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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.

Network151.211.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
151.211.0.0
Broadcast address
151.211.255.255
First usable
151.211.0.1
Last usable
151.211.255.254
Usable hosts
65,534 (65,536 less the network and broadcast addresses)
Subnet mask
255.255.0.0
Wildcard mask
0.0.255.255 (Cisco ACLs, OSPF)
Prefix length
/16
Type
Public public
Old class
B (default /16)
As numbers
Hex 97D30000 · Integer 2547187712 to 2547253247
Reverse DNS zone
211.151.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10010111.11010011..00000000.00000000151.211.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10010111.11010011..00000000.00000000151.211.0.0
Broadcast10010111.11010011..11111111.11111111151.211.255.255
Split into smaller subnets/23
/17 (2)/18 (4)/19 (8)/20 (16)/21 (32)/22 (64)/23 (128)/24 (256)/25 (512)/26 (1,024)/27 (2,048)/28 (4,096)

151.211.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1151.211.0.0/23151.211.0.1 to 151.211.1.254151.211.1.255510
2151.211.2.0/23151.211.2.1 to 151.211.3.254151.211.3.255510
3151.211.4.0/23151.211.4.1 to 151.211.5.254151.211.5.255510
4151.211.6.0/23151.211.6.1 to 151.211.7.254151.211.7.255510
5151.211.8.0/23151.211.8.1 to 151.211.9.254151.211.9.255510
6151.211.10.0/23151.211.10.1 to 151.211.11.254151.211.11.255510
7151.211.12.0/23151.211.12.1 to 151.211.13.254151.211.13.255510
8151.211.14.0/23151.211.14.1 to 151.211.15.254151.211.15.255510
9151.211.16.0/23151.211.16.1 to 151.211.17.254151.211.17.255510
10151.211.18.0/23151.211.18.1 to 151.211.19.254151.211.19.255510
11151.211.20.0/23151.211.20.1 to 151.211.21.254151.211.21.255510
12151.211.22.0/23151.211.22.1 to 151.211.23.254151.211.23.255510
13151.211.24.0/23151.211.24.1 to 151.211.25.254151.211.25.255510
14151.211.26.0/23151.211.26.1 to 151.211.27.254151.211.27.255510
15151.211.28.0/23151.211.28.1 to 151.211.29.254151.211.29.255510
16151.211.30.0/23151.211.30.1 to 151.211.31.254151.211.31.255510
17151.211.32.0/23151.211.32.1 to 151.211.33.254151.211.33.255510
18151.211.34.0/23151.211.34.1 to 151.211.35.254151.211.35.255510
19151.211.36.0/23151.211.36.1 to 151.211.37.254151.211.37.255510
20151.211.38.0/23151.211.38.1 to 151.211.39.254151.211.39.255510
21151.211.40.0/23151.211.40.1 to 151.211.41.254151.211.41.255510
22151.211.42.0/23151.211.42.1 to 151.211.43.254151.211.43.255510
23151.211.44.0/23151.211.44.1 to 151.211.45.254151.211.45.255510
24151.211.46.0/23151.211.46.1 to 151.211.47.254151.211.47.255510
25151.211.48.0/23151.211.48.1 to 151.211.49.254151.211.49.255510
26151.211.50.0/23151.211.50.1 to 151.211.51.254151.211.51.255510
27151.211.52.0/23151.211.52.1 to 151.211.53.254151.211.53.255510
28151.211.54.0/23151.211.54.1 to 151.211.55.254151.211.55.255510
29151.211.56.0/23151.211.56.1 to 151.211.57.254151.211.57.255510
30151.211.58.0/23151.211.58.1 to 151.211.59.254151.211.59.255510
31151.211.60.0/23151.211.60.1 to 151.211.61.254151.211.61.255510
32151.211.62.0/23151.211.62.1 to 151.211.63.254151.211.63.255510
33151.211.64.0/23151.211.64.1 to 151.211.65.254151.211.65.255510
34151.211.66.0/23151.211.66.1 to 151.211.67.254151.211.67.255510
35151.211.68.0/23151.211.68.1 to 151.211.69.254151.211.69.255510
