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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.

Network170.2.192.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
170.2.192.0
Broadcast address
170.2.223.255
First usable
170.2.192.1
Last usable
170.2.223.254
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
Public public
Old class
B (default /16)
As numbers
Hex AA02C000 · Integer 2852306944 to 2852315135
Reverse DNS zones
192.2.170.in-addr.arpa
193.2.170.in-addr.arpa
194.2.170.in-addr.arpa
195.2.170.in-addr.arpa
196.2.170.in-addr.arpa
197.2.170.in-addr.arpa
198.2.170.in-addr.arpa
199.2.170.in-addr.arpa
200.2.170.in-addr.arpa
201.2.170.in-addr.arpa
202.2.170.in-addr.arpa
203.2.170.in-addr.arpa
204.2.170.in-addr.arpa
205.2.170.in-addr.arpa
206.2.170.in-addr.arpa
207.2.170.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
Address10101010.00000010.11000000.00000000170.2.192.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network10101010.00000010.11000000.00000000170.2.192.0
Broadcast10101010.00000010.11011111.11111111170.2.223.255
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)

170.2.192.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1170.2.192.0/26170.2.192.1 to 170.2.192.62170.2.192.6362
2170.2.192.64/26170.2.192.65 to 170.2.192.126170.2.192.12762
3170.2.192.128/26170.2.192.129 to 170.2.192.190170.2.192.19162
4170.2.192.192/26170.2.192.193 to 170.2.192.254170.2.192.25562
5170.2.193.0/26170.2.193.1 to 170.2.193.62170.2.193.6362
6170.2.193.64/26170.2.193.65 to 170.2.193.126170.2.193.12762
7170.2.193.128/26170.2.193.129 to 170.2.193.190170.2.193.19162
8170.2.193.192/26170.2.193.193 to 170.2.193.254170.2.193.25562
9170.2.194.0/26170.2.194.1 to 170.2.194.62170.2.194.6362
10170.2.194.64/26170.2.194.65 to 170.2.194.126170.2.194.12762
11170.2.194.128/26170.2.194.129 to 170.2.194.190170.2.194.19162
12170.2.194.192/26170.2.194.193 to 170.2.194.254170.2.194.25562
13170.2.195.0/26170.2.195.1 to 170.2.195.62170.2.195.6362
14170.2.195.64/26170.2.195.65 to 170.2.195.126170.2.195.12762
15170.2.195.128/26170.2.195.129 to 170.2.195.190170.2.195.19162
16170.2.195.192/26170.2.195.193 to 170.2.195.254170.2.195.25562
17170.2.196.0/26170.2.196.1 to 170.2.196.62170.2.196.6362
18170.2.196.64/26170.2.196.65 to 170.2.196.126170.2.196.12762
19170.2.196.128/26170.2.196.129 to 170.2.196.190170.2.196.19162
20170.2.196.192/26170.2.196.193 to 170.2.196.254170.2.196.25562
21170.2.197.0/26170.2.197.1 to 170.2.197.62170.2.197.6362
22170.2.197.64/26170.2.197.65 to 170.2.197.126170.2.197.12762
23170.2.197.128/26170.2.197.129 to 170.2.197.190170.2.197.19162
24170.2.197.192/26170.2.197.193 to 170.2.197.254170.2.197.25562
25170.2.198.0/26170.2.198.1 to 170.2.198.62170.2.198.6362
26170.2.198.64/26170.2.198.65 to 170.2.198.126170.2.198.12762
27170.2.198.128/26170.2.198.129 to 170.2.198.190170.2.198.19162
28170.2.198.192/26170.2.198.193 to 170.2.198.254170.2.198.25562
29170.2.199.0/26170.2.199.1 to 170.2.199.62170.2.199.6362
30170.2.199.64/26170.2.199.65 to 170.2.199.126170.2.199.12762
