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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.

Network66.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
66.0.0.0
Broadcast address
67.255.255.255
First usable
66.0.0.1
Last usable
67.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
A (default /8)
As numbers
Hex 42000000 · Integer 1107296256 to 1140850687
Reverse DNS zones
66.in-addr.arpa
67.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01000010.00000000.00000000.0000000066.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network01000010.00000000.00000000.0000000066.0.0.0
Broadcast01000011.11111111.11111111.1111111167.255.255.255
Split into smaller subnets/14
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

66.0.0.0/7 makes 128 subnets of /14.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
166.0.0.0/1466.0.0.1 to 66.3.255.25466.3.255.255262,142
266.4.0.0/1466.4.0.1 to 66.7.255.25466.7.255.255262,142
366.8.0.0/1466.8.0.1 to 66.11.255.25466.11.255.255262,142
466.12.0.0/1466.12.0.1 to 66.15.255.25466.15.255.255262,142
566.16.0.0/1466.16.0.1 to 66.19.255.25466.19.255.255262,142
666.20.0.0/1466.20.0.1 to 66.23.255.25466.23.255.255262,142
766.24.0.0/1466.24.0.1 to 66.27.255.25466.27.255.255262,142
866.28.0.0/1466.28.0.1 to 66.31.255.25466.31.255.255262,142
966.32.0.0/1466.32.0.1 to 66.35.255.25466.35.255.255262,142
1066.36.0.0/1466.36.0.1 to 66.39.255.25466.39.255.255262,142
1166.40.0.0/1466.40.0.1 to 66.43.255.25466.43.255.255262,142
1266.44.0.0/1466.44.0.1 to 66.47.255.25466.47.255.255262,142
1366.48.0.0/1466.48.0.1 to 66.51.255.25466.51.255.255262,142
1466.52.0.0/1466.52.0.1 to 66.55.255.25466.55.255.255262,142
1566.56.0.0/1466.56.0.1 to 66.59.255.25466.59.255.255262,142
1666.60.0.0/1466.60.0.1 to 66.63.255.25466.63.255.255262,142
1766.64.0.0/1466.64.0.1 to 66.67.255.25466.67.255.255262,142
1866.68.0.0/1466.68.0.1 to 66.71.255.25466.71.255.255262,142
1966.72.0.0/1466.72.0.1 to 66.75.255.25466.75.255.255262,142
2066.76.0.0/1466.76.0.1 to 66.79.255.25466.79.255.255262,142
2166.80.0.0/1466.80.0.1 to 66.83.255.25466.83.255.255262,142
2266.84.0.0/1466.84.0.1 to 66.87.255.25466.87.255.255262,142
2366.88.0.0/1466.88.0.1 to 66.91.255.25466.91.255.255262,142
2466.92.0.0/1466.92.0.1 to 66.95.255.25466.95.255.255262,142
2566.96.0.0/1466.96.0.1 to 66.99.255.25466.99.255.255262,142
2666.100.0.0/1466.100.0.1 to 66.103.255.25466.103.255.255262,142
2766.104.0.0/1466.104.0.1 to 66.107.255.25466.107.255.255262,142
2866.108.0.0/1466.108.0.1 to 66.111.255.25466.111.255.255262,142
2966.112.0.0/1466.112.0.1 to 66.115.255.25466.115.255.255262,142
3066.116.0.0/1466.116.0.1 to 66.119.255.25466.119.255.255262,142
3166.120.0.0/1466.120.0.1 to 66.123.255.25466.123.255.255262,142
3266.124.0.0/1466.124.0.1 to 66.127.255.25466.127.255.255262,142
3366.128.0.0/1466.128.0.1 to 66.131.255.25466.131.255.255262,142
3466.132.0.0/1466.132.0.1 to 66.135.255.25466.135.255.255262,142
3566.136.0.0/1466.136.0.1 to 66.139.255.25466.139.255.255262,142
