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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.

Network178.2.0.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
178.2.0.0
Broadcast address
178.2.63.255
First usable
178.2.0.1
Last usable
178.2.63.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
B (default /16)
As numbers
Hex B2020000 · Integer 2986475520 to 2986491903
Reverse DNS zones
0.2.178.in-addr.arpa
1.2.178.in-addr.arpa
2.2.178.in-addr.arpa
3.2.178.in-addr.arpa
4.2.178.in-addr.arpa
5.2.178.in-addr.arpa
6.2.178.in-addr.arpa
7.2.178.in-addr.arpa
8.2.178.in-addr.arpa
9.2.178.in-addr.arpa
10.2.178.in-addr.arpa
11.2.178.in-addr.arpa
12.2.178.in-addr.arpa
13.2.178.in-addr.arpa
14.2.178.in-addr.arpa
15.2.178.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10110010.00000010.00000000.00000000178.2.0.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network10110010.00000010.00000000.00000000178.2.0.0
Broadcast10110010.00000010.00111111.11111111178.2.63.255
Split into smaller subnets/25
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

178.2.0.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1178.2.0.0/25178.2.0.1 to 178.2.0.126178.2.0.127126
2178.2.0.128/25178.2.0.129 to 178.2.0.254178.2.0.255126
3178.2.1.0/25178.2.1.1 to 178.2.1.126178.2.1.127126
4178.2.1.128/25178.2.1.129 to 178.2.1.254178.2.1.255126
5178.2.2.0/25178.2.2.1 to 178.2.2.126178.2.2.127126
6178.2.2.128/25178.2.2.129 to 178.2.2.254178.2.2.255126
7178.2.3.0/25178.2.3.1 to 178.2.3.126178.2.3.127126
8178.2.3.128/25178.2.3.129 to 178.2.3.254178.2.3.255126
9178.2.4.0/25178.2.4.1 to 178.2.4.126178.2.4.127126
10178.2.4.128/25178.2.4.129 to 178.2.4.254178.2.4.255126
11178.2.5.0/25178.2.5.1 to 178.2.5.126178.2.5.127126
12178.2.5.128/25178.2.5.129 to 178.2.5.254178.2.5.255126
13178.2.6.0/25178.2.6.1 to 178.2.6.126178.2.6.127126
14178.2.6.128/25178.2.6.129 to 178.2.6.254178.2.6.255126
15178.2.7.0/25178.2.7.1 to 178.2.7.126178.2.7.127126
16178.2.7.128/25178.2.7.129 to 178.2.7.254178.2.7.255126
17178.2.8.0/25178.2.8.1 to 178.2.8.126178.2.8.127126
18178.2.8.128/25178.2.8.129 to 178.2.8.254178.2.8.255126
19178.2.9.0/25178.2.9.1 to 178.2.9.126178.2.9.127126
20178.2.9.128/25178.2.9.129 to 178.2.9.254178.2.9.255126
21178.2.10.0/25178.2.10.1 to 178.2.10.126178.2.10.127126
22178.2.10.128/25178.2.10.129 to 178.2.10.254178.2.10.255126
23178.2.11.0/25178.2.11.1 to 178.2.11.126178.2.11.127126
24178.2.11.128/25178.2.11.129 to 178.2.11.254178.2.11.255126
25178.2.12.0/25178.2.12.1 to 178.2.12.126178.2.12.127126
26178.2.12.128/25178.2.12.129 to 178.2.12.254178.2.12.255126
27178.2.13.0/25178.2.13.1 to 178.2.13.126178.2.13.127126
28178.2.13.128/25178.2.13.129 to 178.2.13.254178.2.13.255126
29178.2.14.0/25178.2.14.1 to 178.2.14.126178.2.14.127126
30178.2.14.128/25178.2.14.129 to 178.2.14.254178.2.14.255126
31178.2.15.0/25178.2.15.1 to 178.2.15.126178.2.15.127126
