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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.

Network255.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
255.128.0.0
Broadcast address
255.255.255.255
First usable
255.128.0.1
Last usable
255.255.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FF800000 · Integer 4286578688 to 4294967295
Reverse DNS zones
128.255.in-addr.arpa
129.255.in-addr.arpa
130.255.in-addr.arpa
131.255.in-addr.arpa
132.255.in-addr.arpa
133.255.in-addr.arpa
134.255.in-addr.arpa
135.255.in-addr.arpa
136.255.in-addr.arpa
137.255.in-addr.arpa
138.255.in-addr.arpa
139.255.in-addr.arpa
140.255.in-addr.arpa
141.255.in-addr.arpa
142.255.in-addr.arpa
143.255.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
Address11111111.10000000.00000000.00000000255.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11111111.10000000.00000000.00000000255.128.0.0
Broadcast11111111.11111111.11111111.11111111255.255.255.255
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)

255.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1255.128.0.0/16255.128.0.1 to 255.128.255.254255.128.255.25565,534
2255.129.0.0/16255.129.0.1 to 255.129.255.254255.129.255.25565,534
3255.130.0.0/16255.130.0.1 to 255.130.255.254255.130.255.25565,534
4255.131.0.0/16255.131.0.1 to 255.131.255.254255.131.255.25565,534
5255.132.0.0/16255.132.0.1 to 255.132.255.254255.132.255.25565,534
6255.133.0.0/16255.133.0.1 to 255.133.255.254255.133.255.25565,534
7255.134.0.0/16255.134.0.1 to 255.134.255.254255.134.255.25565,534
8255.135.0.0/16255.135.0.1 to 255.135.255.254255.135.255.25565,534
9255.136.0.0/16255.136.0.1 to 255.136.255.254255.136.255.25565,534
10255.137.0.0/16255.137.0.1 to 255.137.255.254255.137.255.25565,534
11255.138.0.0/16255.138.0.1 to 255.138.255.254255.138.255.25565,534
12255.139.0.0/16255.139.0.1 to 255.139.255.254255.139.255.25565,534
13255.140.0.0/16255.140.0.1 to 255.140.255.254255.140.255.25565,534
14255.141.0.0/16255.141.0.1 to 255.141.255.254255.141.255.25565,534
15255.142.0.0/16255.142.0.1 to 255.142.255.254255.142.255.25565,534
16255.143.0.0/16255.143.0.1 to 255.143.255.254255.143.255.25565,534
17255.144.0.0/16255.144.0.1 to 255.144.255.254255.144.255.25565,534
18255.145.0.0/16255.145.0.1 to 255.145.255.254255.145.255.25565,534
19255.146.0.0/16255.146.0.1 to 255.146.255.254255.146.255.25565,534
20255.147.0.0/16255.147.0.1 to 255.147.255.254255.147.255.25565,534
21255.148.0.0/16255.148.0.1 to 255.148.255.254255.148.255.25565,534
22255.149.0.0/16255.149.0.1 to 255.149.255.254255.149.255.25565,534
23255.150.0.0/16255.150.0.1 to 255.150.255.254255.150.255.25565,534
24255.151.0.0/16255.151.0.1 to 255.151.255.254255.151.255.25565,534
25255.152.0.0/16255.152.0.1 to 255.152.255.254255.152.255.25565,534
26255.153.0.0/16255.153.0.1 to 255.153.255.254255.153.255.25565,534
27255.154.0.0/16255.154.0.1 to 255.154.255.254255.154.255.25565,534
28255.155.0.0/16255.155.0.1 to 255.155.255.254255.155.255.25565,534
29255.156.0.0/16255.156.0.1 to 255.156.255.254255.156.255.25565,534
30255.157.0.0/16255.157.0.1 to 255.157.255.254255.157.255.25565,534
31255.158.0.0/16255.158.0.1 to 255.158.255.254255.158.255.25565,534
32255.159.0.0/16255.159.0.1 to 255.159.255.254255.159.255.25565,534
33255.160.0.0/16255.160.0.1 to 255.160.255.254255.160.255.25565,534
