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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.

Network129.76.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
129.76.0.0
Broadcast address
129.77.255.255
First usable
129.76.0.1
Last usable
129.77.255.254
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 814C0000 · Integer 2169241600 to 2169372671
Reverse DNS zones
76.129.in-addr.arpa
77.129.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
Address10000001.01001100.00000000.00000000129.76.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network10000001.01001100.00000000.00000000129.76.0.0
Broadcast10000001.01001101.11111111.11111111129.77.255.255
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)

129.76.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1129.76.0.0/22129.76.0.1 to 129.76.3.254129.76.3.2551,022
2129.76.4.0/22129.76.4.1 to 129.76.7.254129.76.7.2551,022
3129.76.8.0/22129.76.8.1 to 129.76.11.254129.76.11.2551,022
4129.76.12.0/22129.76.12.1 to 129.76.15.254129.76.15.2551,022
5129.76.16.0/22129.76.16.1 to 129.76.19.254129.76.19.2551,022
6129.76.20.0/22129.76.20.1 to 129.76.23.254129.76.23.2551,022
7129.76.24.0/22129.76.24.1 to 129.76.27.254129.76.27.2551,022
8129.76.28.0/22129.76.28.1 to 129.76.31.254129.76.31.2551,022
9129.76.32.0/22129.76.32.1 to 129.76.35.254129.76.35.2551,022
10129.76.36.0/22129.76.36.1 to 129.76.39.254129.76.39.2551,022
11129.76.40.0/22129.76.40.1 to 129.76.43.254129.76.43.2551,022
12129.76.44.0/22129.76.44.1 to 129.76.47.254129.76.47.2551,022
13129.76.48.0/22129.76.48.1 to 129.76.51.254129.76.51.2551,022
14129.76.52.0/22129.76.52.1 to 129.76.55.254129.76.55.2551,022
15129.76.56.0/22129.76.56.1 to 129.76.59.254129.76.59.2551,022
16129.76.60.0/22129.76.60.1 to 129.76.63.254129.76.63.2551,022
17129.76.64.0/22129.76.64.1 to 129.76.67.254129.76.67.2551,022
18129.76.68.0/22129.76.68.1 to 129.76.71.254129.76.71.2551,022
19129.76.72.0/22129.76.72.1 to 129.76.75.254129.76.75.2551,022
20129.76.76.0/22129.76.76.1 to 129.76.79.254129.76.79.2551,022
21129.76.80.0/22129.76.80.1 to 129.76.83.254129.76.83.2551,022
22129.76.84.0/22129.76.84.1 to 129.76.87.254129.76.87.2551,022
23129.76.88.0/22129.76.88.1 to 129.76.91.254129.76.91.2551,022
24129.76.92.0/22129.76.92.1 to 129.76.95.254129.76.95.2551,022
25129.76.96.0/22129.76.96.1 to 129.76.99.254129.76.99.2551,022
26129.76.100.0/22129.76.100.1 to 129.76.103.254129.76.103.2551,022
27129.76.104.0/22129.76.104.1 to 129.76.107.254129.76.107.2551,022
28129.76.108.0/22129.76.108.1 to 129.76.111.254129.76.111.2551,022
29129.76.112.0/22129.76.112.1 to 129.76.115.254129.76.115.2551,022
30129.76.116.0/22129.76.116.1 to 129.76.119.254129.76.119.2551,022
31129.76.120.0/22129.76.120.1 to 129.76.123.254129.76.123.2551,022
32129.76.124.0/22129.76.124.1 to 129.76.127.254129.76.127.2551,022
33129.76.128.0/22129.76.128.1 to 129.76.131.254129.76.131.2551,022
34129.76.132.0/22129.76.132.1 to 129.76.135.254129.76.135.2551,022
35129.76.136.0/22129.76.136.1 to 129.76.139.254129.76.139.2551,022
36129.76.140.0/22129.76.140.1 to 129.76.143.254129.76.143.2551,022
