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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.

Network51.136.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
51.136.0.0
Broadcast address
51.143.255.255
First usable
51.136.0.1
Last usable
51.143.255.254
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 33880000 · Integer 864550912 to 865075199
Reverse DNS zones
136.51.in-addr.arpa
137.51.in-addr.arpa
138.51.in-addr.arpa
139.51.in-addr.arpa
140.51.in-addr.arpa
141.51.in-addr.arpa
142.51.in-addr.arpa
143.51.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
Address00110011.10001000.00000000.0000000051.136.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network00110011.10001000.00000000.0000000051.136.0.0
Broadcast00110011.10001111.11111111.1111111151.143.255.255
Split into smaller subnets/20
/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)

51.136.0.0/13 makes 128 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
151.136.0.0/2051.136.0.1 to 51.136.15.25451.136.15.2554,094
251.136.16.0/2051.136.16.1 to 51.136.31.25451.136.31.2554,094
351.136.32.0/2051.136.32.1 to 51.136.47.25451.136.47.2554,094
451.136.48.0/2051.136.48.1 to 51.136.63.25451.136.63.2554,094
551.136.64.0/2051.136.64.1 to 51.136.79.25451.136.79.2554,094
651.136.80.0/2051.136.80.1 to 51.136.95.25451.136.95.2554,094
751.136.96.0/2051.136.96.1 to 51.136.111.25451.136.111.2554,094
851.136.112.0/2051.136.112.1 to 51.136.127.25451.136.127.2554,094
951.136.128.0/2051.136.128.1 to 51.136.143.25451.136.143.2554,094
1051.136.144.0/2051.136.144.1 to 51.136.159.25451.136.159.2554,094
1151.136.160.0/2051.136.160.1 to 51.136.175.25451.136.175.2554,094
1251.136.176.0/2051.136.176.1 to 51.136.191.25451.136.191.2554,094
1351.136.192.0/2051.136.192.1 to 51.136.207.25451.136.207.2554,094
1451.136.208.0/2051.136.208.1 to 51.136.223.25451.136.223.2554,094
1551.136.224.0/2051.136.224.1 to 51.136.239.25451.136.239.2554,094
1651.136.240.0/2051.136.240.1 to 51.136.255.25451.136.255.2554,094
1751.137.0.0/2051.137.0.1 to 51.137.15.25451.137.15.2554,094
1851.137.16.0/2051.137.16.1 to 51.137.31.25451.137.31.2554,094
1951.137.32.0/2051.137.32.1 to 51.137.47.25451.137.47.2554,094
2051.137.48.0/2051.137.48.1 to 51.137.63.25451.137.63.2554,094
2151.137.64.0/2051.137.64.1 to 51.137.79.25451.137.79.2554,094
2251.137.80.0/2051.137.80.1 to 51.137.95.25451.137.95.2554,094
2351.137.96.0/2051.137.96.1 to 51.137.111.25451.137.111.2554,094
2451.137.112.0/2051.137.112.1 to 51.137.127.25451.137.127.2554,094
2551.137.128.0/2051.137.128.1 to 51.137.143.25451.137.143.2554,094
2651.137.144.0/2051.137.144.1 to 51.137.159.25451.137.159.2554,094
2751.137.160.0/2051.137.160.1 to 51.137.175.25451.137.175.2554,094
2851.137.176.0/2051.137.176.1 to 51.137.191.25451.137.191.2554,094
2951.137.192.0/2051.137.192.1 to 51.137.207.25451.137.207.2554,094
3051.137.208.0/2051.137.208.1 to 51.137.223.25451.137.223.2554,094
3151.137.224.0/2051.137.224.1 to 51.137.239.25451.137.239.2554,094
3251.137.240.0/2051.137.240.1 to 51.137.255.25451.137.255.2554,094
3351.138.0.0/2051.138.0.1 to 51.138.15.25451.138.15.2554,094
