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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.

Network145.72.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
145.72.0.0
Broadcast address
145.73.255.255
First usable
145.72.0.1
Last usable
145.73.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
B (default /16)
As numbers
Hex 91480000 · Integer 2437414912 to 2437545983
Reverse DNS zones
72.145.in-addr.arpa
73.145.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10010001.01001000.00000000.00000000145.72.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network10010001.01001000.00000000.00000000145.72.0.0
Broadcast10010001.01001001.11111111.11111111145.73.255.255
Split into smaller subnets/22
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

145.72.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1145.72.0.0/22145.72.0.1 to 145.72.3.254145.72.3.2551,022
2145.72.4.0/22145.72.4.1 to 145.72.7.254145.72.7.2551,022
3145.72.8.0/22145.72.8.1 to 145.72.11.254145.72.11.2551,022
4145.72.12.0/22145.72.12.1 to 145.72.15.254145.72.15.2551,022
5145.72.16.0/22145.72.16.1 to 145.72.19.254145.72.19.2551,022
6145.72.20.0/22145.72.20.1 to 145.72.23.254145.72.23.2551,022
7145.72.24.0/22145.72.24.1 to 145.72.27.254145.72.27.2551,022
8145.72.28.0/22145.72.28.1 to 145.72.31.254145.72.31.2551,022
9145.72.32.0/22145.72.32.1 to 145.72.35.254145.72.35.2551,022
10145.72.36.0/22145.72.36.1 to 145.72.39.254145.72.39.2551,022
11145.72.40.0/22145.72.40.1 to 145.72.43.254145.72.43.2551,022
12145.72.44.0/22145.72.44.1 to 145.72.47.254145.72.47.2551,022
13145.72.48.0/22145.72.48.1 to 145.72.51.254145.72.51.2551,022
14145.72.52.0/22145.72.52.1 to 145.72.55.254145.72.55.2551,022
15145.72.56.0/22145.72.56.1 to 145.72.59.254145.72.59.2551,022
16145.72.60.0/22145.72.60.1 to 145.72.63.254145.72.63.2551,022
17145.72.64.0/22145.72.64.1 to 145.72.67.254145.72.67.2551,022
18145.72.68.0/22145.72.68.1 to 145.72.71.254145.72.71.2551,022
19145.72.72.0/22145.72.72.1 to 145.72.75.254145.72.75.2551,022
20145.72.76.0/22145.72.76.1 to 145.72.79.254145.72.79.2551,022
21145.72.80.0/22145.72.80.1 to 145.72.83.254145.72.83.2551,022
22145.72.84.0/22145.72.84.1 to 145.72.87.254145.72.87.2551,022
23145.72.88.0/22145.72.88.1 to 145.72.91.254145.72.91.2551,022
24145.72.92.0/22145.72.92.1 to 145.72.95.254145.72.95.2551,022
25145.72.96.0/22145.72.96.1 to 145.72.99.254145.72.99.2551,022
26145.72.100.0/22145.72.100.1 to 145.72.103.254145.72.103.2551,022
27145.72.104.0/22145.72.104.1 to 145.72.107.254145.72.107.2551,022
28145.72.108.0/22145.72.108.1 to 145.72.111.254145.72.111.2551,022
29145.72.112.0/22145.72.112.1 to 145.72.115.254145.72.115.2551,022
30145.72.116.0/22145.72.116.1 to 145.72.119.254145.72.119.2551,022
31145.72.120.0/22145.72.120.1 to 145.72.123.254145.72.123.2551,022
32145.72.124.0/22145.72.124.1 to 145.72.127.254145.72.127.2551,022
33145.72.128.0/22145.72.128.1 to 145.72.131.254145.72.131.2551,022
34145.72.132.0/22145.72.132.1 to 145.72.135.254145.72.135.2551,022
35145.72.136.0/22145.72.136.1 to 145.72.139.254145.72.139.2551,022
