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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.

Network240.167.80.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
240.167.80.0
Broadcast address
240.167.95.255
First usable
240.167.80.1
Last usable
240.167.95.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F0A75000 · Integer 4037496832 to 4037500927
Reverse DNS zones
80.167.240.in-addr.arpa
81.167.240.in-addr.arpa
82.167.240.in-addr.arpa
83.167.240.in-addr.arpa
84.167.240.in-addr.arpa
85.167.240.in-addr.arpa
86.167.240.in-addr.arpa
87.167.240.in-addr.arpa
88.167.240.in-addr.arpa
89.167.240.in-addr.arpa
90.167.240.in-addr.arpa
91.167.240.in-addr.arpa
92.167.240.in-addr.arpa
93.167.240.in-addr.arpa
94.167.240.in-addr.arpa
95.167.240.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
Address11110000.10100111.01010000.00000000240.167.80.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network11110000.10100111.01010000.00000000240.167.80.0
Broadcast11110000.10100111.01011111.11111111240.167.95.255
Split into smaller subnets/27
/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)

240.167.80.0/20 makes 128 subnets of /27.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1240.167.80.0/27240.167.80.1 to 240.167.80.30240.167.80.3130
2240.167.80.32/27240.167.80.33 to 240.167.80.62240.167.80.6330
3240.167.80.64/27240.167.80.65 to 240.167.80.94240.167.80.9530
4240.167.80.96/27240.167.80.97 to 240.167.80.126240.167.80.12730
5240.167.80.128/27240.167.80.129 to 240.167.80.158240.167.80.15930
6240.167.80.160/27240.167.80.161 to 240.167.80.190240.167.80.19130
7240.167.80.192/27240.167.80.193 to 240.167.80.222240.167.80.22330
8240.167.80.224/27240.167.80.225 to 240.167.80.254240.167.80.25530
9240.167.81.0/27240.167.81.1 to 240.167.81.30240.167.81.3130
10240.167.81.32/27240.167.81.33 to 240.167.81.62240.167.81.6330
11240.167.81.64/27240.167.81.65 to 240.167.81.94240.167.81.9530
12240.167.81.96/27240.167.81.97 to 240.167.81.126240.167.81.12730
13240.167.81.128/27240.167.81.129 to 240.167.81.158240.167.81.15930
14240.167.81.160/27240.167.81.161 to 240.167.81.190240.167.81.19130
15240.167.81.192/27240.167.81.193 to 240.167.81.222240.167.81.22330
16240.167.81.224/27240.167.81.225 to 240.167.81.254240.167.81.25530
17240.167.82.0/27240.167.82.1 to 240.167.82.30240.167.82.3130
18240.167.82.32/27240.167.82.33 to 240.167.82.62240.167.82.6330
19240.167.82.64/27240.167.82.65 to 240.167.82.94240.167.82.9530
20240.167.82.96/27240.167.82.97 to 240.167.82.126240.167.82.12730
21240.167.82.128/27240.167.82.129 to 240.167.82.158240.167.82.15930
22240.167.82.160/27240.167.82.161 to 240.167.82.190240.167.82.19130
23240.167.82.192/27240.167.82.193 to 240.167.82.222240.167.82.22330
24240.167.82.224/27240.167.82.225 to 240.167.82.254240.167.82.25530
25240.167.83.0/27240.167.83.1 to 240.167.83.30240.167.83.3130
26240.167.83.32/27240.167.83.33 to 240.167.83.62240.167.83.6330
27240.167.83.64/27240.167.83.65 to 240.167.83.94240.167.83.9530
28240.167.83.96/27240.167.83.97 to 240.167.83.126240.167.83.12730
29240.167.83.128/27240.167.83.129 to 240.167.83.158240.167.83.15930
30240.167.83.160/27240.167.83.161 to 240.167.83.190240.167.83.19130
31240.167.83.192/27240.167.83.193 to 240.167.83.222240.167.83.22330