3451.138.16.0/2051.138.16.1 to 51.138.31.25451.138.31.2554,094
3551.138.32.0/2051.138.32.1 to 51.138.47.25451.138.47.2554,094
3651.138.48.0/2051.138.48.1 to 51.138.63.25451.138.63.2554,094
3751.138.64.0/2051.138.64.1 to 51.138.79.25451.138.79.2554,094
3851.138.80.0/2051.138.80.1 to 51.138.95.25451.138.95.2554,094
3951.138.96.0/2051.138.96.1 to 51.138.111.25451.138.111.2554,094
4051.138.112.0/2051.138.112.1 to 51.138.127.25451.138.127.2554,094
4151.138.128.0/2051.138.128.1 to 51.138.143.25451.138.143.2554,094
4251.138.144.0/2051.138.144.1 to 51.138.159.25451.138.159.2554,094
4351.138.160.0/2051.138.160.1 to 51.138.175.25451.138.175.2554,094
4451.138.176.0/2051.138.176.1 to 51.138.191.25451.138.191.2554,094
4551.138.192.0/2051.138.192.1 to 51.138.207.25451.138.207.2554,094
4651.138.208.0/2051.138.208.1 to 51.138.223.25451.138.223.2554,094
4751.138.224.0/2051.138.224.1 to 51.138.239.25451.138.239.2554,094
4851.138.240.0/2051.138.240.1 to 51.138.255.25451.138.255.2554,094
4951.139.0.0/2051.139.0.1 to 51.139.15.25451.139.15.2554,094
5051.139.16.0/2051.139.16.1 to 51.139.31.25451.139.31.2554,094
5151.139.32.0/2051.139.32.1 to 51.139.47.25451.139.47.2554,094
5251.139.48.0/2051.139.48.1 to 51.139.63.25451.139.63.2554,094
5351.139.64.0/2051.139.64.1 to 51.139.79.25451.139.79.2554,094
5451.139.80.0/2051.139.80.1 to 51.139.95.25451.139.95.2554,094
5551.139.96.0/2051.139.96.1 to 51.139.111.25451.139.111.2554,094
5651.139.112.0/2051.139.112.1 to 51.139.127.25451.139.127.2554,094
5751.139.128.0/2051.139.128.1 to 51.139.143.25451.139.143.2554,094
5851.139.144.0/2051.139.144.1 to 51.139.159.25451.139.159.2554,094
5951.139.160.0/2051.139.160.1 to 51.139.175.25451.139.175.2554,094
6051.139.176.0/2051.139.176.1 to 51.139.191.25451.139.191.2554,094
6151.139.192.0/2051.139.192.1 to 51.139.207.25451.139.207.2554,094
6251.139.208.0/2051.139.208.1 to 51.139.223.25451.139.223.2554,094
6351.139.224.0/2051.139.224.1 to 51.139.239.25451.139.239.2554,094
6451.139.240.0/2051.139.240.1 to 51.139.255.25451.139.255.2554,094
6551.140.0.0/2051.140.0.1 to 51.140.15.25451.140.15.2554,094
6651.140.16.0/2051.140.16.1 to 51.140.31.25451.140.31.2554,094
6751.140.32.0/2051.140.32.1 to 51.140.47.25451.140.47.2554,094
6851.140.48.0/2051.140.48.1 to 51.140.63.25451.140.63.2554,094
6951.140.64.0/2051.140.64.1 to 51.140.79.25451.140.79.2554,094
7051.140.80.0/2051.140.80.1 to 51.140.95.25451.140.95.2554,094
7151.140.96.0/2051.140.96.1 to 51.140.111.25451.140.111.2554,094
7251.140.112.0/2051.140.112.1 to 51.140.127.25451.140.127.2554,094
7351.140.128.0/2051.140.128.1 to 51.140.143.25451.140.143.2554,094
7451.140.144.0/2051.140.144.1 to 51.140.159.25451.140.159.2554,094
7551.140.160.0/2051.140.160.1 to 51.140.175.25451.140.175.2554,094
7651.140.176.0/2051.140.176.1 to 51.140.191.25451.140.191.2554,094
7751.140.192.0/2051.140.192.1 to 51.140.207.25451.140.207.2554,094
7851.140.208.0/2051.140.208.1 to 51.140.223.25451.140.223.2554,094
7951.140.224.0/2051.140.224.1 to 51.140.239.25451.140.239.2554,094
8051.140.240.0/2051.140.240.1 to 51.140.255.25451.140.255.2554,094
8151.141.0.0/2051.141.0.1 to 51.141.15.25451.141.15.2554,094
