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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.

Network115.2.80.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
115.2.80.0
Broadcast address
115.2.95.255
First usable
115.2.80.1
Last usable
115.2.95.254
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 73025000 · Integer 1929531392 to 1929535487
Reverse DNS zones
80.2.115.in-addr.arpa
81.2.115.in-addr.arpa
82.2.115.in-addr.arpa
83.2.115.in-addr.arpa
84.2.115.in-addr.arpa
85.2.115.in-addr.arpa
86.2.115.in-addr.arpa
87.2.115.in-addr.arpa
88.2.115.in-addr.arpa
89.2.115.in-addr.arpa
90.2.115.in-addr.arpa
91.2.115.in-addr.arpa
92.2.115.in-addr.arpa
93.2.115.in-addr.arpa
94.2.115.in-addr.arpa
95.2.115.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
Address01110011.00000010.01010000.00000000115.2.80.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network01110011.00000010.01010000.00000000115.2.80.0
Broadcast01110011.00000010.01011111.11111111115.2.95.255
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)

115.2.80.0/20 makes 64 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1115.2.80.0/26115.2.80.1 to 115.2.80.62115.2.80.6362
2115.2.80.64/26115.2.80.65 to 115.2.80.126115.2.80.12762
3115.2.80.128/26115.2.80.129 to 115.2.80.190115.2.80.19162
4115.2.80.192/26115.2.80.193 to 115.2.80.254115.2.80.25562
5115.2.81.0/26115.2.81.1 to 115.2.81.62115.2.81.6362
6115.2.81.64/26115.2.81.65 to 115.2.81.126115.2.81.12762
7115.2.81.128/26115.2.81.129 to 115.2.81.190115.2.81.19162
8115.2.81.192/26115.2.81.193 to 115.2.81.254115.2.81.25562
9115.2.82.0/26115.2.82.1 to 115.2.82.62115.2.82.6362
10115.2.82.64/26115.2.82.65 to 115.2.82.126115.2.82.12762
11115.2.82.128/26115.2.82.129 to 115.2.82.190115.2.82.19162
12115.2.82.192/26115.2.82.193 to 115.2.82.254115.2.82.25562
13115.2.83.0/26115.2.83.1 to 115.2.83.62115.2.83.6362
14115.2.83.64/26115.2.83.65 to 115.2.83.126115.2.83.12762
15115.2.83.128/26115.2.83.129 to 115.2.83.190115.2.83.19162
16115.2.83.192/26115.2.83.193 to 115.2.83.254115.2.83.25562
17115.2.84.0/26115.2.84.1 to 115.2.84.62115.2.84.6362
18115.2.84.64/26115.2.84.65 to 115.2.84.126115.2.84.12762
19115.2.84.128/26115.2.84.129 to 115.2.84.190115.2.84.19162
20115.2.84.192/26115.2.84.193 to 115.2.84.254115.2.84.25562
21115.2.85.0/26115.2.85.1 to 115.2.85.62115.2.85.6362
22115.2.85.64/26115.2.85.65 to 115.2.85.126115.2.85.12762
23115.2.85.128/26115.2.85.129 to 115.2.85.190115.2.85.19162
24115.2.85.192/26115.2.85.193 to 115.2.85.254115.2.85.25562
25115.2.86.0/26115.2.86.1 to 115.2.86.62115.2.86.6362
26115.2.86.64/26115.2.86.65 to 115.2.86.126115.2.86.12762
27115.2.86.128/26115.2.86.129 to 115.2.86.190115.2.86.19162
28115.2.86.192/26115.2.86.193 to 115.2.86.254115.2.86.25562
29115.2.87.0/26115.2.87.1 to 115.2.87.62115.2.87.6362
30115.2.87.64/26115.2.87.65 to 115.2.87.126115.2.87.12762
31115.2.87.128/26115.2.87.129 to 115.2.87.190115.2.87.19162
32115.2.87.192/26115.2.87.193 to 115.2.87.254115.2.87.25562
33115.2.88.0/26115.2.88.1 to 115.2.88.62115.2.88.6362
34115.2.88.64/26115.2.88.65 to 115.2.88.126115.2.88.12762
35115.2.88.128/26115.2.88.129 to 115.2.88.190115.2.88.19162
36115.2.88.192/26115.2.88.193 to 115.2.88.254115.2.88.25562
37115.2.89.0/26115.2.89.1 to 115.2.89.62115.2.89.6362
38115.2.89.64/26115.2.89.65 to 115.2.89.126115.2.89.12762
39115.2.89.128/26115.2.89.129 to 115.2.89.190115.2.89.19162
40115.2.89.192/26115.2.89.193 to 115.2.89.254115.2.89.25562
41115.2.90.0/26115.2.90.1 to 115.2.90.62115.2.90.6362
42115.2.90.64/26115.2.90.65 to 115.2.90.126115.2.90.12762
43115.2.90.128/26115.2.90.129 to 115.2.90.190115.2.90.19162
44115.2.90.192/26115.2.90.193 to 115.2.90.254115.2.90.25562
45115.2.91.0/26115.2.91.1 to 115.2.91.62115.2.91.6362
46115.2.91.64/26115.2.91.65 to 115.2.91.126115.2.91.12762
47115.2.91.128/26115.2.91.129 to 115.2.91.190115.2.91.19162
48115.2.91.192/26115.2.91.193 to 115.2.91.254115.2.91.25562
49115.2.92.0/26115.2.92.1 to 115.2.92.62115.2.92.6362
50115.2.92.64/26115.2.92.65 to 115.2.92.126115.2.92.12762
51115.2.92.128/26115.2.92.129 to 115.2.92.190115.2.92.19162
52115.2.92.192/26115.2.92.193 to 115.2.92.254115.2.92.25562
53115.2.93.0/26115.2.93.1 to 115.2.93.62115.2.93.6362
54115.2.93.64/26115.2.93.65 to 115.2.93.126115.2.93.12762
55115.2.93.128/26115.2.93.129 to 115.2.93.190115.2.93.19162
56115.2.93.192/26115.2.93.193 to 115.2.93.254115.2.93.25562
57115.2.94.0/26115.2.94.1 to 115.2.94.62115.2.94.6362
58115.2.94.64/26115.2.94.65 to 115.2.94.126115.2.94.12762
59115.2.94.128/26115.2.94.129 to 115.2.94.190115.2.94.19162
60115.2.94.192/26115.2.94.193 to 115.2.94.254115.2.94.25562
61115.2.95.0/26115.2.95.1 to 115.2.95.62115.2.95.6362
62115.2.95.64/26115.2.95.65 to 115.2.95.126115.2.95.12762
63115.2.95.128/26115.2.95.129 to 115.2.95.190115.2.95.19162
64115.2.95.192/26115.2.95.193 to 115.2.95.254115.2.95.25562

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.