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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.

Network236.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
236.128.0.0
Broadcast address
236.255.255.255
First usable
236.128.0.1
Last usable
236.255.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex EC800000 · Integer 3967811584 to 3976200191
Reverse DNS zones
128.236.in-addr.arpa
129.236.in-addr.arpa
130.236.in-addr.arpa
131.236.in-addr.arpa
132.236.in-addr.arpa
133.236.in-addr.arpa
134.236.in-addr.arpa
135.236.in-addr.arpa
136.236.in-addr.arpa
137.236.in-addr.arpa
138.236.in-addr.arpa
139.236.in-addr.arpa
140.236.in-addr.arpa
141.236.in-addr.arpa
142.236.in-addr.arpa
143.236.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11101100.10000000.00000000.00000000236.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11101100.10000000.00000000.00000000236.128.0.0
Broadcast11101100.11111111.11111111.11111111236.255.255.255
Split into smaller subnets/16
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

236.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1236.128.0.0/16236.128.0.1 to 236.128.255.254236.128.255.25565,534
2236.129.0.0/16236.129.0.1 to 236.129.255.254236.129.255.25565,534
3236.130.0.0/16236.130.0.1 to 236.130.255.254236.130.255.25565,534
4236.131.0.0/16236.131.0.1 to 236.131.255.254236.131.255.25565,534
5236.132.0.0/16236.132.0.1 to 236.132.255.254236.132.255.25565,534
6236.133.0.0/16236.133.0.1 to 236.133.255.254236.133.255.25565,534
7236.134.0.0/16236.134.0.1 to 236.134.255.254236.134.255.25565,534
8236.135.0.0/16236.135.0.1 to 236.135.255.254236.135.255.25565,534
9236.136.0.0/16236.136.0.1 to 236.136.255.254236.136.255.25565,534
10236.137.0.0/16236.137.0.1 to 236.137.255.254236.137.255.25565,534
11236.138.0.0/16236.138.0.1 to 236.138.255.254236.138.255.25565,534
12236.139.0.0/16236.139.0.1 to 236.139.255.254236.139.255.25565,534
13236.140.0.0/16236.140.0.1 to 236.140.255.254236.140.255.25565,534
14236.141.0.0/16236.141.0.1 to 236.141.255.254236.141.255.25565,534
15236.142.0.0/16236.142.0.1 to 236.142.255.254236.142.255.25565,534
16236.143.0.0/16236.143.0.1 to 236.143.255.254236.143.255.25565,534
17236.144.0.0/16236.144.0.1 to 236.144.255.254236.144.255.25565,534
18236.145.0.0/16236.145.0.1 to 236.145.255.254236.145.255.25565,534
19236.146.0.0/16236.146.0.1 to 236.146.255.254236.146.255.25565,534
20236.147.0.0/16236.147.0.1 to 236.147.255.254236.147.255.25565,534
21236.148.0.0/16236.148.0.1 to 236.148.255.254236.148.255.25565,534
22236.149.0.0/16236.149.0.1 to 236.149.255.254236.149.255.25565,534
23236.150.0.0/16236.150.0.1 to 236.150.255.254236.150.255.25565,534
24236.151.0.0/16236.151.0.1 to 236.151.255.254236.151.255.25565,534
25236.152.0.0/16236.152.0.1 to 236.152.255.254236.152.255.25565,534
26236.153.0.0/16236.153.0.1 to 236.153.255.254236.153.255.25565,534
27236.154.0.0/16236.154.0.1 to 236.154.255.254236.154.255.25565,534
28236.155.0.0/16236.155.0.1 to 236.155.255.254236.155.255.25565,534
29236.156.0.0/16236.156.0.1 to 236.156.255.254236.156.255.25565,534
30236.157.0.0/16236.157.0.1 to 236.157.255.254236.157.255.25565,534
31236.158.0.0/16236.158.0.1 to 236.158.255.254236.158.255.25565,534
32236.159.0.0/16236.159.0.1 to 236.159.255.254236.159.255.25565,534