36151.211.70.0/23151.211.70.1 to 151.211.71.254151.211.71.255510
37151.211.72.0/23151.211.72.1 to 151.211.73.254151.211.73.255510
38151.211.74.0/23151.211.74.1 to 151.211.75.254151.211.75.255510
39151.211.76.0/23151.211.76.1 to 151.211.77.254151.211.77.255510
40151.211.78.0/23151.211.78.1 to 151.211.79.254151.211.79.255510
41151.211.80.0/23151.211.80.1 to 151.211.81.254151.211.81.255510
42151.211.82.0/23151.211.82.1 to 151.211.83.254151.211.83.255510
43151.211.84.0/23151.211.84.1 to 151.211.85.254151.211.85.255510
44151.211.86.0/23151.211.86.1 to 151.211.87.254151.211.87.255510
45151.211.88.0/23151.211.88.1 to 151.211.89.254151.211.89.255510
46151.211.90.0/23151.211.90.1 to 151.211.91.254151.211.91.255510
47151.211.92.0/23151.211.92.1 to 151.211.93.254151.211.93.255510
48151.211.94.0/23151.211.94.1 to 151.211.95.254151.211.95.255510
49151.211.96.0/23151.211.96.1 to 151.211.97.254151.211.97.255510
50151.211.98.0/23151.211.98.1 to 151.211.99.254151.211.99.255510
51151.211.100.0/23151.211.100.1 to 151.211.101.254151.211.101.255510
52151.211.102.0/23151.211.102.1 to 151.211.103.254151.211.103.255510
53151.211.104.0/23151.211.104.1 to 151.211.105.254151.211.105.255510
54151.211.106.0/23151.211.106.1 to 151.211.107.254151.211.107.255510
55151.211.108.0/23151.211.108.1 to 151.211.109.254151.211.109.255510
56151.211.110.0/23151.211.110.1 to 151.211.111.254151.211.111.255510
57151.211.112.0/23151.211.112.1 to 151.211.113.254151.211.113.255510
58151.211.114.0/23151.211.114.1 to 151.211.115.254151.211.115.255510
59151.211.116.0/23151.211.116.1 to 151.211.117.254151.211.117.255510
60151.211.118.0/23151.211.118.1 to 151.211.119.254151.211.119.255510
61151.211.120.0/23151.211.120.1 to 151.211.121.254151.211.121.255510
62151.211.122.0/23151.211.122.1 to 151.211.123.254151.211.123.255510
63151.211.124.0/23151.211.124.1 to 151.211.125.254151.211.125.255510
64151.211.126.0/23151.211.126.1 to 151.211.127.254151.211.127.255510
65151.211.128.0/23151.211.128.1 to 151.211.129.254151.211.129.255510
66151.211.130.0/23151.211.130.1 to 151.211.131.254151.211.131.255510
67151.211.132.0/23151.211.132.1 to 151.211.133.254151.211.133.255510
68151.211.134.0/23151.211.134.1 to 151.211.135.254151.211.135.255510
69151.211.136.0/23151.211.136.1 to 151.211.137.254151.211.137.255510
70151.211.138.0/23151.211.138.1 to 151.211.139.254151.211.139.255510
71151.211.140.0/23151.211.140.1 to 151.211.141.254151.211.141.255510
72151.211.142.0/23151.211.142.1 to 151.211.143.254151.211.143.255510
73151.211.144.0/23151.211.144.1 to 151.211.145.254151.211.145.255510
74151.211.146.0/23151.211.146.1 to 151.211.147.254151.211.147.255510
75151.211.148.0/23151.211.148.1 to 151.211.149.254151.211.149.255510
76151.211.150.0/23151.211.150.1 to 151.211.151.254151.211.151.255510
77151.211.152.0/23151.211.152.1 to 151.211.153.254151.211.153.255510
78151.211.154.0/23151.211.154.1 to 151.211.155.254151.211.155.255510
79151.211.156.0/23151.211.156.1 to 151.211.157.254151.211.157.255510
80151.211.158.0/23151.211.158.1 to 151.211.159.254151.211.159.255510
81151.211.160.0/23151.211.160.1 to 151.211.161.254151.211.161.255510
82151.211.162.0/23151.211.162.1 to 151.211.163.254151.211.163.255510
