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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.

Network242.2.112.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
242.2.112.0
Broadcast address
242.2.127.255
First usable
242.2.112.1
Last usable
242.2.127.254
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 F2027000 · Integer 4060246016 to 4060250111
Reverse DNS zones
112.2.242.in-addr.arpa
113.2.242.in-addr.arpa
114.2.242.in-addr.arpa
115.2.242.in-addr.arpa
116.2.242.in-addr.arpa
117.2.242.in-addr.arpa
118.2.242.in-addr.arpa
119.2.242.in-addr.arpa
120.2.242.in-addr.arpa
121.2.242.in-addr.arpa
122.2.242.in-addr.arpa
123.2.242.in-addr.arpa
124.2.242.in-addr.arpa
125.2.242.in-addr.arpa
126.2.242.in-addr.arpa
127.2.242.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
Address11110010.00000010.01110000.00000000242.2.112.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network11110010.00000010.01110000.00000000242.2.112.0
Broadcast11110010.00000010.01111111.11111111242.2.127.255
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)

242.2.112.0/20 makes 128 subnets of /27.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1242.2.112.0/27242.2.112.1 to 242.2.112.30242.2.112.3130
2242.2.112.32/27242.2.112.33 to 242.2.112.62242.2.112.6330
3242.2.112.64/27242.2.112.65 to 242.2.112.94242.2.112.9530
4242.2.112.96/27242.2.112.97 to 242.2.112.126242.2.112.12730
5242.2.112.128/27242.2.112.129 to 242.2.112.158242.2.112.15930
6242.2.112.160/27242.2.112.161 to 242.2.112.190242.2.112.19130
7242.2.112.192/27242.2.112.193 to 242.2.112.222242.2.112.22330
8242.2.112.224/27242.2.112.225 to 242.2.112.254242.2.112.25530
9242.2.113.0/27242.2.113.1 to 242.2.113.30242.2.113.3130
10242.2.113.32/27242.2.113.33 to 242.2.113.62242.2.113.6330
11242.2.113.64/27242.2.113.65 to 242.2.113.94242.2.113.9530
12242.2.113.96/27242.2.113.97 to 242.2.113.126242.2.113.12730
13242.2.113.128/27242.2.113.129 to 242.2.113.158242.2.113.15930
14242.2.113.160/27242.2.113.161 to 242.2.113.190242.2.113.19130
15242.2.113.192/27242.2.113.193 to 242.2.113.222242.2.113.22330
16242.2.113.224/27242.2.113.225 to 242.2.113.254242.2.113.25530
17242.2.114.0/27242.2.114.1 to 242.2.114.30242.2.114.3130
18242.2.114.32/27242.2.114.33 to 242.2.114.62242.2.114.6330
19242.2.114.64/27242.2.114.65 to 242.2.114.94242.2.114.9530
20242.2.114.96/27242.2.114.97 to 242.2.114.126242.2.114.12730
21242.2.114.128/27242.2.114.129 to 242.2.114.158242.2.114.15930
22242.2.114.160/27242.2.114.161 to 242.2.114.190242.2.114.19130
23242.2.114.192/27242.2.114.193 to 242.2.114.222242.2.114.22330
24242.2.114.224/27242.2.114.225 to 242.2.114.254242.2.114.25530
25242.2.115.0/27242.2.115.1 to 242.2.115.30242.2.115.3130
26242.2.115.32/27242.2.115.33 to 242.2.115.62242.2.115.6330
27242.2.115.64/27242.2.115.65 to 242.2.115.94242.2.115.9530
28242.2.115.96/27242.2.115.97 to 242.2.115.126242.2.115.12730
29242.2.115.128/27242.2.115.129 to 242.2.115.158242.2.115.15930
30242.2.115.160/27242.2.115.161 to 242.2.115.190242.2.115.19130
31242.2.115.192/27242.2.115.193 to 242.2.115.222242.2.115.22330
