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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.

Network155.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
155.0.0.0
Broadcast address
155.255.255.255
First usable
155.0.0.1
Last usable
155.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
B (default /16)
As numbers
Hex 9B000000 · Integer 2600468480 to 2617245695
Reverse DNS zone
155.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10011011..00000000.00000000.00000000155.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10011011..00000000.00000000.00000000155.0.0.0
Broadcast10011011..11111111.11111111.11111111155.255.255.255
Split into smaller subnets/15
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

155.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1155.0.0.0/15155.0.0.1 to 155.1.255.254155.1.255.255131,070
2155.2.0.0/15155.2.0.1 to 155.3.255.254155.3.255.255131,070
3155.4.0.0/15155.4.0.1 to 155.5.255.254155.5.255.255131,070
4155.6.0.0/15155.6.0.1 to 155.7.255.254155.7.255.255131,070
5155.8.0.0/15155.8.0.1 to 155.9.255.254155.9.255.255131,070
6155.10.0.0/15155.10.0.1 to 155.11.255.254155.11.255.255131,070
7155.12.0.0/15155.12.0.1 to 155.13.255.254155.13.255.255131,070
8155.14.0.0/15155.14.0.1 to 155.15.255.254155.15.255.255131,070
9155.16.0.0/15155.16.0.1 to 155.17.255.254155.17.255.255131,070
10155.18.0.0/15155.18.0.1 to 155.19.255.254155.19.255.255131,070
11155.20.0.0/15155.20.0.1 to 155.21.255.254155.21.255.255131,070
12155.22.0.0/15155.22.0.1 to 155.23.255.254155.23.255.255131,070
13155.24.0.0/15155.24.0.1 to 155.25.255.254155.25.255.255131,070
14155.26.0.0/15155.26.0.1 to 155.27.255.254155.27.255.255131,070
15155.28.0.0/15155.28.0.1 to 155.29.255.254155.29.255.255131,070
16155.30.0.0/15155.30.0.1 to 155.31.255.254155.31.255.255131,070
17155.32.0.0/15155.32.0.1 to 155.33.255.254155.33.255.255131,070
18155.34.0.0/15155.34.0.1 to 155.35.255.254155.35.255.255131,070
19155.36.0.0/15155.36.0.1 to 155.37.255.254155.37.255.255131,070
20155.38.0.0/15155.38.0.1 to 155.39.255.254155.39.255.255131,070
21155.40.0.0/15155.40.0.1 to 155.41.255.254155.41.255.255131,070
22155.42.0.0/15155.42.0.1 to 155.43.255.254155.43.255.255131,070
23155.44.0.0/15155.44.0.1 to 155.45.255.254155.45.255.255131,070
24155.46.0.0/15155.46.0.1 to 155.47.255.254155.47.255.255131,070
25155.48.0.0/15155.48.0.1 to 155.49.255.254155.49.255.255131,070
26155.50.0.0/15155.50.0.1 to 155.51.255.254155.51.255.255131,070
27155.52.0.0/15155.52.0.1 to 155.53.255.254155.53.255.255131,070
28155.54.0.0/15155.54.0.1 to 155.55.255.254155.55.255.255131,070
29155.56.0.0/15155.56.0.1 to 155.57.255.254155.57.255.255131,070
30155.58.0.0/15155.58.0.1 to 155.59.255.254155.59.255.255131,070
31155.60.0.0/15155.60.0.1 to 155.61.255.254155.61.255.255131,070
32155.62.0.0/15155.62.0.1 to 155.63.255.254155.63.255.255131,070
33155.64.0.0/15155.64.0.1 to 155.65.255.254155.65.255.255131,070
34155.66.0.0/15155.66.0.1 to 155.67.255.254155.67.255.255131,070
35155.68.0.0/15155.68.0.1 to 155.69.255.254155.69.255.255131,070
36155.70.0.0/15155.70.0.1 to 155.71.255.254155.71.255.255131,070
37155.72.0.0/15155.72.0.1 to 155.73.255.254155.73.255.255131,070