8251.141.16.0/2051.141.16.1 to 51.141.31.25451.141.31.2554,094
8351.141.32.0/2051.141.32.1 to 51.141.47.25451.141.47.2554,094
8451.141.48.0/2051.141.48.1 to 51.141.63.25451.141.63.2554,094
8551.141.64.0/2051.141.64.1 to 51.141.79.25451.141.79.2554,094
8651.141.80.0/2051.141.80.1 to 51.141.95.25451.141.95.2554,094
8751.141.96.0/2051.141.96.1 to 51.141.111.25451.141.111.2554,094
8851.141.112.0/2051.141.112.1 to 51.141.127.25451.141.127.2554,094
8951.141.128.0/2051.141.128.1 to 51.141.143.25451.141.143.2554,094
9051.141.144.0/2051.141.144.1 to 51.141.159.25451.141.159.2554,094
9151.141.160.0/2051.141.160.1 to 51.141.175.25451.141.175.2554,094
9251.141.176.0/2051.141.176.1 to 51.141.191.25451.141.191.2554,094
9351.141.192.0/2051.141.192.1 to 51.141.207.25451.141.207.2554,094
9451.141.208.0/2051.141.208.1 to 51.141.223.25451.141.223.2554,094
9551.141.224.0/2051.141.224.1 to 51.141.239.25451.141.239.2554,094
9651.141.240.0/2051.141.240.1 to 51.141.255.25451.141.255.2554,094
9751.142.0.0/2051.142.0.1 to 51.142.15.25451.142.15.2554,094
9851.142.16.0/2051.142.16.1 to 51.142.31.25451.142.31.2554,094
9951.142.32.0/2051.142.32.1 to 51.142.47.25451.142.47.2554,094
10051.142.48.0/2051.142.48.1 to 51.142.63.25451.142.63.2554,094
10151.142.64.0/2051.142.64.1 to 51.142.79.25451.142.79.2554,094
10251.142.80.0/2051.142.80.1 to 51.142.95.25451.142.95.2554,094
10351.142.96.0/2051.142.96.1 to 51.142.111.25451.142.111.2554,094
10451.142.112.0/2051.142.112.1 to 51.142.127.25451.142.127.2554,094
10551.142.128.0/2051.142.128.1 to 51.142.143.25451.142.143.2554,094
10651.142.144.0/2051.142.144.1 to 51.142.159.25451.142.159.2554,094
10751.142.160.0/2051.142.160.1 to 51.142.175.25451.142.175.2554,094
10851.142.176.0/2051.142.176.1 to 51.142.191.25451.142.191.2554,094
10951.142.192.0/2051.142.192.1 to 51.142.207.25451.142.207.2554,094
11051.142.208.0/2051.142.208.1 to 51.142.223.25451.142.223.2554,094
11151.142.224.0/2051.142.224.1 to 51.142.239.25451.142.239.2554,094
11251.142.240.0/2051.142.240.1 to 51.142.255.25451.142.255.2554,094
11351.143.0.0/2051.143.0.1 to 51.143.15.25451.143.15.2554,094
11451.143.16.0/2051.143.16.1 to 51.143.31.25451.143.31.2554,094
11551.143.32.0/2051.143.32.1 to 51.143.47.25451.143.47.2554,094
11651.143.48.0/2051.143.48.1 to 51.143.63.25451.143.63.2554,094
11751.143.64.0/2051.143.64.1 to 51.143.79.25451.143.79.2554,094
11851.143.80.0/2051.143.80.1 to 51.143.95.25451.143.95.2554,094
11951.143.96.0/2051.143.96.1 to 51.143.111.25451.143.111.2554,094
12051.143.112.0/2051.143.112.1 to 51.143.127.25451.143.127.2554,094
12151.143.128.0/2051.143.128.1 to 51.143.143.25451.143.143.2554,094
12251.143.144.0/2051.143.144.1 to 51.143.159.25451.143.159.2554,094
12351.143.160.0/2051.143.160.1 to 51.143.175.25451.143.175.2554,094
12451.143.176.0/2051.143.176.1 to 51.143.191.25451.143.191.2554,094
12551.143.192.0/2051.143.192.1 to 51.143.207.25451.143.207.2554,094
12651.143.208.0/2051.143.208.1 to 51.143.223.25451.143.223.2554,094
12751.143.224.0/2051.143.224.1 to 51.143.239.25451.143.239.2554,094
12851.143.240.0/2051.143.240.1 to 51.143.255.25451.143.255.2554,094

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.