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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.

Network252.63.0.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
252.63.0.0
Broadcast address
252.63.63.255
First usable
252.63.0.1
Last usable
252.63.63.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FC3F0000 · Integer 4231987200 to 4232003583
Reverse DNS zones
0.63.252.in-addr.arpa
1.63.252.in-addr.arpa
2.63.252.in-addr.arpa
3.63.252.in-addr.arpa
4.63.252.in-addr.arpa
5.63.252.in-addr.arpa
6.63.252.in-addr.arpa
7.63.252.in-addr.arpa
8.63.252.in-addr.arpa
9.63.252.in-addr.arpa
10.63.252.in-addr.arpa
11.63.252.in-addr.arpa
12.63.252.in-addr.arpa
13.63.252.in-addr.arpa
14.63.252.in-addr.arpa
15.63.252.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
Address11111100.00111111.00000000.00000000252.63.0.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network11111100.00111111.00000000.00000000252.63.0.0
Broadcast11111100.00111111.00111111.11111111252.63.63.255
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)

252.63.0.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1252.63.0.0/25252.63.0.1 to 252.63.0.126252.63.0.127126
2252.63.0.128/25252.63.0.129 to 252.63.0.254252.63.0.255126
3252.63.1.0/25252.63.1.1 to 252.63.1.126252.63.1.127126
4252.63.1.128/25252.63.1.129 to 252.63.1.254252.63.1.255126
5252.63.2.0/25252.63.2.1 to 252.63.2.126252.63.2.127126
6252.63.2.128/25252.63.2.129 to 252.63.2.254252.63.2.255126
7252.63.3.0/25252.63.3.1 to 252.63.3.126252.63.3.127126
8252.63.3.128/25252.63.3.129 to 252.63.3.254252.63.3.255126
9252.63.4.0/25252.63.4.1 to 252.63.4.126252.63.4.127126
10252.63.4.128/25252.63.4.129 to 252.63.4.254252.63.4.255126
11252.63.5.0/25252.63.5.1 to 252.63.5.126252.63.5.127126
12252.63.5.128/25252.63.5.129 to 252.63.5.254252.63.5.255126
13252.63.6.0/25252.63.6.1 to 252.63.6.126252.63.6.127126
14252.63.6.128/25252.63.6.129 to 252.63.6.254252.63.6.255126
15252.63.7.0/25252.63.7.1 to 252.63.7.126252.63.7.127126
16252.63.7.128/25252.63.7.129 to 252.63.7.254252.63.7.255126
17252.63.8.0/25252.63.8.1 to 252.63.8.126252.63.8.127126
18252.63.8.128/25252.63.8.129 to 252.63.8.254252.63.8.255126
19252.63.9.0/25252.63.9.1 to 252.63.9.126252.63.9.127126
20252.63.9.128/25252.63.9.129 to 252.63.9.254252.63.9.255126
21252.63.10.0/25252.63.10.1 to 252.63.10.126252.63.10.127126
22252.63.10.128/25252.63.10.129 to 252.63.10.254252.63.10.255126
23252.63.11.0/25252.63.11.1 to 252.63.11.126252.63.11.127126
24252.63.11.128/25252.63.11.129 to 252.63.11.254252.63.11.255126
25252.63.12.0/25252.63.12.1 to 252.63.12.126252.63.12.127126
26252.63.12.128/25252.63.12.129 to 252.63.12.254252.63.12.255126
27252.63.13.0/25252.63.13.1 to 252.63.13.126252.63.13.127126
28252.63.13.128/25252.63.13.129 to 252.63.13.254252.63.13.255126
29252.63.14.0/25252.63.14.1 to 252.63.14.126252.63.14.127126
30252.63.14.128/25252.63.14.129 to 252.63.14.254252.63.14.255126
31252.63.15.0/25252.63.15.1 to 252.63.15.126252.63.15.127126
32252.63.15.128/25252.63.15.129 to 252.63.15.254252.63.15.255126