32178.2.15.128/25178.2.15.129 to 178.2.15.254178.2.15.255126
33178.2.16.0/25178.2.16.1 to 178.2.16.126178.2.16.127126
34178.2.16.128/25178.2.16.129 to 178.2.16.254178.2.16.255126
35178.2.17.0/25178.2.17.1 to 178.2.17.126178.2.17.127126
36178.2.17.128/25178.2.17.129 to 178.2.17.254178.2.17.255126
37178.2.18.0/25178.2.18.1 to 178.2.18.126178.2.18.127126
38178.2.18.128/25178.2.18.129 to 178.2.18.254178.2.18.255126
39178.2.19.0/25178.2.19.1 to 178.2.19.126178.2.19.127126
40178.2.19.128/25178.2.19.129 to 178.2.19.254178.2.19.255126
41178.2.20.0/25178.2.20.1 to 178.2.20.126178.2.20.127126
42178.2.20.128/25178.2.20.129 to 178.2.20.254178.2.20.255126
43178.2.21.0/25178.2.21.1 to 178.2.21.126178.2.21.127126
44178.2.21.128/25178.2.21.129 to 178.2.21.254178.2.21.255126
45178.2.22.0/25178.2.22.1 to 178.2.22.126178.2.22.127126
46178.2.22.128/25178.2.22.129 to 178.2.22.254178.2.22.255126
47178.2.23.0/25178.2.23.1 to 178.2.23.126178.2.23.127126
48178.2.23.128/25178.2.23.129 to 178.2.23.254178.2.23.255126
49178.2.24.0/25178.2.24.1 to 178.2.24.126178.2.24.127126
50178.2.24.128/25178.2.24.129 to 178.2.24.254178.2.24.255126
51178.2.25.0/25178.2.25.1 to 178.2.25.126178.2.25.127126
52178.2.25.128/25178.2.25.129 to 178.2.25.254178.2.25.255126
53178.2.26.0/25178.2.26.1 to 178.2.26.126178.2.26.127126
54178.2.26.128/25178.2.26.129 to 178.2.26.254178.2.26.255126
55178.2.27.0/25178.2.27.1 to 178.2.27.126178.2.27.127126
56178.2.27.128/25178.2.27.129 to 178.2.27.254178.2.27.255126
57178.2.28.0/25178.2.28.1 to 178.2.28.126178.2.28.127126
58178.2.28.128/25178.2.28.129 to 178.2.28.254178.2.28.255126
59178.2.29.0/25178.2.29.1 to 178.2.29.126178.2.29.127126
60178.2.29.128/25178.2.29.129 to 178.2.29.254178.2.29.255126
61178.2.30.0/25178.2.30.1 to 178.2.30.126178.2.30.127126
62178.2.30.128/25178.2.30.129 to 178.2.30.254178.2.30.255126
63178.2.31.0/25178.2.31.1 to 178.2.31.126178.2.31.127126
64178.2.31.128/25178.2.31.129 to 178.2.31.254178.2.31.255126
65178.2.32.0/25178.2.32.1 to 178.2.32.126178.2.32.127126
66178.2.32.128/25178.2.32.129 to 178.2.32.254178.2.32.255126
67178.2.33.0/25178.2.33.1 to 178.2.33.126178.2.33.127126
68178.2.33.128/25178.2.33.129 to 178.2.33.254178.2.33.255126
69178.2.34.0/25178.2.34.1 to 178.2.34.126178.2.34.127126
70178.2.34.128/25178.2.34.129 to 178.2.34.254178.2.34.255126
71178.2.35.0/25178.2.35.1 to 178.2.35.126178.2.35.127126
72178.2.35.128/25178.2.35.129 to 178.2.35.254178.2.35.255126
73178.2.36.0/25178.2.36.1 to 178.2.36.126178.2.36.127126
74178.2.36.128/25178.2.36.129 to 178.2.36.254178.2.36.255126
75178.2.37.0/25178.2.37.1 to 178.2.37.126178.2.37.127126
76178.2.37.128/25178.2.37.129 to 178.2.37.254178.2.37.255126
77178.2.38.0/25178.2.38.1 to 178.2.38.126178.2.38.127126
78178.2.38.128/25178.2.38.129 to 178.2.38.254178.2.38.255126
79178.2.39.0/25178.2.39.1 to 178.2.39.126178.2.39.127126
80178.2.39.128/25178.2.39.129 to 178.2.39.254178.2.39.255126
