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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.

Network64.16.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
64.16.0.0
Broadcast address
64.31.255.255
First usable
64.16.0.1
Last usable
64.31.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
A (default /8)
As numbers
Hex 40100000 · Integer 1074790400 to 1075838975
Reverse DNS zones
16.64.in-addr.arpa
17.64.in-addr.arpa
18.64.in-addr.arpa
19.64.in-addr.arpa
20.64.in-addr.arpa
21.64.in-addr.arpa
22.64.in-addr.arpa
23.64.in-addr.arpa
24.64.in-addr.arpa
25.64.in-addr.arpa
26.64.in-addr.arpa
27.64.in-addr.arpa
28.64.in-addr.arpa
29.64.in-addr.arpa
30.64.in-addr.arpa
31.64.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01000000.00010000.00000000.0000000064.16.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network01000000.00010000.00000000.0000000064.16.0.0
Broadcast01000000.00011111.11111111.1111111164.31.255.255
Split into smaller subnets/19
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

64.16.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
164.16.0.0/1964.16.0.1 to 64.16.31.25464.16.31.2558,190
264.16.32.0/1964.16.32.1 to 64.16.63.25464.16.63.2558,190
364.16.64.0/1964.16.64.1 to 64.16.95.25464.16.95.2558,190
464.16.96.0/1964.16.96.1 to 64.16.127.25464.16.127.2558,190
564.16.128.0/1964.16.128.1 to 64.16.159.25464.16.159.2558,190
664.16.160.0/1964.16.160.1 to 64.16.191.25464.16.191.2558,190
764.16.192.0/1964.16.192.1 to 64.16.223.25464.16.223.2558,190
864.16.224.0/1964.16.224.1 to 64.16.255.25464.16.255.2558,190
964.17.0.0/1964.17.0.1 to 64.17.31.25464.17.31.2558,190
1064.17.32.0/1964.17.32.1 to 64.17.63.25464.17.63.2558,190
1164.17.64.0/1964.17.64.1 to 64.17.95.25464.17.95.2558,190
1264.17.96.0/1964.17.96.1 to 64.17.127.25464.17.127.2558,190
1364.17.128.0/1964.17.128.1 to 64.17.159.25464.17.159.2558,190
1464.17.160.0/1964.17.160.1 to 64.17.191.25464.17.191.2558,190
1564.17.192.0/1964.17.192.1 to 64.17.223.25464.17.223.2558,190
1664.17.224.0/1964.17.224.1 to 64.17.255.25464.17.255.2558,190
1764.18.0.0/1964.18.0.1 to 64.18.31.25464.18.31.2558,190
1864.18.32.0/1964.18.32.1 to 64.18.63.25464.18.63.2558,190
1964.18.64.0/1964.18.64.1 to 64.18.95.25464.18.95.2558,190
2064.18.96.0/1964.18.96.1 to 64.18.127.25464.18.127.2558,190
2164.18.128.0/1964.18.128.1 to 64.18.159.25464.18.159.2558,190
2264.18.160.0/1964.18.160.1 to 64.18.191.25464.18.191.2558,190
2364.18.192.0/1964.18.192.1 to 64.18.223.25464.18.223.2558,190
2464.18.224.0/1964.18.224.1 to 64.18.255.25464.18.255.2558,190
2564.19.0.0/1964.19.0.1 to 64.19.31.25464.19.31.2558,190
2664.19.32.0/1964.19.32.1 to 64.19.63.25464.19.63.2558,190
2764.19.64.0/1964.19.64.1 to 64.19.95.25464.19.95.2558,190
2864.19.96.0/1964.19.96.1 to 64.19.127.25464.19.127.2558,190
2964.19.128.0/1964.19.128.1 to 64.19.159.25464.19.159.2558,190
3064.19.160.0/1964.19.160.1 to 64.19.191.25464.19.191.2558,190
3164.19.192.0/1964.19.192.1 to 64.19.223.25464.19.223.2558,190
