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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.

Network243.64.0.0/11
Usable hosts2,097,150
Subnet mask255.224.0.0
Addresses2,097,152
Network address
243.64.0.0
Broadcast address
243.95.255.255
First usable
243.64.0.1
Last usable
243.95.255.254
Usable hosts
2,097,150 (2,097,152 less the network and broadcast addresses)
Subnet mask
255.224.0.0
Wildcard mask
0.31.255.255 (Cisco ACLs, OSPF)
Prefix length
/11
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F3400000 · Integer 4081057792 to 4083154943
Reverse DNS zones
64.243.in-addr.arpa
65.243.in-addr.arpa
66.243.in-addr.arpa
67.243.in-addr.arpa
68.243.in-addr.arpa
69.243.in-addr.arpa
70.243.in-addr.arpa
71.243.in-addr.arpa
72.243.in-addr.arpa
73.243.in-addr.arpa
74.243.in-addr.arpa
75.243.in-addr.arpa
76.243.in-addr.arpa
77.243.in-addr.arpa
78.243.in-addr.arpa
79.243.in-addr.arpa
and 16 more
/11 is not on a 8-bit boundary, so it takes 32 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110011.01000000.00000000.00000000243.64.0.0
Subnet mask11111111.11100000.00000000.00000000255.224.0.0
Network11110011.01000000.00000000.00000000243.64.0.0
Broadcast11110011.01011111.11111111.11111111243.95.255.255
Split into smaller subnets/18
/12 (2)/13 (4)/14 (8)/15 (16)/16 (32)/17 (64)/18 (128)/19 (256)/20 (512)/21 (1,024)/22 (2,048)/23 (4,096)

243.64.0.0/11 makes 128 subnets of /18.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1243.64.0.0/18243.64.0.1 to 243.64.63.254243.64.63.25516,382
2243.64.64.0/18243.64.64.1 to 243.64.127.254243.64.127.25516,382
3243.64.128.0/18243.64.128.1 to 243.64.191.254243.64.191.25516,382
4243.64.192.0/18243.64.192.1 to 243.64.255.254243.64.255.25516,382
5243.65.0.0/18243.65.0.1 to 243.65.63.254243.65.63.25516,382
6243.65.64.0/18243.65.64.1 to 243.65.127.254243.65.127.25516,382
7243.65.128.0/18243.65.128.1 to 243.65.191.254243.65.191.25516,382
8243.65.192.0/18243.65.192.1 to 243.65.255.254243.65.255.25516,382
9243.66.0.0/18243.66.0.1 to 243.66.63.254243.66.63.25516,382
10243.66.64.0/18243.66.64.1 to 243.66.127.254243.66.127.25516,382
11243.66.128.0/18243.66.128.1 to 243.66.191.254243.66.191.25516,382
12243.66.192.0/18243.66.192.1 to 243.66.255.254243.66.255.25516,382
13243.67.0.0/18243.67.0.1 to 243.67.63.254243.67.63.25516,382
14243.67.64.0/18243.67.64.1 to 243.67.127.254243.67.127.25516,382
15243.67.128.0/18243.67.128.1 to 243.67.191.254243.67.191.25516,382
16243.67.192.0/18243.67.192.1 to 243.67.255.254243.67.255.25516,382
17243.68.0.0/18243.68.0.1 to 243.68.63.254243.68.63.25516,382
18243.68.64.0/18243.68.64.1 to 243.68.127.254243.68.127.25516,382
19243.68.128.0/18243.68.128.1 to 243.68.191.254243.68.191.25516,382
20243.68.192.0/18243.68.192.1 to 243.68.255.254243.68.255.25516,382
21243.69.0.0/18243.69.0.1 to 243.69.63.254243.69.63.25516,382
22243.69.64.0/18243.69.64.1 to 243.69.127.254243.69.127.25516,382
23243.69.128.0/18243.69.128.1 to 243.69.191.254243.69.191.25516,382
24243.69.192.0/18243.69.192.1 to 243.69.255.254243.69.255.25516,382
25243.70.0.0/18243.70.0.1 to 243.70.63.254243.70.63.25516,382
26243.70.64.0/18243.70.64.1 to 243.70.127.254243.70.127.25516,382
27243.70.128.0/18243.70.128.1 to 243.70.191.254243.70.191.25516,382
28243.70.192.0/18243.70.192.1 to 243.70.255.254243.70.255.25516,382