32242.2.115.224/27242.2.115.225 to 242.2.115.254242.2.115.25530
33242.2.116.0/27242.2.116.1 to 242.2.116.30242.2.116.3130
34242.2.116.32/27242.2.116.33 to 242.2.116.62242.2.116.6330
35242.2.116.64/27242.2.116.65 to 242.2.116.94242.2.116.9530
36242.2.116.96/27242.2.116.97 to 242.2.116.126242.2.116.12730
37242.2.116.128/27242.2.116.129 to 242.2.116.158242.2.116.15930
38242.2.116.160/27242.2.116.161 to 242.2.116.190242.2.116.19130
39242.2.116.192/27242.2.116.193 to 242.2.116.222242.2.116.22330
40242.2.116.224/27242.2.116.225 to 242.2.116.254242.2.116.25530
41242.2.117.0/27242.2.117.1 to 242.2.117.30242.2.117.3130
42242.2.117.32/27242.2.117.33 to 242.2.117.62242.2.117.6330
43242.2.117.64/27242.2.117.65 to 242.2.117.94242.2.117.9530
44242.2.117.96/27242.2.117.97 to 242.2.117.126242.2.117.12730
45242.2.117.128/27242.2.117.129 to 242.2.117.158242.2.117.15930
46242.2.117.160/27242.2.117.161 to 242.2.117.190242.2.117.19130
47242.2.117.192/27242.2.117.193 to 242.2.117.222242.2.117.22330
48242.2.117.224/27242.2.117.225 to 242.2.117.254242.2.117.25530
49242.2.118.0/27242.2.118.1 to 242.2.118.30242.2.118.3130
50242.2.118.32/27242.2.118.33 to 242.2.118.62242.2.118.6330
51242.2.118.64/27242.2.118.65 to 242.2.118.94242.2.118.9530
52242.2.118.96/27242.2.118.97 to 242.2.118.126242.2.118.12730
53242.2.118.128/27242.2.118.129 to 242.2.118.158242.2.118.15930
54242.2.118.160/27242.2.118.161 to 242.2.118.190242.2.118.19130
55242.2.118.192/27242.2.118.193 to 242.2.118.222242.2.118.22330
56242.2.118.224/27242.2.118.225 to 242.2.118.254242.2.118.25530
57242.2.119.0/27242.2.119.1 to 242.2.119.30242.2.119.3130
58242.2.119.32/27242.2.119.33 to 242.2.119.62242.2.119.6330
59242.2.119.64/27242.2.119.65 to 242.2.119.94242.2.119.9530
60242.2.119.96/27242.2.119.97 to 242.2.119.126242.2.119.12730
61242.2.119.128/27242.2.119.129 to 242.2.119.158242.2.119.15930
62242.2.119.160/27242.2.119.161 to 242.2.119.190242.2.119.19130
63242.2.119.192/27242.2.119.193 to 242.2.119.222242.2.119.22330
64242.2.119.224/27242.2.119.225 to 242.2.119.254242.2.119.25530
65242.2.120.0/27242.2.120.1 to 242.2.120.30242.2.120.3130
66242.2.120.32/27242.2.120.33 to 242.2.120.62242.2.120.6330
67242.2.120.64/27242.2.120.65 to 242.2.120.94242.2.120.9530
68242.2.120.96/27242.2.120.97 to 242.2.120.126242.2.120.12730
69242.2.120.128/27242.2.120.129 to 242.2.120.158242.2.120.15930
70242.2.120.160/27242.2.120.161 to 242.2.120.190242.2.120.19130
71242.2.120.192/27242.2.120.193 to 242.2.120.222242.2.120.22330
72242.2.120.224/27242.2.120.225 to 242.2.120.254242.2.120.25530
73242.2.121.0/27242.2.121.1 to 242.2.121.30242.2.121.3130
74242.2.121.32/27242.2.121.33 to 242.2.121.62242.2.121.6330
75242.2.121.64/27242.2.121.65 to 242.2.121.94242.2.121.9530
76242.2.121.96/27242.2.121.97 to 242.2.121.126242.2.121.12730
77242.2.121.128/27242.2.121.129 to 242.2.121.158242.2.121.15930
78242.2.121.160/27242.2.121.161 to 242.2.121.190242.2.121.19130
79242.2.121.192/27242.2.121.193 to 242.2.121.222242.2.121.22330
80242.2.121.224/27242.2.121.225 to 242.2.121.254242.2.121.25530
