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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.

Network128.66.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
128.66.0.0
Broadcast address
128.67.255.255
First usable
128.66.0.1
Last usable
128.67.255.254
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 80420000 · Integer 2151809024 to 2151940095
Reverse DNS zones
66.128.in-addr.arpa
67.128.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
Address10000000.01000010.00000000.00000000128.66.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network10000000.01000010.00000000.00000000128.66.0.0
Broadcast10000000.01000011.11111111.11111111128.67.255.255
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)

128.66.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1128.66.0.0/22128.66.0.1 to 128.66.3.254128.66.3.2551,022
2128.66.4.0/22128.66.4.1 to 128.66.7.254128.66.7.2551,022
3128.66.8.0/22128.66.8.1 to 128.66.11.254128.66.11.2551,022
4128.66.12.0/22128.66.12.1 to 128.66.15.254128.66.15.2551,022
5128.66.16.0/22128.66.16.1 to 128.66.19.254128.66.19.2551,022
6128.66.20.0/22128.66.20.1 to 128.66.23.254128.66.23.2551,022
7128.66.24.0/22128.66.24.1 to 128.66.27.254128.66.27.2551,022
8128.66.28.0/22128.66.28.1 to 128.66.31.254128.66.31.2551,022
9128.66.32.0/22128.66.32.1 to 128.66.35.254128.66.35.2551,022
10128.66.36.0/22128.66.36.1 to 128.66.39.254128.66.39.2551,022
11128.66.40.0/22128.66.40.1 to 128.66.43.254128.66.43.2551,022
12128.66.44.0/22128.66.44.1 to 128.66.47.254128.66.47.2551,022
13128.66.48.0/22128.66.48.1 to 128.66.51.254128.66.51.2551,022
14128.66.52.0/22128.66.52.1 to 128.66.55.254128.66.55.2551,022
15128.66.56.0/22128.66.56.1 to 128.66.59.254128.66.59.2551,022
16128.66.60.0/22128.66.60.1 to 128.66.63.254128.66.63.2551,022
17128.66.64.0/22128.66.64.1 to 128.66.67.254128.66.67.2551,022
18128.66.68.0/22128.66.68.1 to 128.66.71.254128.66.71.2551,022
19128.66.72.0/22128.66.72.1 to 128.66.75.254128.66.75.2551,022
20128.66.76.0/22128.66.76.1 to 128.66.79.254128.66.79.2551,022
21128.66.80.0/22128.66.80.1 to 128.66.83.254128.66.83.2551,022
22128.66.84.0/22128.66.84.1 to 128.66.87.254128.66.87.2551,022
23128.66.88.0/22128.66.88.1 to 128.66.91.254128.66.91.2551,022
24128.66.92.0/22128.66.92.1 to 128.66.95.254128.66.95.2551,022
25128.66.96.0/22128.66.96.1 to 128.66.99.254128.66.99.2551,022
26128.66.100.0/22128.66.100.1 to 128.66.103.254128.66.103.2551,022
27128.66.104.0/22128.66.104.1 to 128.66.107.254128.66.107.2551,022
28128.66.108.0/22128.66.108.1 to 128.66.111.254128.66.111.2551,022
29128.66.112.0/22128.66.112.1 to 128.66.115.254128.66.115.2551,022
30128.66.116.0/22128.66.116.1 to 128.66.119.254128.66.119.2551,022
31128.66.120.0/22128.66.120.1 to 128.66.123.254128.66.123.2551,022
32128.66.124.0/22128.66.124.1 to 128.66.127.254128.66.127.2551,022
33128.66.128.0/22128.66.128.1 to 128.66.131.254128.66.131.2551,022
34128.66.132.0/22128.66.132.1 to 128.66.135.254128.66.135.2551,022
35128.66.136.0/22128.66.136.1 to 128.66.139.254128.66.139.2551,022
36128.66.140.0/22128.66.140.1 to 128.66.143.254128.66.143.2551,022
