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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.

Network64.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
64.0.0.0
Broadcast address
64.127.255.255
First usable
64.0.0.1
Last usable
64.127.255.254
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 40000000 · Integer 1073741824 to 1082130431
Reverse DNS zones
0.64.in-addr.arpa
1.64.in-addr.arpa
2.64.in-addr.arpa
3.64.in-addr.arpa
4.64.in-addr.arpa
5.64.in-addr.arpa
6.64.in-addr.arpa
7.64.in-addr.arpa
8.64.in-addr.arpa
9.64.in-addr.arpa
10.64.in-addr.arpa
11.64.in-addr.arpa
12.64.in-addr.arpa
13.64.in-addr.arpa
14.64.in-addr.arpa
15.64.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
Address01000000.00000000.00000000.0000000064.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network01000000.00000000.00000000.0000000064.0.0.0
Broadcast01000000.01111111.11111111.1111111164.127.255.255
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)

64.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
164.0.0.0/1664.0.0.1 to 64.0.255.25464.0.255.25565,534
264.1.0.0/1664.1.0.1 to 64.1.255.25464.1.255.25565,534
364.2.0.0/1664.2.0.1 to 64.2.255.25464.2.255.25565,534
464.3.0.0/1664.3.0.1 to 64.3.255.25464.3.255.25565,534
564.4.0.0/1664.4.0.1 to 64.4.255.25464.4.255.25565,534
664.5.0.0/1664.5.0.1 to 64.5.255.25464.5.255.25565,534
764.6.0.0/1664.6.0.1 to 64.6.255.25464.6.255.25565,534
864.7.0.0/1664.7.0.1 to 64.7.255.25464.7.255.25565,534
964.8.0.0/1664.8.0.1 to 64.8.255.25464.8.255.25565,534
1064.9.0.0/1664.9.0.1 to 64.9.255.25464.9.255.25565,534
1164.10.0.0/1664.10.0.1 to 64.10.255.25464.10.255.25565,534
1264.11.0.0/1664.11.0.1 to 64.11.255.25464.11.255.25565,534
1364.12.0.0/1664.12.0.1 to 64.12.255.25464.12.255.25565,534
1464.13.0.0/1664.13.0.1 to 64.13.255.25464.13.255.25565,534
1564.14.0.0/1664.14.0.1 to 64.14.255.25464.14.255.25565,534
1664.15.0.0/1664.15.0.1 to 64.15.255.25464.15.255.25565,534
1764.16.0.0/1664.16.0.1 to 64.16.255.25464.16.255.25565,534
1864.17.0.0/1664.17.0.1 to 64.17.255.25464.17.255.25565,534
1964.18.0.0/1664.18.0.1 to 64.18.255.25464.18.255.25565,534
2064.19.0.0/1664.19.0.1 to 64.19.255.25464.19.255.25565,534
2164.20.0.0/1664.20.0.1 to 64.20.255.25464.20.255.25565,534
2264.21.0.0/1664.21.0.1 to 64.21.255.25464.21.255.25565,534
2364.22.0.0/1664.22.0.1 to 64.22.255.25464.22.255.25565,534
2464.23.0.0/1664.23.0.1 to 64.23.255.25464.23.255.25565,534
2564.24.0.0/1664.24.0.1 to 64.24.255.25464.24.255.25565,534
2664.25.0.0/1664.25.0.1 to 64.25.255.25464.25.255.25565,534
2764.26.0.0/1664.26.0.1 to 64.26.255.25464.26.255.25565,534
2864.27.0.0/1664.27.0.1 to 64.27.255.25464.27.255.25565,534
2964.28.0.0/1664.28.0.1 to 64.28.255.25464.28.255.25565,534
3064.29.0.0/1664.29.0.1 to 64.29.255.25464.29.255.25565,534
3164.30.0.0/1664.30.0.1 to 64.30.255.25464.30.255.25565,534
3264.31.0.0/1664.31.0.1 to 64.31.255.25464.31.255.25565,534
3364.32.0.0/1664.32.0.1 to 64.32.255.25464.32.255.25565,534