38155.74.0.0/15155.74.0.1 to 155.75.255.254155.75.255.255131,070
39155.76.0.0/15155.76.0.1 to 155.77.255.254155.77.255.255131,070
40155.78.0.0/15155.78.0.1 to 155.79.255.254155.79.255.255131,070
41155.80.0.0/15155.80.0.1 to 155.81.255.254155.81.255.255131,070
42155.82.0.0/15155.82.0.1 to 155.83.255.254155.83.255.255131,070
43155.84.0.0/15155.84.0.1 to 155.85.255.254155.85.255.255131,070
44155.86.0.0/15155.86.0.1 to 155.87.255.254155.87.255.255131,070
45155.88.0.0/15155.88.0.1 to 155.89.255.254155.89.255.255131,070
46155.90.0.0/15155.90.0.1 to 155.91.255.254155.91.255.255131,070
47155.92.0.0/15155.92.0.1 to 155.93.255.254155.93.255.255131,070
48155.94.0.0/15155.94.0.1 to 155.95.255.254155.95.255.255131,070
49155.96.0.0/15155.96.0.1 to 155.97.255.254155.97.255.255131,070
50155.98.0.0/15155.98.0.1 to 155.99.255.254155.99.255.255131,070
51155.100.0.0/15155.100.0.1 to 155.101.255.254155.101.255.255131,070
52155.102.0.0/15155.102.0.1 to 155.103.255.254155.103.255.255131,070
53155.104.0.0/15155.104.0.1 to 155.105.255.254155.105.255.255131,070
54155.106.0.0/15155.106.0.1 to 155.107.255.254155.107.255.255131,070
55155.108.0.0/15155.108.0.1 to 155.109.255.254155.109.255.255131,070
56155.110.0.0/15155.110.0.1 to 155.111.255.254155.111.255.255131,070
57155.112.0.0/15155.112.0.1 to 155.113.255.254155.113.255.255131,070
58155.114.0.0/15155.114.0.1 to 155.115.255.254155.115.255.255131,070
59155.116.0.0/15155.116.0.1 to 155.117.255.254155.117.255.255131,070
60155.118.0.0/15155.118.0.1 to 155.119.255.254155.119.255.255131,070
61155.120.0.0/15155.120.0.1 to 155.121.255.254155.121.255.255131,070
62155.122.0.0/15155.122.0.1 to 155.123.255.254155.123.255.255131,070
63155.124.0.0/15155.124.0.1 to 155.125.255.254155.125.255.255131,070
64155.126.0.0/15155.126.0.1 to 155.127.255.254155.127.255.255131,070
65155.128.0.0/15155.128.0.1 to 155.129.255.254155.129.255.255131,070
66155.130.0.0/15155.130.0.1 to 155.131.255.254155.131.255.255131,070
67155.132.0.0/15155.132.0.1 to 155.133.255.254155.133.255.255131,070
68155.134.0.0/15155.134.0.1 to 155.135.255.254155.135.255.255131,070
69155.136.0.0/15155.136.0.1 to 155.137.255.254155.137.255.255131,070
70155.138.0.0/15155.138.0.1 to 155.139.255.254155.139.255.255131,070
71155.140.0.0/15155.140.0.1 to 155.141.255.254155.141.255.255131,070
72155.142.0.0/15155.142.0.1 to 155.143.255.254155.143.255.255131,070
73155.144.0.0/15155.144.0.1 to 155.145.255.254155.145.255.255131,070
74155.146.0.0/15155.146.0.1 to 155.147.255.254155.147.255.255131,070
75155.148.0.0/15155.148.0.1 to 155.149.255.254155.149.255.255131,070
76155.150.0.0/15155.150.0.1 to 155.151.255.254155.151.255.255131,070
77155.152.0.0/15155.152.0.1 to 155.153.255.254155.153.255.255131,070
78155.154.0.0/15155.154.0.1 to 155.155.255.254155.155.255.255131,070
79155.156.0.0/15155.156.0.1 to 155.157.255.254155.157.255.255131,070
80155.158.0.0/15155.158.0.1 to 155.159.255.254155.159.255.255131,070
81155.160.0.0/15155.160.0.1 to 155.161.255.254155.161.255.255131,070
82155.162.0.0/15155.162.0.1 to 155.163.255.254155.163.255.255131,070
83155.164.0.0/15155.164.0.1 to 155.165.255.254155.165.255.255131,070
