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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.

Network23.37.32.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
23.37.32.0
Broadcast address
23.37.63.255
First usable
23.37.32.1
Last usable
23.37.63.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Public public
Old class
A (default /8)
As numbers
Hex 17252000 · Integer 388308992 to 388317183
Reverse DNS zones
32.37.23.in-addr.arpa
33.37.23.in-addr.arpa
34.37.23.in-addr.arpa
35.37.23.in-addr.arpa
36.37.23.in-addr.arpa
37.37.23.in-addr.arpa
38.37.23.in-addr.arpa
39.37.23.in-addr.arpa
40.37.23.in-addr.arpa
41.37.23.in-addr.arpa
42.37.23.in-addr.arpa
43.37.23.in-addr.arpa
44.37.23.in-addr.arpa
45.37.23.in-addr.arpa
46.37.23.in-addr.arpa
47.37.23.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010111.00100101.00100000.0000000023.37.32.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network00010111.00100101.00100000.0000000023.37.32.0
Broadcast00010111.00100101.00111111.1111111123.37.63.255
Split into smaller subnets/26
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

23.37.32.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
123.37.32.0/2623.37.32.1 to 23.37.32.6223.37.32.6362
223.37.32.64/2623.37.32.65 to 23.37.32.12623.37.32.12762
323.37.32.128/2623.37.32.129 to 23.37.32.19023.37.32.19162
423.37.32.192/2623.37.32.193 to 23.37.32.25423.37.32.25562
523.37.33.0/2623.37.33.1 to 23.37.33.6223.37.33.6362
623.37.33.64/2623.37.33.65 to 23.37.33.12623.37.33.12762
723.37.33.128/2623.37.33.129 to 23.37.33.19023.37.33.19162
823.37.33.192/2623.37.33.193 to 23.37.33.25423.37.33.25562
923.37.34.0/2623.37.34.1 to 23.37.34.6223.37.34.6362
1023.37.34.64/2623.37.34.65 to 23.37.34.12623.37.34.12762
1123.37.34.128/2623.37.34.129 to 23.37.34.19023.37.34.19162
1223.37.34.192/2623.37.34.193 to 23.37.34.25423.37.34.25562
1323.37.35.0/2623.37.35.1 to 23.37.35.6223.37.35.6362
1423.37.35.64/2623.37.35.65 to 23.37.35.12623.37.35.12762
1523.37.35.128/2623.37.35.129 to 23.37.35.19023.37.35.19162
1623.37.35.192/2623.37.35.193 to 23.37.35.25423.37.35.25562
1723.37.36.0/2623.37.36.1 to 23.37.36.6223.37.36.6362
1823.37.36.64/2623.37.36.65 to 23.37.36.12623.37.36.12762
1923.37.36.128/2623.37.36.129 to 23.37.36.19023.37.36.19162
2023.37.36.192/2623.37.36.193 to 23.37.36.25423.37.36.25562
2123.37.37.0/2623.37.37.1 to 23.37.37.6223.37.37.6362
2223.37.37.64/2623.37.37.65 to 23.37.37.12623.37.37.12762
2323.37.37.128/2623.37.37.129 to 23.37.37.19023.37.37.19162
2423.37.37.192/2623.37.37.193 to 23.37.37.25423.37.37.25562
2523.37.38.0/2623.37.38.1 to 23.37.38.6223.37.38.6362
2623.37.38.64/2623.37.38.65 to 23.37.38.12623.37.38.12762
2723.37.38.128/2623.37.38.129 to 23.37.38.19023.37.38.19162
2823.37.38.192/2623.37.38.193 to 23.37.38.25423.37.38.25562
2923.37.39.0/2623.37.39.1 to 23.37.39.6223.37.39.6362
3023.37.39.64/2623.37.39.65 to 23.37.39.12623.37.39.12762