3464.33.0.0/1664.33.0.1 to 64.33.255.25464.33.255.25565,534
3564.34.0.0/1664.34.0.1 to 64.34.255.25464.34.255.25565,534
3664.35.0.0/1664.35.0.1 to 64.35.255.25464.35.255.25565,534
3764.36.0.0/1664.36.0.1 to 64.36.255.25464.36.255.25565,534
3864.37.0.0/1664.37.0.1 to 64.37.255.25464.37.255.25565,534
3964.38.0.0/1664.38.0.1 to 64.38.255.25464.38.255.25565,534
4064.39.0.0/1664.39.0.1 to 64.39.255.25464.39.255.25565,534
4164.40.0.0/1664.40.0.1 to 64.40.255.25464.40.255.25565,534
4264.41.0.0/1664.41.0.1 to 64.41.255.25464.41.255.25565,534
4364.42.0.0/1664.42.0.1 to 64.42.255.25464.42.255.25565,534
4464.43.0.0/1664.43.0.1 to 64.43.255.25464.43.255.25565,534
4564.44.0.0/1664.44.0.1 to 64.44.255.25464.44.255.25565,534
4664.45.0.0/1664.45.0.1 to 64.45.255.25464.45.255.25565,534
4764.46.0.0/1664.46.0.1 to 64.46.255.25464.46.255.25565,534
4864.47.0.0/1664.47.0.1 to 64.47.255.25464.47.255.25565,534
4964.48.0.0/1664.48.0.1 to 64.48.255.25464.48.255.25565,534
5064.49.0.0/1664.49.0.1 to 64.49.255.25464.49.255.25565,534
5164.50.0.0/1664.50.0.1 to 64.50.255.25464.50.255.25565,534
5264.51.0.0/1664.51.0.1 to 64.51.255.25464.51.255.25565,534
5364.52.0.0/1664.52.0.1 to 64.52.255.25464.52.255.25565,534
5464.53.0.0/1664.53.0.1 to 64.53.255.25464.53.255.25565,534
5564.54.0.0/1664.54.0.1 to 64.54.255.25464.54.255.25565,534
5664.55.0.0/1664.55.0.1 to 64.55.255.25464.55.255.25565,534
5764.56.0.0/1664.56.0.1 to 64.56.255.25464.56.255.25565,534
5864.57.0.0/1664.57.0.1 to 64.57.255.25464.57.255.25565,534
5964.58.0.0/1664.58.0.1 to 64.58.255.25464.58.255.25565,534
6064.59.0.0/1664.59.0.1 to 64.59.255.25464.59.255.25565,534
6164.60.0.0/1664.60.0.1 to 64.60.255.25464.60.255.25565,534
6264.61.0.0/1664.61.0.1 to 64.61.255.25464.61.255.25565,534
6364.62.0.0/1664.62.0.1 to 64.62.255.25464.62.255.25565,534
6464.63.0.0/1664.63.0.1 to 64.63.255.25464.63.255.25565,534
6564.64.0.0/1664.64.0.1 to 64.64.255.25464.64.255.25565,534
6664.65.0.0/1664.65.0.1 to 64.65.255.25464.65.255.25565,534
6764.66.0.0/1664.66.0.1 to 64.66.255.25464.66.255.25565,534
6864.67.0.0/1664.67.0.1 to 64.67.255.25464.67.255.25565,534
6964.68.0.0/1664.68.0.1 to 64.68.255.25464.68.255.25565,534
7064.69.0.0/1664.69.0.1 to 64.69.255.25464.69.255.25565,534
7164.70.0.0/1664.70.0.1 to 64.70.255.25464.70.255.25565,534
7264.71.0.0/1664.71.0.1 to 64.71.255.25464.71.255.25565,534
7364.72.0.0/1664.72.0.1 to 64.72.255.25464.72.255.25565,534
7464.73.0.0/1664.73.0.1 to 64.73.255.25464.73.255.25565,534
7564.74.0.0/1664.74.0.1 to 64.74.255.25464.74.255.25565,534
7664.75.0.0/1664.75.0.1 to 64.75.255.25464.75.255.25565,534
7764.76.0.0/1664.76.0.1 to 64.76.255.25464.76.255.25565,534
7864.77.0.0/1664.77.0.1 to 64.77.255.25464.77.255.25565,534
7964.78.0.0/1664.78.0.1 to 64.78.255.25464.78.255.25565,534
8064.79.0.0/1664.79.0.1 to 64.79.255.25464.79.255.25565,534
8164.80.0.0/1664.80.0.1 to 64.80.255.25464.80.255.25565,534
8264.81.0.0/1664.81.0.1 to 64.81.255.25464.81.255.25565,534
