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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.

Network208.0.0.0/4
Usable hosts268,435,454
Subnet mask240.0.0.0
Addresses268,435,456
Network address
208.0.0.0
Broadcast address
223.255.255.255
First usable
208.0.0.1
Last usable
223.255.255.254
Usable hosts
268,435,454 (268,435,456 less the network and broadcast addresses)
Subnet mask
240.0.0.0
Wildcard mask
15.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/4
Type
Public public
Old class
C (default /24)
As numbers
Hex D0000000 · Integer 3489660928 to 3758096383
Reverse DNS zones
208.in-addr.arpa
209.in-addr.arpa
210.in-addr.arpa
211.in-addr.arpa
212.in-addr.arpa
213.in-addr.arpa
214.in-addr.arpa
215.in-addr.arpa
216.in-addr.arpa
217.in-addr.arpa
218.in-addr.arpa
219.in-addr.arpa
220.in-addr.arpa
221.in-addr.arpa
222.in-addr.arpa
223.in-addr.arpa
/4 is not on a 8-bit boundary, so it takes 16 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11010000.00000000.00000000.00000000208.0.0.0
Subnet mask11110000.00000000.00000000.00000000240.0.0.0
Network11010000.00000000.00000000.00000000208.0.0.0
Broadcast11011111.11111111.11111111.11111111223.255.255.255
Split into smaller subnets/11
/5 (2)/6 (4)/7 (8)/8 (16)/9 (32)/10 (64)/11 (128)/12 (256)/13 (512)/14 (1,024)/15 (2,048)/16 (4,096)

208.0.0.0/4 makes 128 subnets of /11.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1208.0.0.0/11208.0.0.1 to 208.31.255.254208.31.255.2552,097,150
2208.32.0.0/11208.32.0.1 to 208.63.255.254208.63.255.2552,097,150
3208.64.0.0/11208.64.0.1 to 208.95.255.254208.95.255.2552,097,150
4208.96.0.0/11208.96.0.1 to 208.127.255.254208.127.255.2552,097,150
5208.128.0.0/11208.128.0.1 to 208.159.255.254208.159.255.2552,097,150
6208.160.0.0/11208.160.0.1 to 208.191.255.254208.191.255.2552,097,150
7208.192.0.0/11208.192.0.1 to 208.223.255.254208.223.255.2552,097,150
8208.224.0.0/11208.224.0.1 to 208.255.255.254208.255.255.2552,097,150
9209.0.0.0/11209.0.0.1 to 209.31.255.254209.31.255.2552,097,150
10209.32.0.0/11209.32.0.1 to 209.63.255.254209.63.255.2552,097,150
11209.64.0.0/11209.64.0.1 to 209.95.255.254209.95.255.2552,097,150
12209.96.0.0/11209.96.0.1 to 209.127.255.254209.127.255.2552,097,150
13209.128.0.0/11209.128.0.1 to 209.159.255.254209.159.255.2552,097,150
14209.160.0.0/11209.160.0.1 to 209.191.255.254209.191.255.2552,097,150
15209.192.0.0/11209.192.0.1 to 209.223.255.254209.223.255.2552,097,150
16209.224.0.0/11209.224.0.1 to 209.255.255.254209.255.255.2552,097,150
17210.0.0.0/11210.0.0.1 to 210.31.255.254210.31.255.2552,097,150
18210.32.0.0/11210.32.0.1 to 210.63.255.254210.63.255.2552,097,150
19210.64.0.0/11210.64.0.1 to 210.95.255.254210.95.255.2552,097,150
20210.96.0.0/11210.96.0.1 to 210.127.255.254210.127.255.2552,097,150
21210.128.0.0/11210.128.0.1 to 210.159.255.254210.159.255.2552,097,150
22210.160.0.0/11210.160.0.1 to 210.191.255.254210.191.255.2552,097,150
23210.192.0.0/11210.192.0.1 to 210.223.255.254210.223.255.2552,097,150
24210.224.0.0/11210.224.0.1 to 210.255.255.254210.255.255.2552,097,150
25211.0.0.0/11211.0.0.1 to 211.31.255.254211.31.255.2552,097,150
26211.32.0.0/11211.32.0.1 to 211.63.255.254211.63.255.2552,097,150
27211.64.0.0/11211.64.0.1 to 211.95.255.254211.95.255.2552,097,150
28211.96.0.0/11211.96.0.1 to 211.127.255.254211.127.255.2552,097,150
29211.128.0.0/11211.128.0.1 to 211.159.255.254211.159.255.2552,097,150
30211.160.0.0/11211.160.0.1 to 211.191.255.254211.191.255.2552,097,150