3666.140.0.0/1466.140.0.1 to 66.143.255.25466.143.255.255262,142
3766.144.0.0/1466.144.0.1 to 66.147.255.25466.147.255.255262,142
3866.148.0.0/1466.148.0.1 to 66.151.255.25466.151.255.255262,142
3966.152.0.0/1466.152.0.1 to 66.155.255.25466.155.255.255262,142
4066.156.0.0/1466.156.0.1 to 66.159.255.25466.159.255.255262,142
4166.160.0.0/1466.160.0.1 to 66.163.255.25466.163.255.255262,142
4266.164.0.0/1466.164.0.1 to 66.167.255.25466.167.255.255262,142
4366.168.0.0/1466.168.0.1 to 66.171.255.25466.171.255.255262,142
4466.172.0.0/1466.172.0.1 to 66.175.255.25466.175.255.255262,142
4566.176.0.0/1466.176.0.1 to 66.179.255.25466.179.255.255262,142
4666.180.0.0/1466.180.0.1 to 66.183.255.25466.183.255.255262,142
4766.184.0.0/1466.184.0.1 to 66.187.255.25466.187.255.255262,142
4866.188.0.0/1466.188.0.1 to 66.191.255.25466.191.255.255262,142
4966.192.0.0/1466.192.0.1 to 66.195.255.25466.195.255.255262,142
5066.196.0.0/1466.196.0.1 to 66.199.255.25466.199.255.255262,142
5166.200.0.0/1466.200.0.1 to 66.203.255.25466.203.255.255262,142
5266.204.0.0/1466.204.0.1 to 66.207.255.25466.207.255.255262,142
5366.208.0.0/1466.208.0.1 to 66.211.255.25466.211.255.255262,142
5466.212.0.0/1466.212.0.1 to 66.215.255.25466.215.255.255262,142
5566.216.0.0/1466.216.0.1 to 66.219.255.25466.219.255.255262,142
5666.220.0.0/1466.220.0.1 to 66.223.255.25466.223.255.255262,142
5766.224.0.0/1466.224.0.1 to 66.227.255.25466.227.255.255262,142
5866.228.0.0/1466.228.0.1 to 66.231.255.25466.231.255.255262,142
5966.232.0.0/1466.232.0.1 to 66.235.255.25466.235.255.255262,142
6066.236.0.0/1466.236.0.1 to 66.239.255.25466.239.255.255262,142
6166.240.0.0/1466.240.0.1 to 66.243.255.25466.243.255.255262,142
6266.244.0.0/1466.244.0.1 to 66.247.255.25466.247.255.255262,142
6366.248.0.0/1466.248.0.1 to 66.251.255.25466.251.255.255262,142
6466.252.0.0/1466.252.0.1 to 66.255.255.25466.255.255.255262,142
6567.0.0.0/1467.0.0.1 to 67.3.255.25467.3.255.255262,142
6667.4.0.0/1467.4.0.1 to 67.7.255.25467.7.255.255262,142
6767.8.0.0/1467.8.0.1 to 67.11.255.25467.11.255.255262,142
6867.12.0.0/1467.12.0.1 to 67.15.255.25467.15.255.255262,142
6967.16.0.0/1467.16.0.1 to 67.19.255.25467.19.255.255262,142
7067.20.0.0/1467.20.0.1 to 67.23.255.25467.23.255.255262,142
7167.24.0.0/1467.24.0.1 to 67.27.255.25467.27.255.255262,142
7267.28.0.0/1467.28.0.1 to 67.31.255.25467.31.255.255262,142
7367.32.0.0/1467.32.0.1 to 67.35.255.25467.35.255.255262,142
7467.36.0.0/1467.36.0.1 to 67.39.255.25467.39.255.255262,142
7567.40.0.0/1467.40.0.1 to 67.43.255.25467.43.255.255262,142
7667.44.0.0/1467.44.0.1 to 67.47.255.25467.47.255.255262,142
7767.48.0.0/1467.48.0.1 to 67.51.255.25467.51.255.255262,142
7867.52.0.0/1467.52.0.1 to 67.55.255.25467.55.255.255262,142
7967.56.0.0/1467.56.0.1 to 67.59.255.25467.59.255.255262,142
8067.60.0.0/1467.60.0.1 to 67.63.255.25467.63.255.255262,142
8167.64.0.0/1467.64.0.1 to 67.67.255.25467.67.255.255262,142
8267.68.0.0/1467.68.0.1 to 67.71.255.25467.71.255.255262,142
8367.72.0.0/1467.72.0.1 to 67.75.255.25467.75.255.255262,142