33252.63.16.0/25252.63.16.1 to 252.63.16.126252.63.16.127126
34252.63.16.128/25252.63.16.129 to 252.63.16.254252.63.16.255126
35252.63.17.0/25252.63.17.1 to 252.63.17.126252.63.17.127126
36252.63.17.128/25252.63.17.129 to 252.63.17.254252.63.17.255126
37252.63.18.0/25252.63.18.1 to 252.63.18.126252.63.18.127126
38252.63.18.128/25252.63.18.129 to 252.63.18.254252.63.18.255126
39252.63.19.0/25252.63.19.1 to 252.63.19.126252.63.19.127126
40252.63.19.128/25252.63.19.129 to 252.63.19.254252.63.19.255126
41252.63.20.0/25252.63.20.1 to 252.63.20.126252.63.20.127126
42252.63.20.128/25252.63.20.129 to 252.63.20.254252.63.20.255126
43252.63.21.0/25252.63.21.1 to 252.63.21.126252.63.21.127126
44252.63.21.128/25252.63.21.129 to 252.63.21.254252.63.21.255126
45252.63.22.0/25252.63.22.1 to 252.63.22.126252.63.22.127126
46252.63.22.128/25252.63.22.129 to 252.63.22.254252.63.22.255126
47252.63.23.0/25252.63.23.1 to 252.63.23.126252.63.23.127126
48252.63.23.128/25252.63.23.129 to 252.63.23.254252.63.23.255126
49252.63.24.0/25252.63.24.1 to 252.63.24.126252.63.24.127126
50252.63.24.128/25252.63.24.129 to 252.63.24.254252.63.24.255126
51252.63.25.0/25252.63.25.1 to 252.63.25.126252.63.25.127126
52252.63.25.128/25252.63.25.129 to 252.63.25.254252.63.25.255126
53252.63.26.0/25252.63.26.1 to 252.63.26.126252.63.26.127126
54252.63.26.128/25252.63.26.129 to 252.63.26.254252.63.26.255126
55252.63.27.0/25252.63.27.1 to 252.63.27.126252.63.27.127126
56252.63.27.128/25252.63.27.129 to 252.63.27.254252.63.27.255126
57252.63.28.0/25252.63.28.1 to 252.63.28.126252.63.28.127126
58252.63.28.128/25252.63.28.129 to 252.63.28.254252.63.28.255126
59252.63.29.0/25252.63.29.1 to 252.63.29.126252.63.29.127126
60252.63.29.128/25252.63.29.129 to 252.63.29.254252.63.29.255126
61252.63.30.0/25252.63.30.1 to 252.63.30.126252.63.30.127126
62252.63.30.128/25252.63.30.129 to 252.63.30.254252.63.30.255126
63252.63.31.0/25252.63.31.1 to 252.63.31.126252.63.31.127126
64252.63.31.128/25252.63.31.129 to 252.63.31.254252.63.31.255126
65252.63.32.0/25252.63.32.1 to 252.63.32.126252.63.32.127126
66252.63.32.128/25252.63.32.129 to 252.63.32.254252.63.32.255126
67252.63.33.0/25252.63.33.1 to 252.63.33.126252.63.33.127126
68252.63.33.128/25252.63.33.129 to 252.63.33.254252.63.33.255126
69252.63.34.0/25252.63.34.1 to 252.63.34.126252.63.34.127126
70252.63.34.128/25252.63.34.129 to 252.63.34.254252.63.34.255126
71252.63.35.0/25252.63.35.1 to 252.63.35.126252.63.35.127126
72252.63.35.128/25252.63.35.129 to 252.63.35.254252.63.35.255126
73252.63.36.0/25252.63.36.1 to 252.63.36.126252.63.36.127126
74252.63.36.128/25252.63.36.129 to 252.63.36.254252.63.36.255126
75252.63.37.0/25252.63.37.1 to 252.63.37.126252.63.37.127126
76252.63.37.128/25252.63.37.129 to 252.63.37.254252.63.37.255126
77252.63.38.0/25252.63.38.1 to 252.63.38.126252.63.38.127126
78252.63.38.128/25252.63.38.129 to 252.63.38.254252.63.38.255126
79252.63.39.0/25252.63.39.1 to 252.63.39.126252.63.39.127126
80252.63.39.128/25252.63.39.129 to 252.63.39.254252.63.39.255126
81252.63.40.0/25252.63.40.1 to 252.63.40.126252.63.40.127126
