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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.

Network238.240.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
238.240.0.0
Broadcast address
238.255.255.255
First usable
238.240.0.1
Last usable
238.255.255.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex EEF00000 · Integer 4008706048 to 4009754623
Reverse DNS zones
240.238.in-addr.arpa
241.238.in-addr.arpa
242.238.in-addr.arpa
243.238.in-addr.arpa
244.238.in-addr.arpa
245.238.in-addr.arpa
246.238.in-addr.arpa
247.238.in-addr.arpa
248.238.in-addr.arpa
249.238.in-addr.arpa
250.238.in-addr.arpa
251.238.in-addr.arpa
252.238.in-addr.arpa
253.238.in-addr.arpa
254.238.in-addr.arpa
255.238.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
Address11101110.11110000.00000000.00000000238.240.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11101110.11110000.00000000.00000000238.240.0.0
Broadcast11101110.11111111.11111111.11111111238.255.255.255
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)

238.240.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1238.240.0.0/19238.240.0.1 to 238.240.31.254238.240.31.2558,190
2238.240.32.0/19238.240.32.1 to 238.240.63.254238.240.63.2558,190
3238.240.64.0/19238.240.64.1 to 238.240.95.254238.240.95.2558,190
4238.240.96.0/19238.240.96.1 to 238.240.127.254238.240.127.2558,190
5238.240.128.0/19238.240.128.1 to 238.240.159.254238.240.159.2558,190
6238.240.160.0/19238.240.160.1 to 238.240.191.254238.240.191.2558,190
7238.240.192.0/19238.240.192.1 to 238.240.223.254238.240.223.2558,190
8238.240.224.0/19238.240.224.1 to 238.240.255.254238.240.255.2558,190
9238.241.0.0/19238.241.0.1 to 238.241.31.254238.241.31.2558,190
10238.241.32.0/19238.241.32.1 to 238.241.63.254238.241.63.2558,190
11238.241.64.0/19238.241.64.1 to 238.241.95.254238.241.95.2558,190
12238.241.96.0/19238.241.96.1 to 238.241.127.254238.241.127.2558,190
13238.241.128.0/19238.241.128.1 to 238.241.159.254238.241.159.2558,190
14238.241.160.0/19238.241.160.1 to 238.241.191.254238.241.191.2558,190
15238.241.192.0/19238.241.192.1 to 238.241.223.254238.241.223.2558,190
16238.241.224.0/19238.241.224.1 to 238.241.255.254238.241.255.2558,190
17238.242.0.0/19238.242.0.1 to 238.242.31.254238.242.31.2558,190
18238.242.32.0/19238.242.32.1 to 238.242.63.254238.242.63.2558,190
19238.242.64.0/19238.242.64.1 to 238.242.95.254238.242.95.2558,190
20238.242.96.0/19238.242.96.1 to 238.242.127.254238.242.127.2558,190
21238.242.128.0/19238.242.128.1 to 238.242.159.254238.242.159.2558,190
22238.242.160.0/19238.242.160.1 to 238.242.191.254238.242.191.2558,190
23238.242.192.0/19238.242.192.1 to 238.242.223.254238.242.223.2558,190
24238.242.224.0/19238.242.224.1 to 238.242.255.254238.242.255.2558,190
25238.243.0.0/19238.243.0.1 to 238.243.31.254238.243.31.2558,190
26238.243.32.0/19238.243.32.1 to 238.243.63.254238.243.63.2558,190
27238.243.64.0/19238.243.64.1 to 238.243.95.254238.243.95.2558,190
28238.243.96.0/19238.243.96.1 to 238.243.127.254238.243.127.2558,190
29238.243.128.0/19238.243.128.1 to 238.243.159.254238.243.159.2558,190
30238.243.160.0/19238.243.160.1 to 238.243.191.254238.243.191.2558,190
31238.243.192.0/19238.243.192.1 to 238.243.223.254238.243.223.2558,190
32238.243.224.0/19238.243.224.1 to 238.243.255.254238.243.255.2558,190
33238.244.0.0/19238.244.0.1 to 238.244.31.254238.244.31.2558,190
