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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.

Network103.40.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
103.40.0.0
Broadcast address
103.47.255.255
First usable
103.40.0.1
Last usable
103.47.255.254
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
A (default /8)
As numbers
Hex 67280000 · Integer 1730674688 to 1731198975
Reverse DNS zones
40.103.in-addr.arpa
41.103.in-addr.arpa
42.103.in-addr.arpa
43.103.in-addr.arpa
44.103.in-addr.arpa
45.103.in-addr.arpa
46.103.in-addr.arpa
47.103.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
Address01100111.00101000.00000000.00000000103.40.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network01100111.00101000.00000000.00000000103.40.0.0
Broadcast01100111.00101111.11111111.11111111103.47.255.255
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)

103.40.0.0/13 makes 128 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1103.40.0.0/20103.40.0.1 to 103.40.15.254103.40.15.2554,094
2103.40.16.0/20103.40.16.1 to 103.40.31.254103.40.31.2554,094
3103.40.32.0/20103.40.32.1 to 103.40.47.254103.40.47.2554,094
4103.40.48.0/20103.40.48.1 to 103.40.63.254103.40.63.2554,094
5103.40.64.0/20103.40.64.1 to 103.40.79.254103.40.79.2554,094
6103.40.80.0/20103.40.80.1 to 103.40.95.254103.40.95.2554,094
7103.40.96.0/20103.40.96.1 to 103.40.111.254103.40.111.2554,094
8103.40.112.0/20103.40.112.1 to 103.40.127.254103.40.127.2554,094
9103.40.128.0/20103.40.128.1 to 103.40.143.254103.40.143.2554,094
10103.40.144.0/20103.40.144.1 to 103.40.159.254103.40.159.2554,094
11103.40.160.0/20103.40.160.1 to 103.40.175.254103.40.175.2554,094
12103.40.176.0/20103.40.176.1 to 103.40.191.254103.40.191.2554,094
13103.40.192.0/20103.40.192.1 to 103.40.207.254103.40.207.2554,094
14103.40.208.0/20103.40.208.1 to 103.40.223.254103.40.223.2554,094
15103.40.224.0/20103.40.224.1 to 103.40.239.254103.40.239.2554,094
16103.40.240.0/20103.40.240.1 to 103.40.255.254103.40.255.2554,094
17103.41.0.0/20103.41.0.1 to 103.41.15.254103.41.15.2554,094
18103.41.16.0/20103.41.16.1 to 103.41.31.254103.41.31.2554,094
19103.41.32.0/20103.41.32.1 to 103.41.47.254103.41.47.2554,094
20103.41.48.0/20103.41.48.1 to 103.41.63.254103.41.63.2554,094
21103.41.64.0/20103.41.64.1 to 103.41.79.254103.41.79.2554,094
22103.41.80.0/20103.41.80.1 to 103.41.95.254103.41.95.2554,094
23103.41.96.0/20103.41.96.1 to 103.41.111.254103.41.111.2554,094
24103.41.112.0/20103.41.112.1 to 103.41.127.254103.41.127.2554,094
25103.41.128.0/20103.41.128.1 to 103.41.143.254103.41.143.2554,094
26103.41.144.0/20103.41.144.1 to 103.41.159.254103.41.159.2554,094
27103.41.160.0/20103.41.160.1 to 103.41.175.254103.41.175.2554,094
28103.41.176.0/20103.41.176.1 to 103.41.191.254103.41.191.2554,094
29103.41.192.0/20103.41.192.1 to 103.41.207.254103.41.207.2554,094
30103.41.208.0/20103.41.208.1 to 103.41.223.254103.41.223.2554,094
31103.41.224.0/20103.41.224.1 to 103.41.239.254103.41.239.2554,094
32103.41.240.0/20103.41.240.1 to 103.41.255.254103.41.255.2554,094
33103.42.0.0/20103.42.0.1 to 103.42.15.254103.42.15.2554,094
