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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.

Network101.72.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
101.72.0.0
Broadcast address
101.79.255.255
First usable
101.72.0.1
Last usable
101.79.255.254
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 65480000 · Integer 1699217408 to 1699741695
Reverse DNS zones
72.101.in-addr.arpa
73.101.in-addr.arpa
74.101.in-addr.arpa
75.101.in-addr.arpa
76.101.in-addr.arpa
77.101.in-addr.arpa
78.101.in-addr.arpa
79.101.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
Address01100101.01001000.00000000.00000000101.72.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network01100101.01001000.00000000.00000000101.72.0.0
Broadcast01100101.01001111.11111111.11111111101.79.255.255
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)

101.72.0.0/13 makes 128 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1101.72.0.0/20101.72.0.1 to 101.72.15.254101.72.15.2554,094
2101.72.16.0/20101.72.16.1 to 101.72.31.254101.72.31.2554,094
3101.72.32.0/20101.72.32.1 to 101.72.47.254101.72.47.2554,094
4101.72.48.0/20101.72.48.1 to 101.72.63.254101.72.63.2554,094
5101.72.64.0/20101.72.64.1 to 101.72.79.254101.72.79.2554,094
6101.72.80.0/20101.72.80.1 to 101.72.95.254101.72.95.2554,094
7101.72.96.0/20101.72.96.1 to 101.72.111.254101.72.111.2554,094
8101.72.112.0/20101.72.112.1 to 101.72.127.254101.72.127.2554,094
9101.72.128.0/20101.72.128.1 to 101.72.143.254101.72.143.2554,094
10101.72.144.0/20101.72.144.1 to 101.72.159.254101.72.159.2554,094
11101.72.160.0/20101.72.160.1 to 101.72.175.254101.72.175.2554,094
12101.72.176.0/20101.72.176.1 to 101.72.191.254101.72.191.2554,094
13101.72.192.0/20101.72.192.1 to 101.72.207.254101.72.207.2554,094
14101.72.208.0/20101.72.208.1 to 101.72.223.254101.72.223.2554,094
15101.72.224.0/20101.72.224.1 to 101.72.239.254101.72.239.2554,094
16101.72.240.0/20101.72.240.1 to 101.72.255.254101.72.255.2554,094
17101.73.0.0/20101.73.0.1 to 101.73.15.254101.73.15.2554,094
18101.73.16.0/20101.73.16.1 to 101.73.31.254101.73.31.2554,094
19101.73.32.0/20101.73.32.1 to 101.73.47.254101.73.47.2554,094
20101.73.48.0/20101.73.48.1 to 101.73.63.254101.73.63.2554,094
21101.73.64.0/20101.73.64.1 to 101.73.79.254101.73.79.2554,094
22101.73.80.0/20101.73.80.1 to 101.73.95.254101.73.95.2554,094
23101.73.96.0/20101.73.96.1 to 101.73.111.254101.73.111.2554,094
24101.73.112.0/20101.73.112.1 to 101.73.127.254101.73.127.2554,094
25101.73.128.0/20101.73.128.1 to 101.73.143.254101.73.143.2554,094
26101.73.144.0/20101.73.144.1 to 101.73.159.254101.73.159.2554,094
27101.73.160.0/20101.73.160.1 to 101.73.175.254101.73.175.2554,094
28101.73.176.0/20101.73.176.1 to 101.73.191.254101.73.191.2554,094
29101.73.192.0/20101.73.192.1 to 101.73.207.254101.73.207.2554,094
30101.73.208.0/20101.73.208.1 to 101.73.223.254101.73.223.2554,094
31101.73.224.0/20101.73.224.1 to 101.73.239.254101.73.239.2554,094
32101.73.240.0/20101.73.240.1 to 101.73.255.254101.73.255.2554,094
33101.74.0.0/20101.74.0.1 to 101.74.15.254101.74.15.2554,094
34101.74.16.0/20101.74.16.1 to 101.74.31.254101.74.31.2554,094
