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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.

Network36.80.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
36.80.0.0
Broadcast address
36.95.255.255
First usable
36.80.0.1
Last usable
36.95.255.254
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 24500000 · Integer 609222656 to 610271231
Reverse DNS zones
80.36.in-addr.arpa
81.36.in-addr.arpa
82.36.in-addr.arpa
83.36.in-addr.arpa
84.36.in-addr.arpa
85.36.in-addr.arpa
86.36.in-addr.arpa
87.36.in-addr.arpa
88.36.in-addr.arpa
89.36.in-addr.arpa
90.36.in-addr.arpa
91.36.in-addr.arpa
92.36.in-addr.arpa
93.36.in-addr.arpa
94.36.in-addr.arpa
95.36.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
Address00100100.01010000.00000000.0000000036.80.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00100100.01010000.00000000.0000000036.80.0.0
Broadcast00100100.01011111.11111111.1111111136.95.255.255
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)

36.80.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
136.80.0.0/1936.80.0.1 to 36.80.31.25436.80.31.2558,190
236.80.32.0/1936.80.32.1 to 36.80.63.25436.80.63.2558,190
336.80.64.0/1936.80.64.1 to 36.80.95.25436.80.95.2558,190
436.80.96.0/1936.80.96.1 to 36.80.127.25436.80.127.2558,190
536.80.128.0/1936.80.128.1 to 36.80.159.25436.80.159.2558,190
636.80.160.0/1936.80.160.1 to 36.80.191.25436.80.191.2558,190
736.80.192.0/1936.80.192.1 to 36.80.223.25436.80.223.2558,190
836.80.224.0/1936.80.224.1 to 36.80.255.25436.80.255.2558,190
936.81.0.0/1936.81.0.1 to 36.81.31.25436.81.31.2558,190
1036.81.32.0/1936.81.32.1 to 36.81.63.25436.81.63.2558,190
1136.81.64.0/1936.81.64.1 to 36.81.95.25436.81.95.2558,190
1236.81.96.0/1936.81.96.1 to 36.81.127.25436.81.127.2558,190
1336.81.128.0/1936.81.128.1 to 36.81.159.25436.81.159.2558,190
1436.81.160.0/1936.81.160.1 to 36.81.191.25436.81.191.2558,190
1536.81.192.0/1936.81.192.1 to 36.81.223.25436.81.223.2558,190
1636.81.224.0/1936.81.224.1 to 36.81.255.25436.81.255.2558,190
1736.82.0.0/1936.82.0.1 to 36.82.31.25436.82.31.2558,190
1836.82.32.0/1936.82.32.1 to 36.82.63.25436.82.63.2558,190
1936.82.64.0/1936.82.64.1 to 36.82.95.25436.82.95.2558,190
2036.82.96.0/1936.82.96.1 to 36.82.127.25436.82.127.2558,190
2136.82.128.0/1936.82.128.1 to 36.82.159.25436.82.159.2558,190
2236.82.160.0/1936.82.160.1 to 36.82.191.25436.82.191.2558,190
2336.82.192.0/1936.82.192.1 to 36.82.223.25436.82.223.2558,190
2436.82.224.0/1936.82.224.1 to 36.82.255.25436.82.255.2558,190
2536.83.0.0/1936.83.0.1 to 36.83.31.25436.83.31.2558,190
2636.83.32.0/1936.83.32.1 to 36.83.63.25436.83.63.2558,190
2736.83.64.0/1936.83.64.1 to 36.83.95.25436.83.95.2558,190
2836.83.96.0/1936.83.96.1 to 36.83.127.25436.83.127.2558,190
2936.83.128.0/1936.83.128.1 to 36.83.159.25436.83.159.2558,190
3036.83.160.0/1936.83.160.1 to 36.83.191.25436.83.191.2558,190
3136.83.192.0/1936.83.192.1 to 36.83.223.25436.83.223.2558,190
3236.83.224.0/1936.83.224.1 to 36.83.255.25436.83.255.2558,190
