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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.

Network40.40.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
40.40.0.0
Broadcast address
40.47.255.255
First usable
40.40.0.1
Last usable
40.47.255.254
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 28280000 · Integer 673710080 to 674234367
Reverse DNS zones
40.40.in-addr.arpa
41.40.in-addr.arpa
42.40.in-addr.arpa
43.40.in-addr.arpa
44.40.in-addr.arpa
45.40.in-addr.arpa
46.40.in-addr.arpa
47.40.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
Address00101000.00101000.00000000.0000000040.40.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network00101000.00101000.00000000.0000000040.40.0.0
Broadcast00101000.00101111.11111111.1111111140.47.255.255
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)

40.40.0.0/13 makes 128 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
140.40.0.0/2040.40.0.1 to 40.40.15.25440.40.15.2554,094
240.40.16.0/2040.40.16.1 to 40.40.31.25440.40.31.2554,094
340.40.32.0/2040.40.32.1 to 40.40.47.25440.40.47.2554,094
440.40.48.0/2040.40.48.1 to 40.40.63.25440.40.63.2554,094
540.40.64.0/2040.40.64.1 to 40.40.79.25440.40.79.2554,094
640.40.80.0/2040.40.80.1 to 40.40.95.25440.40.95.2554,094
740.40.96.0/2040.40.96.1 to 40.40.111.25440.40.111.2554,094
840.40.112.0/2040.40.112.1 to 40.40.127.25440.40.127.2554,094
940.40.128.0/2040.40.128.1 to 40.40.143.25440.40.143.2554,094
1040.40.144.0/2040.40.144.1 to 40.40.159.25440.40.159.2554,094
1140.40.160.0/2040.40.160.1 to 40.40.175.25440.40.175.2554,094
1240.40.176.0/2040.40.176.1 to 40.40.191.25440.40.191.2554,094
1340.40.192.0/2040.40.192.1 to 40.40.207.25440.40.207.2554,094
1440.40.208.0/2040.40.208.1 to 40.40.223.25440.40.223.2554,094
1540.40.224.0/2040.40.224.1 to 40.40.239.25440.40.239.2554,094
1640.40.240.0/2040.40.240.1 to 40.40.255.25440.40.255.2554,094
1740.41.0.0/2040.41.0.1 to 40.41.15.25440.41.15.2554,094
1840.41.16.0/2040.41.16.1 to 40.41.31.25440.41.31.2554,094
1940.41.32.0/2040.41.32.1 to 40.41.47.25440.41.47.2554,094
2040.41.48.0/2040.41.48.1 to 40.41.63.25440.41.63.2554,094
2140.41.64.0/2040.41.64.1 to 40.41.79.25440.41.79.2554,094
2240.41.80.0/2040.41.80.1 to 40.41.95.25440.41.95.2554,094
2340.41.96.0/2040.41.96.1 to 40.41.111.25440.41.111.2554,094
2440.41.112.0/2040.41.112.1 to 40.41.127.25440.41.127.2554,094
2540.41.128.0/2040.41.128.1 to 40.41.143.25440.41.143.2554,094
2640.41.144.0/2040.41.144.1 to 40.41.159.25440.41.159.2554,094
2740.41.160.0/2040.41.160.1 to 40.41.175.25440.41.175.2554,094
2840.41.176.0/2040.41.176.1 to 40.41.191.25440.41.191.2554,094
2940.41.192.0/2040.41.192.1 to 40.41.207.25440.41.207.2554,094
3040.41.208.0/2040.41.208.1 to 40.41.223.25440.41.223.2554,094
3140.41.224.0/2040.41.224.1 to 40.41.239.25440.41.239.2554,094
3240.41.240.0/2040.41.240.1 to 40.41.255.25440.41.255.2554,094
3340.42.0.0/2040.42.0.1 to 40.42.15.25440.42.15.2554,094