34255.161.0.0/16255.161.0.1 to 255.161.255.254255.161.255.25565,534
35255.162.0.0/16255.162.0.1 to 255.162.255.254255.162.255.25565,534
36255.163.0.0/16255.163.0.1 to 255.163.255.254255.163.255.25565,534
37255.164.0.0/16255.164.0.1 to 255.164.255.254255.164.255.25565,534
38255.165.0.0/16255.165.0.1 to 255.165.255.254255.165.255.25565,534
39255.166.0.0/16255.166.0.1 to 255.166.255.254255.166.255.25565,534
40255.167.0.0/16255.167.0.1 to 255.167.255.254255.167.255.25565,534
41255.168.0.0/16255.168.0.1 to 255.168.255.254255.168.255.25565,534
42255.169.0.0/16255.169.0.1 to 255.169.255.254255.169.255.25565,534
43255.170.0.0/16255.170.0.1 to 255.170.255.254255.170.255.25565,534
44255.171.0.0/16255.171.0.1 to 255.171.255.254255.171.255.25565,534
45255.172.0.0/16255.172.0.1 to 255.172.255.254255.172.255.25565,534
46255.173.0.0/16255.173.0.1 to 255.173.255.254255.173.255.25565,534
47255.174.0.0/16255.174.0.1 to 255.174.255.254255.174.255.25565,534
48255.175.0.0/16255.175.0.1 to 255.175.255.254255.175.255.25565,534
49255.176.0.0/16255.176.0.1 to 255.176.255.254255.176.255.25565,534
50255.177.0.0/16255.177.0.1 to 255.177.255.254255.177.255.25565,534
51255.178.0.0/16255.178.0.1 to 255.178.255.254255.178.255.25565,534
52255.179.0.0/16255.179.0.1 to 255.179.255.254255.179.255.25565,534
53255.180.0.0/16255.180.0.1 to 255.180.255.254255.180.255.25565,534
54255.181.0.0/16255.181.0.1 to 255.181.255.254255.181.255.25565,534
55255.182.0.0/16255.182.0.1 to 255.182.255.254255.182.255.25565,534
56255.183.0.0/16255.183.0.1 to 255.183.255.254255.183.255.25565,534
57255.184.0.0/16255.184.0.1 to 255.184.255.254255.184.255.25565,534
58255.185.0.0/16255.185.0.1 to 255.185.255.254255.185.255.25565,534
59255.186.0.0/16255.186.0.1 to 255.186.255.254255.186.255.25565,534
60255.187.0.0/16255.187.0.1 to 255.187.255.254255.187.255.25565,534
61255.188.0.0/16255.188.0.1 to 255.188.255.254255.188.255.25565,534
62255.189.0.0/16255.189.0.1 to 255.189.255.254255.189.255.25565,534
63255.190.0.0/16255.190.0.1 to 255.190.255.254255.190.255.25565,534
64255.191.0.0/16255.191.0.1 to 255.191.255.254255.191.255.25565,534
65255.192.0.0/16255.192.0.1 to 255.192.255.254255.192.255.25565,534
66255.193.0.0/16255.193.0.1 to 255.193.255.254255.193.255.25565,534
67255.194.0.0/16255.194.0.1 to 255.194.255.254255.194.255.25565,534
68255.195.0.0/16255.195.0.1 to 255.195.255.254255.195.255.25565,534
69255.196.0.0/16255.196.0.1 to 255.196.255.254255.196.255.25565,534
70255.197.0.0/16255.197.0.1 to 255.197.255.254255.197.255.25565,534
71255.198.0.0/16255.198.0.1 to 255.198.255.254255.198.255.25565,534
72255.199.0.0/16255.199.0.1 to 255.199.255.254255.199.255.25565,534
73255.200.0.0/16255.200.0.1 to 255.200.255.254255.200.255.25565,534
74255.201.0.0/16255.201.0.1 to 255.201.255.254255.201.255.25565,534
75255.202.0.0/16255.202.0.1 to 255.202.255.254255.202.255.25565,534
76255.203.0.0/16255.203.0.1 to 255.203.255.254255.203.255.25565,534
77255.204.0.0/16255.204.0.1 to 255.204.255.254255.204.255.25565,534
78255.205.0.0/16255.205.0.1 to 255.205.255.254255.205.255.25565,534
79255.206.0.0/16255.206.0.1 to 255.206.255.254255.206.255.25565,534
80255.207.0.0/16255.207.0.1 to 255.207.255.254255.207.255.25565,534
81255.208.0.0/16255.208.0.1 to 255.208.255.254255.208.255.25565,534
