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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.

Network131.64.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
131.64.0.0
Broadcast address
131.71.255.255
First usable
131.64.0.1
Last usable
131.71.255.254
Usable hosts
524,286 (524,288 less the network and broadcast addresses)
Subnet mask
255.248.0.0
Wildcard mask
0.7.255.255 (Cisco ACLs, OSPF)
Prefix length
/13
Type
Public public
Old class
B (default /16)
As numbers
Hex 83400000 · Integer 2202009600 to 2202533887
Reverse DNS zones
64.131.in-addr.arpa
65.131.in-addr.arpa
66.131.in-addr.arpa
67.131.in-addr.arpa
68.131.in-addr.arpa
69.131.in-addr.arpa
70.131.in-addr.arpa
71.131.in-addr.arpa
/13 is not on a 8-bit boundary, so it takes 8 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000011.01000000.00000000.00000000131.64.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network10000011.01000000.00000000.00000000131.64.0.0
Broadcast10000011.01000111.11111111.11111111131.71.255.255
Split into smaller subnets/20
/14 (2)/15 (4)/16 (8)/17 (16)/18 (32)/19 (64)/20 (128)/21 (256)/22 (512)/23 (1,024)/24 (2,048)/25 (4,096)

131.64.0.0/13 makes 128 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1131.64.0.0/20131.64.0.1 to 131.64.15.254131.64.15.2554,094
2131.64.16.0/20131.64.16.1 to 131.64.31.254131.64.31.2554,094
3131.64.32.0/20131.64.32.1 to 131.64.47.254131.64.47.2554,094
4131.64.48.0/20131.64.48.1 to 131.64.63.254131.64.63.2554,094
5131.64.64.0/20131.64.64.1 to 131.64.79.254131.64.79.2554,094
6131.64.80.0/20131.64.80.1 to 131.64.95.254131.64.95.2554,094
7131.64.96.0/20131.64.96.1 to 131.64.111.254131.64.111.2554,094
8131.64.112.0/20131.64.112.1 to 131.64.127.254131.64.127.2554,094
9131.64.128.0/20131.64.128.1 to 131.64.143.254131.64.143.2554,094
10131.64.144.0/20131.64.144.1 to 131.64.159.254131.64.159.2554,094
11131.64.160.0/20131.64.160.1 to 131.64.175.254131.64.175.2554,094
12131.64.176.0/20131.64.176.1 to 131.64.191.254131.64.191.2554,094
13131.64.192.0/20131.64.192.1 to 131.64.207.254131.64.207.2554,094
14131.64.208.0/20131.64.208.1 to 131.64.223.254131.64.223.2554,094
15131.64.224.0/20131.64.224.1 to 131.64.239.254131.64.239.2554,094
16131.64.240.0/20131.64.240.1 to 131.64.255.254131.64.255.2554,094
17131.65.0.0/20131.65.0.1 to 131.65.15.254131.65.15.2554,094
18131.65.16.0/20131.65.16.1 to 131.65.31.254131.65.31.2554,094
19131.65.32.0/20131.65.32.1 to 131.65.47.254131.65.47.2554,094
20131.65.48.0/20131.65.48.1 to 131.65.63.254131.65.63.2554,094
21131.65.64.0/20131.65.64.1 to 131.65.79.254131.65.79.2554,094
22131.65.80.0/20131.65.80.1 to 131.65.95.254131.65.95.2554,094
23131.65.96.0/20131.65.96.1 to 131.65.111.254131.65.111.2554,094
24131.65.112.0/20131.65.112.1 to 131.65.127.254131.65.127.2554,094
25131.65.128.0/20131.65.128.1 to 131.65.143.254131.65.143.2554,094
26131.65.144.0/20131.65.144.1 to 131.65.159.254131.65.159.2554,094
27131.65.160.0/20131.65.160.1 to 131.65.175.254131.65.175.2554,094
28131.65.176.0/20131.65.176.1 to 131.65.191.254131.65.191.2554,094
29131.65.192.0/20131.65.192.1 to 131.65.207.254131.65.207.2554,094
30131.65.208.0/20131.65.208.1 to 131.65.223.254131.65.223.2554,094
31131.65.224.0/20131.65.224.1 to 131.65.239.254131.65.239.2554,094
