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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.

Network96.4.80.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
96.4.80.0
Broadcast address
96.4.95.255
First usable
96.4.80.1
Last usable
96.4.95.254
Usable hosts
4,094 (4,096 less the network and broadcast addresses)
Subnet mask
255.255.240.0
Wildcard mask
0.0.15.255 (Cisco ACLs, OSPF)
Prefix length
/20
Type
Public public
Old class
A (default /8)
As numbers
Hex 60045000 · Integer 1610895360 to 1610899455
Reverse DNS zones
80.4.96.in-addr.arpa
81.4.96.in-addr.arpa
82.4.96.in-addr.arpa
83.4.96.in-addr.arpa
84.4.96.in-addr.arpa
85.4.96.in-addr.arpa
86.4.96.in-addr.arpa
87.4.96.in-addr.arpa
88.4.96.in-addr.arpa
89.4.96.in-addr.arpa
90.4.96.in-addr.arpa
91.4.96.in-addr.arpa
92.4.96.in-addr.arpa
93.4.96.in-addr.arpa
94.4.96.in-addr.arpa
95.4.96.in-addr.arpa
/20 is not on a 8-bit boundary, so it takes 16 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01100000.00000100.01010000.0000000096.4.80.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network01100000.00000100.01010000.0000000096.4.80.0
Broadcast01100000.00000100.01011111.1111111196.4.95.255
Split into smaller subnets/26
/21 (2)/22 (4)/23 (8)/24 (16)/25 (32)/26 (64)/27 (128)/28 (256)/29 (512)/30 (1,024)/31 (2,048)/32 (4,096)

96.4.80.0/20 makes 64 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
196.4.80.0/2696.4.80.1 to 96.4.80.6296.4.80.6362
296.4.80.64/2696.4.80.65 to 96.4.80.12696.4.80.12762
396.4.80.128/2696.4.80.129 to 96.4.80.19096.4.80.19162
496.4.80.192/2696.4.80.193 to 96.4.80.25496.4.80.25562
596.4.81.0/2696.4.81.1 to 96.4.81.6296.4.81.6362
696.4.81.64/2696.4.81.65 to 96.4.81.12696.4.81.12762
796.4.81.128/2696.4.81.129 to 96.4.81.19096.4.81.19162
896.4.81.192/2696.4.81.193 to 96.4.81.25496.4.81.25562
996.4.82.0/2696.4.82.1 to 96.4.82.6296.4.82.6362
1096.4.82.64/2696.4.82.65 to 96.4.82.12696.4.82.12762
1196.4.82.128/2696.4.82.129 to 96.4.82.19096.4.82.19162
1296.4.82.192/2696.4.82.193 to 96.4.82.25496.4.82.25562
1396.4.83.0/2696.4.83.1 to 96.4.83.6296.4.83.6362
1496.4.83.64/2696.4.83.65 to 96.4.83.12696.4.83.12762
1596.4.83.128/2696.4.83.129 to 96.4.83.19096.4.83.19162
1696.4.83.192/2696.4.83.193 to 96.4.83.25496.4.83.25562
1796.4.84.0/2696.4.84.1 to 96.4.84.6296.4.84.6362
1896.4.84.64/2696.4.84.65 to 96.4.84.12696.4.84.12762
1996.4.84.128/2696.4.84.129 to 96.4.84.19096.4.84.19162
2096.4.84.192/2696.4.84.193 to 96.4.84.25496.4.84.25562
2196.4.85.0/2696.4.85.1 to 96.4.85.6296.4.85.6362
2296.4.85.64/2696.4.85.65 to 96.4.85.12696.4.85.12762
2396.4.85.128/2696.4.85.129 to 96.4.85.19096.4.85.19162
2496.4.85.192/2696.4.85.193 to 96.4.85.25496.4.85.25562
2596.4.86.0/2696.4.86.1 to 96.4.86.6296.4.86.6362
2696.4.86.64/2696.4.86.65 to 96.4.86.12696.4.86.12762
2796.4.86.128/2696.4.86.129 to 96.4.86.19096.4.86.19162
2896.4.86.192/2696.4.86.193 to 96.4.86.25496.4.86.25562
2996.4.87.0/2696.4.87.1 to 96.4.87.6296.4.87.6362
3096.4.87.64/2696.4.87.65 to 96.4.87.12696.4.87.12762
3196.4.87.128/2696.4.87.129 to 96.4.87.19096.4.87.19162
3296.4.87.192/2696.4.87.193 to 96.4.87.25496.4.87.25562
3396.4.88.0/2696.4.88.1 to 96.4.88.6296.4.88.6362
3496.4.88.64/2696.4.88.65 to 96.4.88.12696.4.88.12762
3596.4.88.128/2696.4.88.129 to 96.4.88.19096.4.88.19162
3696.4.88.192/2696.4.88.193 to 96.4.88.25496.4.88.25562
3796.4.89.0/2696.4.89.1 to 96.4.89.6296.4.89.6362
3896.4.89.64/2696.4.89.65 to 96.4.89.12696.4.89.12762
3996.4.89.128/2696.4.89.129 to 96.4.89.19096.4.89.19162
4096.4.89.192/2696.4.89.193 to 96.4.89.25496.4.89.25562
4196.4.90.0/2696.4.90.1 to 96.4.90.6296.4.90.6362
4296.4.90.64/2696.4.90.65 to 96.4.90.12696.4.90.12762
4396.4.90.128/2696.4.90.129 to 96.4.90.19096.4.90.19162
4496.4.90.192/2696.4.90.193 to 96.4.90.25496.4.90.25562
4596.4.91.0/2696.4.91.1 to 96.4.91.6296.4.91.6362
4696.4.91.64/2696.4.91.65 to 96.4.91.12696.4.91.12762
4796.4.91.128/2696.4.91.129 to 96.4.91.19096.4.91.19162
4896.4.91.192/2696.4.91.193 to 96.4.91.25496.4.91.25562
4996.4.92.0/2696.4.92.1 to 96.4.92.6296.4.92.6362
5096.4.92.64/2696.4.92.65 to 96.4.92.12696.4.92.12762
5196.4.92.128/2696.4.92.129 to 96.4.92.19096.4.92.19162
5296.4.92.192/2696.4.92.193 to 96.4.92.25496.4.92.25562
5396.4.93.0/2696.4.93.1 to 96.4.93.6296.4.93.6362
5496.4.93.64/2696.4.93.65 to 96.4.93.12696.4.93.12762
5596.4.93.128/2696.4.93.129 to 96.4.93.19096.4.93.19162
5696.4.93.192/2696.4.93.193 to 96.4.93.25496.4.93.25562
5796.4.94.0/2696.4.94.1 to 96.4.94.6296.4.94.6362
5896.4.94.64/2696.4.94.65 to 96.4.94.12696.4.94.12762
5996.4.94.128/2696.4.94.129 to 96.4.94.19096.4.94.19162
6096.4.94.192/2696.4.94.193 to 96.4.94.25496.4.94.25562
6196.4.95.0/2696.4.95.1 to 96.4.95.6296.4.95.6362
6296.4.95.64/2696.4.95.65 to 96.4.95.12696.4.95.12762
6396.4.95.128/2696.4.95.129 to 96.4.95.19096.4.95.19162
6496.4.95.192/2696.4.95.193 to 96.4.95.25496.4.95.25562

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.