82255.209.0.0/16255.209.0.1 to 255.209.255.254255.209.255.25565,534
83255.210.0.0/16255.210.0.1 to 255.210.255.254255.210.255.25565,534
84255.211.0.0/16255.211.0.1 to 255.211.255.254255.211.255.25565,534
85255.212.0.0/16255.212.0.1 to 255.212.255.254255.212.255.25565,534
86255.213.0.0/16255.213.0.1 to 255.213.255.254255.213.255.25565,534
87255.214.0.0/16255.214.0.1 to 255.214.255.254255.214.255.25565,534
88255.215.0.0/16255.215.0.1 to 255.215.255.254255.215.255.25565,534
89255.216.0.0/16255.216.0.1 to 255.216.255.254255.216.255.25565,534
90255.217.0.0/16255.217.0.1 to 255.217.255.254255.217.255.25565,534
91255.218.0.0/16255.218.0.1 to 255.218.255.254255.218.255.25565,534
92255.219.0.0/16255.219.0.1 to 255.219.255.254255.219.255.25565,534
93255.220.0.0/16255.220.0.1 to 255.220.255.254255.220.255.25565,534
94255.221.0.0/16255.221.0.1 to 255.221.255.254255.221.255.25565,534
95255.222.0.0/16255.222.0.1 to 255.222.255.254255.222.255.25565,534
96255.223.0.0/16255.223.0.1 to 255.223.255.254255.223.255.25565,534
97255.224.0.0/16255.224.0.1 to 255.224.255.254255.224.255.25565,534
98255.225.0.0/16255.225.0.1 to 255.225.255.254255.225.255.25565,534
99255.226.0.0/16255.226.0.1 to 255.226.255.254255.226.255.25565,534
100255.227.0.0/16255.227.0.1 to 255.227.255.254255.227.255.25565,534
101255.228.0.0/16255.228.0.1 to 255.228.255.254255.228.255.25565,534
102255.229.0.0/16255.229.0.1 to 255.229.255.254255.229.255.25565,534
103255.230.0.0/16255.230.0.1 to 255.230.255.254255.230.255.25565,534
104255.231.0.0/16255.231.0.1 to 255.231.255.254255.231.255.25565,534
105255.232.0.0/16255.232.0.1 to 255.232.255.254255.232.255.25565,534
106255.233.0.0/16255.233.0.1 to 255.233.255.254255.233.255.25565,534
107255.234.0.0/16255.234.0.1 to 255.234.255.254255.234.255.25565,534
108255.235.0.0/16255.235.0.1 to 255.235.255.254255.235.255.25565,534
109255.236.0.0/16255.236.0.1 to 255.236.255.254255.236.255.25565,534
110255.237.0.0/16255.237.0.1 to 255.237.255.254255.237.255.25565,534
111255.238.0.0/16255.238.0.1 to 255.238.255.254255.238.255.25565,534
112255.239.0.0/16255.239.0.1 to 255.239.255.254255.239.255.25565,534
113255.240.0.0/16255.240.0.1 to 255.240.255.254255.240.255.25565,534
114255.241.0.0/16255.241.0.1 to 255.241.255.254255.241.255.25565,534
115255.242.0.0/16255.242.0.1 to 255.242.255.254255.242.255.25565,534
116255.243.0.0/16255.243.0.1 to 255.243.255.254255.243.255.25565,534
117255.244.0.0/16255.244.0.1 to 255.244.255.254255.244.255.25565,534
118255.245.0.0/16255.245.0.1 to 255.245.255.254255.245.255.25565,534
119255.246.0.0/16255.246.0.1 to 255.246.255.254255.246.255.25565,534
120255.247.0.0/16255.247.0.1 to 255.247.255.254255.247.255.25565,534
121255.248.0.0/16255.248.0.1 to 255.248.255.254255.248.255.25565,534
122255.249.0.0/16255.249.0.1 to 255.249.255.254255.249.255.25565,534
123255.250.0.0/16255.250.0.1 to 255.250.255.254255.250.255.25565,534
124255.251.0.0/16255.251.0.1 to 255.251.255.254255.251.255.25565,534
125255.252.0.0/16255.252.0.1 to 255.252.255.254255.252.255.25565,534
126255.253.0.0/16255.253.0.1 to 255.253.255.254255.253.255.25565,534
127255.254.0.0/16255.254.0.1 to 255.254.255.254255.254.255.25565,534
128255.255.0.0/16255.255.0.1 to 255.255.255.254255.255.255.25565,534

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.