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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.

Network216.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
216.0.0.0
Broadcast address
217.255.255.255
First usable
216.0.0.1
Last usable
217.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
C (default /24)
As numbers
Hex D8000000 · Integer 3623878656 to 3657433087
Reverse DNS zones
216.in-addr.arpa
217.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11011000.00000000.00000000.00000000216.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network11011000.00000000.00000000.00000000216.0.0.0
Broadcast11011001.11111111.11111111.11111111217.255.255.255
Split into smaller subnets/13
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

216.0.0.0/7 makes 64 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1216.0.0.0/13216.0.0.1 to 216.7.255.254216.7.255.255524,286
2216.8.0.0/13216.8.0.1 to 216.15.255.254216.15.255.255524,286
3216.16.0.0/13216.16.0.1 to 216.23.255.254216.23.255.255524,286
4216.24.0.0/13216.24.0.1 to 216.31.255.254216.31.255.255524,286
5216.32.0.0/13216.32.0.1 to 216.39.255.254216.39.255.255524,286
6216.40.0.0/13216.40.0.1 to 216.47.255.254216.47.255.255524,286
7216.48.0.0/13216.48.0.1 to 216.55.255.254216.55.255.255524,286
8216.56.0.0/13216.56.0.1 to 216.63.255.254216.63.255.255524,286
9216.64.0.0/13216.64.0.1 to 216.71.255.254216.71.255.255524,286
10216.72.0.0/13216.72.0.1 to 216.79.255.254216.79.255.255524,286
11216.80.0.0/13216.80.0.1 to 216.87.255.254216.87.255.255524,286
12216.88.0.0/13216.88.0.1 to 216.95.255.254216.95.255.255524,286
13216.96.0.0/13216.96.0.1 to 216.103.255.254216.103.255.255524,286
14216.104.0.0/13216.104.0.1 to 216.111.255.254216.111.255.255524,286
15216.112.0.0/13216.112.0.1 to 216.119.255.254216.119.255.255524,286
16216.120.0.0/13216.120.0.1 to 216.127.255.254216.127.255.255524,286
17216.128.0.0/13216.128.0.1 to 216.135.255.254216.135.255.255524,286
18216.136.0.0/13216.136.0.1 to 216.143.255.254216.143.255.255524,286
19216.144.0.0/13216.144.0.1 to 216.151.255.254216.151.255.255524,286
20216.152.0.0/13216.152.0.1 to 216.159.255.254216.159.255.255524,286
21216.160.0.0/13216.160.0.1 to 216.167.255.254216.167.255.255524,286
22216.168.0.0/13216.168.0.1 to 216.175.255.254216.175.255.255524,286
23216.176.0.0/13216.176.0.1 to 216.183.255.254216.183.255.255524,286
24216.184.0.0/13216.184.0.1 to 216.191.255.254216.191.255.255524,286
25216.192.0.0/13216.192.0.1 to 216.199.255.254216.199.255.255524,286
26216.200.0.0/13216.200.0.1 to 216.207.255.254216.207.255.255524,286
27216.208.0.0/13216.208.0.1 to 216.215.255.254216.215.255.255524,286
28216.216.0.0/13216.216.0.1 to 216.223.255.254216.223.255.255524,286
29216.224.0.0/13216.224.0.1 to 216.231.255.254216.231.255.255524,286
30216.232.0.0/13216.232.0.1 to 216.239.255.254216.239.255.255524,286
31216.240.0.0/13216.240.0.1 to 216.247.255.254216.247.255.255524,286
32216.248.0.0/13216.248.0.1 to 216.255.255.254216.255.255.255524,286
33217.0.0.0/13217.0.0.1 to 217.7.255.254217.7.255.255524,286
34217.8.0.0/13217.8.0.1 to 217.15.255.254217.15.255.255524,286
35217.16.0.0/13217.16.0.1 to 217.23.255.254217.23.255.255524,286
36217.24.0.0/13217.24.0.1 to 217.31.255.254217.31.255.255524,286
37217.32.0.0/13217.32.0.1 to 217.39.255.254217.39.255.255524,286
38217.40.0.0/13217.40.0.1 to 217.47.255.254217.47.255.255524,286
39217.48.0.0/13217.48.0.1 to 217.55.255.254217.55.255.255524,286
40217.56.0.0/13217.56.0.1 to 217.63.255.254217.63.255.255524,286
41217.64.0.0/13217.64.0.1 to 217.71.255.254217.71.255.255524,286
42217.72.0.0/13217.72.0.1 to 217.79.255.254217.79.255.255524,286
43217.80.0.0/13217.80.0.1 to 217.87.255.254217.87.255.255524,286
44217.88.0.0/13217.88.0.1 to 217.95.255.254217.95.255.255524,286
45217.96.0.0/13217.96.0.1 to 217.103.255.254217.103.255.255524,286
46217.104.0.0/13217.104.0.1 to 217.111.255.254217.111.255.255524,286
47217.112.0.0/13217.112.0.1 to 217.119.255.254217.119.255.255524,286
48217.120.0.0/13217.120.0.1 to 217.127.255.254217.127.255.255524,286
49217.128.0.0/13217.128.0.1 to 217.135.255.254217.135.255.255524,286
50217.136.0.0/13217.136.0.1 to 217.143.255.254217.143.255.255524,286
51217.144.0.0/13217.144.0.1 to 217.151.255.254217.151.255.255524,286
52217.152.0.0/13217.152.0.1 to 217.159.255.254217.159.255.255524,286
53217.160.0.0/13217.160.0.1 to 217.167.255.254217.167.255.255524,286
54217.168.0.0/13217.168.0.1 to 217.175.255.254217.175.255.255524,286
55217.176.0.0/13217.176.0.1 to 217.183.255.254217.183.255.255524,286
56217.184.0.0/13217.184.0.1 to 217.191.255.254217.191.255.255524,286
57217.192.0.0/13217.192.0.1 to 217.199.255.254217.199.255.255524,286
58217.200.0.0/13217.200.0.1 to 217.207.255.254217.207.255.255524,286
59217.208.0.0/13217.208.0.1 to 217.215.255.254217.215.255.255524,286
60217.216.0.0/13217.216.0.1 to 217.223.255.254217.223.255.255524,286
61217.224.0.0/13217.224.0.1 to 217.231.255.254217.231.255.255524,286
62217.232.0.0/13217.232.0.1 to 217.239.255.254217.239.255.255524,286
63217.240.0.0/13217.240.0.1 to 217.247.255.254217.247.255.255524,286
64217.248.0.0/13217.248.0.1 to 217.255.255.254217.255.255.255524,286

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.