37128.66.144.0/22128.66.144.1 to 128.66.147.254128.66.147.2551,022
38128.66.148.0/22128.66.148.1 to 128.66.151.254128.66.151.2551,022
39128.66.152.0/22128.66.152.1 to 128.66.155.254128.66.155.2551,022
40128.66.156.0/22128.66.156.1 to 128.66.159.254128.66.159.2551,022
41128.66.160.0/22128.66.160.1 to 128.66.163.254128.66.163.2551,022
42128.66.164.0/22128.66.164.1 to 128.66.167.254128.66.167.2551,022
43128.66.168.0/22128.66.168.1 to 128.66.171.254128.66.171.2551,022
44128.66.172.0/22128.66.172.1 to 128.66.175.254128.66.175.2551,022
45128.66.176.0/22128.66.176.1 to 128.66.179.254128.66.179.2551,022
46128.66.180.0/22128.66.180.1 to 128.66.183.254128.66.183.2551,022
47128.66.184.0/22128.66.184.1 to 128.66.187.254128.66.187.2551,022
48128.66.188.0/22128.66.188.1 to 128.66.191.254128.66.191.2551,022
49128.66.192.0/22128.66.192.1 to 128.66.195.254128.66.195.2551,022
50128.66.196.0/22128.66.196.1 to 128.66.199.254128.66.199.2551,022
51128.66.200.0/22128.66.200.1 to 128.66.203.254128.66.203.2551,022
52128.66.204.0/22128.66.204.1 to 128.66.207.254128.66.207.2551,022
53128.66.208.0/22128.66.208.1 to 128.66.211.254128.66.211.2551,022
54128.66.212.0/22128.66.212.1 to 128.66.215.254128.66.215.2551,022
55128.66.216.0/22128.66.216.1 to 128.66.219.254128.66.219.2551,022
56128.66.220.0/22128.66.220.1 to 128.66.223.254128.66.223.2551,022
57128.66.224.0/22128.66.224.1 to 128.66.227.254128.66.227.2551,022
58128.66.228.0/22128.66.228.1 to 128.66.231.254128.66.231.2551,022
59128.66.232.0/22128.66.232.1 to 128.66.235.254128.66.235.2551,022
60128.66.236.0/22128.66.236.1 to 128.66.239.254128.66.239.2551,022
61128.66.240.0/22128.66.240.1 to 128.66.243.254128.66.243.2551,022
62128.66.244.0/22128.66.244.1 to 128.66.247.254128.66.247.2551,022
63128.66.248.0/22128.66.248.1 to 128.66.251.254128.66.251.2551,022
64128.66.252.0/22128.66.252.1 to 128.66.255.254128.66.255.2551,022
65128.67.0.0/22128.67.0.1 to 128.67.3.254128.67.3.2551,022
66128.67.4.0/22128.67.4.1 to 128.67.7.254128.67.7.2551,022
67128.67.8.0/22128.67.8.1 to 128.67.11.254128.67.11.2551,022
68128.67.12.0/22128.67.12.1 to 128.67.15.254128.67.15.2551,022
69128.67.16.0/22128.67.16.1 to 128.67.19.254128.67.19.2551,022
70128.67.20.0/22128.67.20.1 to 128.67.23.254128.67.23.2551,022
71128.67.24.0/22128.67.24.1 to 128.67.27.254128.67.27.2551,022
72128.67.28.0/22128.67.28.1 to 128.67.31.254128.67.31.2551,022
73128.67.32.0/22128.67.32.1 to 128.67.35.254128.67.35.2551,022
74128.67.36.0/22128.67.36.1 to 128.67.39.254128.67.39.2551,022
75128.67.40.0/22128.67.40.1 to 128.67.43.254128.67.43.2551,022
76128.67.44.0/22128.67.44.1 to 128.67.47.254128.67.47.2551,022
77128.67.48.0/22128.67.48.1 to 128.67.51.254128.67.51.2551,022
78128.67.52.0/22128.67.52.1 to 128.67.55.254128.67.55.2551,022
79128.67.56.0/22128.67.56.1 to 128.67.59.254128.67.59.2551,022
80128.67.60.0/22128.67.60.1 to 128.67.63.254128.67.63.2551,022
81128.67.64.0/22128.67.64.1 to 128.67.67.254128.67.67.2551,022
82128.67.68.0/22128.67.68.1 to 128.67.71.254128.67.71.2551,022
83128.67.72.0/22128.67.72.1 to 128.67.75.254128.67.75.2551,022