32131.65.240.0/20131.65.240.1 to 131.65.255.254131.65.255.2554,094
33131.66.0.0/20131.66.0.1 to 131.66.15.254131.66.15.2554,094
34131.66.16.0/20131.66.16.1 to 131.66.31.254131.66.31.2554,094
35131.66.32.0/20131.66.32.1 to 131.66.47.254131.66.47.2554,094
36131.66.48.0/20131.66.48.1 to 131.66.63.254131.66.63.2554,094
37131.66.64.0/20131.66.64.1 to 131.66.79.254131.66.79.2554,094
38131.66.80.0/20131.66.80.1 to 131.66.95.254131.66.95.2554,094
39131.66.96.0/20131.66.96.1 to 131.66.111.254131.66.111.2554,094
40131.66.112.0/20131.66.112.1 to 131.66.127.254131.66.127.2554,094
41131.66.128.0/20131.66.128.1 to 131.66.143.254131.66.143.2554,094
42131.66.144.0/20131.66.144.1 to 131.66.159.254131.66.159.2554,094
43131.66.160.0/20131.66.160.1 to 131.66.175.254131.66.175.2554,094
44131.66.176.0/20131.66.176.1 to 131.66.191.254131.66.191.2554,094
45131.66.192.0/20131.66.192.1 to 131.66.207.254131.66.207.2554,094
46131.66.208.0/20131.66.208.1 to 131.66.223.254131.66.223.2554,094
47131.66.224.0/20131.66.224.1 to 131.66.239.254131.66.239.2554,094
48131.66.240.0/20131.66.240.1 to 131.66.255.254131.66.255.2554,094
49131.67.0.0/20131.67.0.1 to 131.67.15.254131.67.15.2554,094
50131.67.16.0/20131.67.16.1 to 131.67.31.254131.67.31.2554,094
51131.67.32.0/20131.67.32.1 to 131.67.47.254131.67.47.2554,094
52131.67.48.0/20131.67.48.1 to 131.67.63.254131.67.63.2554,094
53131.67.64.0/20131.67.64.1 to 131.67.79.254131.67.79.2554,094
54131.67.80.0/20131.67.80.1 to 131.67.95.254131.67.95.2554,094
55131.67.96.0/20131.67.96.1 to 131.67.111.254131.67.111.2554,094
56131.67.112.0/20131.67.112.1 to 131.67.127.254131.67.127.2554,094
57131.67.128.0/20131.67.128.1 to 131.67.143.254131.67.143.2554,094
58131.67.144.0/20131.67.144.1 to 131.67.159.254131.67.159.2554,094
59131.67.160.0/20131.67.160.1 to 131.67.175.254131.67.175.2554,094
60131.67.176.0/20131.67.176.1 to 131.67.191.254131.67.191.2554,094
61131.67.192.0/20131.67.192.1 to 131.67.207.254131.67.207.2554,094
62131.67.208.0/20131.67.208.1 to 131.67.223.254131.67.223.2554,094
63131.67.224.0/20131.67.224.1 to 131.67.239.254131.67.239.2554,094
64131.67.240.0/20131.67.240.1 to 131.67.255.254131.67.255.2554,094
65131.68.0.0/20131.68.0.1 to 131.68.15.254131.68.15.2554,094
66131.68.16.0/20131.68.16.1 to 131.68.31.254131.68.31.2554,094
67131.68.32.0/20131.68.32.1 to 131.68.47.254131.68.47.2554,094
68131.68.48.0/20131.68.48.1 to 131.68.63.254131.68.63.2554,094
69131.68.64.0/20131.68.64.1 to 131.68.79.254131.68.79.2554,094
70131.68.80.0/20131.68.80.1 to 131.68.95.254131.68.95.2554,094
71131.68.96.0/20131.68.96.1 to 131.68.111.254131.68.111.2554,094
72131.68.112.0/20131.68.112.1 to 131.68.127.254131.68.127.2554,094
73131.68.128.0/20131.68.128.1 to 131.68.143.254131.68.143.2554,094
74131.68.144.0/20131.68.144.1 to 131.68.159.254131.68.159.2554,094
75131.68.160.0/20131.68.160.1 to 131.68.175.254131.68.175.2554,094
76131.68.176.0/20131.68.176.1 to 131.68.191.254131.68.191.2554,094
77131.68.192.0/20131.68.192.1 to 131.68.207.254131.68.207.2554,094
78131.68.208.0/20131.68.208.1 to 131.68.223.254131.68.223.2554,094
79131.68.224.0/20131.68.224.1 to 131.68.239.254131.68.239.2554,094
80131.68.240.0/20131.68.240.1 to 131.68.255.254131.68.255.2554,094
