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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.

Network55.64.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
55.64.0.0
Broadcast address
55.71.255.255
First usable
55.64.0.1
Last usable
55.71.255.254
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
A (default /8)
As numbers
Hex 37400000 · Integer 926941184 to 927465471
Reverse DNS zones
64.55.in-addr.arpa
65.55.in-addr.arpa
66.55.in-addr.arpa
67.55.in-addr.arpa
68.55.in-addr.arpa
69.55.in-addr.arpa
70.55.in-addr.arpa
71.55.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
Address00110111.01000000.00000000.0000000055.64.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network00110111.01000000.00000000.0000000055.64.0.0
Broadcast00110111.01000111.11111111.1111111155.71.255.255
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)

55.64.0.0/13 makes 64 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
155.64.0.0/1955.64.0.1 to 55.64.31.25455.64.31.2558,190
255.64.32.0/1955.64.32.1 to 55.64.63.25455.64.63.2558,190
355.64.64.0/1955.64.64.1 to 55.64.95.25455.64.95.2558,190
455.64.96.0/1955.64.96.1 to 55.64.127.25455.64.127.2558,190
555.64.128.0/1955.64.128.1 to 55.64.159.25455.64.159.2558,190
655.64.160.0/1955.64.160.1 to 55.64.191.25455.64.191.2558,190
755.64.192.0/1955.64.192.1 to 55.64.223.25455.64.223.2558,190
855.64.224.0/1955.64.224.1 to 55.64.255.25455.64.255.2558,190
955.65.0.0/1955.65.0.1 to 55.65.31.25455.65.31.2558,190
1055.65.32.0/1955.65.32.1 to 55.65.63.25455.65.63.2558,190
1155.65.64.0/1955.65.64.1 to 55.65.95.25455.65.95.2558,190
1255.65.96.0/1955.65.96.1 to 55.65.127.25455.65.127.2558,190
1355.65.128.0/1955.65.128.1 to 55.65.159.25455.65.159.2558,190
1455.65.160.0/1955.65.160.1 to 55.65.191.25455.65.191.2558,190
1555.65.192.0/1955.65.192.1 to 55.65.223.25455.65.223.2558,190
1655.65.224.0/1955.65.224.1 to 55.65.255.25455.65.255.2558,190
1755.66.0.0/1955.66.0.1 to 55.66.31.25455.66.31.2558,190
1855.66.32.0/1955.66.32.1 to 55.66.63.25455.66.63.2558,190
1955.66.64.0/1955.66.64.1 to 55.66.95.25455.66.95.2558,190
2055.66.96.0/1955.66.96.1 to 55.66.127.25455.66.127.2558,190
2155.66.128.0/1955.66.128.1 to 55.66.159.25455.66.159.2558,190
2255.66.160.0/1955.66.160.1 to 55.66.191.25455.66.191.2558,190
2355.66.192.0/1955.66.192.1 to 55.66.223.25455.66.223.2558,190
2455.66.224.0/1955.66.224.1 to 55.66.255.25455.66.255.2558,190
2555.67.0.0/1955.67.0.1 to 55.67.31.25455.67.31.2558,190
2655.67.32.0/1955.67.32.1 to 55.67.63.25455.67.63.2558,190
2755.67.64.0/1955.67.64.1 to 55.67.95.25455.67.95.2558,190
2855.67.96.0/1955.67.96.1 to 55.67.127.25455.67.127.2558,190
2955.67.128.0/1955.67.128.1 to 55.67.159.25455.67.159.2558,190
3055.67.160.0/1955.67.160.1 to 55.67.191.25455.67.191.2558,190
3155.67.192.0/1955.67.192.1 to 55.67.223.25455.67.223.2558,190
3255.67.224.0/1955.67.224.1 to 55.67.255.25455.67.255.2558,190
3355.68.0.0/1955.68.0.1 to 55.68.31.25455.68.31.2558,190
3455.68.32.0/1955.68.32.1 to 55.68.63.25455.68.63.2558,190
3555.68.64.0/1955.68.64.1 to 55.68.95.25455.68.95.2558,190
3655.68.96.0/1955.68.96.1 to 55.68.127.25455.68.127.2558,190
3755.68.128.0/1955.68.128.1 to 55.68.159.25455.68.159.2558,190
3855.68.160.0/1955.68.160.1 to 55.68.191.25455.68.191.2558,190
3955.68.192.0/1955.68.192.1 to 55.68.223.25455.68.223.2558,190
4055.68.224.0/1955.68.224.1 to 55.68.255.25455.68.255.2558,190
4155.69.0.0/1955.69.0.1 to 55.69.31.25455.69.31.2558,190
4255.69.32.0/1955.69.32.1 to 55.69.63.25455.69.63.2558,190
4355.69.64.0/1955.69.64.1 to 55.69.95.25455.69.95.2558,190
4455.69.96.0/1955.69.96.1 to 55.69.127.25455.69.127.2558,190
4555.69.128.0/1955.69.128.1 to 55.69.159.25455.69.159.2558,190
4655.69.160.0/1955.69.160.1 to 55.69.191.25455.69.191.2558,190
4755.69.192.0/1955.69.192.1 to 55.69.223.25455.69.223.2558,190
4855.69.224.0/1955.69.224.1 to 55.69.255.25455.69.255.2558,190
4955.70.0.0/1955.70.0.1 to 55.70.31.25455.70.31.2558,190
5055.70.32.0/1955.70.32.1 to 55.70.63.25455.70.63.2558,190
5155.70.64.0/1955.70.64.1 to 55.70.95.25455.70.95.2558,190
5255.70.96.0/1955.70.96.1 to 55.70.127.25455.70.127.2558,190
5355.70.128.0/1955.70.128.1 to 55.70.159.25455.70.159.2558,190
5455.70.160.0/1955.70.160.1 to 55.70.191.25455.70.191.2558,190
5555.70.192.0/1955.70.192.1 to 55.70.223.25455.70.223.2558,190
5655.70.224.0/1955.70.224.1 to 55.70.255.25455.70.255.2558,190
5755.71.0.0/1955.71.0.1 to 55.71.31.25455.71.31.2558,190
5855.71.32.0/1955.71.32.1 to 55.71.63.25455.71.63.2558,190
5955.71.64.0/1955.71.64.1 to 55.71.95.25455.71.95.2558,190
6055.71.96.0/1955.71.96.1 to 55.71.127.25455.71.127.2558,190
6155.71.128.0/1955.71.128.1 to 55.71.159.25455.71.159.2558,190
6255.71.160.0/1955.71.160.1 to 55.71.191.25455.71.191.2558,190
6355.71.192.0/1955.71.192.1 to 55.71.223.25455.71.223.2558,190
6455.71.224.0/1955.71.224.1 to 55.71.255.25455.71.255.2558,190

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.