29243.71.0.0/18243.71.0.1 to 243.71.63.254243.71.63.25516,382
30243.71.64.0/18243.71.64.1 to 243.71.127.254243.71.127.25516,382
31243.71.128.0/18243.71.128.1 to 243.71.191.254243.71.191.25516,382
32243.71.192.0/18243.71.192.1 to 243.71.255.254243.71.255.25516,382
33243.72.0.0/18243.72.0.1 to 243.72.63.254243.72.63.25516,382
34243.72.64.0/18243.72.64.1 to 243.72.127.254243.72.127.25516,382
35243.72.128.0/18243.72.128.1 to 243.72.191.254243.72.191.25516,382
36243.72.192.0/18243.72.192.1 to 243.72.255.254243.72.255.25516,382
37243.73.0.0/18243.73.0.1 to 243.73.63.254243.73.63.25516,382
38243.73.64.0/18243.73.64.1 to 243.73.127.254243.73.127.25516,382
39243.73.128.0/18243.73.128.1 to 243.73.191.254243.73.191.25516,382
40243.73.192.0/18243.73.192.1 to 243.73.255.254243.73.255.25516,382
41243.74.0.0/18243.74.0.1 to 243.74.63.254243.74.63.25516,382
42243.74.64.0/18243.74.64.1 to 243.74.127.254243.74.127.25516,382
43243.74.128.0/18243.74.128.1 to 243.74.191.254243.74.191.25516,382
44243.74.192.0/18243.74.192.1 to 243.74.255.254243.74.255.25516,382
45243.75.0.0/18243.75.0.1 to 243.75.63.254243.75.63.25516,382
46243.75.64.0/18243.75.64.1 to 243.75.127.254243.75.127.25516,382
47243.75.128.0/18243.75.128.1 to 243.75.191.254243.75.191.25516,382
48243.75.192.0/18243.75.192.1 to 243.75.255.254243.75.255.25516,382
49243.76.0.0/18243.76.0.1 to 243.76.63.254243.76.63.25516,382
50243.76.64.0/18243.76.64.1 to 243.76.127.254243.76.127.25516,382
51243.76.128.0/18243.76.128.1 to 243.76.191.254243.76.191.25516,382
52243.76.192.0/18243.76.192.1 to 243.76.255.254243.76.255.25516,382
53243.77.0.0/18243.77.0.1 to 243.77.63.254243.77.63.25516,382
54243.77.64.0/18243.77.64.1 to 243.77.127.254243.77.127.25516,382
55243.77.128.0/18243.77.128.1 to 243.77.191.254243.77.191.25516,382
56243.77.192.0/18243.77.192.1 to 243.77.255.254243.77.255.25516,382
57243.78.0.0/18243.78.0.1 to 243.78.63.254243.78.63.25516,382
58243.78.64.0/18243.78.64.1 to 243.78.127.254243.78.127.25516,382
59243.78.128.0/18243.78.128.1 to 243.78.191.254243.78.191.25516,382
60243.78.192.0/18243.78.192.1 to 243.78.255.254243.78.255.25516,382
61243.79.0.0/18243.79.0.1 to 243.79.63.254243.79.63.25516,382
62243.79.64.0/18243.79.64.1 to 243.79.127.254243.79.127.25516,382
63243.79.128.0/18243.79.128.1 to 243.79.191.254243.79.191.25516,382
64243.79.192.0/18243.79.192.1 to 243.79.255.254243.79.255.25516,382
65243.80.0.0/18243.80.0.1 to 243.80.63.254243.80.63.25516,382
66243.80.64.0/18243.80.64.1 to 243.80.127.254243.80.127.25516,382
67243.80.128.0/18243.80.128.1 to 243.80.191.254243.80.191.25516,382
68243.80.192.0/18243.80.192.1 to 243.80.255.254243.80.255.25516,382
69243.81.0.0/18243.81.0.1 to 243.81.63.254243.81.63.25516,382
70243.81.64.0/18243.81.64.1 to 243.81.127.254243.81.127.25516,382
71243.81.128.0/18243.81.128.1 to 243.81.191.254243.81.191.25516,382
72243.81.192.0/18243.81.192.1 to 243.81.255.254243.81.255.25516,382
73243.82.0.0/18243.82.0.1 to 243.82.63.254243.82.63.25516,382
74243.82.64.0/18243.82.64.1 to 243.82.127.254243.82.127.25516,382
75243.82.128.0/18243.82.128.1 to 243.82.191.254243.82.191.25516,382
76243.82.192.0/18243.82.192.1 to 243.82.255.254243.82.255.25516,382
77243.83.0.0/18243.83.0.1 to 243.83.63.254243.83.63.25516,382
78243.83.64.0/18243.83.64.1 to 243.83.127.254243.83.127.25516,382
79243.83.128.0/18243.83.128.1 to 243.83.191.254243.83.191.25516,382
