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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.

Network127.12.192.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
127.12.192.0
Broadcast address
127.12.223.255
First usable
127.12.192.1
Last usable
127.12.223.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Loopback 127.0.0.0/8
This computer
Old class
A (default /8)
As numbers
Hex 7F0CC000 · Integer 2131542016 to 2131550207
Reverse DNS zones
192.12.127.in-addr.arpa
193.12.127.in-addr.arpa
194.12.127.in-addr.arpa
195.12.127.in-addr.arpa
196.12.127.in-addr.arpa
197.12.127.in-addr.arpa
198.12.127.in-addr.arpa
199.12.127.in-addr.arpa
200.12.127.in-addr.arpa
201.12.127.in-addr.arpa
202.12.127.in-addr.arpa
203.12.127.in-addr.arpa
204.12.127.in-addr.arpa
205.12.127.in-addr.arpa
206.12.127.in-addr.arpa
207.12.127.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01111111.00001100.11000000.00000000127.12.192.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network01111111.00001100.11000000.00000000127.12.192.0
Broadcast01111111.00001100.11011111.11111111127.12.223.255
Split into smaller subnets/26
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

127.12.192.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1127.12.192.0/26127.12.192.1 to 127.12.192.62127.12.192.6362
2127.12.192.64/26127.12.192.65 to 127.12.192.126127.12.192.12762
3127.12.192.128/26127.12.192.129 to 127.12.192.190127.12.192.19162
4127.12.192.192/26127.12.192.193 to 127.12.192.254127.12.192.25562
5127.12.193.0/26127.12.193.1 to 127.12.193.62127.12.193.6362
6127.12.193.64/26127.12.193.65 to 127.12.193.126127.12.193.12762
7127.12.193.128/26127.12.193.129 to 127.12.193.190127.12.193.19162
8127.12.193.192/26127.12.193.193 to 127.12.193.254127.12.193.25562
9127.12.194.0/26127.12.194.1 to 127.12.194.62127.12.194.6362
10127.12.194.64/26127.12.194.65 to 127.12.194.126127.12.194.12762
11127.12.194.128/26127.12.194.129 to 127.12.194.190127.12.194.19162
12127.12.194.192/26127.12.194.193 to 127.12.194.254127.12.194.25562
13127.12.195.0/26127.12.195.1 to 127.12.195.62127.12.195.6362
14127.12.195.64/26127.12.195.65 to 127.12.195.126127.12.195.12762
15127.12.195.128/26127.12.195.129 to 127.12.195.190127.12.195.19162
16127.12.195.192/26127.12.195.193 to 127.12.195.254127.12.195.25562
17127.12.196.0/26127.12.196.1 to 127.12.196.62127.12.196.6362
18127.12.196.64/26127.12.196.65 to 127.12.196.126127.12.196.12762
19127.12.196.128/26127.12.196.129 to 127.12.196.190127.12.196.19162
20127.12.196.192/26127.12.196.193 to 127.12.196.254127.12.196.25562
21127.12.197.0/26127.12.197.1 to 127.12.197.62127.12.197.6362
22127.12.197.64/26127.12.197.65 to 127.12.197.126127.12.197.12762
23127.12.197.128/26127.12.197.129 to 127.12.197.190127.12.197.19162
24127.12.197.192/26127.12.197.193 to 127.12.197.254127.12.197.25562
25127.12.198.0/26127.12.198.1 to 127.12.198.62127.12.198.6362
26127.12.198.64/26127.12.198.65 to 127.12.198.126127.12.198.12762
27127.12.198.128/26127.12.198.129 to 127.12.198.190127.12.198.19162
28127.12.198.192/26127.12.198.193 to 127.12.198.254127.12.198.25562
29127.12.199.0/26127.12.199.1 to 127.12.199.62127.12.199.6362
30127.12.199.64/26127.12.199.65 to 127.12.199.126127.12.199.12762
31127.12.199.128/26127.12.199.129 to 127.12.199.190127.12.199.19162