35101.74.32.0/20101.74.32.1 to 101.74.47.254101.74.47.2554,094
36101.74.48.0/20101.74.48.1 to 101.74.63.254101.74.63.2554,094
37101.74.64.0/20101.74.64.1 to 101.74.79.254101.74.79.2554,094
38101.74.80.0/20101.74.80.1 to 101.74.95.254101.74.95.2554,094
39101.74.96.0/20101.74.96.1 to 101.74.111.254101.74.111.2554,094
40101.74.112.0/20101.74.112.1 to 101.74.127.254101.74.127.2554,094
41101.74.128.0/20101.74.128.1 to 101.74.143.254101.74.143.2554,094
42101.74.144.0/20101.74.144.1 to 101.74.159.254101.74.159.2554,094
43101.74.160.0/20101.74.160.1 to 101.74.175.254101.74.175.2554,094
44101.74.176.0/20101.74.176.1 to 101.74.191.254101.74.191.2554,094
45101.74.192.0/20101.74.192.1 to 101.74.207.254101.74.207.2554,094
46101.74.208.0/20101.74.208.1 to 101.74.223.254101.74.223.2554,094
47101.74.224.0/20101.74.224.1 to 101.74.239.254101.74.239.2554,094
48101.74.240.0/20101.74.240.1 to 101.74.255.254101.74.255.2554,094
49101.75.0.0/20101.75.0.1 to 101.75.15.254101.75.15.2554,094
50101.75.16.0/20101.75.16.1 to 101.75.31.254101.75.31.2554,094
51101.75.32.0/20101.75.32.1 to 101.75.47.254101.75.47.2554,094
52101.75.48.0/20101.75.48.1 to 101.75.63.254101.75.63.2554,094
53101.75.64.0/20101.75.64.1 to 101.75.79.254101.75.79.2554,094
54101.75.80.0/20101.75.80.1 to 101.75.95.254101.75.95.2554,094
55101.75.96.0/20101.75.96.1 to 101.75.111.254101.75.111.2554,094
56101.75.112.0/20101.75.112.1 to 101.75.127.254101.75.127.2554,094
57101.75.128.0/20101.75.128.1 to 101.75.143.254101.75.143.2554,094
58101.75.144.0/20101.75.144.1 to 101.75.159.254101.75.159.2554,094
59101.75.160.0/20101.75.160.1 to 101.75.175.254101.75.175.2554,094
60101.75.176.0/20101.75.176.1 to 101.75.191.254101.75.191.2554,094
61101.75.192.0/20101.75.192.1 to 101.75.207.254101.75.207.2554,094
62101.75.208.0/20101.75.208.1 to 101.75.223.254101.75.223.2554,094
63101.75.224.0/20101.75.224.1 to 101.75.239.254101.75.239.2554,094
64101.75.240.0/20101.75.240.1 to 101.75.255.254101.75.255.2554,094
65101.76.0.0/20101.76.0.1 to 101.76.15.254101.76.15.2554,094
66101.76.16.0/20101.76.16.1 to 101.76.31.254101.76.31.2554,094
67101.76.32.0/20101.76.32.1 to 101.76.47.254101.76.47.2554,094
68101.76.48.0/20101.76.48.1 to 101.76.63.254101.76.63.2554,094
69101.76.64.0/20101.76.64.1 to 101.76.79.254101.76.79.2554,094
70101.76.80.0/20101.76.80.1 to 101.76.95.254101.76.95.2554,094
71101.76.96.0/20101.76.96.1 to 101.76.111.254101.76.111.2554,094
72101.76.112.0/20101.76.112.1 to 101.76.127.254101.76.127.2554,094
73101.76.128.0/20101.76.128.1 to 101.76.143.254101.76.143.2554,094
74101.76.144.0/20101.76.144.1 to 101.76.159.254101.76.159.2554,094
75101.76.160.0/20101.76.160.1 to 101.76.175.254101.76.175.2554,094
76101.76.176.0/20101.76.176.1 to 101.76.191.254101.76.191.2554,094
77101.76.192.0/20101.76.192.1 to 101.76.207.254101.76.207.2554,094
78101.76.208.0/20101.76.208.1 to 101.76.223.254101.76.223.2554,094
79101.76.224.0/20101.76.224.1 to 101.76.239.254101.76.239.2554,094
80101.76.240.0/20101.76.240.1 to 101.76.255.254101.76.255.2554,094
81101.77.0.0/20101.77.0.1 to 101.77.15.254101.77.15.2554,094
82101.77.16.0/20101.77.16.1 to 101.77.31.254101.77.31.2554,094