3264.19.224.0/1964.19.224.1 to 64.19.255.25464.19.255.2558,190
3364.20.0.0/1964.20.0.1 to 64.20.31.25464.20.31.2558,190
3464.20.32.0/1964.20.32.1 to 64.20.63.25464.20.63.2558,190
3564.20.64.0/1964.20.64.1 to 64.20.95.25464.20.95.2558,190
3664.20.96.0/1964.20.96.1 to 64.20.127.25464.20.127.2558,190
3764.20.128.0/1964.20.128.1 to 64.20.159.25464.20.159.2558,190
3864.20.160.0/1964.20.160.1 to 64.20.191.25464.20.191.2558,190
3964.20.192.0/1964.20.192.1 to 64.20.223.25464.20.223.2558,190
4064.20.224.0/1964.20.224.1 to 64.20.255.25464.20.255.2558,190
4164.21.0.0/1964.21.0.1 to 64.21.31.25464.21.31.2558,190
4264.21.32.0/1964.21.32.1 to 64.21.63.25464.21.63.2558,190
4364.21.64.0/1964.21.64.1 to 64.21.95.25464.21.95.2558,190
4464.21.96.0/1964.21.96.1 to 64.21.127.25464.21.127.2558,190
4564.21.128.0/1964.21.128.1 to 64.21.159.25464.21.159.2558,190
4664.21.160.0/1964.21.160.1 to 64.21.191.25464.21.191.2558,190
4764.21.192.0/1964.21.192.1 to 64.21.223.25464.21.223.2558,190
4864.21.224.0/1964.21.224.1 to 64.21.255.25464.21.255.2558,190
4964.22.0.0/1964.22.0.1 to 64.22.31.25464.22.31.2558,190
5064.22.32.0/1964.22.32.1 to 64.22.63.25464.22.63.2558,190
5164.22.64.0/1964.22.64.1 to 64.22.95.25464.22.95.2558,190
5264.22.96.0/1964.22.96.1 to 64.22.127.25464.22.127.2558,190
5364.22.128.0/1964.22.128.1 to 64.22.159.25464.22.159.2558,190
5464.22.160.0/1964.22.160.1 to 64.22.191.25464.22.191.2558,190
5564.22.192.0/1964.22.192.1 to 64.22.223.25464.22.223.2558,190
5664.22.224.0/1964.22.224.1 to 64.22.255.25464.22.255.2558,190
5764.23.0.0/1964.23.0.1 to 64.23.31.25464.23.31.2558,190
5864.23.32.0/1964.23.32.1 to 64.23.63.25464.23.63.2558,190
5964.23.64.0/1964.23.64.1 to 64.23.95.25464.23.95.2558,190
6064.23.96.0/1964.23.96.1 to 64.23.127.25464.23.127.2558,190
6164.23.128.0/1964.23.128.1 to 64.23.159.25464.23.159.2558,190
6264.23.160.0/1964.23.160.1 to 64.23.191.25464.23.191.2558,190
6364.23.192.0/1964.23.192.1 to 64.23.223.25464.23.223.2558,190
6464.23.224.0/1964.23.224.1 to 64.23.255.25464.23.255.2558,190
6564.24.0.0/1964.24.0.1 to 64.24.31.25464.24.31.2558,190
6664.24.32.0/1964.24.32.1 to 64.24.63.25464.24.63.2558,190
6764.24.64.0/1964.24.64.1 to 64.24.95.25464.24.95.2558,190
6864.24.96.0/1964.24.96.1 to 64.24.127.25464.24.127.2558,190
6964.24.128.0/1964.24.128.1 to 64.24.159.25464.24.159.2558,190
7064.24.160.0/1964.24.160.1 to 64.24.191.25464.24.191.2558,190
7164.24.192.0/1964.24.192.1 to 64.24.223.25464.24.223.2558,190
7264.24.224.0/1964.24.224.1 to 64.24.255.25464.24.255.2558,190
7364.25.0.0/1964.25.0.1 to 64.25.31.25464.25.31.2558,190
7464.25.32.0/1964.25.32.1 to 64.25.63.25464.25.63.2558,190
7564.25.64.0/1964.25.64.1 to 64.25.95.25464.25.95.2558,190
7664.25.96.0/1964.25.96.1 to 64.25.127.25464.25.127.2558,190
7764.25.128.0/1964.25.128.1 to 64.25.159.25464.25.159.2558,190
7864.25.160.0/1964.25.160.1 to 64.25.191.25464.25.191.2558,190
7964.25.192.0/1964.25.192.1 to 64.25.223.25464.25.223.2558,190
8064.25.224.0/1964.25.224.1 to 64.25.255.25464.25.255.2558,190
