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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.

Network31.167.192.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
31.167.192.0
Broadcast address
31.167.207.255
First usable
31.167.192.1
Last usable
31.167.207.254
Usable hosts
4,094 (4,096 less the network and broadcast addresses)
Subnet mask
255.255.240.0
Wildcard mask
0.0.15.255 (Cisco ACLs, OSPF)
Prefix length
/20
Type
Public public
Old class
A (default /8)
As numbers
Hex 1FA7C000 · Integer 531087360 to 531091455
Reverse DNS zones
192.167.31.in-addr.arpa
193.167.31.in-addr.arpa
194.167.31.in-addr.arpa
195.167.31.in-addr.arpa
196.167.31.in-addr.arpa
197.167.31.in-addr.arpa
198.167.31.in-addr.arpa
199.167.31.in-addr.arpa
200.167.31.in-addr.arpa
201.167.31.in-addr.arpa
202.167.31.in-addr.arpa
203.167.31.in-addr.arpa
204.167.31.in-addr.arpa
205.167.31.in-addr.arpa
206.167.31.in-addr.arpa
207.167.31.in-addr.arpa
/20 is not on a 8-bit boundary, so it takes 16 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011111.10100111.11000000.0000000031.167.192.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network00011111.10100111.11000000.0000000031.167.192.0
Broadcast00011111.10100111.11001111.1111111131.167.207.255
Split into smaller subnets/26
/21 (2)/22 (4)/23 (8)/24 (16)/25 (32)/26 (64)/27 (128)/28 (256)/29 (512)/30 (1,024)/31 (2,048)/32 (4,096)

31.167.192.0/20 makes 64 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
131.167.192.0/2631.167.192.1 to 31.167.192.6231.167.192.6362
231.167.192.64/2631.167.192.65 to 31.167.192.12631.167.192.12762
331.167.192.128/2631.167.192.129 to 31.167.192.19031.167.192.19162
431.167.192.192/2631.167.192.193 to 31.167.192.25431.167.192.25562
531.167.193.0/2631.167.193.1 to 31.167.193.6231.167.193.6362
631.167.193.64/2631.167.193.65 to 31.167.193.12631.167.193.12762
731.167.193.128/2631.167.193.129 to 31.167.193.19031.167.193.19162
831.167.193.192/2631.167.193.193 to 31.167.193.25431.167.193.25562
931.167.194.0/2631.167.194.1 to 31.167.194.6231.167.194.6362
1031.167.194.64/2631.167.194.65 to 31.167.194.12631.167.194.12762
1131.167.194.128/2631.167.194.129 to 31.167.194.19031.167.194.19162
1231.167.194.192/2631.167.194.193 to 31.167.194.25431.167.194.25562
1331.167.195.0/2631.167.195.1 to 31.167.195.6231.167.195.6362
1431.167.195.64/2631.167.195.65 to 31.167.195.12631.167.195.12762
1531.167.195.128/2631.167.195.129 to 31.167.195.19031.167.195.19162
1631.167.195.192/2631.167.195.193 to 31.167.195.25431.167.195.25562
1731.167.196.0/2631.167.196.1 to 31.167.196.6231.167.196.6362
1831.167.196.64/2631.167.196.65 to 31.167.196.12631.167.196.12762
1931.167.196.128/2631.167.196.129 to 31.167.196.19031.167.196.19162
2031.167.196.192/2631.167.196.193 to 31.167.196.25431.167.196.25562
2131.167.197.0/2631.167.197.1 to 31.167.197.6231.167.197.6362
2231.167.197.64/2631.167.197.65 to 31.167.197.12631.167.197.12762
2331.167.197.128/2631.167.197.129 to 31.167.197.19031.167.197.19162
2431.167.197.192/2631.167.197.193 to 31.167.197.25431.167.197.25562
2531.167.198.0/2631.167.198.1 to 31.167.198.6231.167.198.6362
2631.167.198.64/2631.167.198.65 to 31.167.198.12631.167.198.12762
2731.167.198.128/2631.167.198.129 to 31.167.198.19031.167.198.19162
2831.167.198.192/2631.167.198.193 to 31.167.198.25431.167.198.25562
2931.167.199.0/2631.167.199.1 to 31.167.199.6231.167.199.6362
3031.167.199.64/2631.167.199.65 to 31.167.199.12631.167.199.12762
3131.167.199.128/2631.167.199.129 to 31.167.199.19031.167.199.19162
3231.167.199.192/2631.167.199.193 to 31.167.199.25431.167.199.25562
3331.167.200.0/2631.167.200.1 to 31.167.200.6231.167.200.6362
3431.167.200.64/2631.167.200.65 to 31.167.200.12631.167.200.12762
3531.167.200.128/2631.167.200.129 to 31.167.200.19031.167.200.19162
3631.167.200.192/2631.167.200.193 to 31.167.200.25431.167.200.25562
3731.167.201.0/2631.167.201.1 to 31.167.201.6231.167.201.6362
3831.167.201.64/2631.167.201.65 to 31.167.201.12631.167.201.12762
3931.167.201.128/2631.167.201.129 to 31.167.201.19031.167.201.19162
4031.167.201.192/2631.167.201.193 to 31.167.201.25431.167.201.25562
4131.167.202.0/2631.167.202.1 to 31.167.202.6231.167.202.6362
4231.167.202.64/2631.167.202.65 to 31.167.202.12631.167.202.12762
4331.167.202.128/2631.167.202.129 to 31.167.202.19031.167.202.19162
4431.167.202.192/2631.167.202.193 to 31.167.202.25431.167.202.25562
4531.167.203.0/2631.167.203.1 to 31.167.203.6231.167.203.6362
4631.167.203.64/2631.167.203.65 to 31.167.203.12631.167.203.12762
4731.167.203.128/2631.167.203.129 to 31.167.203.19031.167.203.19162
4831.167.203.192/2631.167.203.193 to 31.167.203.25431.167.203.25562
4931.167.204.0/2631.167.204.1 to 31.167.204.6231.167.204.6362
5031.167.204.64/2631.167.204.65 to 31.167.204.12631.167.204.12762
5131.167.204.128/2631.167.204.129 to 31.167.204.19031.167.204.19162
5231.167.204.192/2631.167.204.193 to 31.167.204.25431.167.204.25562
5331.167.205.0/2631.167.205.1 to 31.167.205.6231.167.205.6362
5431.167.205.64/2631.167.205.65 to 31.167.205.12631.167.205.12762
5531.167.205.128/2631.167.205.129 to 31.167.205.19031.167.205.19162
5631.167.205.192/2631.167.205.193 to 31.167.205.25431.167.205.25562
5731.167.206.0/2631.167.206.1 to 31.167.206.6231.167.206.6362
5831.167.206.64/2631.167.206.65 to 31.167.206.12631.167.206.12762
5931.167.206.128/2631.167.206.129 to 31.167.206.19031.167.206.19162
6031.167.206.192/2631.167.206.193 to 31.167.206.25431.167.206.25562
6131.167.207.0/2631.167.207.1 to 31.167.207.6231.167.207.6362
6231.167.207.64/2631.167.207.65 to 31.167.207.12631.167.207.12762
6331.167.207.128/2631.167.207.129 to 31.167.207.19031.167.207.19162
6431.167.207.192/2631.167.207.193 to 31.167.207.25431.167.207.25562

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.