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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.

Network135.2.0.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
135.2.0.0
Broadcast address
135.2.63.255
First usable
135.2.0.1
Last usable
135.2.63.254
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 87020000 · Integer 2265055232 to 2265071615
Reverse DNS zones
0.2.135.in-addr.arpa
1.2.135.in-addr.arpa
2.2.135.in-addr.arpa
3.2.135.in-addr.arpa
4.2.135.in-addr.arpa
5.2.135.in-addr.arpa
6.2.135.in-addr.arpa
7.2.135.in-addr.arpa
8.2.135.in-addr.arpa
9.2.135.in-addr.arpa
10.2.135.in-addr.arpa
11.2.135.in-addr.arpa
12.2.135.in-addr.arpa
13.2.135.in-addr.arpa
14.2.135.in-addr.arpa
15.2.135.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
Address10000111.00000010.00000000.00000000135.2.0.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network10000111.00000010.00000000.00000000135.2.0.0
Broadcast10000111.00000010.00111111.11111111135.2.63.255
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)

135.2.0.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1135.2.0.0/25135.2.0.1 to 135.2.0.126135.2.0.127126
2135.2.0.128/25135.2.0.129 to 135.2.0.254135.2.0.255126
3135.2.1.0/25135.2.1.1 to 135.2.1.126135.2.1.127126
4135.2.1.128/25135.2.1.129 to 135.2.1.254135.2.1.255126
5135.2.2.0/25135.2.2.1 to 135.2.2.126135.2.2.127126
6135.2.2.128/25135.2.2.129 to 135.2.2.254135.2.2.255126
7135.2.3.0/25135.2.3.1 to 135.2.3.126135.2.3.127126
8135.2.3.128/25135.2.3.129 to 135.2.3.254135.2.3.255126
9135.2.4.0/25135.2.4.1 to 135.2.4.126135.2.4.127126
10135.2.4.128/25135.2.4.129 to 135.2.4.254135.2.4.255126
11135.2.5.0/25135.2.5.1 to 135.2.5.126135.2.5.127126
12135.2.5.128/25135.2.5.129 to 135.2.5.254135.2.5.255126
13135.2.6.0/25135.2.6.1 to 135.2.6.126135.2.6.127126
14135.2.6.128/25135.2.6.129 to 135.2.6.254135.2.6.255126
15135.2.7.0/25135.2.7.1 to 135.2.7.126135.2.7.127126
16135.2.7.128/25135.2.7.129 to 135.2.7.254135.2.7.255126
17135.2.8.0/25135.2.8.1 to 135.2.8.126135.2.8.127126
18135.2.8.128/25135.2.8.129 to 135.2.8.254135.2.8.255126
19135.2.9.0/25135.2.9.1 to 135.2.9.126135.2.9.127126
20135.2.9.128/25135.2.9.129 to 135.2.9.254135.2.9.255126
21135.2.10.0/25135.2.10.1 to 135.2.10.126135.2.10.127126
22135.2.10.128/25135.2.10.129 to 135.2.10.254135.2.10.255126
23135.2.11.0/25135.2.11.1 to 135.2.11.126135.2.11.127126
24135.2.11.128/25135.2.11.129 to 135.2.11.254135.2.11.255126
25135.2.12.0/25135.2.12.1 to 135.2.12.126135.2.12.127126
26135.2.12.128/25135.2.12.129 to 135.2.12.254135.2.12.255126
27135.2.13.0/25135.2.13.1 to 135.2.13.126135.2.13.127126
28135.2.13.128/25135.2.13.129 to 135.2.13.254135.2.13.255126
29135.2.14.0/25135.2.14.1 to 135.2.14.126135.2.14.127126
30135.2.14.128/25135.2.14.129 to 135.2.14.254135.2.14.255126
31135.2.15.0/25135.2.15.1 to 135.2.15.126135.2.15.127126
32135.2.15.128/25135.2.15.129 to 135.2.15.254135.2.15.255126
