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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.

Network242.208.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
242.208.0.0
Broadcast address
242.223.255.255
First usable
242.208.0.1
Last usable
242.223.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F2D00000 · Integer 4073717760 to 4074766335
Reverse DNS zones
208.242.in-addr.arpa
209.242.in-addr.arpa
210.242.in-addr.arpa
211.242.in-addr.arpa
212.242.in-addr.arpa
213.242.in-addr.arpa
214.242.in-addr.arpa
215.242.in-addr.arpa
216.242.in-addr.arpa
217.242.in-addr.arpa
218.242.in-addr.arpa
219.242.in-addr.arpa
220.242.in-addr.arpa
221.242.in-addr.arpa
222.242.in-addr.arpa
223.242.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
Address11110010.11010000.00000000.00000000242.208.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11110010.11010000.00000000.00000000242.208.0.0
Broadcast11110010.11011111.11111111.11111111242.223.255.255
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)

242.208.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1242.208.0.0/19242.208.0.1 to 242.208.31.254242.208.31.2558,190
2242.208.32.0/19242.208.32.1 to 242.208.63.254242.208.63.2558,190
3242.208.64.0/19242.208.64.1 to 242.208.95.254242.208.95.2558,190
4242.208.96.0/19242.208.96.1 to 242.208.127.254242.208.127.2558,190
5242.208.128.0/19242.208.128.1 to 242.208.159.254242.208.159.2558,190
6242.208.160.0/19242.208.160.1 to 242.208.191.254242.208.191.2558,190
7242.208.192.0/19242.208.192.1 to 242.208.223.254242.208.223.2558,190
8242.208.224.0/19242.208.224.1 to 242.208.255.254242.208.255.2558,190
9242.209.0.0/19242.209.0.1 to 242.209.31.254242.209.31.2558,190
10242.209.32.0/19242.209.32.1 to 242.209.63.254242.209.63.2558,190
11242.209.64.0/19242.209.64.1 to 242.209.95.254242.209.95.2558,190
12242.209.96.0/19242.209.96.1 to 242.209.127.254242.209.127.2558,190
13242.209.128.0/19242.209.128.1 to 242.209.159.254242.209.159.2558,190
14242.209.160.0/19242.209.160.1 to 242.209.191.254242.209.191.2558,190
15242.209.192.0/19242.209.192.1 to 242.209.223.254242.209.223.2558,190
16242.209.224.0/19242.209.224.1 to 242.209.255.254242.209.255.2558,190
17242.210.0.0/19242.210.0.1 to 242.210.31.254242.210.31.2558,190
18242.210.32.0/19242.210.32.1 to 242.210.63.254242.210.63.2558,190
19242.210.64.0/19242.210.64.1 to 242.210.95.254242.210.95.2558,190
20242.210.96.0/19242.210.96.1 to 242.210.127.254242.210.127.2558,190
21242.210.128.0/19242.210.128.1 to 242.210.159.254242.210.159.2558,190
22242.210.160.0/19242.210.160.1 to 242.210.191.254242.210.191.2558,190
23242.210.192.0/19242.210.192.1 to 242.210.223.254242.210.223.2558,190
24242.210.224.0/19242.210.224.1 to 242.210.255.254242.210.255.2558,190
25242.211.0.0/19242.211.0.1 to 242.211.31.254242.211.31.2558,190
26242.211.32.0/19242.211.32.1 to 242.211.63.254242.211.63.2558,190
27242.211.64.0/19242.211.64.1 to 242.211.95.254242.211.95.2558,190
28242.211.96.0/19242.211.96.1 to 242.211.127.254242.211.127.2558,190
29242.211.128.0/19242.211.128.1 to 242.211.159.254242.211.159.2558,190
30242.211.160.0/19242.211.160.1 to 242.211.191.254242.211.191.2558,190
31242.211.192.0/19242.211.192.1 to 242.211.223.254242.211.223.2558,190
32242.211.224.0/19242.211.224.1 to 242.211.255.254242.211.255.2558,190
33242.212.0.0/19242.212.0.1 to 242.212.31.254242.212.31.2558,190