36145.72.140.0/22145.72.140.1 to 145.72.143.254145.72.143.2551,022
37145.72.144.0/22145.72.144.1 to 145.72.147.254145.72.147.2551,022
38145.72.148.0/22145.72.148.1 to 145.72.151.254145.72.151.2551,022
39145.72.152.0/22145.72.152.1 to 145.72.155.254145.72.155.2551,022
40145.72.156.0/22145.72.156.1 to 145.72.159.254145.72.159.2551,022
41145.72.160.0/22145.72.160.1 to 145.72.163.254145.72.163.2551,022
42145.72.164.0/22145.72.164.1 to 145.72.167.254145.72.167.2551,022
43145.72.168.0/22145.72.168.1 to 145.72.171.254145.72.171.2551,022
44145.72.172.0/22145.72.172.1 to 145.72.175.254145.72.175.2551,022
45145.72.176.0/22145.72.176.1 to 145.72.179.254145.72.179.2551,022
46145.72.180.0/22145.72.180.1 to 145.72.183.254145.72.183.2551,022
47145.72.184.0/22145.72.184.1 to 145.72.187.254145.72.187.2551,022
48145.72.188.0/22145.72.188.1 to 145.72.191.254145.72.191.2551,022
49145.72.192.0/22145.72.192.1 to 145.72.195.254145.72.195.2551,022
50145.72.196.0/22145.72.196.1 to 145.72.199.254145.72.199.2551,022
51145.72.200.0/22145.72.200.1 to 145.72.203.254145.72.203.2551,022
52145.72.204.0/22145.72.204.1 to 145.72.207.254145.72.207.2551,022
53145.72.208.0/22145.72.208.1 to 145.72.211.254145.72.211.2551,022
54145.72.212.0/22145.72.212.1 to 145.72.215.254145.72.215.2551,022
55145.72.216.0/22145.72.216.1 to 145.72.219.254145.72.219.2551,022
56145.72.220.0/22145.72.220.1 to 145.72.223.254145.72.223.2551,022
57145.72.224.0/22145.72.224.1 to 145.72.227.254145.72.227.2551,022
58145.72.228.0/22145.72.228.1 to 145.72.231.254145.72.231.2551,022
59145.72.232.0/22145.72.232.1 to 145.72.235.254145.72.235.2551,022
60145.72.236.0/22145.72.236.1 to 145.72.239.254145.72.239.2551,022
61145.72.240.0/22145.72.240.1 to 145.72.243.254145.72.243.2551,022
62145.72.244.0/22145.72.244.1 to 145.72.247.254145.72.247.2551,022
63145.72.248.0/22145.72.248.1 to 145.72.251.254145.72.251.2551,022
64145.72.252.0/22145.72.252.1 to 145.72.255.254145.72.255.2551,022
65145.73.0.0/22145.73.0.1 to 145.73.3.254145.73.3.2551,022
66145.73.4.0/22145.73.4.1 to 145.73.7.254145.73.7.2551,022
67145.73.8.0/22145.73.8.1 to 145.73.11.254145.73.11.2551,022
68145.73.12.0/22145.73.12.1 to 145.73.15.254145.73.15.2551,022
69145.73.16.0/22145.73.16.1 to 145.73.19.254145.73.19.2551,022
70145.73.20.0/22145.73.20.1 to 145.73.23.254145.73.23.2551,022
71145.73.24.0/22145.73.24.1 to 145.73.27.254145.73.27.2551,022
72145.73.28.0/22145.73.28.1 to 145.73.31.254145.73.31.2551,022
73145.73.32.0/22145.73.32.1 to 145.73.35.254145.73.35.2551,022
74145.73.36.0/22145.73.36.1 to 145.73.39.254145.73.39.2551,022
75145.73.40.0/22145.73.40.1 to 145.73.43.254145.73.43.2551,022
76145.73.44.0/22145.73.44.1 to 145.73.47.254145.73.47.2551,022
77145.73.48.0/22145.73.48.1 to 145.73.51.254145.73.51.2551,022
78145.73.52.0/22145.73.52.1 to 145.73.55.254145.73.55.2551,022
79145.73.56.0/22145.73.56.1 to 145.73.59.254145.73.59.2551,022
80145.73.60.0/22145.73.60.1 to 145.73.63.254145.73.63.2551,022
81145.73.64.0/22145.73.64.1 to 145.73.67.254145.73.67.2551,022
82145.73.68.0/22145.73.68.1 to 145.73.71.254145.73.71.2551,022
83145.73.72.0/22145.73.72.1 to 145.73.75.254145.73.75.2551,022
