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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.

Network124.192.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
124.192.0.0
Broadcast address
124.207.255.255
First usable
124.192.0.1
Last usable
124.207.255.254
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
Public public
Old class
A (default /8)
As numbers
Hex 7CC00000 · Integer 2092957696 to 2094006271
Reverse DNS zones
192.124.in-addr.arpa
193.124.in-addr.arpa
194.124.in-addr.arpa
195.124.in-addr.arpa
196.124.in-addr.arpa
197.124.in-addr.arpa
198.124.in-addr.arpa
199.124.in-addr.arpa
200.124.in-addr.arpa
201.124.in-addr.arpa
202.124.in-addr.arpa
203.124.in-addr.arpa
204.124.in-addr.arpa
205.124.in-addr.arpa
206.124.in-addr.arpa
207.124.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
Address01111100.11000000.00000000.00000000124.192.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network01111100.11000000.00000000.00000000124.192.0.0
Broadcast01111100.11001111.11111111.11111111124.207.255.255
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)

124.192.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1124.192.0.0/19124.192.0.1 to 124.192.31.254124.192.31.2558,190
2124.192.32.0/19124.192.32.1 to 124.192.63.254124.192.63.2558,190
3124.192.64.0/19124.192.64.1 to 124.192.95.254124.192.95.2558,190
4124.192.96.0/19124.192.96.1 to 124.192.127.254124.192.127.2558,190
5124.192.128.0/19124.192.128.1 to 124.192.159.254124.192.159.2558,190
6124.192.160.0/19124.192.160.1 to 124.192.191.254124.192.191.2558,190
7124.192.192.0/19124.192.192.1 to 124.192.223.254124.192.223.2558,190
8124.192.224.0/19124.192.224.1 to 124.192.255.254124.192.255.2558,190
9124.193.0.0/19124.193.0.1 to 124.193.31.254124.193.31.2558,190
10124.193.32.0/19124.193.32.1 to 124.193.63.254124.193.63.2558,190
11124.193.64.0/19124.193.64.1 to 124.193.95.254124.193.95.2558,190
12124.193.96.0/19124.193.96.1 to 124.193.127.254124.193.127.2558,190
13124.193.128.0/19124.193.128.1 to 124.193.159.254124.193.159.2558,190
14124.193.160.0/19124.193.160.1 to 124.193.191.254124.193.191.2558,190
15124.193.192.0/19124.193.192.1 to 124.193.223.254124.193.223.2558,190
16124.193.224.0/19124.193.224.1 to 124.193.255.254124.193.255.2558,190
17124.194.0.0/19124.194.0.1 to 124.194.31.254124.194.31.2558,190
18124.194.32.0/19124.194.32.1 to 124.194.63.254124.194.63.2558,190
19124.194.64.0/19124.194.64.1 to 124.194.95.254124.194.95.2558,190
20124.194.96.0/19124.194.96.1 to 124.194.127.254124.194.127.2558,190
21124.194.128.0/19124.194.128.1 to 124.194.159.254124.194.159.2558,190
22124.194.160.0/19124.194.160.1 to 124.194.191.254124.194.191.2558,190
23124.194.192.0/19124.194.192.1 to 124.194.223.254124.194.223.2558,190
24124.194.224.0/19124.194.224.1 to 124.194.255.254124.194.255.2558,190
25124.195.0.0/19124.195.0.1 to 124.195.31.254124.195.31.2558,190
26124.195.32.0/19124.195.32.1 to 124.195.63.254124.195.63.2558,190
27124.195.64.0/19124.195.64.1 to 124.195.95.254124.195.95.2558,190
28124.195.96.0/19124.195.96.1 to 124.195.127.254124.195.127.2558,190
29124.195.128.0/19124.195.128.1 to 124.195.159.254124.195.159.2558,190
30124.195.160.0/19124.195.160.1 to 124.195.191.254124.195.191.2558,190
31124.195.192.0/19124.195.192.1 to 124.195.223.254124.195.223.2558,190
32124.195.224.0/19124.195.224.1 to 124.195.255.254124.195.255.2558,190