8467.76.0.0/1467.76.0.1 to 67.79.255.25467.79.255.255262,142
8567.80.0.0/1467.80.0.1 to 67.83.255.25467.83.255.255262,142
8667.84.0.0/1467.84.0.1 to 67.87.255.25467.87.255.255262,142
8767.88.0.0/1467.88.0.1 to 67.91.255.25467.91.255.255262,142
8867.92.0.0/1467.92.0.1 to 67.95.255.25467.95.255.255262,142
8967.96.0.0/1467.96.0.1 to 67.99.255.25467.99.255.255262,142
9067.100.0.0/1467.100.0.1 to 67.103.255.25467.103.255.255262,142
9167.104.0.0/1467.104.0.1 to 67.107.255.25467.107.255.255262,142
9267.108.0.0/1467.108.0.1 to 67.111.255.25467.111.255.255262,142
9367.112.0.0/1467.112.0.1 to 67.115.255.25467.115.255.255262,142
9467.116.0.0/1467.116.0.1 to 67.119.255.25467.119.255.255262,142
9567.120.0.0/1467.120.0.1 to 67.123.255.25467.123.255.255262,142
9667.124.0.0/1467.124.0.1 to 67.127.255.25467.127.255.255262,142
9767.128.0.0/1467.128.0.1 to 67.131.255.25467.131.255.255262,142
9867.132.0.0/1467.132.0.1 to 67.135.255.25467.135.255.255262,142
9967.136.0.0/1467.136.0.1 to 67.139.255.25467.139.255.255262,142
10067.140.0.0/1467.140.0.1 to 67.143.255.25467.143.255.255262,142
10167.144.0.0/1467.144.0.1 to 67.147.255.25467.147.255.255262,142
10267.148.0.0/1467.148.0.1 to 67.151.255.25467.151.255.255262,142
10367.152.0.0/1467.152.0.1 to 67.155.255.25467.155.255.255262,142
10467.156.0.0/1467.156.0.1 to 67.159.255.25467.159.255.255262,142
10567.160.0.0/1467.160.0.1 to 67.163.255.25467.163.255.255262,142
10667.164.0.0/1467.164.0.1 to 67.167.255.25467.167.255.255262,142
10767.168.0.0/1467.168.0.1 to 67.171.255.25467.171.255.255262,142
10867.172.0.0/1467.172.0.1 to 67.175.255.25467.175.255.255262,142
10967.176.0.0/1467.176.0.1 to 67.179.255.25467.179.255.255262,142
11067.180.0.0/1467.180.0.1 to 67.183.255.25467.183.255.255262,142
11167.184.0.0/1467.184.0.1 to 67.187.255.25467.187.255.255262,142
11267.188.0.0/1467.188.0.1 to 67.191.255.25467.191.255.255262,142
11367.192.0.0/1467.192.0.1 to 67.195.255.25467.195.255.255262,142
11467.196.0.0/1467.196.0.1 to 67.199.255.25467.199.255.255262,142
11567.200.0.0/1467.200.0.1 to 67.203.255.25467.203.255.255262,142
11667.204.0.0/1467.204.0.1 to 67.207.255.25467.207.255.255262,142
11767.208.0.0/1467.208.0.1 to 67.211.255.25467.211.255.255262,142
11867.212.0.0/1467.212.0.1 to 67.215.255.25467.215.255.255262,142
11967.216.0.0/1467.216.0.1 to 67.219.255.25467.219.255.255262,142
12067.220.0.0/1467.220.0.1 to 67.223.255.25467.223.255.255262,142
12167.224.0.0/1467.224.0.1 to 67.227.255.25467.227.255.255262,142
12267.228.0.0/1467.228.0.1 to 67.231.255.25467.231.255.255262,142
12367.232.0.0/1467.232.0.1 to 67.235.255.25467.235.255.255262,142
12467.236.0.0/1467.236.0.1 to 67.239.255.25467.239.255.255262,142
12567.240.0.0/1467.240.0.1 to 67.243.255.25467.243.255.255262,142
12667.244.0.0/1467.244.0.1 to 67.247.255.25467.247.255.255262,142
12767.248.0.0/1467.248.0.1 to 67.251.255.25467.251.255.255262,142
12867.252.0.0/1467.252.0.1 to 67.255.255.25467.255.255.255262,142

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.