31211.192.0.0/11211.192.0.1 to 211.223.255.254211.223.255.2552,097,150
32211.224.0.0/11211.224.0.1 to 211.255.255.254211.255.255.2552,097,150
33212.0.0.0/11212.0.0.1 to 212.31.255.254212.31.255.2552,097,150
34212.32.0.0/11212.32.0.1 to 212.63.255.254212.63.255.2552,097,150
35212.64.0.0/11212.64.0.1 to 212.95.255.254212.95.255.2552,097,150
36212.96.0.0/11212.96.0.1 to 212.127.255.254212.127.255.2552,097,150
37212.128.0.0/11212.128.0.1 to 212.159.255.254212.159.255.2552,097,150
38212.160.0.0/11212.160.0.1 to 212.191.255.254212.191.255.2552,097,150
39212.192.0.0/11212.192.0.1 to 212.223.255.254212.223.255.2552,097,150
40212.224.0.0/11212.224.0.1 to 212.255.255.254212.255.255.2552,097,150
41213.0.0.0/11213.0.0.1 to 213.31.255.254213.31.255.2552,097,150
42213.32.0.0/11213.32.0.1 to 213.63.255.254213.63.255.2552,097,150
43213.64.0.0/11213.64.0.1 to 213.95.255.254213.95.255.2552,097,150
44213.96.0.0/11213.96.0.1 to 213.127.255.254213.127.255.2552,097,150
45213.128.0.0/11213.128.0.1 to 213.159.255.254213.159.255.2552,097,150
46213.160.0.0/11213.160.0.1 to 213.191.255.254213.191.255.2552,097,150
47213.192.0.0/11213.192.0.1 to 213.223.255.254213.223.255.2552,097,150
48213.224.0.0/11213.224.0.1 to 213.255.255.254213.255.255.2552,097,150
49214.0.0.0/11214.0.0.1 to 214.31.255.254214.31.255.2552,097,150
50214.32.0.0/11214.32.0.1 to 214.63.255.254214.63.255.2552,097,150
51214.64.0.0/11214.64.0.1 to 214.95.255.254214.95.255.2552,097,150
52214.96.0.0/11214.96.0.1 to 214.127.255.254214.127.255.2552,097,150
53214.128.0.0/11214.128.0.1 to 214.159.255.254214.159.255.2552,097,150
54214.160.0.0/11214.160.0.1 to 214.191.255.254214.191.255.2552,097,150
55214.192.0.0/11214.192.0.1 to 214.223.255.254214.223.255.2552,097,150
56214.224.0.0/11214.224.0.1 to 214.255.255.254214.255.255.2552,097,150
57215.0.0.0/11215.0.0.1 to 215.31.255.254215.31.255.2552,097,150
58215.32.0.0/11215.32.0.1 to 215.63.255.254215.63.255.2552,097,150
59215.64.0.0/11215.64.0.1 to 215.95.255.254215.95.255.2552,097,150
60215.96.0.0/11215.96.0.1 to 215.127.255.254215.127.255.2552,097,150
61215.128.0.0/11215.128.0.1 to 215.159.255.254215.159.255.2552,097,150
62215.160.0.0/11215.160.0.1 to 215.191.255.254215.191.255.2552,097,150
63215.192.0.0/11215.192.0.1 to 215.223.255.254215.223.255.2552,097,150
64215.224.0.0/11215.224.0.1 to 215.255.255.254215.255.255.2552,097,150
65216.0.0.0/11216.0.0.1 to 216.31.255.254216.31.255.2552,097,150
66216.32.0.0/11216.32.0.1 to 216.63.255.254216.63.255.2552,097,150
67216.64.0.0/11216.64.0.1 to 216.95.255.254216.95.255.2552,097,150
68216.96.0.0/11216.96.0.1 to 216.127.255.254216.127.255.2552,097,150
69216.128.0.0/11216.128.0.1 to 216.159.255.254216.159.255.2552,097,150
70216.160.0.0/11216.160.0.1 to 216.191.255.254216.191.255.2552,097,150
71216.192.0.0/11216.192.0.1 to 216.223.255.254216.223.255.2552,097,150
72216.224.0.0/11216.224.0.1 to 216.255.255.254216.255.255.2552,097,150
73217.0.0.0/11217.0.0.1 to 217.31.255.254217.31.255.2552,097,150
74217.32.0.0/11217.32.0.1 to 217.63.255.254217.63.255.2552,097,150
75217.64.0.0/11217.64.0.1 to 217.95.255.254217.95.255.2552,097,150
76217.96.0.0/11217.96.0.1 to 217.127.255.254217.127.255.2552,097,150
77217.128.0.0/11217.128.0.1 to 217.159.255.254217.159.255.2552,097,150
78217.160.0.0/11217.160.0.1 to 217.191.255.254217.191.255.2552,097,150
79217.192.0.0/11217.192.0.1 to 217.223.255.254217.223.255.2552,097,150