37129.76.144.0/22129.76.144.1 to 129.76.147.254129.76.147.2551,022
38129.76.148.0/22129.76.148.1 to 129.76.151.254129.76.151.2551,022
39129.76.152.0/22129.76.152.1 to 129.76.155.254129.76.155.2551,022
40129.76.156.0/22129.76.156.1 to 129.76.159.254129.76.159.2551,022
41129.76.160.0/22129.76.160.1 to 129.76.163.254129.76.163.2551,022
42129.76.164.0/22129.76.164.1 to 129.76.167.254129.76.167.2551,022
43129.76.168.0/22129.76.168.1 to 129.76.171.254129.76.171.2551,022
44129.76.172.0/22129.76.172.1 to 129.76.175.254129.76.175.2551,022
45129.76.176.0/22129.76.176.1 to 129.76.179.254129.76.179.2551,022
46129.76.180.0/22129.76.180.1 to 129.76.183.254129.76.183.2551,022
47129.76.184.0/22129.76.184.1 to 129.76.187.254129.76.187.2551,022
48129.76.188.0/22129.76.188.1 to 129.76.191.254129.76.191.2551,022
49129.76.192.0/22129.76.192.1 to 129.76.195.254129.76.195.2551,022
50129.76.196.0/22129.76.196.1 to 129.76.199.254129.76.199.2551,022
51129.76.200.0/22129.76.200.1 to 129.76.203.254129.76.203.2551,022
52129.76.204.0/22129.76.204.1 to 129.76.207.254129.76.207.2551,022
53129.76.208.0/22129.76.208.1 to 129.76.211.254129.76.211.2551,022
54129.76.212.0/22129.76.212.1 to 129.76.215.254129.76.215.2551,022
55129.76.216.0/22129.76.216.1 to 129.76.219.254129.76.219.2551,022
56129.76.220.0/22129.76.220.1 to 129.76.223.254129.76.223.2551,022
57129.76.224.0/22129.76.224.1 to 129.76.227.254129.76.227.2551,022
58129.76.228.0/22129.76.228.1 to 129.76.231.254129.76.231.2551,022
59129.76.232.0/22129.76.232.1 to 129.76.235.254129.76.235.2551,022
60129.76.236.0/22129.76.236.1 to 129.76.239.254129.76.239.2551,022
61129.76.240.0/22129.76.240.1 to 129.76.243.254129.76.243.2551,022
62129.76.244.0/22129.76.244.1 to 129.76.247.254129.76.247.2551,022
63129.76.248.0/22129.76.248.1 to 129.76.251.254129.76.251.2551,022
64129.76.252.0/22129.76.252.1 to 129.76.255.254129.76.255.2551,022
65129.77.0.0/22129.77.0.1 to 129.77.3.254129.77.3.2551,022
66129.77.4.0/22129.77.4.1 to 129.77.7.254129.77.7.2551,022
67129.77.8.0/22129.77.8.1 to 129.77.11.254129.77.11.2551,022
68129.77.12.0/22129.77.12.1 to 129.77.15.254129.77.15.2551,022
69129.77.16.0/22129.77.16.1 to 129.77.19.254129.77.19.2551,022
70129.77.20.0/22129.77.20.1 to 129.77.23.254129.77.23.2551,022
71129.77.24.0/22129.77.24.1 to 129.77.27.254129.77.27.2551,022
72129.77.28.0/22129.77.28.1 to 129.77.31.254129.77.31.2551,022
73129.77.32.0/22129.77.32.1 to 129.77.35.254129.77.35.2551,022
74129.77.36.0/22129.77.36.1 to 129.77.39.254129.77.39.2551,022
75129.77.40.0/22129.77.40.1 to 129.77.43.254129.77.43.2551,022
76129.77.44.0/22129.77.44.1 to 129.77.47.254129.77.47.2551,022
77129.77.48.0/22129.77.48.1 to 129.77.51.254129.77.51.2551,022
78129.77.52.0/22129.77.52.1 to 129.77.55.254129.77.55.2551,022
79129.77.56.0/22129.77.56.1 to 129.77.59.254129.77.59.2551,022
80129.77.60.0/22129.77.60.1 to 129.77.63.254129.77.63.2551,022
81129.77.64.0/22129.77.64.1 to 129.77.67.254129.77.67.2551,022
82129.77.68.0/22129.77.68.1 to 129.77.71.254129.77.71.2551,022
83129.77.72.0/22129.77.72.1 to 129.77.75.254129.77.75.2551,022
