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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.

Network40.0.0.0/5
Usable hosts134,217,726
Subnet mask248.0.0.0
Addresses134,217,728
Network address
40.0.0.0
Broadcast address
47.255.255.255
First usable
40.0.0.1
Last usable
47.255.255.254
Usable hosts
134,217,726 (134,217,728 less the network and broadcast addresses)
Subnet mask
248.0.0.0
Wildcard mask
7.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/5
Type
Public public
Old class
A (default /8)
As numbers
Hex 28000000 · Integer 671088640 to 805306367
Reverse DNS zones
40.in-addr.arpa
41.in-addr.arpa
42.in-addr.arpa
43.in-addr.arpa
44.in-addr.arpa
45.in-addr.arpa
46.in-addr.arpa
47.in-addr.arpa
/5 is not on a 8-bit boundary, so it takes 8 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00101000.00000000.00000000.0000000040.0.0.0
Subnet mask11111000.00000000.00000000.00000000248.0.0.0
Network00101000.00000000.00000000.0000000040.0.0.0
Broadcast00101111.11111111.11111111.1111111147.255.255.255
Split into smaller subnets/12
/6 (2)/7 (4)/8 (8)/9 (16)/10 (32)/11 (64)/12 (128)/13 (256)/14 (512)/15 (1,024)/16 (2,048)/17 (4,096)

40.0.0.0/5 makes 128 subnets of /12.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
140.0.0.0/1240.0.0.1 to 40.15.255.25440.15.255.2551,048,574
240.16.0.0/1240.16.0.1 to 40.31.255.25440.31.255.2551,048,574
340.32.0.0/1240.32.0.1 to 40.47.255.25440.47.255.2551,048,574
440.48.0.0/1240.48.0.1 to 40.63.255.25440.63.255.2551,048,574
540.64.0.0/1240.64.0.1 to 40.79.255.25440.79.255.2551,048,574
640.80.0.0/1240.80.0.1 to 40.95.255.25440.95.255.2551,048,574
740.96.0.0/1240.96.0.1 to 40.111.255.25440.111.255.2551,048,574
840.112.0.0/1240.112.0.1 to 40.127.255.25440.127.255.2551,048,574
940.128.0.0/1240.128.0.1 to 40.143.255.25440.143.255.2551,048,574
1040.144.0.0/1240.144.0.1 to 40.159.255.25440.159.255.2551,048,574
1140.160.0.0/1240.160.0.1 to 40.175.255.25440.175.255.2551,048,574
1240.176.0.0/1240.176.0.1 to 40.191.255.25440.191.255.2551,048,574
1340.192.0.0/1240.192.0.1 to 40.207.255.25440.207.255.2551,048,574
1440.208.0.0/1240.208.0.1 to 40.223.255.25440.223.255.2551,048,574
1540.224.0.0/1240.224.0.1 to 40.239.255.25440.239.255.2551,048,574
1640.240.0.0/1240.240.0.1 to 40.255.255.25440.255.255.2551,048,574
1741.0.0.0/1241.0.0.1 to 41.15.255.25441.15.255.2551,048,574
1841.16.0.0/1241.16.0.1 to 41.31.255.25441.31.255.2551,048,574
1941.32.0.0/1241.32.0.1 to 41.47.255.25441.47.255.2551,048,574
2041.48.0.0/1241.48.0.1 to 41.63.255.25441.63.255.2551,048,574
2141.64.0.0/1241.64.0.1 to 41.79.255.25441.79.255.2551,048,574
2241.80.0.0/1241.80.0.1 to 41.95.255.25441.95.255.2551,048,574
2341.96.0.0/1241.96.0.1 to 41.111.255.25441.111.255.2551,048,574
2441.112.0.0/1241.112.0.1 to 41.127.255.25441.127.255.2551,048,574
2541.128.0.0/1241.128.0.1 to 41.143.255.25441.143.255.2551,048,574
2641.144.0.0/1241.144.0.1 to 41.159.255.25441.159.255.2551,048,574
2741.160.0.0/1241.160.0.1 to 41.175.255.25441.175.255.2551,048,574
2841.176.0.0/1241.176.0.1 to 41.191.255.25441.191.255.2551,048,574
2941.192.0.0/1241.192.0.1 to 41.207.255.25441.207.255.2551,048,574
3041.208.0.0/1241.208.0.1 to 41.223.255.25441.223.255.2551,048,574