33135.2.16.0/25135.2.16.1 to 135.2.16.126135.2.16.127126
34135.2.16.128/25135.2.16.129 to 135.2.16.254135.2.16.255126
35135.2.17.0/25135.2.17.1 to 135.2.17.126135.2.17.127126
36135.2.17.128/25135.2.17.129 to 135.2.17.254135.2.17.255126
37135.2.18.0/25135.2.18.1 to 135.2.18.126135.2.18.127126
38135.2.18.128/25135.2.18.129 to 135.2.18.254135.2.18.255126
39135.2.19.0/25135.2.19.1 to 135.2.19.126135.2.19.127126
40135.2.19.128/25135.2.19.129 to 135.2.19.254135.2.19.255126
41135.2.20.0/25135.2.20.1 to 135.2.20.126135.2.20.127126
42135.2.20.128/25135.2.20.129 to 135.2.20.254135.2.20.255126
43135.2.21.0/25135.2.21.1 to 135.2.21.126135.2.21.127126
44135.2.21.128/25135.2.21.129 to 135.2.21.254135.2.21.255126
45135.2.22.0/25135.2.22.1 to 135.2.22.126135.2.22.127126
46135.2.22.128/25135.2.22.129 to 135.2.22.254135.2.22.255126
47135.2.23.0/25135.2.23.1 to 135.2.23.126135.2.23.127126
48135.2.23.128/25135.2.23.129 to 135.2.23.254135.2.23.255126
49135.2.24.0/25135.2.24.1 to 135.2.24.126135.2.24.127126
50135.2.24.128/25135.2.24.129 to 135.2.24.254135.2.24.255126
51135.2.25.0/25135.2.25.1 to 135.2.25.126135.2.25.127126
52135.2.25.128/25135.2.25.129 to 135.2.25.254135.2.25.255126
53135.2.26.0/25135.2.26.1 to 135.2.26.126135.2.26.127126
54135.2.26.128/25135.2.26.129 to 135.2.26.254135.2.26.255126
55135.2.27.0/25135.2.27.1 to 135.2.27.126135.2.27.127126
56135.2.27.128/25135.2.27.129 to 135.2.27.254135.2.27.255126
57135.2.28.0/25135.2.28.1 to 135.2.28.126135.2.28.127126
58135.2.28.128/25135.2.28.129 to 135.2.28.254135.2.28.255126
59135.2.29.0/25135.2.29.1 to 135.2.29.126135.2.29.127126
60135.2.29.128/25135.2.29.129 to 135.2.29.254135.2.29.255126
61135.2.30.0/25135.2.30.1 to 135.2.30.126135.2.30.127126
62135.2.30.128/25135.2.30.129 to 135.2.30.254135.2.30.255126
63135.2.31.0/25135.2.31.1 to 135.2.31.126135.2.31.127126
64135.2.31.128/25135.2.31.129 to 135.2.31.254135.2.31.255126
65135.2.32.0/25135.2.32.1 to 135.2.32.126135.2.32.127126
66135.2.32.128/25135.2.32.129 to 135.2.32.254135.2.32.255126
67135.2.33.0/25135.2.33.1 to 135.2.33.126135.2.33.127126
68135.2.33.128/25135.2.33.129 to 135.2.33.254135.2.33.255126
69135.2.34.0/25135.2.34.1 to 135.2.34.126135.2.34.127126
70135.2.34.128/25135.2.34.129 to 135.2.34.254135.2.34.255126
71135.2.35.0/25135.2.35.1 to 135.2.35.126135.2.35.127126
72135.2.35.128/25135.2.35.129 to 135.2.35.254135.2.35.255126
73135.2.36.0/25135.2.36.1 to 135.2.36.126135.2.36.127126
74135.2.36.128/25135.2.36.129 to 135.2.36.254135.2.36.255126
75135.2.37.0/25135.2.37.1 to 135.2.37.126135.2.37.127126
76135.2.37.128/25135.2.37.129 to 135.2.37.254135.2.37.255126
77135.2.38.0/25135.2.38.1 to 135.2.38.126135.2.38.127126
78135.2.38.128/25135.2.38.129 to 135.2.38.254135.2.38.255126
79135.2.39.0/25135.2.39.1 to 135.2.39.126135.2.39.127126
80135.2.39.128/25135.2.39.129 to 135.2.39.254135.2.39.255126
81135.2.40.0/25135.2.40.1 to 135.2.40.126135.2.40.127126