80217.224.0.0/11217.224.0.1 to 217.255.255.254217.255.255.2552,097,150
81218.0.0.0/11218.0.0.1 to 218.31.255.254218.31.255.2552,097,150
82218.32.0.0/11218.32.0.1 to 218.63.255.254218.63.255.2552,097,150
83218.64.0.0/11218.64.0.1 to 218.95.255.254218.95.255.2552,097,150
84218.96.0.0/11218.96.0.1 to 218.127.255.254218.127.255.2552,097,150
85218.128.0.0/11218.128.0.1 to 218.159.255.254218.159.255.2552,097,150
86218.160.0.0/11218.160.0.1 to 218.191.255.254218.191.255.2552,097,150
87218.192.0.0/11218.192.0.1 to 218.223.255.254218.223.255.2552,097,150
88218.224.0.0/11218.224.0.1 to 218.255.255.254218.255.255.2552,097,150
89219.0.0.0/11219.0.0.1 to 219.31.255.254219.31.255.2552,097,150
90219.32.0.0/11219.32.0.1 to 219.63.255.254219.63.255.2552,097,150
91219.64.0.0/11219.64.0.1 to 219.95.255.254219.95.255.2552,097,150
92219.96.0.0/11219.96.0.1 to 219.127.255.254219.127.255.2552,097,150
93219.128.0.0/11219.128.0.1 to 219.159.255.254219.159.255.2552,097,150
94219.160.0.0/11219.160.0.1 to 219.191.255.254219.191.255.2552,097,150
95219.192.0.0/11219.192.0.1 to 219.223.255.254219.223.255.2552,097,150
96219.224.0.0/11219.224.0.1 to 219.255.255.254219.255.255.2552,097,150
97220.0.0.0/11220.0.0.1 to 220.31.255.254220.31.255.2552,097,150
98220.32.0.0/11220.32.0.1 to 220.63.255.254220.63.255.2552,097,150
99220.64.0.0/11220.64.0.1 to 220.95.255.254220.95.255.2552,097,150
100220.96.0.0/11220.96.0.1 to 220.127.255.254220.127.255.2552,097,150
101220.128.0.0/11220.128.0.1 to 220.159.255.254220.159.255.2552,097,150
102220.160.0.0/11220.160.0.1 to 220.191.255.254220.191.255.2552,097,150
103220.192.0.0/11220.192.0.1 to 220.223.255.254220.223.255.2552,097,150
104220.224.0.0/11220.224.0.1 to 220.255.255.254220.255.255.2552,097,150
105221.0.0.0/11221.0.0.1 to 221.31.255.254221.31.255.2552,097,150
106221.32.0.0/11221.32.0.1 to 221.63.255.254221.63.255.2552,097,150
107221.64.0.0/11221.64.0.1 to 221.95.255.254221.95.255.2552,097,150
108221.96.0.0/11221.96.0.1 to 221.127.255.254221.127.255.2552,097,150
109221.128.0.0/11221.128.0.1 to 221.159.255.254221.159.255.2552,097,150
110221.160.0.0/11221.160.0.1 to 221.191.255.254221.191.255.2552,097,150
111221.192.0.0/11221.192.0.1 to 221.223.255.254221.223.255.2552,097,150
112221.224.0.0/11221.224.0.1 to 221.255.255.254221.255.255.2552,097,150
113222.0.0.0/11222.0.0.1 to 222.31.255.254222.31.255.2552,097,150
114222.32.0.0/11222.32.0.1 to 222.63.255.254222.63.255.2552,097,150
115222.64.0.0/11222.64.0.1 to 222.95.255.254222.95.255.2552,097,150
116222.96.0.0/11222.96.0.1 to 222.127.255.254222.127.255.2552,097,150
117222.128.0.0/11222.128.0.1 to 222.159.255.254222.159.255.2552,097,150
118222.160.0.0/11222.160.0.1 to 222.191.255.254222.191.255.2552,097,150
119222.192.0.0/11222.192.0.1 to 222.223.255.254222.223.255.2552,097,150
120222.224.0.0/11222.224.0.1 to 222.255.255.254222.255.255.2552,097,150
121223.0.0.0/11223.0.0.1 to 223.31.255.254223.31.255.2552,097,150
122223.32.0.0/11223.32.0.1 to 223.63.255.254223.63.255.2552,097,150
123223.64.0.0/11223.64.0.1 to 223.95.255.254223.95.255.2552,097,150
124223.96.0.0/11223.96.0.1 to 223.127.255.254223.127.255.2552,097,150
125223.128.0.0/11223.128.0.1 to 223.159.255.254223.159.255.2552,097,150
126223.160.0.0/11223.160.0.1 to 223.191.255.254223.191.255.2552,097,150
127223.192.0.0/11223.192.0.1 to 223.223.255.254223.223.255.2552,097,150
128223.224.0.0/11223.224.0.1 to 223.255.255.254223.255.255.2552,097,150

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.