0.0/1367.144.0.1 to 67.151.255.25467.151.255.255524,286
11667.152.0.0/1367.152.0.1 to 67.159.255.25467.159.255.255524,286
11767.160.0.0/1367.160.0.1 to 67.167.255.25467.167.255.255524,286
11867.168.0.0/1367.168.0.1 to 67.175.255.25467.175.255.255524,286
11967.176.0.0/1367.176.0.1 to 67.183.255.25467.183.255.255524,286
12067.184.0.0/1367.184.0.1 to 67.191.255.25467.191.255.255524,286
12167.192.0.0/1367.192.0.1 to 67.199.255.25467.199.255.255524,286
12267.200.0.0/1367.200.0.1 to 67.207.255.25467.207.255.255524,286
12367.208.0.0/1367.208.0.1 to 67.215.255.25467.215.255.255524,286
12467.216.0.0/1367.216.0.1 to 67.223.255.25467.223.255.255524,286
12567.224.0.0/1367.224.0.1 to 67.231.255.25467.231.255.255524,286
12667.232.0.0/1367.232.0.1 to 67.239.255.25467.239.255.255524,286
12767.240.0.0/1367.240.0.1 to 67.247.255.25467.247.255.255524,286
12867.248.0.0/1367.248.0.1 to 67.255.255.25467.255.255.255524,286

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.