3440.42.16.0/2040.42.16.1 to 40.42.31.25440.42.31.2554,094
3540.42.32.0/2040.42.32.1 to 40.42.47.25440.42.47.2554,094
3640.42.48.0/2040.42.48.1 to 40.42.63.25440.42.63.2554,094
3740.42.64.0/2040.42.64.1 to 40.42.79.25440.42.79.2554,094
3840.42.80.0/2040.42.80.1 to 40.42.95.25440.42.95.2554,094
3940.42.96.0/2040.42.96.1 to 40.42.111.25440.42.111.2554,094
4040.42.112.0/2040.42.112.1 to 40.42.127.25440.42.127.2554,094
4140.42.128.0/2040.42.128.1 to 40.42.143.25440.42.143.2554,094
4240.42.144.0/2040.42.144.1 to 40.42.159.25440.42.159.2554,094
4340.42.160.0/2040.42.160.1 to 40.42.175.25440.42.175.2554,094
4440.42.176.0/2040.42.176.1 to 40.42.191.25440.42.191.2554,094
4540.42.192.0/2040.42.192.1 to 40.42.207.25440.42.207.2554,094
4640.42.208.0/2040.42.208.1 to 40.42.223.25440.42.223.2554,094
4740.42.224.0/2040.42.224.1 to 40.42.239.25440.42.239.2554,094
4840.42.240.0/2040.42.240.1 to 40.42.255.25440.42.255.2554,094
4940.43.0.0/2040.43.0.1 to 40.43.15.25440.43.15.2554,094
5040.43.16.0/2040.43.16.1 to 40.43.31.25440.43.31.2554,094
5140.43.32.0/2040.43.32.1 to 40.43.47.25440.43.47.2554,094
5240.43.48.0/2040.43.48.1 to 40.43.63.25440.43.63.2554,094
5340.43.64.0/2040.43.64.1 to 40.43.79.25440.43.79.2554,094
5440.43.80.0/2040.43.80.1 to 40.43.95.25440.43.95.2554,094
5540.43.96.0/2040.43.96.1 to 40.43.111.25440.43.111.2554,094
5640.43.112.0/2040.43.112.1 to 40.43.127.25440.43.127.2554,094
5740.43.128.0/2040.43.128.1 to 40.43.143.25440.43.143.2554,094
5840.43.144.0/2040.43.144.1 to 40.43.159.25440.43.159.2554,094
5940.43.160.0/2040.43.160.1 to 40.43.175.25440.43.175.2554,094
6040.43.176.0/2040.43.176.1 to 40.43.191.25440.43.191.2554,094
6140.43.192.0/2040.43.192.1 to 40.43.207.25440.43.207.2554,094
6240.43.208.0/2040.43.208.1 to 40.43.223.25440.43.223.2554,094
6340.43.224.0/2040.43.224.1 to 40.43.239.25440.43.239.2554,094
6440.43.240.0/2040.43.240.1 to 40.43.255.25440.43.255.2554,094
6540.44.0.0/2040.44.0.1 to 40.44.15.25440.44.15.2554,094
6640.44.16.0/2040.44.16.1 to 40.44.31.25440.44.31.2554,094
6740.44.32.0/2040.44.32.1 to 40.44.47.25440.44.47.2554,094
6840.44.48.0/2040.44.48.1 to 40.44.63.25440.44.63.2554,094
6940.44.64.0/2040.44.64.1 to 40.44.79.25440.44.79.2554,094
7040.44.80.0/2040.44.80.1 to 40.44.95.25440.44.95.2554,094
7140.44.96.0/2040.44.96.1 to 40.44.111.25440.44.111.2554,094
7240.44.112.0/2040.44.112.1 to 40.44.127.25440.44.127.2554,094
7340.44.128.0/2040.44.128.1 to 40.44.143.25440.44.143.2554,094
7440.44.144.0/2040.44.144.1 to 40.44.159.25440.44.159.2554,094
7540.44.160.0/2040.44.160.1 to 40.44.175.25440.44.175.2554,094
7640.44.176.0/2040.44.176.1 to 40.44.191.25440.44.191.2554,094
7740.44.192.0/2040.44.192.1 to 40.44.207.25440.44.207.2554,094
7840.44.208.0/2040.44.208.1 to 40.44.223.25440.44.223.2554,094
7940.44.224.0/2040.44.224.1 to 40.44.239.25440.44.239.2554,094
8040.44.240.0/2040.44.240.1 to 40.44.255.25440.44.255.2554,094
8140.45.0.0/2040.45.0.1 to 40.45.15.25440.45.15.2554,094