83101.77.32.0/20101.77.32.1 to 101.77.47.254101.77.47.2554,094
84101.77.48.0/20101.77.48.1 to 101.77.63.254101.77.63.2554,094
85101.77.64.0/20101.77.64.1 to 101.77.79.254101.77.79.2554,094
86101.77.80.0/20101.77.80.1 to 101.77.95.254101.77.95.2554,094
87101.77.96.0/20101.77.96.1 to 101.77.111.254101.77.111.2554,094
88101.77.112.0/20101.77.112.1 to 101.77.127.254101.77.127.2554,094
89101.77.128.0/20101.77.128.1 to 101.77.143.254101.77.143.2554,094
90101.77.144.0/20101.77.144.1 to 101.77.159.254101.77.159.2554,094
91101.77.160.0/20101.77.160.1 to 101.77.175.254101.77.175.2554,094
92101.77.176.0/20101.77.176.1 to 101.77.191.254101.77.191.2554,094
93101.77.192.0/20101.77.192.1 to 101.77.207.254101.77.207.2554,094
94101.77.208.0/20101.77.208.1 to 101.77.223.254101.77.223.2554,094
95101.77.224.0/20101.77.224.1 to 101.77.239.254101.77.239.2554,094
96101.77.240.0/20101.77.240.1 to 101.77.255.254101.77.255.2554,094
97101.78.0.0/20101.78.0.1 to 101.78.15.254101.78.15.2554,094
98101.78.16.0/20101.78.16.1 to 101.78.31.254101.78.31.2554,094
99101.78.32.0/20101.78.32.1 to 101.78.47.254101.78.47.2554,094
100101.78.48.0/20101.78.48.1 to 101.78.63.254101.78.63.2554,094
101101.78.64.0/20101.78.64.1 to 101.78.79.254101.78.79.2554,094
102101.78.80.0/20101.78.80.1 to 101.78.95.254101.78.95.2554,094
103101.78.96.0/20101.78.96.1 to 101.78.111.254101.78.111.2554,094
104101.78.112.0/20101.78.112.1 to 101.78.127.254101.78.127.2554,094
105101.78.128.0/20101.78.128.1 to 101.78.143.254101.78.143.2554,094
106101.78.144.0/20101.78.144.1 to 101.78.159.254101.78.159.2554,094
107101.78.160.0/20101.78.160.1 to 101.78.175.254101.78.175.2554,094
108101.78.176.0/20101.78.176.1 to 101.78.191.254101.78.191.2554,094
109101.78.192.0/20101.78.192.1 to 101.78.207.254101.78.207.2554,094
110101.78.208.0/20101.78.208.1 to 101.78.223.254101.78.223.2554,094
111101.78.224.0/20101.78.224.1 to 101.78.239.254101.78.239.2554,094
112101.78.240.0/20101.78.240.1 to 101.78.255.254101.78.255.2554,094
113101.79.0.0/20101.79.0.1 to 101.79.15.254101.79.15.2554,094
114101.79.16.0/20101.79.16.1 to 101.79.31.254101.79.31.2554,094
115101.79.32.0/20101.79.32.1 to 101.79.47.254101.79.47.2554,094
116101.79.48.0/20101.79.48.1 to 101.79.63.254101.79.63.2554,094
117101.79.64.0/20101.79.64.1 to 101.79.79.254101.79.79.2554,094
118101.79.80.0/20101.79.80.1 to 101.79.95.254101.79.95.2554,094
119101.79.96.0/20101.79.96.1 to 101.79.111.254101.79.111.2554,094
120101.79.112.0/20101.79.112.1 to 101.79.127.254101.79.127.2554,094
121101.79.128.0/20101.79.128.1 to 101.79.143.254101.79.143.2554,094
122101.79.144.0/20101.79.144.1 to 101.79.159.254101.79.159.2554,094
123101.79.160.0/20101.79.160.1 to 101.79.175.254101.79.175.2554,094
124101.79.176.0/20101.79.176.1 to 101.79.191.254101.79.191.2554,094
125101.79.192.0/20101.79.192.1 to 101.79.207.254101.79.207.2554,094
126101.79.208.0/20101.79.208.1 to 101.79.223.254101.79.223.2554,094
127101.79.224.0/20101.79.224.1 to 101.79.239.254101.79.239.2554,094
128101.79.240.0/20101.79.240.1 to 101.79.255.254101.79.255.2554,094

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.