34103.42.16.0/20103.42.16.1 to 103.42.31.254103.42.31.2554,094
35103.42.32.0/20103.42.32.1 to 103.42.47.254103.42.47.2554,094
36103.42.48.0/20103.42.48.1 to 103.42.63.254103.42.63.2554,094
37103.42.64.0/20103.42.64.1 to 103.42.79.254103.42.79.2554,094
38103.42.80.0/20103.42.80.1 to 103.42.95.254103.42.95.2554,094
39103.42.96.0/20103.42.96.1 to 103.42.111.254103.42.111.2554,094
40103.42.112.0/20103.42.112.1 to 103.42.127.254103.42.127.2554,094
41103.42.128.0/20103.42.128.1 to 103.42.143.254103.42.143.2554,094
42103.42.144.0/20103.42.144.1 to 103.42.159.254103.42.159.2554,094
43103.42.160.0/20103.42.160.1 to 103.42.175.254103.42.175.2554,094
44103.42.176.0/20103.42.176.1 to 103.42.191.254103.42.191.2554,094
45103.42.192.0/20103.42.192.1 to 103.42.207.254103.42.207.2554,094
46103.42.208.0/20103.42.208.1 to 103.42.223.254103.42.223.2554,094
47103.42.224.0/20103.42.224.1 to 103.42.239.254103.42.239.2554,094
48103.42.240.0/20103.42.240.1 to 103.42.255.254103.42.255.2554,094
49103.43.0.0/20103.43.0.1 to 103.43.15.254103.43.15.2554,094
50103.43.16.0/20103.43.16.1 to 103.43.31.254103.43.31.2554,094
51103.43.32.0/20103.43.32.1 to 103.43.47.254103.43.47.2554,094
52103.43.48.0/20103.43.48.1 to 103.43.63.254103.43.63.2554,094
53103.43.64.0/20103.43.64.1 to 103.43.79.254103.43.79.2554,094
54103.43.80.0/20103.43.80.1 to 103.43.95.254103.43.95.2554,094
55103.43.96.0/20103.43.96.1 to 103.43.111.254103.43.111.2554,094
56103.43.112.0/20103.43.112.1 to 103.43.127.254103.43.127.2554,094
57103.43.128.0/20103.43.128.1 to 103.43.143.254103.43.143.2554,094
58103.43.144.0/20103.43.144.1 to 103.43.159.254103.43.159.2554,094
59103.43.160.0/20103.43.160.1 to 103.43.175.254103.43.175.2554,094
60103.43.176.0/20103.43.176.1 to 103.43.191.254103.43.191.2554,094
61103.43.192.0/20103.43.192.1 to 103.43.207.254103.43.207.2554,094
62103.43.208.0/20103.43.208.1 to 103.43.223.254103.43.223.2554,094
63103.43.224.0/20103.43.224.1 to 103.43.239.254103.43.239.2554,094
64103.43.240.0/20103.43.240.1 to 103.43.255.254103.43.255.2554,094
65103.44.0.0/20103.44.0.1 to 103.44.15.254103.44.15.2554,094
66103.44.16.0/20103.44.16.1 to 103.44.31.254103.44.31.2554,094
67103.44.32.0/20103.44.32.1 to 103.44.47.254103.44.47.2554,094
68103.44.48.0/20103.44.48.1 to 103.44.63.254103.44.63.2554,094
69103.44.64.0/20103.44.64.1 to 103.44.79.254103.44.79.2554,094
70103.44.80.0/20103.44.80.1 to 103.44.95.254103.44.95.2554,094
71103.44.96.0/20103.44.96.1 to 103.44.111.254103.44.111.2554,094
72103.44.112.0/20103.44.112.1 to 103.44.127.254103.44.127.2554,094
73103.44.128.0/20103.44.128.1 to 103.44.143.254103.44.143.2554,094
74103.44.144.0/20103.44.144.1 to 103.44.159.254103.44.159.2554,094
75103.44.160.0/20103.44.160.1 to 103.44.175.254103.44.175.2554,094
76103.44.176.0/20103.44.176.1 to 103.44.191.254103.44.191.2554,094
77103.44.192.0/20103.44.192.1 to 103.44.207.254103.44.207.2554,094
78103.44.208.0/20103.44.208.1 to 103.44.223.254103.44.223.2554,094
79103.44.224.0/20103.44.224.1 to 103.44.239.254103.44.239.2554,094
80103.44.240.0/20103.44.240.1 to 103.44.255.254103.44.255.2554,094
81103.45.0.0/20103.45.0.1 to 103.45.15.254103.45.15.2554,094