3336.84.0.0/1936.84.0.1 to 36.84.31.25436.84.31.2558,190
3436.84.32.0/1936.84.32.1 to 36.84.63.25436.84.63.2558,190
3536.84.64.0/1936.84.64.1 to 36.84.95.25436.84.95.2558,190
3636.84.96.0/1936.84.96.1 to 36.84.127.25436.84.127.2558,190
3736.84.128.0/1936.84.128.1 to 36.84.159.25436.84.159.2558,190
3836.84.160.0/1936.84.160.1 to 36.84.191.25436.84.191.2558,190
3936.84.192.0/1936.84.192.1 to 36.84.223.25436.84.223.2558,190
4036.84.224.0/1936.84.224.1 to 36.84.255.25436.84.255.2558,190
4136.85.0.0/1936.85.0.1 to 36.85.31.25436.85.31.2558,190
4236.85.32.0/1936.85.32.1 to 36.85.63.25436.85.63.2558,190
4336.85.64.0/1936.85.64.1 to 36.85.95.25436.85.95.2558,190
4436.85.96.0/1936.85.96.1 to 36.85.127.25436.85.127.2558,190
4536.85.128.0/1936.85.128.1 to 36.85.159.25436.85.159.2558,190
4636.85.160.0/1936.85.160.1 to 36.85.191.25436.85.191.2558,190
4736.85.192.0/1936.85.192.1 to 36.85.223.25436.85.223.2558,190
4836.85.224.0/1936.85.224.1 to 36.85.255.25436.85.255.2558,190
4936.86.0.0/1936.86.0.1 to 36.86.31.25436.86.31.2558,190
5036.86.32.0/1936.86.32.1 to 36.86.63.25436.86.63.2558,190
5136.86.64.0/1936.86.64.1 to 36.86.95.25436.86.95.2558,190
5236.86.96.0/1936.86.96.1 to 36.86.127.25436.86.127.2558,190
5336.86.128.0/1936.86.128.1 to 36.86.159.25436.86.159.2558,190
5436.86.160.0/1936.86.160.1 to 36.86.191.25436.86.191.2558,190
5536.86.192.0/1936.86.192.1 to 36.86.223.25436.86.223.2558,190
5636.86.224.0/1936.86.224.1 to 36.86.255.25436.86.255.2558,190
5736.87.0.0/1936.87.0.1 to 36.87.31.25436.87.31.2558,190
5836.87.32.0/1936.87.32.1 to 36.87.63.25436.87.63.2558,190
5936.87.64.0/1936.87.64.1 to 36.87.95.25436.87.95.2558,190
6036.87.96.0/1936.87.96.1 to 36.87.127.25436.87.127.2558,190
6136.87.128.0/1936.87.128.1 to 36.87.159.25436.87.159.2558,190
6236.87.160.0/1936.87.160.1 to 36.87.191.25436.87.191.2558,190
6336.87.192.0/1936.87.192.1 to 36.87.223.25436.87.223.2558,190
6436.87.224.0/1936.87.224.1 to 36.87.255.25436.87.255.2558,190
6536.88.0.0/1936.88.0.1 to 36.88.31.25436.88.31.2558,190
6636.88.32.0/1936.88.32.1 to 36.88.63.25436.88.63.2558,190
6736.88.64.0/1936.88.64.1 to 36.88.95.25436.88.95.2558,190
6836.88.96.0/1936.88.96.1 to 36.88.127.25436.88.127.2558,190
6936.88.128.0/1936.88.128.1 to 36.88.159.25436.88.159.2558,190
7036.88.160.0/1936.88.160.1 to 36.88.191.25436.88.191.2558,190
7136.88.192.0/1936.88.192.1 to 36.88.223.25436.88.223.2558,190
7236.88.224.0/1936.88.224.1 to 36.88.255.25436.88.255.2558,190
7336.89.0.0/1936.89.0.1 to 36.89.31.25436.89.31.2558,190
7436.89.32.0/1936.89.32.1 to 36.89.63.25436.89.63.2558,190
7536.89.64.0/1936.89.64.1 to 36.89.95.25436.89.95.2558,190
7636.89.96.0/1936.89.96.1 to 36.89.127.25436.89.127.2558,190
7736.89.128.0/1936.89.128.1 to 36.89.159.25436.89.159.2558,190
7836.89.160.0/1936.89.160.1 to 36.89.191.25436.89.191.2558,190
7936.89.192.0/1936.89.192.1 to 36.89.223.25436.89.223.2558,190
8036.89.224.0/1936.89.224.1 to 36.89.255.25436.89.255.2558,190
8136.90.0.0/1936.90.0.1 to 36.90.31.25436.90.31.2558,190
