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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.

Network236.48.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
236.48.0.0
Broadcast address
236.63.255.255
First usable
236.48.0.1
Last usable
236.63.255.254
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 EC300000 · Integer 3962568704 to 3963617279
Reverse DNS zones
48.236.in-addr.arpa
49.236.in-addr.arpa
50.236.in-addr.arpa
51.236.in-addr.arpa
52.236.in-addr.arpa
53.236.in-addr.arpa
54.236.in-addr.arpa
55.236.in-addr.arpa
56.236.in-addr.arpa
57.236.in-addr.arpa
58.236.in-addr.arpa
59.236.in-addr.arpa
60.236.in-addr.arpa
61.236.in-addr.arpa
62.236.in-addr.arpa
63.236.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
Address11101100.00110000.00000000.00000000236.48.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11101100.00110000.00000000.00000000236.48.0.0
Broadcast11101100.00111111.11111111.11111111236.63.255.255
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)

236.48.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1236.48.0.0/19236.48.0.1 to 236.48.31.254236.48.31.2558,190
2236.48.32.0/19236.48.32.1 to 236.48.63.254236.48.63.2558,190
3236.48.64.0/19236.48.64.1 to 236.48.95.254236.48.95.2558,190
4236.48.96.0/19236.48.96.1 to 236.48.127.254236.48.127.2558,190
5236.48.128.0/19236.48.128.1 to 236.48.159.254236.48.159.2558,190
6236.48.160.0/19236.48.160.1 to 236.48.191.254236.48.191.2558,190
7236.48.192.0/19236.48.192.1 to 236.48.223.254236.48.223.2558,190
8236.48.224.0/19236.48.224.1 to 236.48.255.254236.48.255.2558,190
9236.49.0.0/19236.49.0.1 to 236.49.31.254236.49.31.2558,190
10236.49.32.0/19236.49.32.1 to 236.49.63.254236.49.63.2558,190
11236.49.64.0/19236.49.64.1 to 236.49.95.254236.49.95.2558,190
12236.49.96.0/19236.49.96.1 to 236.49.127.254236.49.127.2558,190
13236.49.128.0/19236.49.128.1 to 236.49.159.254236.49.159.2558,190
14236.49.160.0/19236.49.160.1 to 236.49.191.254236.49.191.2558,190
15236.49.192.0/19236.49.192.1 to 236.49.223.254236.49.223.2558,190
16236.49.224.0/19236.49.224.1 to 236.49.255.254236.49.255.2558,190
17236.50.0.0/19236.50.0.1 to 236.50.31.254236.50.31.2558,190
18236.50.32.0/19236.50.32.1 to 236.50.63.254236.50.63.2558,190
19236.50.64.0/19236.50.64.1 to 236.50.95.254236.50.95.2558,190
20236.50.96.0/19236.50.96.1 to 236.50.127.254236.50.127.2558,190
21236.50.128.0/19236.50.128.1 to 236.50.159.254236.50.159.2558,190
22236.50.160.0/19236.50.160.1 to 236.50.191.254236.50.191.2558,190
23236.50.192.0/19236.50.192.1 to 236.50.223.254236.50.223.2558,190
24236.50.224.0/19236.50.224.1 to 236.50.255.254236.50.255.2558,190
25236.51.0.0/19236.51.0.1 to 236.51.31.254236.51.31.2558,190
26236.51.32.0/19236.51.32.1 to 236.51.63.254236.51.63.2558,190
27236.51.64.0/19236.51.64.1 to 236.51.95.254236.51.95.2558,190
28236.51.96.0/19236.51.96.1 to 236.51.127.254236.51.127.2558,190
29236.51.128.0/19236.51.128.1 to 236.51.159.254236.51.159.2558,190
30236.51.160.0/19236.51.160.1 to 236.51.191.254236.51.191.2558,190
31236.51.192.0/19236.51.192.1 to 236.51.223.254236.51.223.2558,190
32236.51.224.0/19236.51.224.1 to 236.51.255.254236.51.255.2558,190