84129.77.76.0/22129.77.76.1 to 129.77.79.254129.77.79.2551,022
85129.77.80.0/22129.77.80.1 to 129.77.83.254129.77.83.2551,022
86129.77.84.0/22129.77.84.1 to 129.77.87.254129.77.87.2551,022
87129.77.88.0/22129.77.88.1 to 129.77.91.254129.77.91.2551,022
88129.77.92.0/22129.77.92.1 to 129.77.95.254129.77.95.2551,022
89129.77.96.0/22129.77.96.1 to 129.77.99.254129.77.99.2551,022
90129.77.100.0/22129.77.100.1 to 129.77.103.254129.77.103.2551,022
91129.77.104.0/22129.77.104.1 to 129.77.107.254129.77.107.2551,022
92129.77.108.0/22129.77.108.1 to 129.77.111.254129.77.111.2551,022
93129.77.112.0/22129.77.112.1 to 129.77.115.254129.77.115.2551,022
94129.77.116.0/22129.77.116.1 to 129.77.119.254129.77.119.2551,022
95129.77.120.0/22129.77.120.1 to 129.77.123.254129.77.123.2551,022
96129.77.124.0/22129.77.124.1 to 129.77.127.254129.77.127.2551,022
97129.77.128.0/22129.77.128.1 to 129.77.131.254129.77.131.2551,022
98129.77.132.0/22129.77.132.1 to 129.77.135.254129.77.135.2551,022
99129.77.136.0/22129.77.136.1 to 129.77.139.254129.77.139.2551,022
100129.77.140.0/22129.77.140.1 to 129.77.143.254129.77.143.2551,022
101129.77.144.0/22129.77.144.1 to 129.77.147.254129.77.147.2551,022
102129.77.148.0/22129.77.148.1 to 129.77.151.254129.77.151.2551,022
103129.77.152.0/22129.77.152.1 to 129.77.155.254129.77.155.2551,022
104129.77.156.0/22129.77.156.1 to 129.77.159.254129.77.159.2551,022
105129.77.160.0/22129.77.160.1 to 129.77.163.254129.77.163.2551,022
106129.77.164.0/22129.77.164.1 to 129.77.167.254129.77.167.2551,022
107129.77.168.0/22129.77.168.1 to 129.77.171.254129.77.171.2551,022
108129.77.172.0/22129.77.172.1 to 129.77.175.254129.77.175.2551,022
109129.77.176.0/22129.77.176.1 to 129.77.179.254129.77.179.2551,022
110129.77.180.0/22129.77.180.1 to 129.77.183.254129.77.183.2551,022
111129.77.184.0/22129.77.184.1 to 129.77.187.254129.77.187.2551,022
112129.77.188.0/22129.77.188.1 to 129.77.191.254129.77.191.2551,022
113129.77.192.0/22129.77.192.1 to 129.77.195.254129.77.195.2551,022
114129.77.196.0/22129.77.196.1 to 129.77.199.254129.77.199.2551,022
115129.77.200.0/22129.77.200.1 to 129.77.203.254129.77.203.2551,022
116129.77.204.0/22129.77.204.1 to 129.77.207.254129.77.207.2551,022
117129.77.208.0/22129.77.208.1 to 129.77.211.254129.77.211.2551,022
118129.77.212.0/22129.77.212.1 to 129.77.215.254129.77.215.2551,022
119129.77.216.0/22129.77.216.1 to 129.77.219.254129.77.219.2551,022
120129.77.220.0/22129.77.220.1 to 129.77.223.254129.77.223.2551,022
121129.77.224.0/22129.77.224.1 to 129.77.227.254129.77.227.2551,022
122129.77.228.0/22129.77.228.1 to 129.77.231.254129.77.231.2551,022
123129.77.232.0/22129.77.232.1 to 129.77.235.254129.77.235.2551,022
124129.77.236.0/22129.77.236.1 to 129.77.239.254129.77.239.2551,022
125129.77.240.0/22129.77.240.1 to 129.77.243.254129.77.243.2551,022
126129.77.244.0/22129.77.244.1 to 129.77.247.254129.77.247.2551,022
127129.77.248.0/22129.77.248.1 to 129.77.251.254129.77.251.2551,022
128129.77.252.0/22129.77.252.1 to 129.77.255.254129.77.255.2551,022

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.