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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.

Network0.3.112.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
0.3.112.0
Broadcast address
0.3.127.255
First usable
0.3.112.1
Last usable
0.3.127.254
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
This network 0.0.0.0/8
Not routed; 0.0.0.0 means "any address" in settings
Old class
A (default /8)
As numbers
Hex 00037000 · Integer 225280 to 229375
Reverse DNS zones
112.3.0.in-addr.arpa
113.3.0.in-addr.arpa
114.3.0.in-addr.arpa
115.3.0.in-addr.arpa
116.3.0.in-addr.arpa
117.3.0.in-addr.arpa
118.3.0.in-addr.arpa
119.3.0.in-addr.arpa
120.3.0.in-addr.arpa
121.3.0.in-addr.arpa
122.3.0.in-addr.arpa
123.3.0.in-addr.arpa
124.3.0.in-addr.arpa
125.3.0.in-addr.arpa
126.3.0.in-addr.arpa
127.3.0.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
Address00000000.00000011.01110000.000000000.3.112.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network00000000.00000011.01110000.000000000.3.112.0
Broadcast00000000.00000011.01111111.111111110.3.127.255
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)

0.3.112.0/20 makes 64 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
10.3.112.0/260.3.112.1 to 0.3.112.620.3.112.6362
20.3.112.64/260.3.112.65 to 0.3.112.1260.3.112.12762
30.3.112.128/260.3.112.129 to 0.3.112.1900.3.112.19162
40.3.112.192/260.3.112.193 to 0.3.112.2540.3.112.25562
50.3.113.0/260.3.113.1 to 0.3.113.620.3.113.6362
60.3.113.64/260.3.113.65 to 0.3.113.1260.3.113.12762
70.3.113.128/260.3.113.129 to 0.3.113.1900.3.113.19162
80.3.113.192/260.3.113.193 to 0.3.113.2540.3.113.25562
90.3.114.0/260.3.114.1 to 0.3.114.620.3.114.6362
100.3.114.64/260.3.114.65 to 0.3.114.1260.3.114.12762
110.3.114.128/260.3.114.129 to 0.3.114.1900.3.114.19162
120.3.114.192/260.3.114.193 to 0.3.114.2540.3.114.25562
130.3.115.0/260.3.115.1 to 0.3.115.620.3.115.6362
140.3.115.64/260.3.115.65 to 0.3.115.1260.3.115.12762
150.3.115.128/260.3.115.129 to 0.3.115.1900.3.115.19162
160.3.115.192/260.3.115.193 to 0.3.115.2540.3.115.25562
170.3.116.0/260.3.116.1 to 0.3.116.620.3.116.6362
180.3.116.64/260.3.116.65 to 0.3.116.1260.3.116.12762
190.3.116.128/260.3.116.129 to 0.3.116.1900.3.116.19162
200.3.116.192/260.3.116.193 to 0.3.116.2540.3.116.25562
210.3.117.0/260.3.117.1 to 0.3.117.620.3.117.6362
220.3.117.64/260.3.117.65 to 0.3.117.1260.3.117.12762
230.3.117.128/260.3.117.129 to 0.3.117.1900.3.117.19162
240.3.117.192/260.3.117.193 to 0.3.117.2540.3.117.25562
250.3.118.0/260.3.118.1 to 0.3.118.620.3.118.6362
260.3.118.64/260.3.118.65 to 0.3.118.1260.3.118.12762
270.3.118.128/260.3.118.129 to 0.3.118.1900.3.118.19162
280.3.118.192/260.3.118.193 to 0.3.118.2540.3.118.25562
290.3.119.0/260.3.119.1 to 0.3.119.620.3.119.6362
300.3.119.64/260.3.119.65 to 0.3.119.1260.3.119.12762
310.3.119.128/260.3.119.129 to 0.3.119.1900.3.119.19162
320.3.119.192/260.3.119.193 to 0.3.119.2540.3.119.25562
330.3.120.0/260.3.120.1 to 0.3.120.620.3.120.6362
340.3.120.64/260.3.120.65 to 0.3.120.1260.3.120.12762
350.3.120.128/260.3.120.129 to 0.3.120.1900.3.120.19162
360.3.120.192/260.3.120.193 to 0.3.120.2540.3.120.25562
370.3.121.0/260.3.121.1 to 0.3.121.620.3.121.6362
380.3.121.64/260.3.121.65 to 0.3.121.1260.3.121.12762
390.3.121.128/260.3.121.129 to 0.3.121.1900.3.121.19162
400.3.121.192/260.3.121.193 to 0.3.121.2540.3.121.25562
410.3.122.0/260.3.122.1 to 0.3.122.620.3.122.6362
420.3.122.64/260.3.122.65 to 0.3.122.1260.3.122.12762
430.3.122.128/260.3.122.129 to 0.3.122.1900.3.122.19162
440.3.122.192/260.3.122.193 to 0.3.122.2540.3.122.25562
450.3.123.0/260.3.123.1 to 0.3.123.620.3.123.6362
460.3.123.64/260.3.123.65 to 0.3.123.1260.3.123.12762
470.3.123.128/260.3.123.129 to 0.3.123.1900.3.123.19162
480.3.123.192/260.3.123.193 to 0.3.123.2540.3.123.25562
490.3.124.0/260.3.124.1 to 0.3.124.620.3.124.6362
500.3.124.64/260.3.124.65 to 0.3.124.1260.3.124.12762
510.3.124.128/260.3.124.129 to 0.3.124.1900.3.124.19162
520.3.124.192/260.3.124.193 to 0.3.124.2540.3.124.25562
530.3.125.0/260.3.125.1 to 0.3.125.620.3.125.6362
540.3.125.64/260.3.125.65 to 0.3.125.1260.3.125.12762
550.3.125.128/260.3.125.129 to 0.3.125.1900.3.125.19162
560.3.125.192/260.3.125.193 to 0.3.125.2540.3.125.25562
570.3.126.0/260.3.126.1 to 0.3.126.620.3.126.6362
580.3.126.64/260.3.126.65 to 0.3.126.1260.3.126.12762
590.3.126.128/260.3.126.129 to 0.3.126.1900.3.126.19162
600.3.126.192/260.3.126.193 to 0.3.126.2540.3.126.25562
610.3.127.0/260.3.127.1 to 0.3.127.620.3.127.6362
620.3.127.64/260.3.127.65 to 0.3.127.1260.3.127.12762
630.3.127.128/260.3.127.129 to 0.3.127.1900.3.127.19162
640.3.127.192/260.3.127.193 to 0.3.127.2540.3.127.25562

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.