34238.244.32.0/19238.244.32.1 to 238.244.63.254238.244.63.2558,190
35238.244.64.0/19238.244.64.1 to 238.244.95.254238.244.95.2558,190
36238.244.96.0/19238.244.96.1 to 238.244.127.254238.244.127.2558,190
37238.244.128.0/19238.244.128.1 to 238.244.159.254238.244.159.2558,190
38238.244.160.0/19238.244.160.1 to 238.244.191.254238.244.191.2558,190
39238.244.192.0/19238.244.192.1 to 238.244.223.254238.244.223.2558,190
40238.244.224.0/19238.244.224.1 to 238.244.255.254238.244.255.2558,190
41238.245.0.0/19238.245.0.1 to 238.245.31.254238.245.31.2558,190
42238.245.32.0/19238.245.32.1 to 238.245.63.254238.245.63.2558,190
43238.245.64.0/19238.245.64.1 to 238.245.95.254238.245.95.2558,190
44238.245.96.0/19238.245.96.1 to 238.245.127.254238.245.127.2558,190
45238.245.128.0/19238.245.128.1 to 238.245.159.254238.245.159.2558,190
46238.245.160.0/19238.245.160.1 to 238.245.191.254238.245.191.2558,190
47238.245.192.0/19238.245.192.1 to 238.245.223.254238.245.223.2558,190
48238.245.224.0/19238.245.224.1 to 238.245.255.254238.245.255.2558,190
49238.246.0.0/19238.246.0.1 to 238.246.31.254238.246.31.2558,190
50238.246.32.0/19238.246.32.1 to 238.246.63.254238.246.63.2558,190
51238.246.64.0/19238.246.64.1 to 238.246.95.254238.246.95.2558,190
52238.246.96.0/19238.246.96.1 to 238.246.127.254238.246.127.2558,190
53238.246.128.0/19238.246.128.1 to 238.246.159.254238.246.159.2558,190
54238.246.160.0/19238.246.160.1 to 238.246.191.254238.246.191.2558,190
55238.246.192.0/19238.246.192.1 to 238.246.223.254238.246.223.2558,190
56238.246.224.0/19238.246.224.1 to 238.246.255.254238.246.255.2558,190
57238.247.0.0/19238.247.0.1 to 238.247.31.254238.247.31.2558,190
58238.247.32.0/19238.247.32.1 to 238.247.63.254238.247.63.2558,190
59238.247.64.0/19238.247.64.1 to 238.247.95.254238.247.95.2558,190
60238.247.96.0/19238.247.96.1 to 238.247.127.254238.247.127.2558,190
61238.247.128.0/19238.247.128.1 to 238.247.159.254238.247.159.2558,190
62238.247.160.0/19238.247.160.1 to 238.247.191.254238.247.191.2558,190
63238.247.192.0/19238.247.192.1 to 238.247.223.254238.247.223.2558,190
64238.247.224.0/19238.247.224.1 to 238.247.255.254238.247.255.2558,190
65238.248.0.0/19238.248.0.1 to 238.248.31.254238.248.31.2558,190
66238.248.32.0/19238.248.32.1 to 238.248.63.254238.248.63.2558,190
67238.248.64.0/19238.248.64.1 to 238.248.95.254238.248.95.2558,190
68238.248.96.0/19238.248.96.1 to 238.248.127.254238.248.127.2558,190
69238.248.128.0/19238.248.128.1 to 238.248.159.254238.248.159.2558,190
70238.248.160.0/19238.248.160.1 to 238.248.191.254238.248.191.2558,190
71238.248.192.0/19238.248.192.1 to 238.248.223.254238.248.223.2558,190
72238.248.224.0/19238.248.224.1 to 238.248.255.254238.248.255.2558,190
73238.249.0.0/19238.249.0.1 to 238.249.31.254238.249.31.2558,190
74238.249.32.0/19238.249.32.1 to 238.249.63.254238.249.63.2558,190
75238.249.64.0/19238.249.64.1 to 238.249.95.254238.249.95.2558,190
76238.249.96.0/19238.249.96.1 to 238.249.127.254238.249.127.2558,190
77238.249.128.0/19238.249.128.1 to 238.249.159.254238.249.159.2558,190
78238.249.160.0/19238.249.160.1 to 238.249.191.254238.249.191.2558,190
79238.249.192.0/19238.249.192.1 to 238.249.223.254238.249.223.2558,190
80238.249.224.0/19238.249.224.1 to 238.249.255.254238.249.255.2558,190
81238.250.0.0/19238.250.0.1 to 238.250.31.254238.250.31.2558,190