84155.166.0.0/15155.166.0.1 to 155.167.255.254155.167.255.255131,070
85155.168.0.0/15155.168.0.1 to 155.169.255.254155.169.255.255131,070
86155.170.0.0/15155.170.0.1 to 155.171.255.254155.171.255.255131,070
87155.172.0.0/15155.172.0.1 to 155.173.255.254155.173.255.255131,070
88155.174.0.0/15155.174.0.1 to 155.175.255.254155.175.255.255131,070
89155.176.0.0/15155.176.0.1 to 155.177.255.254155.177.255.255131,070
90155.178.0.0/15155.178.0.1 to 155.179.255.254155.179.255.255131,070
91155.180.0.0/15155.180.0.1 to 155.181.255.254155.181.255.255131,070
92155.182.0.0/15155.182.0.1 to 155.183.255.254155.183.255.255131,070
93155.184.0.0/15155.184.0.1 to 155.185.255.254155.185.255.255131,070
94155.186.0.0/15155.186.0.1 to 155.187.255.254155.187.255.255131,070
95155.188.0.0/15155.188.0.1 to 155.189.255.254155.189.255.255131,070
96155.190.0.0/15155.190.0.1 to 155.191.255.254155.191.255.255131,070
97155.192.0.0/15155.192.0.1 to 155.193.255.254155.193.255.255131,070
98155.194.0.0/15155.194.0.1 to 155.195.255.254155.195.255.255131,070
99155.196.0.0/15155.196.0.1 to 155.197.255.254155.197.255.255131,070
100155.198.0.0/15155.198.0.1 to 155.199.255.254155.199.255.255131,070
101155.200.0.0/15155.200.0.1 to 155.201.255.254155.201.255.255131,070
102155.202.0.0/15155.202.0.1 to 155.203.255.254155.203.255.255131,070
103155.204.0.0/15155.204.0.1 to 155.205.255.254155.205.255.255131,070
104155.206.0.0/15155.206.0.1 to 155.207.255.254155.207.255.255131,070
105155.208.0.0/15155.208.0.1 to 155.209.255.254155.209.255.255131,070
106155.210.0.0/15155.210.0.1 to 155.211.255.254155.211.255.255131,070
107155.212.0.0/15155.212.0.1 to 155.213.255.254155.213.255.255131,070
108155.214.0.0/15155.214.0.1 to 155.215.255.254155.215.255.255131,070
109155.216.0.0/15155.216.0.1 to 155.217.255.254155.217.255.255131,070
110155.218.0.0/15155.218.0.1 to 155.219.255.254155.219.255.255131,070
111155.220.0.0/15155.220.0.1 to 155.221.255.254155.221.255.255131,070
112155.222.0.0/15155.222.0.1 to 155.223.255.254155.223.255.255131,070
113155.224.0.0/15155.224.0.1 to 155.225.255.254155.225.255.255131,070
114155.226.0.0/15155.226.0.1 to 155.227.255.254155.227.255.255131,070
115155.228.0.0/15155.228.0.1 to 155.229.255.254155.229.255.255131,070
116155.230.0.0/15155.230.0.1 to 155.231.255.254155.231.255.255131,070
117155.232.0.0/15155.232.0.1 to 155.233.255.254155.233.255.255131,070
118155.234.0.0/15155.234.0.1 to 155.235.255.254155.235.255.255131,070
119155.236.0.0/15155.236.0.1 to 155.237.255.254155.237.255.255131,070
120155.238.0.0/15155.238.0.1 to 155.239.255.254155.239.255.255131,070
121155.240.0.0/15155.240.0.1 to 155.241.255.254155.241.255.255131,070
122155.242.0.0/15155.242.0.1 to 155.243.255.254155.243.255.255131,070
123155.244.0.0/15155.244.0.1 to 155.245.255.254155.245.255.255131,070
124155.246.0.0/15155.246.0.1 to 155.247.255.254155.247.255.255131,070
125155.248.0.0/15155.248.0.1 to 155.249.255.254155.249.255.255131,070
126155.250.0.0/15155.250.0.1 to 155.251.255.254155.251.255.255131,070
127155.252.0.0/15155.252.0.1 to 155.253.255.254155.253.255.255131,070
128155.254.0.0/15155.254.0.1 to 155.255.255.254155.255.255.255131,070

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.