33124.196.0.0/19124.196.0.1 to 124.196.31.254124.196.31.2558,190
34124.196.32.0/19124.196.32.1 to 124.196.63.254124.196.63.2558,190
35124.196.64.0/19124.196.64.1 to 124.196.95.254124.196.95.2558,190
36124.196.96.0/19124.196.96.1 to 124.196.127.254124.196.127.2558,190
37124.196.128.0/19124.196.128.1 to 124.196.159.254124.196.159.2558,190
38124.196.160.0/19124.196.160.1 to 124.196.191.254124.196.191.2558,190
39124.196.192.0/19124.196.192.1 to 124.196.223.254124.196.223.2558,190
40124.196.224.0/19124.196.224.1 to 124.196.255.254124.196.255.2558,190
41124.197.0.0/19124.197.0.1 to 124.197.31.254124.197.31.2558,190
42124.197.32.0/19124.197.32.1 to 124.197.63.254124.197.63.2558,190
43124.197.64.0/19124.197.64.1 to 124.197.95.254124.197.95.2558,190
44124.197.96.0/19124.197.96.1 to 124.197.127.254124.197.127.2558,190
45124.197.128.0/19124.197.128.1 to 124.197.159.254124.197.159.2558,190
46124.197.160.0/19124.197.160.1 to 124.197.191.254124.197.191.2558,190
47124.197.192.0/19124.197.192.1 to 124.197.223.254124.197.223.2558,190
48124.197.224.0/19124.197.224.1 to 124.197.255.254124.197.255.2558,190
49124.198.0.0/19124.198.0.1 to 124.198.31.254124.198.31.2558,190
50124.198.32.0/19124.198.32.1 to 124.198.63.254124.198.63.2558,190
51124.198.64.0/19124.198.64.1 to 124.198.95.254124.198.95.2558,190
52124.198.96.0/19124.198.96.1 to 124.198.127.254124.198.127.2558,190
53124.198.128.0/19124.198.128.1 to 124.198.159.254124.198.159.2558,190
54124.198.160.0/19124.198.160.1 to 124.198.191.254124.198.191.2558,190
55124.198.192.0/19124.198.192.1 to 124.198.223.254124.198.223.2558,190
56124.198.224.0/19124.198.224.1 to 124.198.255.254124.198.255.2558,190
57124.199.0.0/19124.199.0.1 to 124.199.31.254124.199.31.2558,190
58124.199.32.0/19124.199.32.1 to 124.199.63.254124.199.63.2558,190
59124.199.64.0/19124.199.64.1 to 124.199.95.254124.199.95.2558,190
60124.199.96.0/19124.199.96.1 to 124.199.127.254124.199.127.2558,190
61124.199.128.0/19124.199.128.1 to 124.199.159.254124.199.159.2558,190
62124.199.160.0/19124.199.160.1 to 124.199.191.254124.199.191.2558,190
63124.199.192.0/19124.199.192.1 to 124.199.223.254124.199.223.2558,190
64124.199.224.0/19124.199.224.1 to 124.199.255.254124.199.255.2558,190
65124.200.0.0/19124.200.0.1 to 124.200.31.254124.200.31.2558,190
66124.200.32.0/19124.200.32.1 to 124.200.63.254124.200.63.2558,190
67124.200.64.0/19124.200.64.1 to 124.200.95.254124.200.95.2558,190
68124.200.96.0/19124.200.96.1 to 124.200.127.254124.200.127.2558,190
69124.200.128.0/19124.200.128.1 to 124.200.159.254124.200.159.2558,190
70124.200.160.0/19124.200.160.1 to 124.200.191.254124.200.191.2558,190
71124.200.192.0/19124.200.192.1 to 124.200.223.254124.200.223.2558,190
72124.200.224.0/19124.200.224.1 to 124.200.255.254124.200.255.2558,190
73124.201.0.0/19124.201.0.1 to 124.201.31.254124.201.31.2558,190
74124.201.32.0/19124.201.32.1 to 124.201.63.254124.201.63.2558,190
75124.201.64.0/19124.201.64.1 to 124.201.95.254124.201.95.2558,190
76124.201.96.0/19124.201.96.1 to 124.201.127.254124.201.127.2558,190
77124.201.128.0/19124.201.128.1 to 124.201.159.254124.201.159.2558,190
78124.201.160.0/19124.201.160.1 to 124.201.191.254124.201.191.2558,190
79124.201.192.0/19124.201.192.1 to 124.201.223.254124.201.223.2558,190
80124.201.224.0/19124.201.224.1 to 124.201.255.254124.201.255.2558,190
81124.202.0.0/19124.202.0.1 to 124.202.31.254124.202.31.2558,190