32127.12.199.192/26127.12.199.193 to 127.12.199.254127.12.199.25562
33127.12.200.0/26127.12.200.1 to 127.12.200.62127.12.200.6362
34127.12.200.64/26127.12.200.65 to 127.12.200.126127.12.200.12762
35127.12.200.128/26127.12.200.129 to 127.12.200.190127.12.200.19162
36127.12.200.192/26127.12.200.193 to 127.12.200.254127.12.200.25562
37127.12.201.0/26127.12.201.1 to 127.12.201.62127.12.201.6362
38127.12.201.64/26127.12.201.65 to 127.12.201.126127.12.201.12762
39127.12.201.128/26127.12.201.129 to 127.12.201.190127.12.201.19162
40127.12.201.192/26127.12.201.193 to 127.12.201.254127.12.201.25562
41127.12.202.0/26127.12.202.1 to 127.12.202.62127.12.202.6362
42127.12.202.64/26127.12.202.65 to 127.12.202.126127.12.202.12762
43127.12.202.128/26127.12.202.129 to 127.12.202.190127.12.202.19162
44127.12.202.192/26127.12.202.193 to 127.12.202.254127.12.202.25562
45127.12.203.0/26127.12.203.1 to 127.12.203.62127.12.203.6362
46127.12.203.64/26127.12.203.65 to 127.12.203.126127.12.203.12762
47127.12.203.128/26127.12.203.129 to 127.12.203.190127.12.203.19162
48127.12.203.192/26127.12.203.193 to 127.12.203.254127.12.203.25562
49127.12.204.0/26127.12.204.1 to 127.12.204.62127.12.204.6362
50127.12.204.64/26127.12.204.65 to 127.12.204.126127.12.204.12762
51127.12.204.128/26127.12.204.129 to 127.12.204.190127.12.204.19162
52127.12.204.192/26127.12.204.193 to 127.12.204.254127.12.204.25562
53127.12.205.0/26127.12.205.1 to 127.12.205.62127.12.205.6362
54127.12.205.64/26127.12.205.65 to 127.12.205.126127.12.205.12762
55127.12.205.128/26127.12.205.129 to 127.12.205.190127.12.205.19162
56127.12.205.192/26127.12.205.193 to 127.12.205.254127.12.205.25562
57127.12.206.0/26127.12.206.1 to 127.12.206.62127.12.206.6362
58127.12.206.64/26127.12.206.65 to 127.12.206.126127.12.206.12762
59127.12.206.128/26127.12.206.129 to 127.12.206.190127.12.206.19162
60127.12.206.192/26127.12.206.193 to 127.12.206.254127.12.206.25562
61127.12.207.0/26127.12.207.1 to 127.12.207.62127.12.207.6362
62127.12.207.64/26127.12.207.65 to 127.12.207.126127.12.207.12762
63127.12.207.128/26127.12.207.129 to 127.12.207.190127.12.207.19162
64127.12.207.192/26127.12.207.193 to 127.12.207.254127.12.207.25562
65127.12.208.0/26127.12.208.1 to 127.12.208.62127.12.208.6362
66127.12.208.64/26127.12.208.65 to 127.12.208.126127.12.208.12762
67127.12.208.128/26127.12.208.129 to 127.12.208.190127.12.208.19162
68127.12.208.192/26127.12.208.193 to 127.12.208.254127.12.208.25562
69127.12.209.0/26127.12.209.1 to 127.12.209.62127.12.209.6362
70127.12.209.64/26127.12.209.65 to 127.12.209.126127.12.209.12762
71127.12.209.128/26127.12.209.129 to 127.12.209.190127.12.209.19162
72127.12.209.192/26127.12.209.193 to 127.12.209.254127.12.209.25562
73127.12.210.0/26127.12.210.1 to 127.12.210.62127.12.210.6362
74127.12.210.64/26127.12.210.65 to 127.12.210.126127.12.210.12762
75127.12.210.128/26127.12.210.129 to 127.12.210.190127.12.210.19162
76127.12.210.192/26127.12.210.193 to 127.12.210.254127.12.210.25562
77127.12.211.0/26127.12.211.1 to 127.12.211.62127.12.211.6362
78127.12.211.64/26127.12.211.65 to 127.12.211.126127.12.211.12762
79127.12.211.128/26127.12.211.129 to 127.12.211.190127.12.211.19162
80127.12.211.192/26127.12.211.193 to 127.12.211.254127.12.211.25562
