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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.

Network172.28.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
172.28.0.0
Broadcast address
172.28.255.255
First usable
172.28.0.1
Last usable
172.28.255.254
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
Private (RFC 1918) 172.16.0.0/12
Office and home networks; not routed on the internet
Old class
B (default /16)
As numbers
Hex AC1C0000 · Integer 2887516160 to 2887581695
Reverse DNS zone
28.172.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101100.00011100..00000000.00000000172.28.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10101100.00011100..00000000.00000000172.28.0.0
Broadcast10101100.00011100..11111111.11111111172.28.255.255
Split into smaller subnets/22
/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)

172.28.0.0/16 makes 64 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1172.28.0.0/22172.28.0.1 to 172.28.3.254172.28.3.2551,022
2172.28.4.0/22172.28.4.1 to 172.28.7.254172.28.7.2551,022
3172.28.8.0/22172.28.8.1 to 172.28.11.254172.28.11.2551,022
4172.28.12.0/22172.28.12.1 to 172.28.15.254172.28.15.2551,022
5172.28.16.0/22172.28.16.1 to 172.28.19.254172.28.19.2551,022
6172.28.20.0/22172.28.20.1 to 172.28.23.254172.28.23.2551,022
7172.28.24.0/22172.28.24.1 to 172.28.27.254172.28.27.2551,022
8172.28.28.0/22172.28.28.1 to 172.28.31.254172.28.31.2551,022
9172.28.32.0/22172.28.32.1 to 172.28.35.254172.28.35.2551,022
10172.28.36.0/22172.28.36.1 to 172.28.39.254172.28.39.2551,022
11172.28.40.0/22172.28.40.1 to 172.28.43.254172.28.43.2551,022
12172.28.44.0/22172.28.44.1 to 172.28.47.254172.28.47.2551,022
13172.28.48.0/22172.28.48.1 to 172.28.51.254172.28.51.2551,022
14172.28.52.0/22172.28.52.1 to 172.28.55.254172.28.55.2551,022
15172.28.56.0/22172.28.56.1 to 172.28.59.254172.28.59.2551,022
16172.28.60.0/22172.28.60.1 to 172.28.63.254172.28.63.2551,022
17172.28.64.0/22172.28.64.1 to 172.28.67.254172.28.67.2551,022
18172.28.68.0/22172.28.68.1 to 172.28.71.254172.28.71.2551,022
19172.28.72.0/22172.28.72.1 to 172.28.75.254172.28.75.2551,022
20172.28.76.0/22172.28.76.1 to 172.28.79.254172.28.79.2551,022
21172.28.80.0/22172.28.80.1 to 172.28.83.254172.28.83.2551,022
22172.28.84.0/22172.28.84.1 to 172.28.87.254172.28.87.2551,022
23172.28.88.0/22172.28.88.1 to 172.28.91.254172.28.91.2551,022
24172.28.92.0/22172.28.92.1 to 172.28.95.254172.28.95.2551,022
25172.28.96.0/22172.28.96.1 to 172.28.99.254172.28.99.2551,022
26172.28.100.0/22172.28.100.1 to 172.28.103.254172.28.103.2551,022
27172.28.104.0/22172.28.104.1 to 172.28.107.254172.28.107.2551,022
28172.28.108.0/22172.28.108.1 to 172.28.111.254172.28.111.2551,022
29172.28.112.0/22172.28.112.1 to 172.28.115.254172.28.115.2551,022
30172.28.116.0/22172.28.116.1 to 172.28.119.254172.28.119.2551,022
31172.28.120.0/22172.28.120.1 to 172.28.123.254172.28.123.2551,022
32172.28.124.0/22172.28.124.1 to 172.28.127.254172.28.127.2551,022
33172.28.128.0/22172.28.128.1 to 172.28.131.254172.28.131.2551,022
34172.28.132.0/22172.28.132.1 to 172.28.135.254172.28.135.2551,022
35172.28.136.0/22172.28.136.1 to 172.28.139.254172.28.139.2551,022
36172.28.140.0/22172.28.140.1 to 172.28.143.254172.28.143.2551,022
37172.28.144.0/22172.28.144.1 to 172.28.147.254172.28.147.2551,022
38172.28.148.0/22172.28.148.1 to 172.28.151.254172.28.151.2551,022
39172.28.152.0/22172.28.152.1 to 172.28.155.254172.28.155.2551,022
40172.28.156.0/22172.28.156.1 to 172.28.159.254172.28.159.2551,022
41172.28.160.0/22172.28.160.1 to 172.28.163.254172.28.163.2551,022
42172.28.164.0/22172.28.164.1 to 172.28.167.254172.28.167.2551,022
43172.28.168.0/22172.28.168.1 to 172.28.171.254172.28.171.2551,022
44172.28.172.0/22172.28.172.1 to 172.28.175.254172.28.175.2551,022
45172.28.176.0/22172.28.176.1 to 172.28.179.254172.28.179.2551,022
46172.28.180.0/22172.28.180.1 to 172.28.183.254172.28.183.2551,022
47172.28.184.0/22172.28.184.1 to 172.28.187.254172.28.187.2551,022
48172.28.188.0/22172.28.188.1 to 172.28.191.254172.28.191.2551,022
49172.28.192.0/22172.28.192.1 to 172.28.195.254172.28.195.2551,022
50172.28.196.0/22172.28.196.1 to 172.28.199.254172.28.199.2551,022
51172.28.200.0/22172.28.200.1 to 172.28.203.254172.28.203.2551,022
52172.28.204.0/22172.28.204.1 to 172.28.207.254172.28.207.2551,022
53172.28.208.0/22172.28.208.1 to 172.28.211.254172.28.211.2551,022
54172.28.212.0/22172.28.212.1 to 172.28.215.254172.28.215.2551,022
55172.28.216.0/22172.28.216.1 to 172.28.219.254172.28.219.2551,022
56172.28.220.0/22172.28.220.1 to 172.28.223.254172.28.223.2551,022
57172.28.224.0/22172.28.224.1 to 172.28.227.254172.28.227.2551,022
58172.28.228.0/22172.28.228.1 to 172.28.231.254172.28.231.2551,022
59172.28.232.0/22172.28.232.1 to 172.28.235.254172.28.235.2551,022
60172.28.236.0/22172.28.236.1 to 172.28.239.254172.28.239.2551,022
61172.28.240.0/22172.28.240.1 to 172.28.243.254172.28.243.2551,022
62172.28.244.0/22172.28.244.1 to 172.28.247.254172.28.247.2551,022
63172.28.248.0/22172.28.248.1 to 172.28.251.254172.28.251.2551,022
64172.28.252.0/22172.28.252.1 to 172.28.255.254172.28.255.2551,022

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.