3123.37.39.128/2623.37.39.129 to 23.37.39.19023.37.39.19162
3223.37.39.192/2623.37.39.193 to 23.37.39.25423.37.39.25562
3323.37.40.0/2623.37.40.1 to 23.37.40.6223.37.40.6362
3423.37.40.64/2623.37.40.65 to 23.37.40.12623.37.40.12762
3523.37.40.128/2623.37.40.129 to 23.37.40.19023.37.40.19162
3623.37.40.192/2623.37.40.193 to 23.37.40.25423.37.40.25562
3723.37.41.0/2623.37.41.1 to 23.37.41.6223.37.41.6362
3823.37.41.64/2623.37.41.65 to 23.37.41.12623.37.41.12762
3923.37.41.128/2623.37.41.129 to 23.37.41.19023.37.41.19162
4023.37.41.192/2623.37.41.193 to 23.37.41.25423.37.41.25562
4123.37.42.0/2623.37.42.1 to 23.37.42.6223.37.42.6362
4223.37.42.64/2623.37.42.65 to 23.37.42.12623.37.42.12762
4323.37.42.128/2623.37.42.129 to 23.37.42.19023.37.42.19162
4423.37.42.192/2623.37.42.193 to 23.37.42.25423.37.42.25562
4523.37.43.0/2623.37.43.1 to 23.37.43.6223.37.43.6362
4623.37.43.64/2623.37.43.65 to 23.37.43.12623.37.43.12762
4723.37.43.128/2623.37.43.129 to 23.37.43.19023.37.43.19162
4823.37.43.192/2623.37.43.193 to 23.37.43.25423.37.43.25562
4923.37.44.0/2623.37.44.1 to 23.37.44.6223.37.44.6362
5023.37.44.64/2623.37.44.65 to 23.37.44.12623.37.44.12762
5123.37.44.128/2623.37.44.129 to 23.37.44.19023.37.44.19162
5223.37.44.192/2623.37.44.193 to 23.37.44.25423.37.44.25562
5323.37.45.0/2623.37.45.1 to 23.37.45.6223.37.45.6362
5423.37.45.64/2623.37.45.65 to 23.37.45.12623.37.45.12762
5523.37.45.128/2623.37.45.129 to 23.37.45.19023.37.45.19162
5623.37.45.192/2623.37.45.193 to 23.37.45.25423.37.45.25562
5723.37.46.0/2623.37.46.1 to 23.37.46.6223.37.46.6362
5823.37.46.64/2623.37.46.65 to 23.37.46.12623.37.46.12762
5923.37.46.128/2623.37.46.129 to 23.37.46.19023.37.46.19162
6023.37.46.192/2623.37.46.193 to 23.37.46.25423.37.46.25562
6123.37.47.0/2623.37.47.1 to 23.37.47.6223.37.47.6362
6223.37.47.64/2623.37.47.65 to 23.37.47.12623.37.47.12762
6323.37.47.128/2623.37.47.129 to 23.37.47.19023.37.47.19162
6423.37.47.192/2623.37.47.193 to 23.37.47.25423.37.47.25562
6523.37.48.0/2623.37.48.1 to 23.37.48.6223.37.48.6362
6623.37.48.64/2623.37.48.65 to 23.37.48.12623.37.48.12762
6723.37.48.128/2623.37.48.129 to 23.37.48.19023.37.48.19162
6823.37.48.192/2623.37.48.193 to 23.37.48.25423.37.48.25562
6923.37.49.0/2623.37.49.1 to 23.37.49.6223.37.49.6362
7023.37.49.64/2623.37.49.65 to 23.37.49.12623.37.49.12762
7123.37.49.128/2623.37.49.129 to 23.37.49.19023.37.49.19162
7223.37.49.192/2623.37.49.193 to 23.37.49.25423.37.49.25562
7323.37.50.0/2623.37.50.1 to 23.37.50.6223.37.50.6362
7423.37.50.64/2623.37.50.65 to 23.37.50.12623.37.50.12762
7523.37.50.128/2623.37.50.129 to 23.37.50.19023.37.50.19162
7623.37.50.192/2623.37.50.193 to 23.37.50.25423.37.50.25562
7723.37.51.0/2623.37.51.1 to 23.37.51.6223.37.51.6362
7823.37.51.64/2623.37.51.65 to 23.37.51.12623.37.51.12762
7923.37.51.128/2623.37.51.129 to 23.37.51.19023.37.51.19162
8023.37.51.192/2623.37.51.193 to 23.37.51.25423.37.51.25562