82135.2.40.128/25135.2.40.129 to 135.2.40.254135.2.40.255126
83135.2.41.0/25135.2.41.1 to 135.2.41.126135.2.41.127126
84135.2.41.128/25135.2.41.129 to 135.2.41.254135.2.41.255126
85135.2.42.0/25135.2.42.1 to 135.2.42.126135.2.42.127126
86135.2.42.128/25135.2.42.129 to 135.2.42.254135.2.42.255126
87135.2.43.0/25135.2.43.1 to 135.2.43.126135.2.43.127126
88135.2.43.128/25135.2.43.129 to 135.2.43.254135.2.43.255126
89135.2.44.0/25135.2.44.1 to 135.2.44.126135.2.44.127126
90135.2.44.128/25135.2.44.129 to 135.2.44.254135.2.44.255126
91135.2.45.0/25135.2.45.1 to 135.2.45.126135.2.45.127126
92135.2.45.128/25135.2.45.129 to 135.2.45.254135.2.45.255126
93135.2.46.0/25135.2.46.1 to 135.2.46.126135.2.46.127126
94135.2.46.128/25135.2.46.129 to 135.2.46.254135.2.46.255126
95135.2.47.0/25135.2.47.1 to 135.2.47.126135.2.47.127126
96135.2.47.128/25135.2.47.129 to 135.2.47.254135.2.47.255126
97135.2.48.0/25135.2.48.1 to 135.2.48.126135.2.48.127126
98135.2.48.128/25135.2.48.129 to 135.2.48.254135.2.48.255126
99135.2.49.0/25135.2.49.1 to 135.2.49.126135.2.49.127126
100135.2.49.128/25135.2.49.129 to 135.2.49.254135.2.49.255126
101135.2.50.0/25135.2.50.1 to 135.2.50.126135.2.50.127126
102135.2.50.128/25135.2.50.129 to 135.2.50.254135.2.50.255126
103135.2.51.0/25135.2.51.1 to 135.2.51.126135.2.51.127126
104135.2.51.128/25135.2.51.129 to 135.2.51.254135.2.51.255126
105135.2.52.0/25135.2.52.1 to 135.2.52.126135.2.52.127126
106135.2.52.128/25135.2.52.129 to 135.2.52.254135.2.52.255126
107135.2.53.0/25135.2.53.1 to 135.2.53.126135.2.53.127126
108135.2.53.128/25135.2.53.129 to 135.2.53.254135.2.53.255126
109135.2.54.0/25135.2.54.1 to 135.2.54.126135.2.54.127126
110135.2.54.128/25135.2.54.129 to 135.2.54.254135.2.54.255126
111135.2.55.0/25135.2.55.1 to 135.2.55.126135.2.55.127126
112135.2.55.128/25135.2.55.129 to 135.2.55.254135.2.55.255126
113135.2.56.0/25135.2.56.1 to 135.2.56.126135.2.56.127126
114135.2.56.128/25135.2.56.129 to 135.2.56.254135.2.56.255126
115135.2.57.0/25135.2.57.1 to 135.2.57.126135.2.57.127126
116135.2.57.128/25135.2.57.129 to 135.2.57.254135.2.57.255126
117135.2.58.0/25135.2.58.1 to 135.2.58.126135.2.58.127126
118135.2.58.128/25135.2.58.129 to 135.2.58.254135.2.58.255126
119135.2.59.0/25135.2.59.1 to 135.2.59.126135.2.59.127126
120135.2.59.128/25135.2.59.129 to 135.2.59.254135.2.59.255126
121135.2.60.0/25135.2.60.1 to 135.2.60.126135.2.60.127126
122135.2.60.128/25135.2.60.129 to 135.2.60.254135.2.60.255126
123135.2.61.0/25135.2.61.1 to 135.2.61.126135.2.61.127126
124135.2.61.128/25135.2.61.129 to 135.2.61.254135.2.61.255126
125135.2.62.0/25135.2.62.1 to 135.2.62.126135.2.62.127126
126135.2.62.128/25135.2.62.129 to 135.2.62.254135.2.62.255126
127135.2.63.0/25135.2.63.1 to 135.2.63.126135.2.63.127126
128135.2.63.128/25135.2.63.129 to 135.2.63.254135.2.63.255126

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.