8240.45.16.0/2040.45.16.1 to 40.45.31.25440.45.31.2554,094
8340.45.32.0/2040.45.32.1 to 40.45.47.25440.45.47.2554,094
8440.45.48.0/2040.45.48.1 to 40.45.63.25440.45.63.2554,094
8540.45.64.0/2040.45.64.1 to 40.45.79.25440.45.79.2554,094
8640.45.80.0/2040.45.80.1 to 40.45.95.25440.45.95.2554,094
8740.45.96.0/2040.45.96.1 to 40.45.111.25440.45.111.2554,094
8840.45.112.0/2040.45.112.1 to 40.45.127.25440.45.127.2554,094
8940.45.128.0/2040.45.128.1 to 40.45.143.25440.45.143.2554,094
9040.45.144.0/2040.45.144.1 to 40.45.159.25440.45.159.2554,094
9140.45.160.0/2040.45.160.1 to 40.45.175.25440.45.175.2554,094
9240.45.176.0/2040.45.176.1 to 40.45.191.25440.45.191.2554,094
9340.45.192.0/2040.45.192.1 to 40.45.207.25440.45.207.2554,094
9440.45.208.0/2040.45.208.1 to 40.45.223.25440.45.223.2554,094
9540.45.224.0/2040.45.224.1 to 40.45.239.25440.45.239.2554,094
9640.45.240.0/2040.45.240.1 to 40.45.255.25440.45.255.2554,094
9740.46.0.0/2040.46.0.1 to 40.46.15.25440.46.15.2554,094
9840.46.16.0/2040.46.16.1 to 40.46.31.25440.46.31.2554,094
9940.46.32.0/2040.46.32.1 to 40.46.47.25440.46.47.2554,094
10040.46.48.0/2040.46.48.1 to 40.46.63.25440.46.63.2554,094
10140.46.64.0/2040.46.64.1 to 40.46.79.25440.46.79.2554,094
10240.46.80.0/2040.46.80.1 to 40.46.95.25440.46.95.2554,094
10340.46.96.0/2040.46.96.1 to 40.46.111.25440.46.111.2554,094
10440.46.112.0/2040.46.112.1 to 40.46.127.25440.46.127.2554,094
10540.46.128.0/2040.46.128.1 to 40.46.143.25440.46.143.2554,094
10640.46.144.0/2040.46.144.1 to 40.46.159.25440.46.159.2554,094
10740.46.160.0/2040.46.160.1 to 40.46.175.25440.46.175.2554,094
10840.46.176.0/2040.46.176.1 to 40.46.191.25440.46.191.2554,094
10940.46.192.0/2040.46.192.1 to 40.46.207.25440.46.207.2554,094
11040.46.208.0/2040.46.208.1 to 40.46.223.25440.46.223.2554,094
11140.46.224.0/2040.46.224.1 to 40.46.239.25440.46.239.2554,094
11240.46.240.0/2040.46.240.1 to 40.46.255.25440.46.255.2554,094
11340.47.0.0/2040.47.0.1 to 40.47.15.25440.47.15.2554,094
11440.47.16.0/2040.47.16.1 to 40.47.31.25440.47.31.2554,094
11540.47.32.0/2040.47.32.1 to 40.47.47.25440.47.47.2554,094
11640.47.48.0/2040.47.48.1 to 40.47.63.25440.47.63.2554,094
11740.47.64.0/2040.47.64.1 to 40.47.79.25440.47.79.2554,094
11840.47.80.0/2040.47.80.1 to 40.47.95.25440.47.95.2554,094
11940.47.96.0/2040.47.96.1 to 40.47.111.25440.47.111.2554,094
12040.47.112.0/2040.47.112.1 to 40.47.127.25440.47.127.2554,094
12140.47.128.0/2040.47.128.1 to 40.47.143.25440.47.143.2554,094
12240.47.144.0/2040.47.144.1 to 40.47.159.25440.47.159.2554,094
12340.47.160.0/2040.47.160.1 to 40.47.175.25440.47.175.2554,094
12440.47.176.0/2040.47.176.1 to 40.47.191.25440.47.191.2554,094
12540.47.192.0/2040.47.192.1 to 40.47.207.25440.47.207.2554,094
12640.47.208.0/2040.47.208.1 to 40.47.223.25440.47.223.2554,094
12740.47.224.0/2040.47.224.1 to 40.47.239.25440.47.239.2554,094
12840.47.240.0/2040.47.240.1 to 40.47.255.25440.47.255.2554,094

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.