81242.2.122.0/27242.2.122.1 to 242.2.122.30242.2.122.3130
82242.2.122.32/27242.2.122.33 to 242.2.122.62242.2.122.6330
83242.2.122.64/27242.2.122.65 to 242.2.122.94242.2.122.9530
84242.2.122.96/27242.2.122.97 to 242.2.122.126242.2.122.12730
85242.2.122.128/27242.2.122.129 to 242.2.122.158242.2.122.15930
86242.2.122.160/27242.2.122.161 to 242.2.122.190242.2.122.19130
87242.2.122.192/27242.2.122.193 to 242.2.122.222242.2.122.22330
88242.2.122.224/27242.2.122.225 to 242.2.122.254242.2.122.25530
89242.2.123.0/27242.2.123.1 to 242.2.123.30242.2.123.3130
90242.2.123.32/27242.2.123.33 to 242.2.123.62242.2.123.6330
91242.2.123.64/27242.2.123.65 to 242.2.123.94242.2.123.9530
92242.2.123.96/27242.2.123.97 to 242.2.123.126242.2.123.12730
93242.2.123.128/27242.2.123.129 to 242.2.123.158242.2.123.15930
94242.2.123.160/27242.2.123.161 to 242.2.123.190242.2.123.19130
95242.2.123.192/27242.2.123.193 to 242.2.123.222242.2.123.22330
96242.2.123.224/27242.2.123.225 to 242.2.123.254242.2.123.25530
97242.2.124.0/27242.2.124.1 to 242.2.124.30242.2.124.3130
98242.2.124.32/27242.2.124.33 to 242.2.124.62242.2.124.6330
99242.2.124.64/27242.2.124.65 to 242.2.124.94242.2.124.9530
100242.2.124.96/27242.2.124.97 to 242.2.124.126242.2.124.12730
101242.2.124.128/27242.2.124.129 to 242.2.124.158242.2.124.15930
102242.2.124.160/27242.2.124.161 to 242.2.124.190242.2.124.19130
103242.2.124.192/27242.2.124.193 to 242.2.124.222242.2.124.22330
104242.2.124.224/27242.2.124.225 to 242.2.124.254242.2.124.25530
105242.2.125.0/27242.2.125.1 to 242.2.125.30242.2.125.3130
106242.2.125.32/27242.2.125.33 to 242.2.125.62242.2.125.6330
107242.2.125.64/27242.2.125.65 to 242.2.125.94242.2.125.9530
108242.2.125.96/27242.2.125.97 to 242.2.125.126242.2.125.12730
109242.2.125.128/27242.2.125.129 to 242.2.125.158242.2.125.15930
110242.2.125.160/27242.2.125.161 to 242.2.125.190242.2.125.19130
111242.2.125.192/27242.2.125.193 to 242.2.125.222242.2.125.22330
112242.2.125.224/27242.2.125.225 to 242.2.125.254242.2.125.25530
113242.2.126.0/27242.2.126.1 to 242.2.126.30242.2.126.3130
114242.2.126.32/27242.2.126.33 to 242.2.126.62242.2.126.6330
115242.2.126.64/27242.2.126.65 to 242.2.126.94242.2.126.9530
116242.2.126.96/27242.2.126.97 to 242.2.126.126242.2.126.12730
117242.2.126.128/27242.2.126.129 to 242.2.126.158242.2.126.15930
118242.2.126.160/27242.2.126.161 to 242.2.126.190242.2.126.19130
119242.2.126.192/27242.2.126.193 to 242.2.126.222242.2.126.22330
120242.2.126.224/27242.2.126.225 to 242.2.126.254242.2.126.25530
121242.2.127.0/27242.2.127.1 to 242.2.127.30242.2.127.3130
122242.2.127.32/27242.2.127.33 to 242.2.127.62242.2.127.6330
123242.2.127.64/27242.2.127.65 to 242.2.127.94242.2.127.9530
124242.2.127.96/27242.2.127.97 to 242.2.127.126242.2.127.12730
125242.2.127.128/27242.2.127.129 to 242.2.127.158242.2.127.15930
126242.2.127.160/27242.2.127.161 to 242.2.127.190242.2.127.19130
127242.2.127.192/27242.2.127.193 to 242.2.127.222242.2.127.22330
128242.2.127.224/27242.2.127.225 to 242.2.127.254242.2.127.25530

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.