33236.160.0.0/16236.160.0.1 to 236.160.255.254236.160.255.25565,534
34236.161.0.0/16236.161.0.1 to 236.161.255.254236.161.255.25565,534
35236.162.0.0/16236.162.0.1 to 236.162.255.254236.162.255.25565,534
36236.163.0.0/16236.163.0.1 to 236.163.255.254236.163.255.25565,534
37236.164.0.0/16236.164.0.1 to 236.164.255.254236.164.255.25565,534
38236.165.0.0/16236.165.0.1 to 236.165.255.254236.165.255.25565,534
39236.166.0.0/16236.166.0.1 to 236.166.255.254236.166.255.25565,534
40236.167.0.0/16236.167.0.1 to 236.167.255.254236.167.255.25565,534
41236.168.0.0/16236.168.0.1 to 236.168.255.254236.168.255.25565,534
42236.169.0.0/16236.169.0.1 to 236.169.255.254236.169.255.25565,534
43236.170.0.0/16236.170.0.1 to 236.170.255.254236.170.255.25565,534
44236.171.0.0/16236.171.0.1 to 236.171.255.254236.171.255.25565,534
45236.172.0.0/16236.172.0.1 to 236.172.255.254236.172.255.25565,534
46236.173.0.0/16236.173.0.1 to 236.173.255.254236.173.255.25565,534
47236.174.0.0/16236.174.0.1 to 236.174.255.254236.174.255.25565,534
48236.175.0.0/16236.175.0.1 to 236.175.255.254236.175.255.25565,534
49236.176.0.0/16236.176.0.1 to 236.176.255.254236.176.255.25565,534
50236.177.0.0/16236.177.0.1 to 236.177.255.254236.177.255.25565,534
51236.178.0.0/16236.178.0.1 to 236.178.255.254236.178.255.25565,534
52236.179.0.0/16236.179.0.1 to 236.179.255.254236.179.255.25565,534
53236.180.0.0/16236.180.0.1 to 236.180.255.254236.180.255.25565,534
54236.181.0.0/16236.181.0.1 to 236.181.255.254236.181.255.25565,534
55236.182.0.0/16236.182.0.1 to 236.182.255.254236.182.255.25565,534
56236.183.0.0/16236.183.0.1 to 236.183.255.254236.183.255.25565,534
57236.184.0.0/16236.184.0.1 to 236.184.255.254236.184.255.25565,534
58236.185.0.0/16236.185.0.1 to 236.185.255.254236.185.255.25565,534
59236.186.0.0/16236.186.0.1 to 236.186.255.254236.186.255.25565,534
60236.187.0.0/16236.187.0.1 to 236.187.255.254236.187.255.25565,534
61236.188.0.0/16236.188.0.1 to 236.188.255.254236.188.255.25565,534
62236.189.0.0/16236.189.0.1 to 236.189.255.254236.189.255.25565,534
63236.190.0.0/16236.190.0.1 to 236.190.255.254236.190.255.25565,534
64236.191.0.0/16236.191.0.1 to 236.191.255.254236.191.255.25565,534
65236.192.0.0/16236.192.0.1 to 236.192.255.254236.192.255.25565,534
66236.193.0.0/16236.193.0.1 to 236.193.255.254236.193.255.25565,534
67236.194.0.0/16236.194.0.1 to 236.194.255.254236.194.255.25565,534
68236.195.0.0/16236.195.0.1 to 236.195.255.254236.195.255.25565,534
69236.196.0.0/16236.196.0.1 to 236.196.255.254236.196.255.25565,534
70236.197.0.0/16236.197.0.1 to 236.197.255.254236.197.255.25565,534
71236.198.0.0/16236.198.0.1 to 236.198.255.254236.198.255.25565,534
72236.199.0.0/16236.199.0.1 to 236.199.255.254236.199.255.25565,534
73236.200.0.0/16236.200.0.1 to 236.200.255.254236.200.255.25565,534
74236.201.0.0/16236.201.0.1 to 236.201.255.254236.201.255.25565,534
75236.202.0.0/16236.202.0.1 to 236.202.255.254236.202.255.25565,534
76236.203.0.0/16236.203.0.1 to 236.203.255.254236.203.255.25565,534
77236.204.0.0/16236.204.0.1 to 236.204.255.254236.204.255.25565,534
78236.205.0.0/16236.205.0.1 to 236.205.255.254236.205.255.25565,534
79236.206.0.0/16236.206.0.1 to 236.206.255.254236.206.255.25565,534
80236.207.0.0/16236.207.0.1 to 236.207.255.254236.207.255.25565,534
81236.208.0.0/16236.208.0.1 to 236.208.255.254236.208.255.25565,534