8164.26.0.0/1964.26.0.1 to 64.26.31.25464.26.31.2558,190
8264.26.32.0/1964.26.32.1 to 64.26.63.25464.26.63.2558,190
8364.26.64.0/1964.26.64.1 to 64.26.95.25464.26.95.2558,190
8464.26.96.0/1964.26.96.1 to 64.26.127.25464.26.127.2558,190
8564.26.128.0/1964.26.128.1 to 64.26.159.25464.26.159.2558,190
8664.26.160.0/1964.26.160.1 to 64.26.191.25464.26.191.2558,190
8764.26.192.0/1964.26.192.1 to 64.26.223.25464.26.223.2558,190
8864.26.224.0/1964.26.224.1 to 64.26.255.25464.26.255.2558,190
8964.27.0.0/1964.27.0.1 to 64.27.31.25464.27.31.2558,190
9064.27.32.0/1964.27.32.1 to 64.27.63.25464.27.63.2558,190
9164.27.64.0/1964.27.64.1 to 64.27.95.25464.27.95.2558,190
9264.27.96.0/1964.27.96.1 to 64.27.127.25464.27.127.2558,190
9364.27.128.0/1964.27.128.1 to 64.27.159.25464.27.159.2558,190
9464.27.160.0/1964.27.160.1 to 64.27.191.25464.27.191.2558,190
9564.27.192.0/1964.27.192.1 to 64.27.223.25464.27.223.2558,190
9664.27.224.0/1964.27.224.1 to 64.27.255.25464.27.255.2558,190
9764.28.0.0/1964.28.0.1 to 64.28.31.25464.28.31.2558,190
9864.28.32.0/1964.28.32.1 to 64.28.63.25464.28.63.2558,190
9964.28.64.0/1964.28.64.1 to 64.28.95.25464.28.95.2558,190
10064.28.96.0/1964.28.96.1 to 64.28.127.25464.28.127.2558,190
10164.28.128.0/1964.28.128.1 to 64.28.159.25464.28.159.2558,190
10264.28.160.0/1964.28.160.1 to 64.28.191.25464.28.191.2558,190
10364.28.192.0/1964.28.192.1 to 64.28.223.25464.28.223.2558,190
10464.28.224.0/1964.28.224.1 to 64.28.255.25464.28.255.2558,190
10564.29.0.0/1964.29.0.1 to 64.29.31.25464.29.31.2558,190
10664.29.32.0/1964.29.32.1 to 64.29.63.25464.29.63.2558,190
10764.29.64.0/1964.29.64.1 to 64.29.95.25464.29.95.2558,190
10864.29.96.0/1964.29.96.1 to 64.29.127.25464.29.127.2558,190
10964.29.128.0/1964.29.128.1 to 64.29.159.25464.29.159.2558,190
11064.29.160.0/1964.29.160.1 to 64.29.191.25464.29.191.2558,190
11164.29.192.0/1964.29.192.1 to 64.29.223.25464.29.223.2558,190
11264.29.224.0/1964.29.224.1 to 64.29.255.25464.29.255.2558,190
11364.30.0.0/1964.30.0.1 to 64.30.31.25464.30.31.2558,190
11464.30.32.0/1964.30.32.1 to 64.30.63.25464.30.63.2558,190
11564.30.64.0/1964.30.64.1 to 64.30.95.25464.30.95.2558,190
11664.30.96.0/1964.30.96.1 to 64.30.127.25464.30.127.2558,190
11764.30.128.0/1964.30.128.1 to 64.30.159.25464.30.159.2558,190
11864.30.160.0/1964.30.160.1 to 64.30.191.25464.30.191.2558,190
11964.30.192.0/1964.30.192.1 to 64.30.223.25464.30.223.2558,190
12064.30.224.0/1964.30.224.1 to 64.30.255.25464.30.255.2558,190
12164.31.0.0/1964.31.0.1 to 64.31.31.25464.31.31.2558,190
12264.31.32.0/1964.31.32.1 to 64.31.63.25464.31.63.2558,190
12364.31.64.0/1964.31.64.1 to 64.31.95.25464.31.95.2558,190
12464.31.96.0/1964.31.96.1 to 64.31.127.25464.31.127.2558,190
12564.31.128.0/1964.31.128.1 to 64.31.159.25464.31.159.2558,190
12664.31.160.0/1964.31.160.1 to 64.31.191.25464.31.191.2558,190
12764.31.192.0/1964.31.192.1 to 64.31.223.25464.31.223.2558,190
12864.31.224.0/1964.31.224.1 to 64.31.255.25464.31.255.2558,190

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.