8236.90.32.0/1936.90.32.1 to 36.90.63.25436.90.63.2558,190
8336.90.64.0/1936.90.64.1 to 36.90.95.25436.90.95.2558,190
8436.90.96.0/1936.90.96.1 to 36.90.127.25436.90.127.2558,190
8536.90.128.0/1936.90.128.1 to 36.90.159.25436.90.159.2558,190
8636.90.160.0/1936.90.160.1 to 36.90.191.25436.90.191.2558,190
8736.90.192.0/1936.90.192.1 to 36.90.223.25436.90.223.2558,190
8836.90.224.0/1936.90.224.1 to 36.90.255.25436.90.255.2558,190
8936.91.0.0/1936.91.0.1 to 36.91.31.25436.91.31.2558,190
9036.91.32.0/1936.91.32.1 to 36.91.63.25436.91.63.2558,190
9136.91.64.0/1936.91.64.1 to 36.91.95.25436.91.95.2558,190
9236.91.96.0/1936.91.96.1 to 36.91.127.25436.91.127.2558,190
9336.91.128.0/1936.91.128.1 to 36.91.159.25436.91.159.2558,190
9436.91.160.0/1936.91.160.1 to 36.91.191.25436.91.191.2558,190
9536.91.192.0/1936.91.192.1 to 36.91.223.25436.91.223.2558,190
9636.91.224.0/1936.91.224.1 to 36.91.255.25436.91.255.2558,190
9736.92.0.0/1936.92.0.1 to 36.92.31.25436.92.31.2558,190
9836.92.32.0/1936.92.32.1 to 36.92.63.25436.92.63.2558,190
9936.92.64.0/1936.92.64.1 to 36.92.95.25436.92.95.2558,190
10036.92.96.0/1936.92.96.1 to 36.92.127.25436.92.127.2558,190
10136.92.128.0/1936.92.128.1 to 36.92.159.25436.92.159.2558,190
10236.92.160.0/1936.92.160.1 to 36.92.191.25436.92.191.2558,190
10336.92.192.0/1936.92.192.1 to 36.92.223.25436.92.223.2558,190
10436.92.224.0/1936.92.224.1 to 36.92.255.25436.92.255.2558,190
10536.93.0.0/1936.93.0.1 to 36.93.31.25436.93.31.2558,190
10636.93.32.0/1936.93.32.1 to 36.93.63.25436.93.63.2558,190
10736.93.64.0/1936.93.64.1 to 36.93.95.25436.93.95.2558,190
10836.93.96.0/1936.93.96.1 to 36.93.127.25436.93.127.2558,190
10936.93.128.0/1936.93.128.1 to 36.93.159.25436.93.159.2558,190
11036.93.160.0/1936.93.160.1 to 36.93.191.25436.93.191.2558,190
11136.93.192.0/1936.93.192.1 to 36.93.223.25436.93.223.2558,190
11236.93.224.0/1936.93.224.1 to 36.93.255.25436.93.255.2558,190
11336.94.0.0/1936.94.0.1 to 36.94.31.25436.94.31.2558,190
11436.94.32.0/1936.94.32.1 to 36.94.63.25436.94.63.2558,190
11536.94.64.0/1936.94.64.1 to 36.94.95.25436.94.95.2558,190
11636.94.96.0/1936.94.96.1 to 36.94.127.25436.94.127.2558,190
11736.94.128.0/1936.94.128.1 to 36.94.159.25436.94.159.2558,190
11836.94.160.0/1936.94.160.1 to 36.94.191.25436.94.191.2558,190
11936.94.192.0/1936.94.192.1 to 36.94.223.25436.94.223.2558,190
12036.94.224.0/1936.94.224.1 to 36.94.255.25436.94.255.2558,190
12136.95.0.0/1936.95.0.1 to 36.95.31.25436.95.31.2558,190
12236.95.32.0/1936.95.32.1 to 36.95.63.25436.95.63.2558,190
12336.95.64.0/1936.95.64.1 to 36.95.95.25436.95.95.2558,190
12436.95.96.0/1936.95.96.1 to 36.95.127.25436.95.127.2558,190
12536.95.128.0/1936.95.128.1 to 36.95.159.25436.95.159.2558,190
12636.95.160.0/1936.95.160.1 to 36.95.191.25436.95.191.2558,190
12736.95.192.0/1936.95.192.1 to 36.95.223.25436.95.223.2558,190
12836.95.224.0/1936.95.224.1 to 36.95.255.25436.95.255.2558,190

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.