34242.212.32.0/19242.212.32.1 to 242.212.63.254242.212.63.2558,190
35242.212.64.0/19242.212.64.1 to 242.212.95.254242.212.95.2558,190
36242.212.96.0/19242.212.96.1 to 242.212.127.254242.212.127.2558,190
37242.212.128.0/19242.212.128.1 to 242.212.159.254242.212.159.2558,190
38242.212.160.0/19242.212.160.1 to 242.212.191.254242.212.191.2558,190
39242.212.192.0/19242.212.192.1 to 242.212.223.254242.212.223.2558,190
40242.212.224.0/19242.212.224.1 to 242.212.255.254242.212.255.2558,190
41242.213.0.0/19242.213.0.1 to 242.213.31.254242.213.31.2558,190
42242.213.32.0/19242.213.32.1 to 242.213.63.254242.213.63.2558,190
43242.213.64.0/19242.213.64.1 to 242.213.95.254242.213.95.2558,190
44242.213.96.0/19242.213.96.1 to 242.213.127.254242.213.127.2558,190
45242.213.128.0/19242.213.128.1 to 242.213.159.254242.213.159.2558,190
46242.213.160.0/19242.213.160.1 to 242.213.191.254242.213.191.2558,190
47242.213.192.0/19242.213.192.1 to 242.213.223.254242.213.223.2558,190
48242.213.224.0/19242.213.224.1 to 242.213.255.254242.213.255.2558,190
49242.214.0.0/19242.214.0.1 to 242.214.31.254242.214.31.2558,190
50242.214.32.0/19242.214.32.1 to 242.214.63.254242.214.63.2558,190
51242.214.64.0/19242.214.64.1 to 242.214.95.254242.214.95.2558,190
52242.214.96.0/19242.214.96.1 to 242.214.127.254242.214.127.2558,190
53242.214.128.0/19242.214.128.1 to 242.214.159.254242.214.159.2558,190
54242.214.160.0/19242.214.160.1 to 242.214.191.254242.214.191.2558,190
55242.214.192.0/19242.214.192.1 to 242.214.223.254242.214.223.2558,190
56242.214.224.0/19242.214.224.1 to 242.214.255.254242.214.255.2558,190
57242.215.0.0/19242.215.0.1 to 242.215.31.254242.215.31.2558,190
58242.215.32.0/19242.215.32.1 to 242.215.63.254242.215.63.2558,190
59242.215.64.0/19242.215.64.1 to 242.215.95.254242.215.95.2558,190
60242.215.96.0/19242.215.96.1 to 242.215.127.254242.215.127.2558,190
61242.215.128.0/19242.215.128.1 to 242.215.159.254242.215.159.2558,190
62242.215.160.0/19242.215.160.1 to 242.215.191.254242.215.191.2558,190
63242.215.192.0/19242.215.192.1 to 242.215.223.254242.215.223.2558,190
64242.215.224.0/19242.215.224.1 to 242.215.255.254242.215.255.2558,190
65242.216.0.0/19242.216.0.1 to 242.216.31.254242.216.31.2558,190
66242.216.32.0/19242.216.32.1 to 242.216.63.254242.216.63.2558,190
67242.216.64.0/19242.216.64.1 to 242.216.95.254242.216.95.2558,190
68242.216.96.0/19242.216.96.1 to 242.216.127.254242.216.127.2558,190
69242.216.128.0/19242.216.128.1 to 242.216.159.254242.216.159.2558,190
70242.216.160.0/19242.216.160.1 to 242.216.191.254242.216.191.2558,190
71242.216.192.0/19242.216.192.1 to 242.216.223.254242.216.223.2558,190
72242.216.224.0/19242.216.224.1 to 242.216.255.254242.216.255.2558,190
73242.217.0.0/19242.217.0.1 to 242.217.31.254242.217.31.2558,190
74242.217.32.0/19242.217.32.1 to 242.217.63.254242.217.63.2558,190
75242.217.64.0/19242.217.64.1 to 242.217.95.254242.217.95.2558,190
76242.217.96.0/19242.217.96.1 to 242.217.127.254242.217.127.2558,190
77242.217.128.0/19242.217.128.1 to 242.217.159.254242.217.159.2558,190
78242.217.160.0/19242.217.160.1 to 242.217.191.254242.217.191.2558,190
79242.217.192.0/19242.217.192.1 to 242.217.223.254242.217.223.2558,190
80242.217.224.0/19242.217.224.1 to 242.217.255.254242.217.255.2558,190
81242.218.0.0/19242.218.0.1 to 242.218.31.254242.218.31.2558,190