8364.82.0.0/1664.82.0.1 to 64.82.255.25464.82.255.25565,534
8464.83.0.0/1664.83.0.1 to 64.83.255.25464.83.255.25565,534
8564.84.0.0/1664.84.0.1 to 64.84.255.25464.84.255.25565,534
8664.85.0.0/1664.85.0.1 to 64.85.255.25464.85.255.25565,534
8764.86.0.0/1664.86.0.1 to 64.86.255.25464.86.255.25565,534
8864.87.0.0/1664.87.0.1 to 64.87.255.25464.87.255.25565,534
8964.88.0.0/1664.88.0.1 to 64.88.255.25464.88.255.25565,534
9064.89.0.0/1664.89.0.1 to 64.89.255.25464.89.255.25565,534
9164.90.0.0/1664.90.0.1 to 64.90.255.25464.90.255.25565,534
9264.91.0.0/1664.91.0.1 to 64.91.255.25464.91.255.25565,534
9364.92.0.0/1664.92.0.1 to 64.92.255.25464.92.255.25565,534
9464.93.0.0/1664.93.0.1 to 64.93.255.25464.93.255.25565,534
9564.94.0.0/1664.94.0.1 to 64.94.255.25464.94.255.25565,534
9664.95.0.0/1664.95.0.1 to 64.95.255.25464.95.255.25565,534
9764.96.0.0/1664.96.0.1 to 64.96.255.25464.96.255.25565,534
9864.97.0.0/1664.97.0.1 to 64.97.255.25464.97.255.25565,534
9964.98.0.0/1664.98.0.1 to 64.98.255.25464.98.255.25565,534
10064.99.0.0/1664.99.0.1 to 64.99.255.25464.99.255.25565,534
10164.100.0.0/1664.100.0.1 to 64.100.255.25464.100.255.25565,534
10264.101.0.0/1664.101.0.1 to 64.101.255.25464.101.255.25565,534
10364.102.0.0/1664.102.0.1 to 64.102.255.25464.102.255.25565,534
10464.103.0.0/1664.103.0.1 to 64.103.255.25464.103.255.25565,534
10564.104.0.0/1664.104.0.1 to 64.104.255.25464.104.255.25565,534
10664.105.0.0/1664.105.0.1 to 64.105.255.25464.105.255.25565,534
10764.106.0.0/1664.106.0.1 to 64.106.255.25464.106.255.25565,534
10864.107.0.0/1664.107.0.1 to 64.107.255.25464.107.255.25565,534
10964.108.0.0/1664.108.0.1 to 64.108.255.25464.108.255.25565,534
11064.109.0.0/1664.109.0.1 to 64.109.255.25464.109.255.25565,534
11164.110.0.0/1664.110.0.1 to 64.110.255.25464.110.255.25565,534
11264.111.0.0/1664.111.0.1 to 64.111.255.25464.111.255.25565,534
11364.112.0.0/1664.112.0.1 to 64.112.255.25464.112.255.25565,534
11464.113.0.0/1664.113.0.1 to 64.113.255.25464.113.255.25565,534
11564.114.0.0/1664.114.0.1 to 64.114.255.25464.114.255.25565,534
11664.115.0.0/1664.115.0.1 to 64.115.255.25464.115.255.25565,534
11764.116.0.0/1664.116.0.1 to 64.116.255.25464.116.255.25565,534
11864.117.0.0/1664.117.0.1 to 64.117.255.25464.117.255.25565,534
11964.118.0.0/1664.118.0.1 to 64.118.255.25464.118.255.25565,534
12064.119.0.0/1664.119.0.1 to 64.119.255.25464.119.255.25565,534
12164.120.0.0/1664.120.0.1 to 64.120.255.25464.120.255.25565,534
12264.121.0.0/1664.121.0.1 to 64.121.255.25464.121.255.25565,534
12364.122.0.0/1664.122.0.1 to 64.122.255.25464.122.255.25565,534
12464.123.0.0/1664.123.0.1 to 64.123.255.25464.123.255.25565,534
12564.124.0.0/1664.124.0.1 to 64.124.255.25464.124.255.25565,534
12664.125.0.0/1664.125.0.1 to 64.125.255.25464.125.255.25565,534
12764.126.0.0/1664.126.0.1 to 64.126.255.25464.126.255.25565,534
12864.127.0.0/1664.127.0.1 to 64.127.255.25464.127.255.25565,534

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.