32240.167.83.224/27240.167.83.225 to 240.167.83.254240.167.83.25530
33240.167.84.0/27240.167.84.1 to 240.167.84.30240.167.84.3130
34240.167.84.32/27240.167.84.33 to 240.167.84.62240.167.84.6330
35240.167.84.64/27240.167.84.65 to 240.167.84.94240.167.84.9530
36240.167.84.96/27240.167.84.97 to 240.167.84.126240.167.84.12730
37240.167.84.128/27240.167.84.129 to 240.167.84.158240.167.84.15930
38240.167.84.160/27240.167.84.161 to 240.167.84.190240.167.84.19130
39240.167.84.192/27240.167.84.193 to 240.167.84.222240.167.84.22330
40240.167.84.224/27240.167.84.225 to 240.167.84.254240.167.84.25530
41240.167.85.0/27240.167.85.1 to 240.167.85.30240.167.85.3130
42240.167.85.32/27240.167.85.33 to 240.167.85.62240.167.85.6330
43240.167.85.64/27240.167.85.65 to 240.167.85.94240.167.85.9530
44240.167.85.96/27240.167.85.97 to 240.167.85.126240.167.85.12730
45240.167.85.128/27240.167.85.129 to 240.167.85.158240.167.85.15930
46240.167.85.160/27240.167.85.161 to 240.167.85.190240.167.85.19130
47240.167.85.192/27240.167.85.193 to 240.167.85.222240.167.85.22330
48240.167.85.224/27240.167.85.225 to 240.167.85.254240.167.85.25530
49240.167.86.0/27240.167.86.1 to 240.167.86.30240.167.86.3130
50240.167.86.32/27240.167.86.33 to 240.167.86.62240.167.86.6330
51240.167.86.64/27240.167.86.65 to 240.167.86.94240.167.86.9530
52240.167.86.96/27240.167.86.97 to 240.167.86.126240.167.86.12730
53240.167.86.128/27240.167.86.129 to 240.167.86.158240.167.86.15930
54240.167.86.160/27240.167.86.161 to 240.167.86.190240.167.86.19130
55240.167.86.192/27240.167.86.193 to 240.167.86.222240.167.86.22330
56240.167.86.224/27240.167.86.225 to 240.167.86.254240.167.86.25530
57240.167.87.0/27240.167.87.1 to 240.167.87.30240.167.87.3130
58240.167.87.32/27240.167.87.33 to 240.167.87.62240.167.87.6330
59240.167.87.64/27240.167.87.65 to 240.167.87.94240.167.87.9530
60240.167.87.96/27240.167.87.97 to 240.167.87.126240.167.87.12730
61240.167.87.128/27240.167.87.129 to 240.167.87.158240.167.87.15930
62240.167.87.160/27240.167.87.161 to 240.167.87.190240.167.87.19130
63240.167.87.192/27240.167.87.193 to 240.167.87.222240.167.87.22330
64240.167.87.224/27240.167.87.225 to 240.167.87.254240.167.87.25530
65240.167.88.0/27240.167.88.1 to 240.167.88.30240.167.88.3130
66240.167.88.32/27240.167.88.33 to 240.167.88.62240.167.88.6330
67240.167.88.64/27240.167.88.65 to 240.167.88.94240.167.88.9530
68240.167.88.96/27240.167.88.97 to 240.167.88.126240.167.88.12730
69240.167.88.128/27240.167.88.129 to 240.167.88.158240.167.88.15930
70240.167.88.160/27240.167.88.161 to 240.167.88.190240.167.88.19130
71240.167.88.192/27240.167.88.193 to 240.167.88.222240.167.88.22330
72240.167.88.224/27240.167.88.225 to 240.167.88.254240.167.88.25530
73240.167.89.0/27240.167.89.1 to 240.167.89.30240.167.89.3130
74240.167.89.32/27240.167.89.33 to 240.167.89.62240.167.89.6330
75240.167.89.64/27240.167.89.65 to 240.167.89.94240.167.89.9530
76240.167.89.96/27240.167.89.97 to 240.167.89.126240.167.89.12730
77240.167.89.128/27240.167.89.129 to 240.167.89.158240.167.89.15930
78240.167.89.160/27240.167.89.161 to 240.167.89.190240.167.89.19130
79240.167.89.192/27240.167.89.193 to 240.167.89.222240.167.89.22330
80240.167.89.224/27240.167.89.225 to 240.167.89.254240.167.89.25530