82252.63.40.128/25252.63.40.129 to 252.63.40.254252.63.40.255126
83252.63.41.0/25252.63.41.1 to 252.63.41.126252.63.41.127126
84252.63.41.128/25252.63.41.129 to 252.63.41.254252.63.41.255126
85252.63.42.0/25252.63.42.1 to 252.63.42.126252.63.42.127126
86252.63.42.128/25252.63.42.129 to 252.63.42.254252.63.42.255126
87252.63.43.0/25252.63.43.1 to 252.63.43.126252.63.43.127126
88252.63.43.128/25252.63.43.129 to 252.63.43.254252.63.43.255126
89252.63.44.0/25252.63.44.1 to 252.63.44.126252.63.44.127126
90252.63.44.128/25252.63.44.129 to 252.63.44.254252.63.44.255126
91252.63.45.0/25252.63.45.1 to 252.63.45.126252.63.45.127126
92252.63.45.128/25252.63.45.129 to 252.63.45.254252.63.45.255126
93252.63.46.0/25252.63.46.1 to 252.63.46.126252.63.46.127126
94252.63.46.128/25252.63.46.129 to 252.63.46.254252.63.46.255126
95252.63.47.0/25252.63.47.1 to 252.63.47.126252.63.47.127126
96252.63.47.128/25252.63.47.129 to 252.63.47.254252.63.47.255126
97252.63.48.0/25252.63.48.1 to 252.63.48.126252.63.48.127126
98252.63.48.128/25252.63.48.129 to 252.63.48.254252.63.48.255126
99252.63.49.0/25252.63.49.1 to 252.63.49.126252.63.49.127126
100252.63.49.128/25252.63.49.129 to 252.63.49.254252.63.49.255126
101252.63.50.0/25252.63.50.1 to 252.63.50.126252.63.50.127126
102252.63.50.128/25252.63.50.129 to 252.63.50.254252.63.50.255126
103252.63.51.0/25252.63.51.1 to 252.63.51.126252.63.51.127126
104252.63.51.128/25252.63.51.129 to 252.63.51.254252.63.51.255126
105252.63.52.0/25252.63.52.1 to 252.63.52.126252.63.52.127126
106252.63.52.128/25252.63.52.129 to 252.63.52.254252.63.52.255126
107252.63.53.0/25252.63.53.1 to 252.63.53.126252.63.53.127126
108252.63.53.128/25252.63.53.129 to 252.63.53.254252.63.53.255126
109252.63.54.0/25252.63.54.1 to 252.63.54.126252.63.54.127126
110252.63.54.128/25252.63.54.129 to 252.63.54.254252.63.54.255126
111252.63.55.0/25252.63.55.1 to 252.63.55.126252.63.55.127126
112252.63.55.128/25252.63.55.129 to 252.63.55.254252.63.55.255126
113252.63.56.0/25252.63.56.1 to 252.63.56.126252.63.56.127126
114252.63.56.128/25252.63.56.129 to 252.63.56.254252.63.56.255126
115252.63.57.0/25252.63.57.1 to 252.63.57.126252.63.57.127126
116252.63.57.128/25252.63.57.129 to 252.63.57.254252.63.57.255126
117252.63.58.0/25252.63.58.1 to 252.63.58.126252.63.58.127126
118252.63.58.128/25252.63.58.129 to 252.63.58.254252.63.58.255126
119252.63.59.0/25252.63.59.1 to 252.63.59.126252.63.59.127126
120252.63.59.128/25252.63.59.129 to 252.63.59.254252.63.59.255126
121252.63.60.0/25252.63.60.1 to 252.63.60.126252.63.60.127126
122252.63.60.128/25252.63.60.129 to 252.63.60.254252.63.60.255126
123252.63.61.0/25252.63.61.1 to 252.63.61.126252.63.61.127126
124252.63.61.128/25252.63.61.129 to 252.63.61.254252.63.61.255126
125252.63.62.0/25252.63.62.1 to 252.63.62.126252.63.62.127126
126252.63.62.128/25252.63.62.129 to 252.63.62.254252.63.62.255126
127252.63.63.0/25252.63.63.1 to 252.63.63.126252.63.63.127126
128252.63.63.128/25252.63.63.129 to 252.63.63.254252.63.63.255126

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.