33236.52.0.0/19236.52.0.1 to 236.52.31.254236.52.31.2558,190
34236.52.32.0/19236.52.32.1 to 236.52.63.254236.52.63.2558,190
35236.52.64.0/19236.52.64.1 to 236.52.95.254236.52.95.2558,190
36236.52.96.0/19236.52.96.1 to 236.52.127.254236.52.127.2558,190
37236.52.128.0/19236.52.128.1 to 236.52.159.254236.52.159.2558,190
38236.52.160.0/19236.52.160.1 to 236.52.191.254236.52.191.2558,190
39236.52.192.0/19236.52.192.1 to 236.52.223.254236.52.223.2558,190
40236.52.224.0/19236.52.224.1 to 236.52.255.254236.52.255.2558,190
41236.53.0.0/19236.53.0.1 to 236.53.31.254236.53.31.2558,190
42236.53.32.0/19236.53.32.1 to 236.53.63.254236.53.63.2558,190
43236.53.64.0/19236.53.64.1 to 236.53.95.254236.53.95.2558,190
44236.53.96.0/19236.53.96.1 to 236.53.127.254236.53.127.2558,190
45236.53.128.0/19236.53.128.1 to 236.53.159.254236.53.159.2558,190
46236.53.160.0/19236.53.160.1 to 236.53.191.254236.53.191.2558,190
47236.53.192.0/19236.53.192.1 to 236.53.223.254236.53.223.2558,190
48236.53.224.0/19236.53.224.1 to 236.53.255.254236.53.255.2558,190
49236.54.0.0/19236.54.0.1 to 236.54.31.254236.54.31.2558,190
50236.54.32.0/19236.54.32.1 to 236.54.63.254236.54.63.2558,190
51236.54.64.0/19236.54.64.1 to 236.54.95.254236.54.95.2558,190
52236.54.96.0/19236.54.96.1 to 236.54.127.254236.54.127.2558,190
53236.54.128.0/19236.54.128.1 to 236.54.159.254236.54.159.2558,190
54236.54.160.0/19236.54.160.1 to 236.54.191.254236.54.191.2558,190
55236.54.192.0/19236.54.192.1 to 236.54.223.254236.54.223.2558,190
56236.54.224.0/19236.54.224.1 to 236.54.255.254236.54.255.2558,190
57236.55.0.0/19236.55.0.1 to 236.55.31.254236.55.31.2558,190
58236.55.32.0/19236.55.32.1 to 236.55.63.254236.55.63.2558,190
59236.55.64.0/19236.55.64.1 to 236.55.95.254236.55.95.2558,190
60236.55.96.0/19236.55.96.1 to 236.55.127.254236.55.127.2558,190
61236.55.128.0/19236.55.128.1 to 236.55.159.254236.55.159.2558,190
62236.55.160.0/19236.55.160.1 to 236.55.191.254236.55.191.2558,190
63236.55.192.0/19236.55.192.1 to 236.55.223.254236.55.223.2558,190
64236.55.224.0/19236.55.224.1 to 236.55.255.254236.55.255.2558,190
65236.56.0.0/19236.56.0.1 to 236.56.31.254236.56.31.2558,190
66236.56.32.0/19236.56.32.1 to 236.56.63.254236.56.63.2558,190
67236.56.64.0/19236.56.64.1 to 236.56.95.254236.56.95.2558,190
68236.56.96.0/19236.56.96.1 to 236.56.127.254236.56.127.2558,190
69236.56.128.0/19236.56.128.1 to 236.56.159.254236.56.159.2558,190
70236.56.160.0/19236.56.160.1 to 236.56.191.254236.56.191.2558,190
71236.56.192.0/19236.56.192.1 to 236.56.223.254236.56.223.2558,190
72236.56.224.0/19236.56.224.1 to 236.56.255.254236.56.255.2558,190
73236.57.0.0/19236.57.0.1 to 236.57.31.254236.57.31.2558,190
74236.57.32.0/19236.57.32.1 to 236.57.63.254236.57.63.2558,190
75236.57.64.0/19236.57.64.1 to 236.57.95.254236.57.95.2558,190
76236.57.96.0/19236.57.96.1 to 236.57.127.254236.57.127.2558,190
77236.57.128.0/19236.57.128.1 to 236.57.159.254236.57.159.2558,190
78236.57.160.0/19236.57.160.1 to 236.57.191.254236.57.191.2558,190
79236.57.192.0/19236.57.192.1 to 236.57.223.254236.57.223.2558,190
80236.57.224.0/19236.57.224.1 to 236.57.255.254236.57.255.2558,190
81236.58.0.0/19236.58.0.1 to 236.58.31.254236.58.31.2558,190