82103.45.16.0/20103.45.16.1 to 103.45.31.254103.45.31.2554,094
83103.45.32.0/20103.45.32.1 to 103.45.47.254103.45.47.2554,094
84103.45.48.0/20103.45.48.1 to 103.45.63.254103.45.63.2554,094
85103.45.64.0/20103.45.64.1 to 103.45.79.254103.45.79.2554,094
86103.45.80.0/20103.45.80.1 to 103.45.95.254103.45.95.2554,094
87103.45.96.0/20103.45.96.1 to 103.45.111.254103.45.111.2554,094
88103.45.112.0/20103.45.112.1 to 103.45.127.254103.45.127.2554,094
89103.45.128.0/20103.45.128.1 to 103.45.143.254103.45.143.2554,094
90103.45.144.0/20103.45.144.1 to 103.45.159.254103.45.159.2554,094
91103.45.160.0/20103.45.160.1 to 103.45.175.254103.45.175.2554,094
92103.45.176.0/20103.45.176.1 to 103.45.191.254103.45.191.2554,094
93103.45.192.0/20103.45.192.1 to 103.45.207.254103.45.207.2554,094
94103.45.208.0/20103.45.208.1 to 103.45.223.254103.45.223.2554,094
95103.45.224.0/20103.45.224.1 to 103.45.239.254103.45.239.2554,094
96103.45.240.0/20103.45.240.1 to 103.45.255.254103.45.255.2554,094
97103.46.0.0/20103.46.0.1 to 103.46.15.254103.46.15.2554,094
98103.46.16.0/20103.46.16.1 to 103.46.31.254103.46.31.2554,094
99103.46.32.0/20103.46.32.1 to 103.46.47.254103.46.47.2554,094
100103.46.48.0/20103.46.48.1 to 103.46.63.254103.46.63.2554,094
101103.46.64.0/20103.46.64.1 to 103.46.79.254103.46.79.2554,094
102103.46.80.0/20103.46.80.1 to 103.46.95.254103.46.95.2554,094
103103.46.96.0/20103.46.96.1 to 103.46.111.254103.46.111.2554,094
104103.46.112.0/20103.46.112.1 to 103.46.127.254103.46.127.2554,094
105103.46.128.0/20103.46.128.1 to 103.46.143.254103.46.143.2554,094
106103.46.144.0/20103.46.144.1 to 103.46.159.254103.46.159.2554,094
107103.46.160.0/20103.46.160.1 to 103.46.175.254103.46.175.2554,094
108103.46.176.0/20103.46.176.1 to 103.46.191.254103.46.191.2554,094
109103.46.192.0/20103.46.192.1 to 103.46.207.254103.46.207.2554,094
110103.46.208.0/20103.46.208.1 to 103.46.223.254103.46.223.2554,094
111103.46.224.0/20103.46.224.1 to 103.46.239.254103.46.239.2554,094
112103.46.240.0/20103.46.240.1 to 103.46.255.254103.46.255.2554,094
113103.47.0.0/20103.47.0.1 to 103.47.15.254103.47.15.2554,094
114103.47.16.0/20103.47.16.1 to 103.47.31.254103.47.31.2554,094
115103.47.32.0/20103.47.32.1 to 103.47.47.254103.47.47.2554,094
116103.47.48.0/20103.47.48.1 to 103.47.63.254103.47.63.2554,094
117103.47.64.0/20103.47.64.1 to 103.47.79.254103.47.79.2554,094
118103.47.80.0/20103.47.80.1 to 103.47.95.254103.47.95.2554,094
119103.47.96.0/20103.47.96.1 to 103.47.111.254103.47.111.2554,094
120103.47.112.0/20103.47.112.1 to 103.47.127.254103.47.127.2554,094
121103.47.128.0/20103.47.128.1 to 103.47.143.254103.47.143.2554,094
122103.47.144.0/20103.47.144.1 to 103.47.159.254103.47.159.2554,094
123103.47.160.0/20103.47.160.1 to 103.47.175.254103.47.175.2554,094
124103.47.176.0/20103.47.176.1 to 103.47.191.254103.47.191.2554,094
125103.47.192.0/20103.47.192.1 to 103.47.207.254103.47.207.2554,094
126103.47.208.0/20103.47.208.1 to 103.47.223.254103.47.223.2554,094
127103.47.224.0/20103.47.224.1 to 103.47.239.254103.47.239.2554,094
128103.47.240.0/20103.47.240.1 to 103.47.255.254103.47.255.2554,094

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.