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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.

Network23.2.64.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
23.2.64.0
Broadcast address
23.2.127.255
First usable
23.2.64.1
Last usable
23.2.127.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
A (default /8)
As numbers
Hex 17024000 · Integer 386023424 to 386039807
Reverse DNS zones
64.2.23.in-addr.arpa
65.2.23.in-addr.arpa
66.2.23.in-addr.arpa
67.2.23.in-addr.arpa
68.2.23.in-addr.arpa
69.2.23.in-addr.arpa
70.2.23.in-addr.arpa
71.2.23.in-addr.arpa
72.2.23.in-addr.arpa
73.2.23.in-addr.arpa
74.2.23.in-addr.arpa
75.2.23.in-addr.arpa
76.2.23.in-addr.arpa
77.2.23.in-addr.arpa
78.2.23.in-addr.arpa
79.2.23.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010111.00000010.01000000.0000000023.2.64.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network00010111.00000010.01000000.0000000023.2.64.0
Broadcast00010111.00000010.01111111.1111111123.2.127.255
Split into smaller subnets/25
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

23.2.64.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
123.2.64.0/2523.2.64.1 to 23.2.64.12623.2.64.127126
223.2.64.128/2523.2.64.129 to 23.2.64.25423.2.64.255126
323.2.65.0/2523.2.65.1 to 23.2.65.12623.2.65.127126
423.2.65.128/2523.2.65.129 to 23.2.65.25423.2.65.255126
523.2.66.0/2523.2.66.1 to 23.2.66.12623.2.66.127126
623.2.66.128/2523.2.66.129 to 23.2.66.25423.2.66.255126
723.2.67.0/2523.2.67.1 to 23.2.67.12623.2.67.127126
823.2.67.128/2523.2.67.129 to 23.2.67.25423.2.67.255126
923.2.68.0/2523.2.68.1 to 23.2.68.12623.2.68.127126
1023.2.68.128/2523.2.68.129 to 23.2.68.25423.2.68.255126
1123.2.69.0/2523.2.69.1 to 23.2.69.12623.2.69.127126
1223.2.69.128/2523.2.69.129 to 23.2.69.25423.2.69.255126
1323.2.70.0/2523.2.70.1 to 23.2.70.12623.2.70.127126
1423.2.70.128/2523.2.70.129 to 23.2.70.25423.2.70.255126
1523.2.71.0/2523.2.71.1 to 23.2.71.12623.2.71.127126
1623.2.71.128/2523.2.71.129 to 23.2.71.25423.2.71.255126
1723.2.72.0/2523.2.72.1 to 23.2.72.12623.2.72.127126
1823.2.72.128/2523.2.72.129 to 23.2.72.25423.2.72.255126
1923.2.73.0/2523.2.73.1 to 23.2.73.12623.2.73.127126
2023.2.73.128/2523.2.73.129 to 23.2.73.25423.2.73.255126
2123.2.74.0/2523.2.74.1 to 23.2.74.12623.2.74.127126
2223.2.74.128/2523.2.74.129 to 23.2.74.25423.2.74.255126
2323.2.75.0/2523.2.75.1 to 23.2.75.12623.2.75.127126
2423.2.75.128/2523.2.75.129 to 23.2.75.25423.2.75.255126
2523.2.76.0/2523.2.76.1 to 23.2.76.12623.2.76.127126
2623.2.76.128/2523.2.76.129 to 23.2.76.25423.2.76.255126
2723.2.77.0/2523.2.77.1 to 23.2.77.12623.2.77.127126
2823.2.77.128/2523.2.77.129 to 23.2.77.25423.2.77.255126
2923.2.78.0/2523.2.78.1 to 23.2.78.12623.2.78.127126
3023.2.78.128/2523.2.78.129 to 23.2.78.25423.2.78.255126
3123.2.79.0/2523.2.79.1 to 23.2.79.12623.2.79.127126
3223.2.79.128/2523.2.79.129 to 23.2.79.25423.2.79.255126
3323.2.80.0/2523.2.80.1 to 23.2.80.12623.2.80.127126
3423.2.80.128/2523.2.80.129 to 23.2.80.25423.2.80.255126
3523.2.81.0/2523.2.81.1 to 23.2.81.12623.2.81.127126
3623.2.81.128/2523.2.81.129 to 23.2.81.25423.2.81.255126
3723.2.82.0/2523.2.82.1 to 23.2.82.12623.2.82.127126
3823.2.82.128/2523.2.82.129 to 23.2.82.25423.2.82.255126
3923.2.83.0/2523.2.83.1 to 23.2.83.12623.2.83.127126
4023.2.83.128/2523.2.83.129 to 23.2.83.25423.2.83.255126
4123.2.84.0/2523.2.84.1 to 23.2.84.12623.2.84.127126
4223.2.84.128/2523.2.84.129 to 23.2.84.25423.2.84.255126
4323.2.85.0/2523.2.85.1 to 23.2.85.12623.2.85.127126
4423.2.85.128/2523.2.85.129 to 23.2.85.25423.2.85.255126
4523.2.86.0/2523.2.86.1 to 23.2.86.12623.2.86.127126
4623.2.86.128/2523.2.86.129 to 23.2.86.25423.2.86.255126
4723.2.87.0/2523.2.87.1 to 23.2.87.12623.2.87.127126
4823.2.87.128/2523.2.87.129 to 23.2.87.25423.2.87.255126
4923.2.88.0/2523.2.88.1 to 23.2.88.12623.2.88.127126