31170.2.199.128/26170.2.199.129 to 170.2.199.190170.2.199.19162
32170.2.199.192/26170.2.199.193 to 170.2.199.254170.2.199.25562
33170.2.200.0/26170.2.200.1 to 170.2.200.62170.2.200.6362
34170.2.200.64/26170.2.200.65 to 170.2.200.126170.2.200.12762
35170.2.200.128/26170.2.200.129 to 170.2.200.190170.2.200.19162
36170.2.200.192/26170.2.200.193 to 170.2.200.254170.2.200.25562
37170.2.201.0/26170.2.201.1 to 170.2.201.62170.2.201.6362
38170.2.201.64/26170.2.201.65 to 170.2.201.126170.2.201.12762
39170.2.201.128/26170.2.201.129 to 170.2.201.190170.2.201.19162
40170.2.201.192/26170.2.201.193 to 170.2.201.254170.2.201.25562
41170.2.202.0/26170.2.202.1 to 170.2.202.62170.2.202.6362
42170.2.202.64/26170.2.202.65 to 170.2.202.126170.2.202.12762
43170.2.202.128/26170.2.202.129 to 170.2.202.190170.2.202.19162
44170.2.202.192/26170.2.202.193 to 170.2.202.254170.2.202.25562
45170.2.203.0/26170.2.203.1 to 170.2.203.62170.2.203.6362
46170.2.203.64/26170.2.203.65 to 170.2.203.126170.2.203.12762
47170.2.203.128/26170.2.203.129 to 170.2.203.190170.2.203.19162
48170.2.203.192/26170.2.203.193 to 170.2.203.254170.2.203.25562
49170.2.204.0/26170.2.204.1 to 170.2.204.62170.2.204.6362
50170.2.204.64/26170.2.204.65 to 170.2.204.126170.2.204.12762
51170.2.204.128/26170.2.204.129 to 170.2.204.190170.2.204.19162
52170.2.204.192/26170.2.204.193 to 170.2.204.254170.2.204.25562
53170.2.205.0/26170.2.205.1 to 170.2.205.62170.2.205.6362
54170.2.205.64/26170.2.205.65 to 170.2.205.126170.2.205.12762
55170.2.205.128/26170.2.205.129 to 170.2.205.190170.2.205.19162
56170.2.205.192/26170.2.205.193 to 170.2.205.254170.2.205.25562
57170.2.206.0/26170.2.206.1 to 170.2.206.62170.2.206.6362
58170.2.206.64/26170.2.206.65 to 170.2.206.126170.2.206.12762
59170.2.206.128/26170.2.206.129 to 170.2.206.190170.2.206.19162
60170.2.206.192/26170.2.206.193 to 170.2.206.254170.2.206.25562
61170.2.207.0/26170.2.207.1 to 170.2.207.62170.2.207.6362
62170.2.207.64/26170.2.207.65 to 170.2.207.126170.2.207.12762
63170.2.207.128/26170.2.207.129 to 170.2.207.190170.2.207.19162
64170.2.207.192/26170.2.207.193 to 170.2.207.254170.2.207.25562
65170.2.208.0/26170.2.208.1 to 170.2.208.62170.2.208.6362
66170.2.208.64/26170.2.208.65 to 170.2.208.126170.2.208.12762
67170.2.208.128/26170.2.208.129 to 170.2.208.190170.2.208.19162
68170.2.208.192/26170.2.208.193 to 170.2.208.254170.2.208.25562
69170.2.209.0/26170.2.209.1 to 170.2.209.62170.2.209.6362
70170.2.209.64/26170.2.209.65 to 170.2.209.126170.2.209.12762
71170.2.209.128/26170.2.209.129 to 170.2.209.190170.2.209.19162
72170.2.209.192/26170.2.209.193 to 170.2.209.254170.2.209.25562
73170.2.210.0/26170.2.210.1 to 170.2.210.62170.2.210.6362
74170.2.210.64/26170.2.210.65 to 170.2.210.126170.2.210.12762
75170.2.210.128/26170.2.210.129 to 170.2.210.190170.2.210.19162
76170.2.210.192/26170.2.210.193 to 170.2.210.254170.2.210.25562
77170.2.211.0/26170.2.211.1 to 170.2.211.62170.2.211.6362
78170.2.211.64/26170.2.211.65 to 170.2.211.126170.2.211.12762
79170.2.211.128/26170.2.211.129 to 170.2.211.190170.2.211.19162
80170.2.211.192/26170.2.211.193 to 170.2.211.254170.2.211.25562