3141.224.0.0/1241.224.0.1 to 41.239.255.25441.239.255.2551,048,574
3241.240.0.0/1241.240.0.1 to 41.255.255.25441.255.255.2551,048,574
3342.0.0.0/1242.0.0.1 to 42.15.255.25442.15.255.2551,048,574
3442.16.0.0/1242.16.0.1 to 42.31.255.25442.31.255.2551,048,574
3542.32.0.0/1242.32.0.1 to 42.47.255.25442.47.255.2551,048,574
3642.48.0.0/1242.48.0.1 to 42.63.255.25442.63.255.2551,048,574
3742.64.0.0/1242.64.0.1 to 42.79.255.25442.79.255.2551,048,574
3842.80.0.0/1242.80.0.1 to 42.95.255.25442.95.255.2551,048,574
3942.96.0.0/1242.96.0.1 to 42.111.255.25442.111.255.2551,048,574
4042.112.0.0/1242.112.0.1 to 42.127.255.25442.127.255.2551,048,574
4142.128.0.0/1242.128.0.1 to 42.143.255.25442.143.255.2551,048,574
4242.144.0.0/1242.144.0.1 to 42.159.255.25442.159.255.2551,048,574
4342.160.0.0/1242.160.0.1 to 42.175.255.25442.175.255.2551,048,574
4442.176.0.0/1242.176.0.1 to 42.191.255.25442.191.255.2551,048,574
4542.192.0.0/1242.192.0.1 to 42.207.255.25442.207.255.2551,048,574
4642.208.0.0/1242.208.0.1 to 42.223.255.25442.223.255.2551,048,574
4742.224.0.0/1242.224.0.1 to 42.239.255.25442.239.255.2551,048,574
4842.240.0.0/1242.240.0.1 to 42.255.255.25442.255.255.2551,048,574
4943.0.0.0/1243.0.0.1 to 43.15.255.25443.15.255.2551,048,574
5043.16.0.0/1243.16.0.1 to 43.31.255.25443.31.255.2551,048,574
5143.32.0.0/1243.32.0.1 to 43.47.255.25443.47.255.2551,048,574
5243.48.0.0/1243.48.0.1 to 43.63.255.25443.63.255.2551,048,574
5343.64.0.0/1243.64.0.1 to 43.79.255.25443.79.255.2551,048,574
5443.80.0.0/1243.80.0.1 to 43.95.255.25443.95.255.2551,048,574
5543.96.0.0/1243.96.0.1 to 43.111.255.25443.111.255.2551,048,574
5643.112.0.0/1243.112.0.1 to 43.127.255.25443.127.255.2551,048,574
5743.128.0.0/1243.128.0.1 to 43.143.255.25443.143.255.2551,048,574
5843.144.0.0/1243.144.0.1 to 43.159.255.25443.159.255.2551,048,574
5943.160.0.0/1243.160.0.1 to 43.175.255.25443.175.255.2551,048,574
6043.176.0.0/1243.176.0.1 to 43.191.255.25443.191.255.2551,048,574
6143.192.0.0/1243.192.0.1 to 43.207.255.25443.207.255.2551,048,574
6243.208.0.0/1243.208.0.1 to 43.223.255.25443.223.255.2551,048,574
6343.224.0.0/1243.224.0.1 to 43.239.255.25443.239.255.2551,048,574
6443.240.0.0/1243.240.0.1 to 43.255.255.25443.255.255.2551,048,574
6544.0.0.0/1244.0.0.1 to 44.15.255.25444.15.255.2551,048,574
6644.16.0.0/1244.16.0.1 to 44.31.255.25444.31.255.2551,048,574
6744.32.0.0/1244.32.0.1 to 44.47.255.25444.47.255.2551,048,574
6844.48.0.0/1244.48.0.1 to 44.63.255.25444.63.255.2551,048,574
6944.64.0.0/1244.64.0.1 to 44.79.255.25444.79.255.2551,048,574
7044.80.0.0/1244.80.0.1 to 44.95.255.25444.95.255.2551,048,574
7144.96.0.0/1244.96.0.1 to 44.111.255.25444.111.255.2551,048,574
7244.112.0.0/1244.112.0.1 to 44.127.255.25444.127.255.2551,048,574
7344.128.0.0/1244.128.0.1 to 44.143.255.25444.143.255.2551,048,574
7444.144.0.0/1244.144.0.1 to 44.159.255.25444.159.255.2551,048,574
7544.160.0.0/1244.160.0.1 to 44.175.255.25444.175.255.2551,048,574
7644.176.0.0/1244.176.0.1 to 44.191.255.25444.191.255.2551,048,574
7744.192.0.0/1244.192.0.1 to 44.207.255.25444.207.255.2551,048,574
7844.208.0.0/1244.208.0.1 to 44.223.255.25444.223.255.2551,048,574
7944.224.0.0/1244.224.0.1 to 44.239.255.25444.239.255.2551,048,574
8044.240.0.0/1244.240.0.1 to 44.255.255.25444.255.255.2551,048,574