82236.209.0.0/16236.209.0.1 to 236.209.255.254236.209.255.25565,534
83236.210.0.0/16236.210.0.1 to 236.210.255.254236.210.255.25565,534
84236.211.0.0/16236.211.0.1 to 236.211.255.254236.211.255.25565,534
85236.212.0.0/16236.212.0.1 to 236.212.255.254236.212.255.25565,534
86236.213.0.0/16236.213.0.1 to 236.213.255.254236.213.255.25565,534
87236.214.0.0/16236.214.0.1 to 236.214.255.254236.214.255.25565,534
88236.215.0.0/16236.215.0.1 to 236.215.255.254236.215.255.25565,534
89236.216.0.0/16236.216.0.1 to 236.216.255.254236.216.255.25565,534
90236.217.0.0/16236.217.0.1 to 236.217.255.254236.217.255.25565,534
91236.218.0.0/16236.218.0.1 to 236.218.255.254236.218.255.25565,534
92236.219.0.0/16236.219.0.1 to 236.219.255.254236.219.255.25565,534
93236.220.0.0/16236.220.0.1 to 236.220.255.254236.220.255.25565,534
94236.221.0.0/16236.221.0.1 to 236.221.255.254236.221.255.25565,534
95236.222.0.0/16236.222.0.1 to 236.222.255.254236.222.255.25565,534
96236.223.0.0/16236.223.0.1 to 236.223.255.254236.223.255.25565,534
97236.224.0.0/16236.224.0.1 to 236.224.255.254236.224.255.25565,534
98236.225.0.0/16236.225.0.1 to 236.225.255.254236.225.255.25565,534
99236.226.0.0/16236.226.0.1 to 236.226.255.254236.226.255.25565,534
100236.227.0.0/16236.227.0.1 to 236.227.255.254236.227.255.25565,534
101236.228.0.0/16236.228.0.1 to 236.228.255.254236.228.255.25565,534
102236.229.0.0/16236.229.0.1 to 236.229.255.254236.229.255.25565,534
103236.230.0.0/16236.230.0.1 to 236.230.255.254236.230.255.25565,534
104236.231.0.0/16236.231.0.1 to 236.231.255.254236.231.255.25565,534
105236.232.0.0/16236.232.0.1 to 236.232.255.254236.232.255.25565,534
106236.233.0.0/16236.233.0.1 to 236.233.255.254236.233.255.25565,534
107236.234.0.0/16236.234.0.1 to 236.234.255.254236.234.255.25565,534
108236.235.0.0/16236.235.0.1 to 236.235.255.254236.235.255.25565,534
109236.236.0.0/16236.236.0.1 to 236.236.255.254236.236.255.25565,534
110236.237.0.0/16236.237.0.1 to 236.237.255.254236.237.255.25565,534
111236.238.0.0/16236.238.0.1 to 236.238.255.254236.238.255.25565,534
112236.239.0.0/16236.239.0.1 to 236.239.255.254236.239.255.25565,534
113236.240.0.0/16236.240.0.1 to 236.240.255.254236.240.255.25565,534
114236.241.0.0/16236.241.0.1 to 236.241.255.254236.241.255.25565,534
115236.242.0.0/16236.242.0.1 to 236.242.255.254236.242.255.25565,534
116236.243.0.0/16236.243.0.1 to 236.243.255.254236.243.255.25565,534
117236.244.0.0/16236.244.0.1 to 236.244.255.254236.244.255.25565,534
118236.245.0.0/16236.245.0.1 to 236.245.255.254236.245.255.25565,534
119236.246.0.0/16236.246.0.1 to 236.246.255.254236.246.255.25565,534
120236.247.0.0/16236.247.0.1 to 236.247.255.254236.247.255.25565,534
121236.248.0.0/16236.248.0.1 to 236.248.255.254236.248.255.25565,534
122236.249.0.0/16236.249.0.1 to 236.249.255.254236.249.255.25565,534
123236.250.0.0/16236.250.0.1 to 236.250.255.254236.250.255.25565,534
124236.251.0.0/16236.251.0.1 to 236.251.255.254236.251.255.25565,534
125236.252.0.0/16236.252.0.1 to 236.252.255.254236.252.255.25565,534
126236.253.0.0/16236.253.0.1 to 236.253.255.254236.253.255.25565,534
127236.254.0.0/16236.254.0.1 to 236.254.255.254236.254.255.25565,534
128236.255.0.0/16236.255.0.1 to 236.255.255.254236.255.255.25565,534

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.