83151.211.164.0/23151.211.164.1 to 151.211.165.254151.211.165.255510
84151.211.166.0/23151.211.166.1 to 151.211.167.254151.211.167.255510
85151.211.168.0/23151.211.168.1 to 151.211.169.254151.211.169.255510
86151.211.170.0/23151.211.170.1 to 151.211.171.254151.211.171.255510
87151.211.172.0/23151.211.172.1 to 151.211.173.254151.211.173.255510
88151.211.174.0/23151.211.174.1 to 151.211.175.254151.211.175.255510
89151.211.176.0/23151.211.176.1 to 151.211.177.254151.211.177.255510
90151.211.178.0/23151.211.178.1 to 151.211.179.254151.211.179.255510
91151.211.180.0/23151.211.180.1 to 151.211.181.254151.211.181.255510
92151.211.182.0/23151.211.182.1 to 151.211.183.254151.211.183.255510
93151.211.184.0/23151.211.184.1 to 151.211.185.254151.211.185.255510
94151.211.186.0/23151.211.186.1 to 151.211.187.254151.211.187.255510
95151.211.188.0/23151.211.188.1 to 151.211.189.254151.211.189.255510
96151.211.190.0/23151.211.190.1 to 151.211.191.254151.211.191.255510
97151.211.192.0/23151.211.192.1 to 151.211.193.254151.211.193.255510
98151.211.194.0/23151.211.194.1 to 151.211.195.254151.211.195.255510
99151.211.196.0/23151.211.196.1 to 151.211.197.254151.211.197.255510
100151.211.198.0/23151.211.198.1 to 151.211.199.254151.211.199.255510
101151.211.200.0/23151.211.200.1 to 151.211.201.254151.211.201.255510
102151.211.202.0/23151.211.202.1 to 151.211.203.254151.211.203.255510
103151.211.204.0/23151.211.204.1 to 151.211.205.254151.211.205.255510
104151.211.206.0/23151.211.206.1 to 151.211.207.254151.211.207.255510
105151.211.208.0/23151.211.208.1 to 151.211.209.254151.211.209.255510
106151.211.210.0/23151.211.210.1 to 151.211.211.254151.211.211.255510
107151.211.212.0/23151.211.212.1 to 151.211.213.254151.211.213.255510
108151.211.214.0/23151.211.214.1 to 151.211.215.254151.211.215.255510
109151.211.216.0/23151.211.216.1 to 151.211.217.254151.211.217.255510
110151.211.218.0/23151.211.218.1 to 151.211.219.254151.211.219.255510
111151.211.220.0/23151.211.220.1 to 151.211.221.254151.211.221.255510
112151.211.222.0/23151.211.222.1 to 151.211.223.254151.211.223.255510
113151.211.224.0/23151.211.224.1 to 151.211.225.254151.211.225.255510
114151.211.226.0/23151.211.226.1 to 151.211.227.254151.211.227.255510
115151.211.228.0/23151.211.228.1 to 151.211.229.254151.211.229.255510
116151.211.230.0/23151.211.230.1 to 151.211.231.254151.211.231.255510
117151.211.232.0/23151.211.232.1 to 151.211.233.254151.211.233.255510
118151.211.234.0/23151.211.234.1 to 151.211.235.254151.211.235.255510
119151.211.236.0/23151.211.236.1 to 151.211.237.254151.211.237.255510
120151.211.238.0/23151.211.238.1 to 151.211.239.254151.211.239.255510
121151.211.240.0/23151.211.240.1 to 151.211.241.254151.211.241.255510
122151.211.242.0/23151.211.242.1 to 151.211.243.254151.211.243.255510
123151.211.244.0/23151.211.244.1 to 151.211.245.254151.211.245.255510
124151.211.246.0/23151.211.246.1 to 151.211.247.254151.211.247.255510
125151.211.248.0/23151.211.248.1 to 151.211.249.254151.211.249.255510
126151.211.250.0/23151.211.250.1 to 151.211.251.254151.211.251.255510
127151.211.252.0/23151.211.252.1 to 151.211.253.254151.211.253.255510
128151.211.254.0/23151.211.254.1 to 151.211.255.254151.211.255.255510

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.