80243.83.192.0/18243.83.192.1 to 243.83.255.254243.83.255.25516,382
81243.84.0.0/18243.84.0.1 to 243.84.63.254243.84.63.25516,382
82243.84.64.0/18243.84.64.1 to 243.84.127.254243.84.127.25516,382
83243.84.128.0/18243.84.128.1 to 243.84.191.254243.84.191.25516,382
84243.84.192.0/18243.84.192.1 to 243.84.255.254243.84.255.25516,382
85243.85.0.0/18243.85.0.1 to 243.85.63.254243.85.63.25516,382
86243.85.64.0/18243.85.64.1 to 243.85.127.254243.85.127.25516,382
87243.85.128.0/18243.85.128.1 to 243.85.191.254243.85.191.25516,382
88243.85.192.0/18243.85.192.1 to 243.85.255.254243.85.255.25516,382
89243.86.0.0/18243.86.0.1 to 243.86.63.254243.86.63.25516,382
90243.86.64.0/18243.86.64.1 to 243.86.127.254243.86.127.25516,382
91243.86.128.0/18243.86.128.1 to 243.86.191.254243.86.191.25516,382
92243.86.192.0/18243.86.192.1 to 243.86.255.254243.86.255.25516,382
93243.87.0.0/18243.87.0.1 to 243.87.63.254243.87.63.25516,382
94243.87.64.0/18243.87.64.1 to 243.87.127.254243.87.127.25516,382
95243.87.128.0/18243.87.128.1 to 243.87.191.254243.87.191.25516,382
96243.87.192.0/18243.87.192.1 to 243.87.255.254243.87.255.25516,382
97243.88.0.0/18243.88.0.1 to 243.88.63.254243.88.63.25516,382
98243.88.64.0/18243.88.64.1 to 243.88.127.254243.88.127.25516,382
99243.88.128.0/18243.88.128.1 to 243.88.191.254243.88.191.25516,382
100243.88.192.0/18243.88.192.1 to 243.88.255.254243.88.255.25516,382
101243.89.0.0/18243.89.0.1 to 243.89.63.254243.89.63.25516,382
102243.89.64.0/18243.89.64.1 to 243.89.127.254243.89.127.25516,382
103243.89.128.0/18243.89.128.1 to 243.89.191.254243.89.191.25516,382
104243.89.192.0/18243.89.192.1 to 243.89.255.254243.89.255.25516,382
105243.90.0.0/18243.90.0.1 to 243.90.63.254243.90.63.25516,382
106243.90.64.0/18243.90.64.1 to 243.90.127.254243.90.127.25516,382
107243.90.128.0/18243.90.128.1 to 243.90.191.254243.90.191.25516,382
108243.90.192.0/18243.90.192.1 to 243.90.255.254243.90.255.25516,382
109243.91.0.0/18243.91.0.1 to 243.91.63.254243.91.63.25516,382
110243.91.64.0/18243.91.64.1 to 243.91.127.254243.91.127.25516,382
111243.91.128.0/18243.91.128.1 to 243.91.191.254243.91.191.25516,382
112243.91.192.0/18243.91.192.1 to 243.91.255.254243.91.255.25516,382
113243.92.0.0/18243.92.0.1 to 243.92.63.254243.92.63.25516,382
114243.92.64.0/18243.92.64.1 to 243.92.127.254243.92.127.25516,382
115243.92.128.0/18243.92.128.1 to 243.92.191.254243.92.191.25516,382
116243.92.192.0/18243.92.192.1 to 243.92.255.254243.92.255.25516,382
117243.93.0.0/18243.93.0.1 to 243.93.63.254243.93.63.25516,382
118243.93.64.0/18243.93.64.1 to 243.93.127.254243.93.127.25516,382
119243.93.128.0/18243.93.128.1 to 243.93.191.254243.93.191.25516,382
120243.93.192.0/18243.93.192.1 to 243.93.255.254243.93.255.25516,382
121243.94.0.0/18243.94.0.1 to 243.94.63.254243.94.63.25516,382
122243.94.64.0/18243.94.64.1 to 243.94.127.254243.94.127.25516,382
123243.94.128.0/18243.94.128.1 to 243.94.191.254243.94.191.25516,382
124243.94.192.0/18243.94.192.1 to 243.94.255.254243.94.255.25516,382
125243.95.0.0/18243.95.0.1 to 243.95.63.254243.95.63.25516,382
126243.95.64.0/18243.95.64.1 to 243.95.127.254243.95.127.25516,382
127243.95.128.0/18243.95.128.1 to 243.95.191.254243.95.191.25516,382
128243.95.192.0/18243.95.192.1 to 243.95.255.254243.95.255.25516,382

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.