81178.2.40.0/25178.2.40.1 to 178.2.40.126178.2.40.127126
82178.2.40.128/25178.2.40.129 to 178.2.40.254178.2.40.255126
83178.2.41.0/25178.2.41.1 to 178.2.41.126178.2.41.127126
84178.2.41.128/25178.2.41.129 to 178.2.41.254178.2.41.255126
85178.2.42.0/25178.2.42.1 to 178.2.42.126178.2.42.127126
86178.2.42.128/25178.2.42.129 to 178.2.42.254178.2.42.255126
87178.2.43.0/25178.2.43.1 to 178.2.43.126178.2.43.127126
88178.2.43.128/25178.2.43.129 to 178.2.43.254178.2.43.255126
89178.2.44.0/25178.2.44.1 to 178.2.44.126178.2.44.127126
90178.2.44.128/25178.2.44.129 to 178.2.44.254178.2.44.255126
91178.2.45.0/25178.2.45.1 to 178.2.45.126178.2.45.127126
92178.2.45.128/25178.2.45.129 to 178.2.45.254178.2.45.255126
93178.2.46.0/25178.2.46.1 to 178.2.46.126178.2.46.127126
94178.2.46.128/25178.2.46.129 to 178.2.46.254178.2.46.255126
95178.2.47.0/25178.2.47.1 to 178.2.47.126178.2.47.127126
96178.2.47.128/25178.2.47.129 to 178.2.47.254178.2.47.255126
97178.2.48.0/25178.2.48.1 to 178.2.48.126178.2.48.127126
98178.2.48.128/25178.2.48.129 to 178.2.48.254178.2.48.255126
99178.2.49.0/25178.2.49.1 to 178.2.49.126178.2.49.127126
100178.2.49.128/25178.2.49.129 to 178.2.49.254178.2.49.255126
101178.2.50.0/25178.2.50.1 to 178.2.50.126178.2.50.127126
102178.2.50.128/25178.2.50.129 to 178.2.50.254178.2.50.255126
103178.2.51.0/25178.2.51.1 to 178.2.51.126178.2.51.127126
104178.2.51.128/25178.2.51.129 to 178.2.51.254178.2.51.255126
105178.2.52.0/25178.2.52.1 to 178.2.52.126178.2.52.127126
106178.2.52.128/25178.2.52.129 to 178.2.52.254178.2.52.255126
107178.2.53.0/25178.2.53.1 to 178.2.53.126178.2.53.127126
108178.2.53.128/25178.2.53.129 to 178.2.53.254178.2.53.255126
109178.2.54.0/25178.2.54.1 to 178.2.54.126178.2.54.127126
110178.2.54.128/25178.2.54.129 to 178.2.54.254178.2.54.255126
111178.2.55.0/25178.2.55.1 to 178.2.55.126178.2.55.127126
112178.2.55.128/25178.2.55.129 to 178.2.55.254178.2.55.255126
113178.2.56.0/25178.2.56.1 to 178.2.56.126178.2.56.127126
114178.2.56.128/25178.2.56.129 to 178.2.56.254178.2.56.255126
115178.2.57.0/25178.2.57.1 to 178.2.57.126178.2.57.127126
116178.2.57.128/25178.2.57.129 to 178.2.57.254178.2.57.255126
117178.2.58.0/25178.2.58.1 to 178.2.58.126178.2.58.127126
118178.2.58.128/25178.2.58.129 to 178.2.58.254178.2.58.255126
119178.2.59.0/25178.2.59.1 to 178.2.59.126178.2.59.127126
120178.2.59.128/25178.2.59.129 to 178.2.59.254178.2.59.255126
121178.2.60.0/25178.2.60.1 to 178.2.60.126178.2.60.127126
122178.2.60.128/25178.2.60.129 to 178.2.60.254178.2.60.255126
123178.2.61.0/25178.2.61.1 to 178.2.61.126178.2.61.127126
124178.2.61.128/25178.2.61.129 to 178.2.61.254178.2.61.255126
125178.2.62.0/25178.2.62.1 to 178.2.62.126178.2.62.127126
126178.2.62.128/25178.2.62.129 to 178.2.62.254178.2.62.255126
127178.2.63.0/25178.2.63.1 to 178.2.63.126178.2.63.127126
128178.2.63.128/25178.2.63.129 to 178.2.63.254178.2.63.255126

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.