81131.69.0.0/20131.69.0.1 to 131.69.15.254131.69.15.2554,094
82131.69.16.0/20131.69.16.1 to 131.69.31.254131.69.31.2554,094
83131.69.32.0/20131.69.32.1 to 131.69.47.254131.69.47.2554,094
84131.69.48.0/20131.69.48.1 to 131.69.63.254131.69.63.2554,094
85131.69.64.0/20131.69.64.1 to 131.69.79.254131.69.79.2554,094
86131.69.80.0/20131.69.80.1 to 131.69.95.254131.69.95.2554,094
87131.69.96.0/20131.69.96.1 to 131.69.111.254131.69.111.2554,094
88131.69.112.0/20131.69.112.1 to 131.69.127.254131.69.127.2554,094
89131.69.128.0/20131.69.128.1 to 131.69.143.254131.69.143.2554,094
90131.69.144.0/20131.69.144.1 to 131.69.159.254131.69.159.2554,094
91131.69.160.0/20131.69.160.1 to 131.69.175.254131.69.175.2554,094
92131.69.176.0/20131.69.176.1 to 131.69.191.254131.69.191.2554,094
93131.69.192.0/20131.69.192.1 to 131.69.207.254131.69.207.2554,094
94131.69.208.0/20131.69.208.1 to 131.69.223.254131.69.223.2554,094
95131.69.224.0/20131.69.224.1 to 131.69.239.254131.69.239.2554,094
96131.69.240.0/20131.69.240.1 to 131.69.255.254131.69.255.2554,094
97131.70.0.0/20131.70.0.1 to 131.70.15.254131.70.15.2554,094
98131.70.16.0/20131.70.16.1 to 131.70.31.254131.70.31.2554,094
99131.70.32.0/20131.70.32.1 to 131.70.47.254131.70.47.2554,094
100131.70.48.0/20131.70.48.1 to 131.70.63.254131.70.63.2554,094
101131.70.64.0/20131.70.64.1 to 131.70.79.254131.70.79.2554,094
102131.70.80.0/20131.70.80.1 to 131.70.95.254131.70.95.2554,094
103131.70.96.0/20131.70.96.1 to 131.70.111.254131.70.111.2554,094
104131.70.112.0/20131.70.112.1 to 131.70.127.254131.70.127.2554,094
105131.70.128.0/20131.70.128.1 to 131.70.143.254131.70.143.2554,094
106131.70.144.0/20131.70.144.1 to 131.70.159.254131.70.159.2554,094
107131.70.160.0/20131.70.160.1 to 131.70.175.254131.70.175.2554,094
108131.70.176.0/20131.70.176.1 to 131.70.191.254131.70.191.2554,094
109131.70.192.0/20131.70.192.1 to 131.70.207.254131.70.207.2554,094
110131.70.208.0/20131.70.208.1 to 131.70.223.254131.70.223.2554,094
111131.70.224.0/20131.70.224.1 to 131.70.239.254131.70.239.2554,094
112131.70.240.0/20131.70.240.1 to 131.70.255.254131.70.255.2554,094
113131.71.0.0/20131.71.0.1 to 131.71.15.254131.71.15.2554,094
114131.71.16.0/20131.71.16.1 to 131.71.31.254131.71.31.2554,094
115131.71.32.0/20131.71.32.1 to 131.71.47.254131.71.47.2554,094
116131.71.48.0/20131.71.48.1 to 131.71.63.254131.71.63.2554,094
117131.71.64.0/20131.71.64.1 to 131.71.79.254131.71.79.2554,094
118131.71.80.0/20131.71.80.1 to 131.71.95.254131.71.95.2554,094
119131.71.96.0/20131.71.96.1 to 131.71.111.254131.71.111.2554,094
120131.71.112.0/20131.71.112.1 to 131.71.127.254131.71.127.2554,094
121131.71.128.0/20131.71.128.1 to 131.71.143.254131.71.143.2554,094
122131.71.144.0/20131.71.144.1 to 131.71.159.254131.71.159.2554,094
123131.71.160.0/20131.71.160.1 to 131.71.175.254131.71.175.2554,094
124131.71.176.0/20131.71.176.1 to 131.71.191.254131.71.191.2554,094
125131.71.192.0/20131.71.192.1 to 131.71.207.254131.71.207.2554,094
126131.71.208.0/20131.71.208.1 to 131.71.223.254131.71.223.2554,094
127131.71.224.0/20131.71.224.1 to 131.71.239.254131.71.239.2554,094
128131.71.240.0/20131.71.240.1 to 131.71.255.254131.71.255.2554,094

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.