82242.218.32.0/19242.218.32.1 to 242.218.63.254242.218.63.2558,190
83242.218.64.0/19242.218.64.1 to 242.218.95.254242.218.95.2558,190
84242.218.96.0/19242.218.96.1 to 242.218.127.254242.218.127.2558,190
85242.218.128.0/19242.218.128.1 to 242.218.159.254242.218.159.2558,190
86242.218.160.0/19242.218.160.1 to 242.218.191.254242.218.191.2558,190
87242.218.192.0/19242.218.192.1 to 242.218.223.254242.218.223.2558,190
88242.218.224.0/19242.218.224.1 to 242.218.255.254242.218.255.2558,190
89242.219.0.0/19242.219.0.1 to 242.219.31.254242.219.31.2558,190
90242.219.32.0/19242.219.32.1 to 242.219.63.254242.219.63.2558,190
91242.219.64.0/19242.219.64.1 to 242.219.95.254242.219.95.2558,190
92242.219.96.0/19242.219.96.1 to 242.219.127.254242.219.127.2558,190
93242.219.128.0/19242.219.128.1 to 242.219.159.254242.219.159.2558,190
94242.219.160.0/19242.219.160.1 to 242.219.191.254242.219.191.2558,190
95242.219.192.0/19242.219.192.1 to 242.219.223.254242.219.223.2558,190
96242.219.224.0/19242.219.224.1 to 242.219.255.254242.219.255.2558,190
97242.220.0.0/19242.220.0.1 to 242.220.31.254242.220.31.2558,190
98242.220.32.0/19242.220.32.1 to 242.220.63.254242.220.63.2558,190
99242.220.64.0/19242.220.64.1 to 242.220.95.254242.220.95.2558,190
100242.220.96.0/19242.220.96.1 to 242.220.127.254242.220.127.2558,190
101242.220.128.0/19242.220.128.1 to 242.220.159.254242.220.159.2558,190
102242.220.160.0/19242.220.160.1 to 242.220.191.254242.220.191.2558,190
103242.220.192.0/19242.220.192.1 to 242.220.223.254242.220.223.2558,190
104242.220.224.0/19242.220.224.1 to 242.220.255.254242.220.255.2558,190
105242.221.0.0/19242.221.0.1 to 242.221.31.254242.221.31.2558,190
106242.221.32.0/19242.221.32.1 to 242.221.63.254242.221.63.2558,190
107242.221.64.0/19242.221.64.1 to 242.221.95.254242.221.95.2558,190
108242.221.96.0/19242.221.96.1 to 242.221.127.254242.221.127.2558,190
109242.221.128.0/19242.221.128.1 to 242.221.159.254242.221.159.2558,190
110242.221.160.0/19242.221.160.1 to 242.221.191.254242.221.191.2558,190
111242.221.192.0/19242.221.192.1 to 242.221.223.254242.221.223.2558,190
112242.221.224.0/19242.221.224.1 to 242.221.255.254242.221.255.2558,190
113242.222.0.0/19242.222.0.1 to 242.222.31.254242.222.31.2558,190
114242.222.32.0/19242.222.32.1 to 242.222.63.254242.222.63.2558,190
115242.222.64.0/19242.222.64.1 to 242.222.95.254242.222.95.2558,190
116242.222.96.0/19242.222.96.1 to 242.222.127.254242.222.127.2558,190
117242.222.128.0/19242.222.128.1 to 242.222.159.254242.222.159.2558,190
118242.222.160.0/19242.222.160.1 to 242.222.191.254242.222.191.2558,190
119242.222.192.0/19242.222.192.1 to 242.222.223.254242.222.223.2558,190
120242.222.224.0/19242.222.224.1 to 242.222.255.254242.222.255.2558,190
121242.223.0.0/19242.223.0.1 to 242.223.31.254242.223.31.2558,190
122242.223.32.0/19242.223.32.1 to 242.223.63.254242.223.63.2558,190
123242.223.64.0/19242.223.64.1 to 242.223.95.254242.223.95.2558,190
124242.223.96.0/19242.223.96.1 to 242.223.127.254242.223.127.2558,190
125242.223.128.0/19242.223.128.1 to 242.223.159.254242.223.159.2558,190
126242.223.160.0/19242.223.160.1 to 242.223.191.254242.223.191.2558,190
127242.223.192.0/19242.223.192.1 to 242.223.223.254242.223.223.2558,190
128242.223.224.0/19242.223.224.1 to 242.223.255.254242.223.255.2558,190

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.