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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/11
/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 64 subnets of /11.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
140.0.0.0/1140.0.0.1 to 40.31.255.25440.31.255.2552,097,150
240.32.0.0/1140.32.0.1 to 40.63.255.25440.63.255.2552,097,150
340.64.0.0/1140.64.0.1 to 40.95.255.25440.95.255.2552,097,150
440.96.0.0/1140.96.0.1 to 40.127.255.25440.127.255.2552,097,150
540.128.0.0/1140.128.0.1 to 40.159.255.25440.159.255.2552,097,150
640.160.0.0/1140.160.0.1 to 40.191.255.25440.191.255.2552,097,150
740.192.0.0/1140.192.0.1 to 40.223.255.25440.223.255.2552,097,150
840.224.0.0/1140.224.0.1 to 40.255.255.25440.255.255.2552,097,150
941.0.0.0/1141.0.0.1 to 41.31.255.25441.31.255.2552,097,150
1041.32.0.0/1141.32.0.1 to 41.63.255.25441.63.255.2552,097,150
1141.64.0.0/1141.64.0.1 to 41.95.255.25441.95.255.2552,097,150
1241.96.0.0/1141.96.0.1 to 41.127.255.25441.127.255.2552,097,150
1341.128.0.0/1141.128.0.1 to 41.159.255.25441.159.255.2552,097,150
1441.160.0.0/1141.160.0.1 to 41.191.255.25441.191.255.2552,097,150
1541.192.0.0/1141.192.0.1 to 41.223.255.25441.223.255.2552,097,150
1641.224.0.0/1141.224.0.1 to 41.255.255.25441.255.255.2552,097,150
1742.0.0.0/1142.0.0.1 to 42.31.255.25442.31.255.2552,097,150
1842.32.0.0/1142.32.0.1 to 42.63.255.25442.63.255.2552,097,150
1942.64.0.0/1142.64.0.1 to 42.95.255.25442.95.255.2552,097,150
2042.96.0.0/1142.96.0.1 to 42.127.255.25442.127.255.2552,097,150
2142.128.0.0/1142.128.0.1 to 42.159.255.25442.159.255.2552,097,150
2242.160.0.0/1142.160.0.1 to 42.191.255.25442.191.255.2552,097,150
2342.192.0.0/1142.192.0.1 to 42.223.255.25442.223.255.2552,097,150
2442.224.0.0/1142.224.0.1 to 42.255.255.25442.255.255.2552,097,150
2543.0.0.0/1143.0.0.1 to 43.31.255.25443.31.255.2552,097,150
2643.32.0.0/1143.32.0.1 to 43.63.255.25443.63.255.2552,097,150
2743.64.0.0/1143.64.0.1 to 43.95.255.25443.95.255.2552,097,150
2843.96.0.0/1143.96.0.1 to 43.127.255.25443.127.255.2552,097,150
2943.128.0.0/1143.128.0.1 to 43.159.255.25443.159.255.2552,097,150
3043.160.0.0/1143.160.0.1 to 43.191.255.25443.191.255.2552,097,150
3143.192.0.0/1143.192.0.1 to 43.223.255.25443.223.255.2552,097,150
3243.224.0.0/1143.224.0.1 to 43.255.255.25443.255.255.2552,097,150
3344.0.0.0/1144.0.0.1 to 44.31.255.25444.31.255.2552,097,150
3444.32.0.0/1144.32.0.1 to 44.63.255.25444.63.255.2552,097,150
3544.64.0.0/1144.64.0.1 to 44.95.255.25444.95.255.2552,097,150
3644.96.0.0/1144.96.0.1 to 44.127.255.25444.127.255.2552,097,150
3744.128.0.0/1144.128.0.1 to 44.159.255.25444.159.255.2552,097,150
3844.160.0.0/1144.160.0.1 to 44.191.255.25444.191.255.2552,097,150
3944.192.0.0/1144.192.0.1 to 44.223.255.25444.223.255.2552,097,150
4044.224.0.0/1144.224.0.1 to 44.255.255.25444.255.255.2552,097,150
4145.0.0.0/1145.0.0.1 to 45.31.255.25445.31.255.2552,097,150
4245.32.0.0/1145.32.0.1 to 45.63.255.25445.63.255.2552,097,150
4345.64.0.0/1145.64.0.1 to 45.95.255.25445.95.255.2552,097,150
4445.96.0.0/1145.96.0.1 to 45.127.255.25445.127.255.2552,097,150
4545.128.0.0/1145.128.0.1 to 45.159.255.25445.159.255.2552,097,150
4645.160.0.0/1145.160.0.1 to 45.191.255.25445.191.255.2552,097,150
4745.192.0.0/1145.192.0.1 to 45.223.255.25445.223.255.2552,097,150
4845.224.0.0/1145.224.0.1 to 45.255.255.25445.255.255.2552,097,150
4946.0.0.0/1146.0.0.1 to 46.31.255.25446.31.255.2552,097,150
5046.32.0.0/1146.32.0.1 to 46.63.255.25446.63.255.2552,097,150
5146.64.0.0/1146.64.0.1 to 46.95.255.25446.95.255.2552,097,150
5246.96.0.0/1146.96.0.1 to 46.127.255.25446.127.255.2552,097,150
5346.128.0.0/1146.128.0.1 to 46.159.255.25446.159.255.2552,097,150
5446.160.0.0/1146.160.0.1 to 46.191.255.25446.191.255.2552,097,150
5546.192.0.0/1146.192.0.1 to 46.223.255.25446.223.255.2552,097,150
5646.224.0.0/1146.224.0.1 to 46.255.255.25446.255.255.2552,097,150
5747.0.0.0/1147.0.0.1 to 47.31.255.25447.31.255.2552,097,150
5847.32.0.0/1147.32.0.1 to 47.63.255.25447.63.255.2552,097,150
5947.64.0.0/1147.64.0.1 to 47.95.255.25447.95.255.2552,097,150
6047.96.0.0/1147.96.0.1 to 47.127.255.25447.127.255.2552,097,150
6147.128.0.0/1147.128.0.1 to 47.159.255.25447.159.255.2552,097,150
6247.160.0.0/1147.160.0.1 to 47.191.255.25447.191.255.2552,097,150
6347.192.0.0/1147.192.0.1 to 47.223.255.25447.223.255.2552,097,150
6447.224.0.0/1147.224.0.1 to 47.255.255.25447.255.255.2552,097,150

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.