81127.12.212.0/26127.12.212.1 to 127.12.212.62127.12.212.6362
82127.12.212.64/26127.12.212.65 to 127.12.212.126127.12.212.12762
83127.12.212.128/26127.12.212.129 to 127.12.212.190127.12.212.19162
84127.12.212.192/26127.12.212.193 to 127.12.212.254127.12.212.25562
85127.12.213.0/26127.12.213.1 to 127.12.213.62127.12.213.6362
86127.12.213.64/26127.12.213.65 to 127.12.213.126127.12.213.12762
87127.12.213.128/26127.12.213.129 to 127.12.213.190127.12.213.19162
88127.12.213.192/26127.12.213.193 to 127.12.213.254127.12.213.25562
89127.12.214.0/26127.12.214.1 to 127.12.214.62127.12.214.6362
90127.12.214.64/26127.12.214.65 to 127.12.214.126127.12.214.12762
91127.12.214.128/26127.12.214.129 to 127.12.214.190127.12.214.19162
92127.12.214.192/26127.12.214.193 to 127.12.214.254127.12.214.25562
93127.12.215.0/26127.12.215.1 to 127.12.215.62127.12.215.6362
94127.12.215.64/26127.12.215.65 to 127.12.215.126127.12.215.12762
95127.12.215.128/26127.12.215.129 to 127.12.215.190127.12.215.19162
96127.12.215.192/26127.12.215.193 to 127.12.215.254127.12.215.25562
97127.12.216.0/26127.12.216.1 to 127.12.216.62127.12.216.6362
98127.12.216.64/26127.12.216.65 to 127.12.216.126127.12.216.12762
99127.12.216.128/26127.12.216.129 to 127.12.216.190127.12.216.19162
100127.12.216.192/26127.12.216.193 to 127.12.216.254127.12.216.25562
101127.12.217.0/26127.12.217.1 to 127.12.217.62127.12.217.6362
102127.12.217.64/26127.12.217.65 to 127.12.217.126127.12.217.12762
103127.12.217.128/26127.12.217.129 to 127.12.217.190127.12.217.19162
104127.12.217.192/26127.12.217.193 to 127.12.217.254127.12.217.25562
105127.12.218.0/26127.12.218.1 to 127.12.218.62127.12.218.6362
106127.12.218.64/26127.12.218.65 to 127.12.218.126127.12.218.12762
107127.12.218.128/26127.12.218.129 to 127.12.218.190127.12.218.19162
108127.12.218.192/26127.12.218.193 to 127.12.218.254127.12.218.25562
109127.12.219.0/26127.12.219.1 to 127.12.219.62127.12.219.6362
110127.12.219.64/26127.12.219.65 to 127.12.219.126127.12.219.12762
111127.12.219.128/26127.12.219.129 to 127.12.219.190127.12.219.19162
112127.12.219.192/26127.12.219.193 to 127.12.219.254127.12.219.25562
113127.12.220.0/26127.12.220.1 to 127.12.220.62127.12.220.6362
114127.12.220.64/26127.12.220.65 to 127.12.220.126127.12.220.12762
115127.12.220.128/26127.12.220.129 to 127.12.220.190127.12.220.19162
116127.12.220.192/26127.12.220.193 to 127.12.220.254127.12.220.25562
117127.12.221.0/26127.12.221.1 to 127.12.221.62127.12.221.6362
118127.12.221.64/26127.12.221.65 to 127.12.221.126127.12.221.12762
119127.12.221.128/26127.12.221.129 to 127.12.221.190127.12.221.19162
120127.12.221.192/26127.12.221.193 to 127.12.221.254127.12.221.25562
121127.12.222.0/26127.12.222.1 to 127.12.222.62127.12.222.6362
122127.12.222.64/26127.12.222.65 to 127.12.222.126127.12.222.12762
123127.12.222.128/26127.12.222.129 to 127.12.222.190127.12.222.19162
124127.12.222.192/26127.12.222.193 to 127.12.222.254127.12.222.25562
125127.12.223.0/26127.12.223.1 to 127.12.223.62127.12.223.6362
126127.12.223.64/26127.12.223.65 to 127.12.223.126127.12.223.12762
127127.12.223.128/26127.12.223.129 to 127.12.223.190127.12.223.19162
128127.12.223.192/26127.12.223.193 to 127.12.223.254127.12.223.25562

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.