84128.67.76.0/22128.67.76.1 to 128.67.79.254128.67.79.2551,022
85128.67.80.0/22128.67.80.1 to 128.67.83.254128.67.83.2551,022
86128.67.84.0/22128.67.84.1 to 128.67.87.254128.67.87.2551,022
87128.67.88.0/22128.67.88.1 to 128.67.91.254128.67.91.2551,022
88128.67.92.0/22128.67.92.1 to 128.67.95.254128.67.95.2551,022
89128.67.96.0/22128.67.96.1 to 128.67.99.254128.67.99.2551,022
90128.67.100.0/22128.67.100.1 to 128.67.103.254128.67.103.2551,022
91128.67.104.0/22128.67.104.1 to 128.67.107.254128.67.107.2551,022
92128.67.108.0/22128.67.108.1 to 128.67.111.254128.67.111.2551,022
93128.67.112.0/22128.67.112.1 to 128.67.115.254128.67.115.2551,022
94128.67.116.0/22128.67.116.1 to 128.67.119.254128.67.119.2551,022
95128.67.120.0/22128.67.120.1 to 128.67.123.254128.67.123.2551,022
96128.67.124.0/22128.67.124.1 to 128.67.127.254128.67.127.2551,022
97128.67.128.0/22128.67.128.1 to 128.67.131.254128.67.131.2551,022
98128.67.132.0/22128.67.132.1 to 128.67.135.254128.67.135.2551,022
99128.67.136.0/22128.67.136.1 to 128.67.139.254128.67.139.2551,022
100128.67.140.0/22128.67.140.1 to 128.67.143.254128.67.143.2551,022
101128.67.144.0/22128.67.144.1 to 128.67.147.254128.67.147.2551,022
102128.67.148.0/22128.67.148.1 to 128.67.151.254128.67.151.2551,022
103128.67.152.0/22128.67.152.1 to 128.67.155.254128.67.155.2551,022
104128.67.156.0/22128.67.156.1 to 128.67.159.254128.67.159.2551,022
105128.67.160.0/22128.67.160.1 to 128.67.163.254128.67.163.2551,022
106128.67.164.0/22128.67.164.1 to 128.67.167.254128.67.167.2551,022
107128.67.168.0/22128.67.168.1 to 128.67.171.254128.67.171.2551,022
108128.67.172.0/22128.67.172.1 to 128.67.175.254128.67.175.2551,022
109128.67.176.0/22128.67.176.1 to 128.67.179.254128.67.179.2551,022
110128.67.180.0/22128.67.180.1 to 128.67.183.254128.67.183.2551,022
111128.67.184.0/22128.67.184.1 to 128.67.187.254128.67.187.2551,022
112128.67.188.0/22128.67.188.1 to 128.67.191.254128.67.191.2551,022
113128.67.192.0/22128.67.192.1 to 128.67.195.254128.67.195.2551,022
114128.67.196.0/22128.67.196.1 to 128.67.199.254128.67.199.2551,022
115128.67.200.0/22128.67.200.1 to 128.67.203.254128.67.203.2551,022
116128.67.204.0/22128.67.204.1 to 128.67.207.254128.67.207.2551,022
117128.67.208.0/22128.67.208.1 to 128.67.211.254128.67.211.2551,022
118128.67.212.0/22128.67.212.1 to 128.67.215.254128.67.215.2551,022
119128.67.216.0/22128.67.216.1 to 128.67.219.254128.67.219.2551,022
120128.67.220.0/22128.67.220.1 to 128.67.223.254128.67.223.2551,022
121128.67.224.0/22128.67.224.1 to 128.67.227.254128.67.227.2551,022
122128.67.228.0/22128.67.228.1 to 128.67.231.254128.67.231.2551,022
123128.67.232.0/22128.67.232.1 to 128.67.235.254128.67.235.2551,022
124128.67.236.0/22128.67.236.1 to 128.67.239.254128.67.239.2551,022
125128.67.240.0/22128.67.240.1 to 128.67.243.254128.67.243.2551,022
126128.67.244.0/22128.67.244.1 to 128.67.247.254128.67.247.2551,022
127128.67.248.0/22128.67.248.1 to 128.67.251.254128.67.251.2551,022
128128.67.252.0/22128.67.252.1 to 128.67.255.254128.67.255.2551,022

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.