82238.250.32.0/19238.250.32.1 to 238.250.63.254238.250.63.2558,190
83238.250.64.0/19238.250.64.1 to 238.250.95.254238.250.95.2558,190
84238.250.96.0/19238.250.96.1 to 238.250.127.254238.250.127.2558,190
85238.250.128.0/19238.250.128.1 to 238.250.159.254238.250.159.2558,190
86238.250.160.0/19238.250.160.1 to 238.250.191.254238.250.191.2558,190
87238.250.192.0/19238.250.192.1 to 238.250.223.254238.250.223.2558,190
88238.250.224.0/19238.250.224.1 to 238.250.255.254238.250.255.2558,190
89238.251.0.0/19238.251.0.1 to 238.251.31.254238.251.31.2558,190
90238.251.32.0/19238.251.32.1 to 238.251.63.254238.251.63.2558,190
91238.251.64.0/19238.251.64.1 to 238.251.95.254238.251.95.2558,190
92238.251.96.0/19238.251.96.1 to 238.251.127.254238.251.127.2558,190
93238.251.128.0/19238.251.128.1 to 238.251.159.254238.251.159.2558,190
94238.251.160.0/19238.251.160.1 to 238.251.191.254238.251.191.2558,190
95238.251.192.0/19238.251.192.1 to 238.251.223.254238.251.223.2558,190
96238.251.224.0/19238.251.224.1 to 238.251.255.254238.251.255.2558,190
97238.252.0.0/19238.252.0.1 to 238.252.31.254238.252.31.2558,190
98238.252.32.0/19238.252.32.1 to 238.252.63.254238.252.63.2558,190
99238.252.64.0/19238.252.64.1 to 238.252.95.254238.252.95.2558,190
100238.252.96.0/19238.252.96.1 to 238.252.127.254238.252.127.2558,190
101238.252.128.0/19238.252.128.1 to 238.252.159.254238.252.159.2558,190
102238.252.160.0/19238.252.160.1 to 238.252.191.254238.252.191.2558,190
103238.252.192.0/19238.252.192.1 to 238.252.223.254238.252.223.2558,190
104238.252.224.0/19238.252.224.1 to 238.252.255.254238.252.255.2558,190
105238.253.0.0/19238.253.0.1 to 238.253.31.254238.253.31.2558,190
106238.253.32.0/19238.253.32.1 to 238.253.63.254238.253.63.2558,190
107238.253.64.0/19238.253.64.1 to 238.253.95.254238.253.95.2558,190
108238.253.96.0/19238.253.96.1 to 238.253.127.254238.253.127.2558,190
109238.253.128.0/19238.253.128.1 to 238.253.159.254238.253.159.2558,190
110238.253.160.0/19238.253.160.1 to 238.253.191.254238.253.191.2558,190
111238.253.192.0/19238.253.192.1 to 238.253.223.254238.253.223.2558,190
112238.253.224.0/19238.253.224.1 to 238.253.255.254238.253.255.2558,190
113238.254.0.0/19238.254.0.1 to 238.254.31.254238.254.31.2558,190
114238.254.32.0/19238.254.32.1 to 238.254.63.254238.254.63.2558,190
115238.254.64.0/19238.254.64.1 to 238.254.95.254238.254.95.2558,190
116238.254.96.0/19238.254.96.1 to 238.254.127.254238.254.127.2558,190
117238.254.128.0/19238.254.128.1 to 238.254.159.254238.254.159.2558,190
118238.254.160.0/19238.254.160.1 to 238.254.191.254238.254.191.2558,190
119238.254.192.0/19238.254.192.1 to 238.254.223.254238.254.223.2558,190
120238.254.224.0/19238.254.224.1 to 238.254.255.254238.254.255.2558,190
121238.255.0.0/19238.255.0.1 to 238.255.31.254238.255.31.2558,190
122238.255.32.0/19238.255.32.1 to 238.255.63.254238.255.63.2558,190
123238.255.64.0/19238.255.64.1 to 238.255.95.254238.255.95.2558,190
124238.255.96.0/19238.255.96.1 to 238.255.127.254238.255.127.2558,190
125238.255.128.0/19238.255.128.1 to 238.255.159.254238.255.159.2558,190
126238.255.160.0/19238.255.160.1 to 238.255.191.254238.255.191.2558,190
127238.255.192.0/19238.255.192.1 to 238.255.223.254238.255.223.2558,190
128238.255.224.0/19238.255.224.1 to 238.255.255.254238.255.255.2558,190

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.