81240.167.90.0/27240.167.90.1 to 240.167.90.30240.167.90.3130
82240.167.90.32/27240.167.90.33 to 240.167.90.62240.167.90.6330
83240.167.90.64/27240.167.90.65 to 240.167.90.94240.167.90.9530
84240.167.90.96/27240.167.90.97 to 240.167.90.126240.167.90.12730
85240.167.90.128/27240.167.90.129 to 240.167.90.158240.167.90.15930
86240.167.90.160/27240.167.90.161 to 240.167.90.190240.167.90.19130
87240.167.90.192/27240.167.90.193 to 240.167.90.222240.167.90.22330
88240.167.90.224/27240.167.90.225 to 240.167.90.254240.167.90.25530
89240.167.91.0/27240.167.91.1 to 240.167.91.30240.167.91.3130
90240.167.91.32/27240.167.91.33 to 240.167.91.62240.167.91.6330
91240.167.91.64/27240.167.91.65 to 240.167.91.94240.167.91.9530
92240.167.91.96/27240.167.91.97 to 240.167.91.126240.167.91.12730
93240.167.91.128/27240.167.91.129 to 240.167.91.158240.167.91.15930
94240.167.91.160/27240.167.91.161 to 240.167.91.190240.167.91.19130
95240.167.91.192/27240.167.91.193 to 240.167.91.222240.167.91.22330
96240.167.91.224/27240.167.91.225 to 240.167.91.254240.167.91.25530
97240.167.92.0/27240.167.92.1 to 240.167.92.30240.167.92.3130
98240.167.92.32/27240.167.92.33 to 240.167.92.62240.167.92.6330
99240.167.92.64/27240.167.92.65 to 240.167.92.94240.167.92.9530
100240.167.92.96/27240.167.92.97 to 240.167.92.126240.167.92.12730
101240.167.92.128/27240.167.92.129 to 240.167.92.158240.167.92.15930
102240.167.92.160/27240.167.92.161 to 240.167.92.190240.167.92.19130
103240.167.92.192/27240.167.92.193 to 240.167.92.222240.167.92.22330
104240.167.92.224/27240.167.92.225 to 240.167.92.254240.167.92.25530
105240.167.93.0/27240.167.93.1 to 240.167.93.30240.167.93.3130
106240.167.93.32/27240.167.93.33 to 240.167.93.62240.167.93.6330
107240.167.93.64/27240.167.93.65 to 240.167.93.94240.167.93.9530
108240.167.93.96/27240.167.93.97 to 240.167.93.126240.167.93.12730
109240.167.93.128/27240.167.93.129 to 240.167.93.158240.167.93.15930
110240.167.93.160/27240.167.93.161 to 240.167.93.190240.167.93.19130
111240.167.93.192/27240.167.93.193 to 240.167.93.222240.167.93.22330
112240.167.93.224/27240.167.93.225 to 240.167.93.254240.167.93.25530
113240.167.94.0/27240.167.94.1 to 240.167.94.30240.167.94.3130
114240.167.94.32/27240.167.94.33 to 240.167.94.62240.167.94.6330
115240.167.94.64/27240.167.94.65 to 240.167.94.94240.167.94.9530
116240.167.94.96/27240.167.94.97 to 240.167.94.126240.167.94.12730
117240.167.94.128/27240.167.94.129 to 240.167.94.158240.167.94.15930
118240.167.94.160/27240.167.94.161 to 240.167.94.190240.167.94.19130
119240.167.94.192/27240.167.94.193 to 240.167.94.222240.167.94.22330
120240.167.94.224/27240.167.94.225 to 240.167.94.254240.167.94.25530
121240.167.95.0/27240.167.95.1 to 240.167.95.30240.167.95.3130
122240.167.95.32/27240.167.95.33 to 240.167.95.62240.167.95.6330
123240.167.95.64/27240.167.95.65 to 240.167.95.94240.167.95.9530
124240.167.95.96/27240.167.95.97 to 240.167.95.126240.167.95.12730
125240.167.95.128/27240.167.95.129 to 240.167.95.158240.167.95.15930
126240.167.95.160/27240.167.95.161 to 240.167.95.190240.167.95.19130
127240.167.95.192/27240.167.95.193 to 240.167.95.222240.167.95.22330
128240.167.95.224/27240.167.95.225 to 240.167.95.254240.167.95.25530

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.