8145.0.0.0/1245.0.0.1 to 45.15.255.25445.15.255.2551,048,574
8245.16.0.0/1245.16.0.1 to 45.31.255.25445.31.255.2551,048,574
8345.32.0.0/1245.32.0.1 to 45.47.255.25445.47.255.2551,048,574
8445.48.0.0/1245.48.0.1 to 45.63.255.25445.63.255.2551,048,574
8545.64.0.0/1245.64.0.1 to 45.79.255.25445.79.255.2551,048,574
8645.80.0.0/1245.80.0.1 to 45.95.255.25445.95.255.2551,048,574
8745.96.0.0/1245.96.0.1 to 45.111.255.25445.111.255.2551,048,574
8845.112.0.0/1245.112.0.1 to 45.127.255.25445.127.255.2551,048,574
8945.128.0.0/1245.128.0.1 to 45.143.255.25445.143.255.2551,048,574
9045.144.0.0/1245.144.0.1 to 45.159.255.25445.159.255.2551,048,574
9145.160.0.0/1245.160.0.1 to 45.175.255.25445.175.255.2551,048,574
9245.176.0.0/1245.176.0.1 to 45.191.255.25445.191.255.2551,048,574
9345.192.0.0/1245.192.0.1 to 45.207.255.25445.207.255.2551,048,574
9445.208.0.0/1245.208.0.1 to 45.223.255.25445.223.255.2551,048,574
9545.224.0.0/1245.224.0.1 to 45.239.255.25445.239.255.2551,048,574
9645.240.0.0/1245.240.0.1 to 45.255.255.25445.255.255.2551,048,574
9746.0.0.0/1246.0.0.1 to 46.15.255.25446.15.255.2551,048,574
9846.16.0.0/1246.16.0.1 to 46.31.255.25446.31.255.2551,048,574
9946.32.0.0/1246.32.0.1 to 46.47.255.25446.47.255.2551,048,574
10046.48.0.0/1246.48.0.1 to 46.63.255.25446.63.255.2551,048,574
10146.64.0.0/1246.64.0.1 to 46.79.255.25446.79.255.2551,048,574
10246.80.0.0/1246.80.0.1 to 46.95.255.25446.95.255.2551,048,574
10346.96.0.0/1246.96.0.1 to 46.111.255.25446.111.255.2551,048,574
10446.112.0.0/1246.112.0.1 to 46.127.255.25446.127.255.2551,048,574
10546.128.0.0/1246.128.0.1 to 46.143.255.25446.143.255.2551,048,574
10646.144.0.0/1246.144.0.1 to 46.159.255.25446.159.255.2551,048,574
10746.160.0.0/1246.160.0.1 to 46.175.255.25446.175.255.2551,048,574
10846.176.0.0/1246.176.0.1 to 46.191.255.25446.191.255.2551,048,574
10946.192.0.0/1246.192.0.1 to 46.207.255.25446.207.255.2551,048,574
11046.208.0.0/1246.208.0.1 to 46.223.255.25446.223.255.2551,048,574
11146.224.0.0/1246.224.0.1 to 46.239.255.25446.239.255.2551,048,574
11246.240.0.0/1246.240.0.1 to 46.255.255.25446.255.255.2551,048,574
11347.0.0.0/1247.0.0.1 to 47.15.255.25447.15.255.2551,048,574
11447.16.0.0/1247.16.0.1 to 47.31.255.25447.31.255.2551,048,574
11547.32.0.0/1247.32.0.1 to 47.47.255.25447.47.255.2551,048,574
11647.48.0.0/1247.48.0.1 to 47.63.255.25447.63.255.2551,048,574
11747.64.0.0/1247.64.0.1 to 47.79.255.25447.79.255.2551,048,574
11847.80.0.0/1247.80.0.1 to 47.95.255.25447.95.255.2551,048,574
11947.96.0.0/1247.96.0.1 to 47.111.255.25447.111.255.2551,048,574
12047.112.0.0/1247.112.0.1 to 47.127.255.25447.127.255.2551,048,574
12147.128.0.0/1247.128.0.1 to 47.143.255.25447.143.255.2551,048,574
12247.144.0.0/1247.144.0.1 to 47.159.255.25447.159.255.2551,048,574
12347.160.0.0/1247.160.0.1 to 47.175.255.25447.175.255.2551,048,574
12447.176.0.0/1247.176.0.1 to 47.191.255.25447.191.255.2551,048,574
12547.192.0.0/1247.192.0.1 to 47.207.255.25447.207.255.2551,048,574
12647.208.0.0/1247.208.0.1 to 47.223.255.25447.223.255.2551,048,574
12747.224.0.0/1247.224.0.1 to 47.239.255.25447.239.255.2551,048,574
12847.240.0.0/1247.240.0.1 to 47.255.255.25447.255.255.2551,048,574

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.