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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.

Network216.64.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
216.64.0.0
Broadcast address
216.71.255.255
First usable
216.64.0.1
Last usable
216.71.255.254
Usable hosts
524,286 (524,288 less the network and broadcast addresses)
Subnet mask
255.248.0.0
Wildcard mask
0.7.255.255 (Cisco ACLs, OSPF)
Prefix length
/13
Type
Public public
Old class
C (default /24)
As numbers
Hex D8400000 · Integer 3628072960 to 3628597247
Reverse DNS zones
64.216.in-addr.arpa
65.216.in-addr.arpa
66.216.in-addr.arpa
67.216.in-addr.arpa
68.216.in-addr.arpa
69.216.in-addr.arpa
70.216.in-addr.arpa
71.216.in-addr.arpa
/13 is not on a 8-bit boundary, so it takes 8 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11011000.01000000.00000000.00000000216.64.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network11011000.01000000.00000000.00000000216.64.0.0
Broadcast11011000.01000111.11111111.11111111216.71.255.255
Split into smaller subnets/19
/14 (2)/15 (4)/16 (8)/17 (16)/18 (32)/19 (64)/20 (128)/21 (256)/22 (512)/23 (1,024)/24 (2,048)/25 (4,096)

216.64.0.0/13 makes 64 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1216.64.0.0/19216.64.0.1 to 216.64.31.254216.64.31.2558,190
2216.64.32.0/19216.64.32.1 to 216.64.63.254216.64.63.2558,190
3216.64.64.0/19216.64.64.1 to 216.64.95.254216.64.95.2558,190
4216.64.96.0/19216.64.96.1 to 216.64.127.254216.64.127.2558,190
5216.64.128.0/19216.64.128.1 to 216.64.159.254216.64.159.2558,190
6216.64.160.0/19216.64.160.1 to 216.64.191.254216.64.191.2558,190
7216.64.192.0/19216.64.192.1 to 216.64.223.254216.64.223.2558,190
8216.64.224.0/19216.64.224.1 to 216.64.255.254216.64.255.2558,190
9216.65.0.0/19216.65.0.1 to 216.65.31.254216.65.31.2558,190
10216.65.32.0/19216.65.32.1 to 216.65.63.254216.65.63.2558,190
11216.65.64.0/19216.65.64.1 to 216.65.95.254216.65.95.2558,190
12216.65.96.0/19216.65.96.1 to 216.65.127.254216.65.127.2558,190
13216.65.128.0/19216.65.128.1 to 216.65.159.254216.65.159.2558,190
14216.65.160.0/19216.65.160.1 to 216.65.191.254216.65.191.2558,190
15216.65.192.0/19216.65.192.1 to 216.65.223.254216.65.223.2558,190
16216.65.224.0/19216.65.224.1 to 216.65.255.254216.65.255.2558,190
17216.66.0.0/19216.66.0.1 to 216.66.31.254216.66.31.2558,190
18216.66.32.0/19216.66.32.1 to 216.66.63.254216.66.63.2558,190
19216.66.64.0/19216.66.64.1 to 216.66.95.254216.66.95.2558,190
20216.66.96.0/19216.66.96.1 to 216.66.127.254216.66.127.2558,190
21216.66.128.0/19216.66.128.1 to 216.66.159.254216.66.159.2558,190
22216.66.160.0/19216.66.160.1 to 216.66.191.254216.66.191.2558,190
23216.66.192.0/19216.66.192.1 to 216.66.223.254216.66.223.2558,190
24216.66.224.0/19216.66.224.1 to 216.66.255.254216.66.255.2558,190
25216.67.0.0/19216.67.0.1 to 216.67.31.254216.67.31.2558,190
26216.67.32.0/19216.67.32.1 to 216.67.63.254216.67.63.2558,190
27216.67.64.0/19216.67.64.1 to 216.67.95.254216.67.95.2558,190
28216.67.96.0/19216.67.96.1 to 216.67.127.254216.67.127.2558,190
29216.67.128.0/19216.67.128.1 to 216.67.159.254216.67.159.2558,190
30216.67.160.0/19216.67.160.1 to 216.67.191.254216.67.191.2558,190
31216.67.192.0/19216.67.192.1 to 216.67.223.254216.67.223.2558,190
32216.67.224.0/19216.67.224.1 to 216.67.255.254216.67.255.2558,190
33216.68.0.0/19216.68.0.1 to 216.68.31.254216.68.31.2558,190
34216.68.32.0/19216.68.32.1 to 216.68.63.254216.68.63.2558,190
35216.68.64.0/19216.68.64.1 to 216.68.95.254216.68.95.2558,190
36216.68.96.0/19216.68.96.1 to 216.68.127.254216.68.127.2558,190
37216.68.128.0/19216.68.128.1 to 216.68.159.254216.68.159.2558,190
38216.68.160.0/19216.68.160.1 to 216.68.191.254216.68.191.2558,190
39216.68.192.0/19216.68.192.1 to 216.68.223.254216.68.223.2558,190
40216.68.224.0/19216.68.224.1 to 216.68.255.254216.68.255.2558,190
41216.69.0.0/19216.69.0.1 to 216.69.31.254216.69.31.2558,190
42216.69.32.0/19216.69.32.1 to 216.69.63.254216.69.63.2558,190
43216.69.64.0/19216.69.64.1 to 216.69.95.254216.69.95.2558,190
44216.69.96.0/19216.69.96.1 to 216.69.127.254216.69.127.2558,190
45216.69.128.0/19216.69.128.1 to 216.69.159.254216.69.159.2558,190
46216.69.160.0/19216.69.160.1 to 216.69.191.254216.69.191.2558,190
47216.69.192.0/19216.69.192.1 to 216.69.223.254216.69.223.2558,190
48216.69.224.0/19216.69.224.1 to 216.69.255.254216.69.255.2558,190
49216.70.0.0/19216.70.0.1 to 216.70.31.254216.70.31.2558,190
50216.70.32.0/19216.70.32.1 to 216.70.63.254216.70.63.2558,190
51216.70.64.0/19216.70.64.1 to 216.70.95.254216.70.95.2558,190
52216.70.96.0/19216.70.96.1 to 216.70.127.254216.70.127.2558,190
53216.70.128.0/19216.70.128.1 to 216.70.159.254216.70.159.2558,190
54216.70.160.0/19216.70.160.1 to 216.70.191.254216.70.191.2558,190
55216.70.192.0/19216.70.192.1 to 216.70.223.254216.70.223.2558,190
56216.70.224.0/19216.70.224.1 to 216.70.255.254216.70.255.2558,190
57216.71.0.0/19216.71.0.1 to 216.71.31.254216.71.31.2558,190
58216.71.32.0/19216.71.32.1 to 216.71.63.254216.71.63.2558,190
59216.71.64.0/19216.71.64.1 to 216.71.95.254216.71.95.2558,190
60216.71.96.0/19216.71.96.1 to 216.71.127.254216.71.127.2558,190
61216.71.128.0/19216.71.128.1 to 216.71.159.254216.71.159.2558,190
62216.71.160.0/19216.71.160.1 to 216.71.191.254216.71.191.2558,190
63216.71.192.0/19216.71.192.1 to 216.71.223.254216.71.223.2558,190
64216.71.224.0/19216.71.224.1 to 216.71.255.254216.71.255.2558,190

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.