84145.73.76.0/22145.73.76.1 to 145.73.79.254145.73.79.2551,022
85145.73.80.0/22145.73.80.1 to 145.73.83.254145.73.83.2551,022
86145.73.84.0/22145.73.84.1 to 145.73.87.254145.73.87.2551,022
87145.73.88.0/22145.73.88.1 to 145.73.91.254145.73.91.2551,022
88145.73.92.0/22145.73.92.1 to 145.73.95.254145.73.95.2551,022
89145.73.96.0/22145.73.96.1 to 145.73.99.254145.73.99.2551,022
90145.73.100.0/22145.73.100.1 to 145.73.103.254145.73.103.2551,022
91145.73.104.0/22145.73.104.1 to 145.73.107.254145.73.107.2551,022
92145.73.108.0/22145.73.108.1 to 145.73.111.254145.73.111.2551,022
93145.73.112.0/22145.73.112.1 to 145.73.115.254145.73.115.2551,022
94145.73.116.0/22145.73.116.1 to 145.73.119.254145.73.119.2551,022
95145.73.120.0/22145.73.120.1 to 145.73.123.254145.73.123.2551,022
96145.73.124.0/22145.73.124.1 to 145.73.127.254145.73.127.2551,022
97145.73.128.0/22145.73.128.1 to 145.73.131.254145.73.131.2551,022
98145.73.132.0/22145.73.132.1 to 145.73.135.254145.73.135.2551,022
99145.73.136.0/22145.73.136.1 to 145.73.139.254145.73.139.2551,022
100145.73.140.0/22145.73.140.1 to 145.73.143.254145.73.143.2551,022
101145.73.144.0/22145.73.144.1 to 145.73.147.254145.73.147.2551,022
102145.73.148.0/22145.73.148.1 to 145.73.151.254145.73.151.2551,022
103145.73.152.0/22145.73.152.1 to 145.73.155.254145.73.155.2551,022
104145.73.156.0/22145.73.156.1 to 145.73.159.254145.73.159.2551,022
105145.73.160.0/22145.73.160.1 to 145.73.163.254145.73.163.2551,022
106145.73.164.0/22145.73.164.1 to 145.73.167.254145.73.167.2551,022
107145.73.168.0/22145.73.168.1 to 145.73.171.254145.73.171.2551,022
108145.73.172.0/22145.73.172.1 to 145.73.175.254145.73.175.2551,022
109145.73.176.0/22145.73.176.1 to 145.73.179.254145.73.179.2551,022
110145.73.180.0/22145.73.180.1 to 145.73.183.254145.73.183.2551,022
111145.73.184.0/22145.73.184.1 to 145.73.187.254145.73.187.2551,022
112145.73.188.0/22145.73.188.1 to 145.73.191.254145.73.191.2551,022
113145.73.192.0/22145.73.192.1 to 145.73.195.254145.73.195.2551,022
114145.73.196.0/22145.73.196.1 to 145.73.199.254145.73.199.2551,022
115145.73.200.0/22145.73.200.1 to 145.73.203.254145.73.203.2551,022
116145.73.204.0/22145.73.204.1 to 145.73.207.254145.73.207.2551,022
117145.73.208.0/22145.73.208.1 to 145.73.211.254145.73.211.2551,022
118145.73.212.0/22145.73.212.1 to 145.73.215.254145.73.215.2551,022
119145.73.216.0/22145.73.216.1 to 145.73.219.254145.73.219.2551,022
120145.73.220.0/22145.73.220.1 to 145.73.223.254145.73.223.2551,022
121145.73.224.0/22145.73.224.1 to 145.73.227.254145.73.227.2551,022
122145.73.228.0/22145.73.228.1 to 145.73.231.254145.73.231.2551,022
123145.73.232.0/22145.73.232.1 to 145.73.235.254145.73.235.2551,022
124145.73.236.0/22145.73.236.1 to 145.73.239.254145.73.239.2551,022
125145.73.240.0/22145.73.240.1 to 145.73.243.254145.73.243.2551,022
126145.73.244.0/22145.73.244.1 to 145.73.247.254145.73.247.2551,022
127145.73.248.0/22145.73.248.1 to 145.73.251.254145.73.251.2551,022
128145.73.252.0/22145.73.252.1 to 145.73.255.254145.73.255.2551,022

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.