82236.58.32.0/19236.58.32.1 to 236.58.63.254236.58.63.2558,190
83236.58.64.0/19236.58.64.1 to 236.58.95.254236.58.95.2558,190
84236.58.96.0/19236.58.96.1 to 236.58.127.254236.58.127.2558,190
85236.58.128.0/19236.58.128.1 to 236.58.159.254236.58.159.2558,190
86236.58.160.0/19236.58.160.1 to 236.58.191.254236.58.191.2558,190
87236.58.192.0/19236.58.192.1 to 236.58.223.254236.58.223.2558,190
88236.58.224.0/19236.58.224.1 to 236.58.255.254236.58.255.2558,190
89236.59.0.0/19236.59.0.1 to 236.59.31.254236.59.31.2558,190
90236.59.32.0/19236.59.32.1 to 236.59.63.254236.59.63.2558,190
91236.59.64.0/19236.59.64.1 to 236.59.95.254236.59.95.2558,190
92236.59.96.0/19236.59.96.1 to 236.59.127.254236.59.127.2558,190
93236.59.128.0/19236.59.128.1 to 236.59.159.254236.59.159.2558,190
94236.59.160.0/19236.59.160.1 to 236.59.191.254236.59.191.2558,190
95236.59.192.0/19236.59.192.1 to 236.59.223.254236.59.223.2558,190
96236.59.224.0/19236.59.224.1 to 236.59.255.254236.59.255.2558,190
97236.60.0.0/19236.60.0.1 to 236.60.31.254236.60.31.2558,190
98236.60.32.0/19236.60.32.1 to 236.60.63.254236.60.63.2558,190
99236.60.64.0/19236.60.64.1 to 236.60.95.254236.60.95.2558,190
100236.60.96.0/19236.60.96.1 to 236.60.127.254236.60.127.2558,190
101236.60.128.0/19236.60.128.1 to 236.60.159.254236.60.159.2558,190
102236.60.160.0/19236.60.160.1 to 236.60.191.254236.60.191.2558,190
103236.60.192.0/19236.60.192.1 to 236.60.223.254236.60.223.2558,190
104236.60.224.0/19236.60.224.1 to 236.60.255.254236.60.255.2558,190
105236.61.0.0/19236.61.0.1 to 236.61.31.254236.61.31.2558,190
106236.61.32.0/19236.61.32.1 to 236.61.63.254236.61.63.2558,190
107236.61.64.0/19236.61.64.1 to 236.61.95.254236.61.95.2558,190
108236.61.96.0/19236.61.96.1 to 236.61.127.254236.61.127.2558,190
109236.61.128.0/19236.61.128.1 to 236.61.159.254236.61.159.2558,190
110236.61.160.0/19236.61.160.1 to 236.61.191.254236.61.191.2558,190
111236.61.192.0/19236.61.192.1 to 236.61.223.254236.61.223.2558,190
112236.61.224.0/19236.61.224.1 to 236.61.255.254236.61.255.2558,190
113236.62.0.0/19236.62.0.1 to 236.62.31.254236.62.31.2558,190
114236.62.32.0/19236.62.32.1 to 236.62.63.254236.62.63.2558,190
115236.62.64.0/19236.62.64.1 to 236.62.95.254236.62.95.2558,190
116236.62.96.0/19236.62.96.1 to 236.62.127.254236.62.127.2558,190
117236.62.128.0/19236.62.128.1 to 236.62.159.254236.62.159.2558,190
118236.62.160.0/19236.62.160.1 to 236.62.191.254236.62.191.2558,190
119236.62.192.0/19236.62.192.1 to 236.62.223.254236.62.223.2558,190
120236.62.224.0/19236.62.224.1 to 236.62.255.254236.62.255.2558,190
121236.63.0.0/19236.63.0.1 to 236.63.31.254236.63.31.2558,190
122236.63.32.0/19236.63.32.1 to 236.63.63.254236.63.63.2558,190
123236.63.64.0/19236.63.64.1 to 236.63.95.254236.63.95.2558,190
124236.63.96.0/19236.63.96.1 to 236.63.127.254236.63.127.2558,190
125236.63.128.0/19236.63.128.1 to 236.63.159.254236.63.159.2558,190
126236.63.160.0/19236.63.160.1 to 236.63.191.254236.63.191.2558,190
127236.63.192.0/19236.63.192.1 to 236.63.223.254236.63.223.2558,190
128236.63.224.0/19236.63.224.1 to 236.63.255.254236.63.255.2558,190

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.