82124.202.32.0/19124.202.32.1 to 124.202.63.254124.202.63.2558,190
83124.202.64.0/19124.202.64.1 to 124.202.95.254124.202.95.2558,190
84124.202.96.0/19124.202.96.1 to 124.202.127.254124.202.127.2558,190
85124.202.128.0/19124.202.128.1 to 124.202.159.254124.202.159.2558,190
86124.202.160.0/19124.202.160.1 to 124.202.191.254124.202.191.2558,190
87124.202.192.0/19124.202.192.1 to 124.202.223.254124.202.223.2558,190
88124.202.224.0/19124.202.224.1 to 124.202.255.254124.202.255.2558,190
89124.203.0.0/19124.203.0.1 to 124.203.31.254124.203.31.2558,190
90124.203.32.0/19124.203.32.1 to 124.203.63.254124.203.63.2558,190
91124.203.64.0/19124.203.64.1 to 124.203.95.254124.203.95.2558,190
92124.203.96.0/19124.203.96.1 to 124.203.127.254124.203.127.2558,190
93124.203.128.0/19124.203.128.1 to 124.203.159.254124.203.159.2558,190
94124.203.160.0/19124.203.160.1 to 124.203.191.254124.203.191.2558,190
95124.203.192.0/19124.203.192.1 to 124.203.223.254124.203.223.2558,190
96124.203.224.0/19124.203.224.1 to 124.203.255.254124.203.255.2558,190
97124.204.0.0/19124.204.0.1 to 124.204.31.254124.204.31.2558,190
98124.204.32.0/19124.204.32.1 to 124.204.63.254124.204.63.2558,190
99124.204.64.0/19124.204.64.1 to 124.204.95.254124.204.95.2558,190
100124.204.96.0/19124.204.96.1 to 124.204.127.254124.204.127.2558,190
101124.204.128.0/19124.204.128.1 to 124.204.159.254124.204.159.2558,190
102124.204.160.0/19124.204.160.1 to 124.204.191.254124.204.191.2558,190
103124.204.192.0/19124.204.192.1 to 124.204.223.254124.204.223.2558,190
104124.204.224.0/19124.204.224.1 to 124.204.255.254124.204.255.2558,190
105124.205.0.0/19124.205.0.1 to 124.205.31.254124.205.31.2558,190
106124.205.32.0/19124.205.32.1 to 124.205.63.254124.205.63.2558,190
107124.205.64.0/19124.205.64.1 to 124.205.95.254124.205.95.2558,190
108124.205.96.0/19124.205.96.1 to 124.205.127.254124.205.127.2558,190
109124.205.128.0/19124.205.128.1 to 124.205.159.254124.205.159.2558,190
110124.205.160.0/19124.205.160.1 to 124.205.191.254124.205.191.2558,190
111124.205.192.0/19124.205.192.1 to 124.205.223.254124.205.223.2558,190
112124.205.224.0/19124.205.224.1 to 124.205.255.254124.205.255.2558,190
113124.206.0.0/19124.206.0.1 to 124.206.31.254124.206.31.2558,190
114124.206.32.0/19124.206.32.1 to 124.206.63.254124.206.63.2558,190
115124.206.64.0/19124.206.64.1 to 124.206.95.254124.206.95.2558,190
116124.206.96.0/19124.206.96.1 to 124.206.127.254124.206.127.2558,190
117124.206.128.0/19124.206.128.1 to 124.206.159.254124.206.159.2558,190
118124.206.160.0/19124.206.160.1 to 124.206.191.254124.206.191.2558,190
119124.206.192.0/19124.206.192.1 to 124.206.223.254124.206.223.2558,190
120124.206.224.0/19124.206.224.1 to 124.206.255.254124.206.255.2558,190
121124.207.0.0/19124.207.0.1 to 124.207.31.254124.207.31.2558,190
122124.207.32.0/19124.207.32.1 to 124.207.63.254124.207.63.2558,190
123124.207.64.0/19124.207.64.1 to 124.207.95.254124.207.95.2558,190
124124.207.96.0/19124.207.96.1 to 124.207.127.254124.207.127.2558,190
125124.207.128.0/19124.207.128.1 to 124.207.159.254124.207.159.2558,190
126124.207.160.0/19124.207.160.1 to 124.207.191.254124.207.191.2558,190
127124.207.192.0/19124.207.192.1 to 124.207.223.254124.207.223.2558,190
128124.207.224.0/19124.207.224.1 to 124.207.255.254124.207.255.2558,190

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.