81170.2.212.0/26170.2.212.1 to 170.2.212.62170.2.212.6362
82170.2.212.64/26170.2.212.65 to 170.2.212.126170.2.212.12762
83170.2.212.128/26170.2.212.129 to 170.2.212.190170.2.212.19162
84170.2.212.192/26170.2.212.193 to 170.2.212.254170.2.212.25562
85170.2.213.0/26170.2.213.1 to 170.2.213.62170.2.213.6362
86170.2.213.64/26170.2.213.65 to 170.2.213.126170.2.213.12762
87170.2.213.128/26170.2.213.129 to 170.2.213.190170.2.213.19162
88170.2.213.192/26170.2.213.193 to 170.2.213.254170.2.213.25562
89170.2.214.0/26170.2.214.1 to 170.2.214.62170.2.214.6362
90170.2.214.64/26170.2.214.65 to 170.2.214.126170.2.214.12762
91170.2.214.128/26170.2.214.129 to 170.2.214.190170.2.214.19162
92170.2.214.192/26170.2.214.193 to 170.2.214.254170.2.214.25562
93170.2.215.0/26170.2.215.1 to 170.2.215.62170.2.215.6362
94170.2.215.64/26170.2.215.65 to 170.2.215.126170.2.215.12762
95170.2.215.128/26170.2.215.129 to 170.2.215.190170.2.215.19162
96170.2.215.192/26170.2.215.193 to 170.2.215.254170.2.215.25562
97170.2.216.0/26170.2.216.1 to 170.2.216.62170.2.216.6362
98170.2.216.64/26170.2.216.65 to 170.2.216.126170.2.216.12762
99170.2.216.128/26170.2.216.129 to 170.2.216.190170.2.216.19162
100170.2.216.192/26170.2.216.193 to 170.2.216.254170.2.216.25562
101170.2.217.0/26170.2.217.1 to 170.2.217.62170.2.217.6362
102170.2.217.64/26170.2.217.65 to 170.2.217.126170.2.217.12762
103170.2.217.128/26170.2.217.129 to 170.2.217.190170.2.217.19162
104170.2.217.192/26170.2.217.193 to 170.2.217.254170.2.217.25562
105170.2.218.0/26170.2.218.1 to 170.2.218.62170.2.218.6362
106170.2.218.64/26170.2.218.65 to 170.2.218.126170.2.218.12762
107170.2.218.128/26170.2.218.129 to 170.2.218.190170.2.218.19162
108170.2.218.192/26170.2.218.193 to 170.2.218.254170.2.218.25562
109170.2.219.0/26170.2.219.1 to 170.2.219.62170.2.219.6362
110170.2.219.64/26170.2.219.65 to 170.2.219.126170.2.219.12762
111170.2.219.128/26170.2.219.129 to 170.2.219.190170.2.219.19162
112170.2.219.192/26170.2.219.193 to 170.2.219.254170.2.219.25562
113170.2.220.0/26170.2.220.1 to 170.2.220.62170.2.220.6362
114170.2.220.64/26170.2.220.65 to 170.2.220.126170.2.220.12762
115170.2.220.128/26170.2.220.129 to 170.2.220.190170.2.220.19162
116170.2.220.192/26170.2.220.193 to 170.2.220.254170.2.220.25562
117170.2.221.0/26170.2.221.1 to 170.2.221.62170.2.221.6362
118170.2.221.64/26170.2.221.65 to 170.2.221.126170.2.221.12762
119170.2.221.128/26170.2.221.129 to 170.2.221.190170.2.221.19162
120170.2.221.192/26170.2.221.193 to 170.2.221.254170.2.221.25562
121170.2.222.0/26170.2.222.1 to 170.2.222.62170.2.222.6362
122170.2.222.64/26170.2.222.65 to 170.2.222.126170.2.222.12762
123170.2.222.128/26170.2.222.129 to 170.2.222.190170.2.222.19162
124170.2.222.192/26170.2.222.193 to 170.2.222.254170.2.222.25562
125170.2.223.0/26170.2.223.1 to 170.2.223.62170.2.223.6362
126170.2.223.64/26170.2.223.65 to 170.2.223.126170.2.223.12762
127170.2.223.128/26170.2.223.129 to 170.2.223.190170.2.223.19162
128170.2.223.192/26170.2.223.193 to 170.2.223.254170.2.223.25562

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.