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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.

Network255.64.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
255.64.0.0
Broadcast address
255.71.255.255
First usable
255.64.0.1
Last usable
255.71.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FF400000 · Integer 4282384384 to 4282908671
Reverse DNS zones
64.255.in-addr.arpa
65.255.in-addr.arpa
66.255.in-addr.arpa
67.255.in-addr.arpa
68.255.in-addr.arpa
69.255.in-addr.arpa
70.255.in-addr.arpa
71.255.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
Address11111111.01000000.00000000.00000000255.64.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network11111111.01000000.00000000.00000000255.64.0.0
Broadcast11111111.01000111.11111111.11111111255.71.255.255
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)

255.64.0.0/13 makes 64 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1255.64.0.0/19255.64.0.1 to 255.64.31.254255.64.31.2558,190
2255.64.32.0/19255.64.32.1 to 255.64.63.254255.64.63.2558,190
3255.64.64.0/19255.64.64.1 to 255.64.95.254255.64.95.2558,190
4255.64.96.0/19255.64.96.1 to 255.64.127.254255.64.127.2558,190
5255.64.128.0/19255.64.128.1 to 255.64.159.254255.64.159.2558,190
6255.64.160.0/19255.64.160.1 to 255.64.191.254255.64.191.2558,190
7255.64.192.0/19255.64.192.1 to 255.64.223.254255.64.223.2558,190
8255.64.224.0/19255.64.224.1 to 255.64.255.254255.64.255.2558,190
9255.65.0.0/19255.65.0.1 to 255.65.31.254255.65.31.2558,190
10255.65.32.0/19255.65.32.1 to 255.65.63.254255.65.63.2558,190
11255.65.64.0/19255.65.64.1 to 255.65.95.254255.65.95.2558,190
12255.65.96.0/19255.65.96.1 to 255.65.127.254255.65.127.2558,190
13255.65.128.0/19255.65.128.1 to 255.65.159.254255.65.159.2558,190
14255.65.160.0/19255.65.160.1 to 255.65.191.254255.65.191.2558,190
15255.65.192.0/19255.65.192.1 to 255.65.223.254255.65.223.2558,190
16255.65.224.0/19255.65.224.1 to 255.65.255.254255.65.255.2558,190
17255.66.0.0/19255.66.0.1 to 255.66.31.254255.66.31.2558,190
18255.66.32.0/19255.66.32.1 to 255.66.63.254255.66.63.2558,190
19255.66.64.0/19255.66.64.1 to 255.66.95.254255.66.95.2558,190
20255.66.96.0/19255.66.96.1 to 255.66.127.254255.66.127.2558,190
21255.66.128.0/19255.66.128.1 to 255.66.159.254255.66.159.2558,190
22255.66.160.0/19255.66.160.1 to 255.66.191.254255.66.191.2558,190
23255.66.192.0/19255.66.192.1 to 255.66.223.254255.66.223.2558,190
24255.66.224.0/19255.66.224.1 to 255.66.255.254255.66.255.2558,190
25255.67.0.0/19255.67.0.1 to 255.67.31.254255.67.31.2558,190
26255.67.32.0/19255.67.32.1 to 255.67.63.254255.67.63.2558,190
27255.67.64.0/19255.67.64.1 to 255.67.95.254255.67.95.2558,190
28255.67.96.0/19255.67.96.1 to 255.67.127.254255.67.127.2558,190
29255.67.128.0/19255.67.128.1 to 255.67.159.254255.67.159.2558,190
30255.67.160.0/19255.67.160.1 to 255.67.191.254255.67.191.2558,190
31255.67.192.0/19255.67.192.1 to 255.67.223.254255.67.223.2558,190
32255.67.224.0/19255.67.224.1 to 255.67.255.254255.67.255.2558,190
33255.68.0.0/19255.68.0.1 to 255.68.31.254255.68.31.2558,190
34255.68.32.0/19255.68.32.1 to 255.68.63.254255.68.63.2558,190
35255.68.64.0/19255.68.64.1 to 255.68.95.254255.68.95.2558,190
36255.68.96.0/19255.68.96.1 to 255.68.127.254255.68.127.2558,190
37255.68.128.0/19255.68.128.1 to 255.68.159.254255.68.159.2558,190
38255.68.160.0/19255.68.160.1 to 255.68.191.254255.68.191.2558,190
39255.68.192.0/19255.68.192.1 to 255.68.223.254255.68.223.2558,190
40255.68.224.0/19255.68.224.1 to 255.68.255.254255.68.255.2558,190
41255.69.0.0/19255.69.0.1 to 255.69.31.254255.69.31.2558,190
42255.69.32.0/19255.69.32.1 to 255.69.63.254255.69.63.2558,190
43255.69.64.0/19255.69.64.1 to 255.69.95.254255.69.95.2558,190
44255.69.96.0/19255.69.96.1 to 255.69.127.254255.69.127.2558,190
45255.69.128.0/19255.69.128.1 to 255.69.159.254255.69.159.2558,190
46255.69.160.0/19255.69.160.1 to 255.69.191.254255.69.191.2558,190
47255.69.192.0/19255.69.192.1 to 255.69.223.254255.69.223.2558,190
48255.69.224.0/19255.69.224.1 to 255.69.255.254255.69.255.2558,190
49255.70.0.0/19255.70.0.1 to 255.70.31.254255.70.31.2558,190
50255.70.32.0/19255.70.32.1 to 255.70.63.254255.70.63.2558,190
51255.70.64.0/19255.70.64.1 to 255.70.95.254255.70.95.2558,190
52255.70.96.0/19255.70.96.1 to 255.70.127.254255.70.127.2558,190
53255.70.128.0/19255.70.128.1 to 255.70.159.254255.70.159.2558,190
54255.70.160.0/19255.70.160.1 to 255.70.191.254255.70.191.2558,190
55255.70.192.0/19255.70.192.1 to 255.70.223.254255.70.223.2558,190
56255.70.224.0/19255.70.224.1 to 255.70.255.254255.70.255.2558,190
57255.71.0.0/19255.71.0.1 to 255.71.31.254255.71.31.2558,190
58255.71.32.0/19255.71.32.1 to 255.71.63.254255.71.63.2558,190
59255.71.64.0/19255.71.64.1 to 255.71.95.254255.71.95.2558,190
60255.71.96.0/19255.71.96.1 to 255.71.127.254255.71.127.2558,190
61255.71.128.0/19255.71.128.1 to 255.71.159.254255.71.159.2558,190
62255.71.160.0/19255.71.160.1 to 255.71.191.254255.71.191.2558,190
63255.71.192.0/19255.71.192.1 to 255.71.223.254255.71.223.2558,190
64255.71.224.0/19255.71.224.1 to 255.71.255.254255.71.255.2558,190

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.