8123.37.52.0/2623.37.52.1 to 23.37.52.6223.37.52.6362
8223.37.52.64/2623.37.52.65 to 23.37.52.12623.37.52.12762
8323.37.52.128/2623.37.52.129 to 23.37.52.19023.37.52.19162
8423.37.52.192/2623.37.52.193 to 23.37.52.25423.37.52.25562
8523.37.53.0/2623.37.53.1 to 23.37.53.6223.37.53.6362
8623.37.53.64/2623.37.53.65 to 23.37.53.12623.37.53.12762
8723.37.53.128/2623.37.53.129 to 23.37.53.19023.37.53.19162
8823.37.53.192/2623.37.53.193 to 23.37.53.25423.37.53.25562
8923.37.54.0/2623.37.54.1 to 23.37.54.6223.37.54.6362
9023.37.54.64/2623.37.54.65 to 23.37.54.12623.37.54.12762
9123.37.54.128/2623.37.54.129 to 23.37.54.19023.37.54.19162
9223.37.54.192/2623.37.54.193 to 23.37.54.25423.37.54.25562
9323.37.55.0/2623.37.55.1 to 23.37.55.6223.37.55.6362
9423.37.55.64/2623.37.55.65 to 23.37.55.12623.37.55.12762
9523.37.55.128/2623.37.55.129 to 23.37.55.19023.37.55.19162
9623.37.55.192/2623.37.55.193 to 23.37.55.25423.37.55.25562
9723.37.56.0/2623.37.56.1 to 23.37.56.6223.37.56.6362
9823.37.56.64/2623.37.56.65 to 23.37.56.12623.37.56.12762
9923.37.56.128/2623.37.56.129 to 23.37.56.19023.37.56.19162
10023.37.56.192/2623.37.56.193 to 23.37.56.25423.37.56.25562
10123.37.57.0/2623.37.57.1 to 23.37.57.6223.37.57.6362
10223.37.57.64/2623.37.57.65 to 23.37.57.12623.37.57.12762
10323.37.57.128/2623.37.57.129 to 23.37.57.19023.37.57.19162
10423.37.57.192/2623.37.57.193 to 23.37.57.25423.37.57.25562
10523.37.58.0/2623.37.58.1 to 23.37.58.6223.37.58.6362
10623.37.58.64/2623.37.58.65 to 23.37.58.12623.37.58.12762
10723.37.58.128/2623.37.58.129 to 23.37.58.19023.37.58.19162
10823.37.58.192/2623.37.58.193 to 23.37.58.25423.37.58.25562
10923.37.59.0/2623.37.59.1 to 23.37.59.6223.37.59.6362
11023.37.59.64/2623.37.59.65 to 23.37.59.12623.37.59.12762
11123.37.59.128/2623.37.59.129 to 23.37.59.19023.37.59.19162
11223.37.59.192/2623.37.59.193 to 23.37.59.25423.37.59.25562
11323.37.60.0/2623.37.60.1 to 23.37.60.6223.37.60.6362
11423.37.60.64/2623.37.60.65 to 23.37.60.12623.37.60.12762
11523.37.60.128/2623.37.60.129 to 23.37.60.19023.37.60.19162
11623.37.60.192/2623.37.60.193 to 23.37.60.25423.37.60.25562
11723.37.61.0/2623.37.61.1 to 23.37.61.6223.37.61.6362
11823.37.61.64/2623.37.61.65 to 23.37.61.12623.37.61.12762
11923.37.61.128/2623.37.61.129 to 23.37.61.19023.37.61.19162
12023.37.61.192/2623.37.61.193 to 23.37.61.25423.37.61.25562
12123.37.62.0/2623.37.62.1 to 23.37.62.6223.37.62.6362
12223.37.62.64/2623.37.62.65 to 23.37.62.12623.37.62.12762
12323.37.62.128/2623.37.62.129 to 23.37.62.19023.37.62.19162
12423.37.62.192/2623.37.62.193 to 23.37.62.25423.37.62.25562
12523.37.63.0/2623.37.63.1 to 23.37.63.6223.37.63.6362
12623.37.63.64/2623.37.63.65 to 23.37.63.12623.37.63.12762
12723.37.63.128/2623.37.63.129 to 23.37.63.19023.37.63.19162
12823.37.63.192/2623.37.63.193 to 23.37.63.25423.37.63.25562

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.