5023.2.88.128/2523.2.88.129 to 23.2.88.25423.2.88.255126
5123.2.89.0/2523.2.89.1 to 23.2.89.12623.2.89.127126
5223.2.89.128/2523.2.89.129 to 23.2.89.25423.2.89.255126
5323.2.90.0/2523.2.90.1 to 23.2.90.12623.2.90.127126
5423.2.90.128/2523.2.90.129 to 23.2.90.25423.2.90.255126
5523.2.91.0/2523.2.91.1 to 23.2.91.12623.2.91.127126
5623.2.91.128/2523.2.91.129 to 23.2.91.25423.2.91.255126
5723.2.92.0/2523.2.92.1 to 23.2.92.12623.2.92.127126
5823.2.92.128/2523.2.92.129 to 23.2.92.25423.2.92.255126
5923.2.93.0/2523.2.93.1 to 23.2.93.12623.2.93.127126
6023.2.93.128/2523.2.93.129 to 23.2.93.25423.2.93.255126
6123.2.94.0/2523.2.94.1 to 23.2.94.12623.2.94.127126
6223.2.94.128/2523.2.94.129 to 23.2.94.25423.2.94.255126
6323.2.95.0/2523.2.95.1 to 23.2.95.12623.2.95.127126
6423.2.95.128/2523.2.95.129 to 23.2.95.25423.2.95.255126
6523.2.96.0/2523.2.96.1 to 23.2.96.12623.2.96.127126
6623.2.96.128/2523.2.96.129 to 23.2.96.25423.2.96.255126
6723.2.97.0/2523.2.97.1 to 23.2.97.12623.2.97.127126
6823.2.97.128/2523.2.97.129 to 23.2.97.25423.2.97.255126
6923.2.98.0/2523.2.98.1 to 23.2.98.12623.2.98.127126
7023.2.98.128/2523.2.98.129 to 23.2.98.25423.2.98.255126
7123.2.99.0/2523.2.99.1 to 23.2.99.12623.2.99.127126
7223.2.99.128/2523.2.99.129 to 23.2.99.25423.2.99.255126
7323.2.100.0/2523.2.100.1 to 23.2.100.12623.2.100.127126
7423.2.100.128/2523.2.100.129 to 23.2.100.25423.2.100.255126
7523.2.101.0/2523.2.101.1 to 23.2.101.12623.2.101.127126
7623.2.101.128/2523.2.101.129 to 23.2.101.25423.2.101.255126
7723.2.102.0/2523.2.102.1 to 23.2.102.12623.2.102.127126
7823.2.102.128/2523.2.102.129 to 23.2.102.25423.2.102.255126
7923.2.103.0/2523.2.103.1 to 23.2.103.12623.2.103.127126
8023.2.103.128/2523.2.103.129 to 23.2.103.25423.2.103.255126
8123.2.104.0/2523.2.104.1 to 23.2.104.12623.2.104.127126
8223.2.104.128/2523.2.104.129 to 23.2.104.25423.2.104.255126
8323.2.105.0/2523.2.105.1 to 23.2.105.12623.2.105.127126
8423.2.105.128/2523.2.105.129 to 23.2.105.25423.2.105.255126
8523.2.106.0/2523.2.106.1 to 23.2.106.12623.2.106.127126
8623.2.106.128/2523.2.106.129 to 23.2.106.25423.2.106.255126
8723.2.107.0/2523.2.107.1 to 23.2.107.12623.2.107.127126
8823.2.107.128/2523.2.107.129 to 23.2.107.25423.2.107.255126
8923.2.108.0/2523.2.108.1 to 23.2.108.12623.2.108.127126
9023.2.108.128/2523.2.108.129 to 23.2.108.25423.2.108.255126
9123.2.109.0/2523.2.109.1 to 23.2.109.12623.2.109.127126
9223.2.109.128/2523.2.109.129 to 23.2.109.25423.2.109.255126
9323.2.110.0/2523.2.110.1 to 23.2.110.12623.2.110.127126
9423.2.110.128/2523.2.110.129 to 23.2.110.25423.2.110.255126
9523.2.111.0/2523.2.111.1 to 23.2.111.12623.2.111.127126
9623.2.111.128/2523.2.111.129 to 23.2.111.25423.2.111.255126
9723.2.112.0/2523.2.112.1 to 23.2.112.12623.2.112.127126
9823.2.112.128/2523.2.112.129 to 23.2.112.25423.2.112.255126
9923.2.113.0/2523.2.113.1 to 23.2.113.12623.2.113.127126
10023.2.113.128/2523.2.113.129 to 23.2.113.25423.2.113.255126
10123.2.114.0/2523.2.114.1 to 23.2.114.12623.2.114.127126
10223.2.114.128/2523.2.114.129 to 23.2.114.25423.2.114.255126
10323.2.115.0/2523.2.115.1 to 23.2.115.12623.2.115.127126
10423.2.115.128/2523.2.115.129 to 23.2.115.25423.2.115.255126
10523.2.116.0/2523.2.116.1 to 23.2.116.12623.2.116.127126
10623.2.116.128/2523.2.116.129 to 23.2.116.25423.2.116.255126
10723.2.117.0/2523.2.117.1 to 23.2.117.12623.2.117.127126
10823.2.117.128/2523.2.117.129 to 23.2.117.25423.2.117.255126
10923.2.118.0/2523.2.118.1 to 23.2.118.12623.2.118.127126
11023.2.118.128/2523.2.118.129 to 23.2.118.25423.2.118.255126
11123.2.119.0/2523.2.119.1 to 23.2.119.12623.2.119.127126
11223.2.119.128/2523.2.119.129 to 23.2.119.25423.2.119.255126
11323.2.120.0/2523.2.120.1 to 23.2.120.12623.2.120.127126
11423.2.120.128/2523.2.120.129 to 23.2.120.25423.2.120.255126
11523.2.121.0/2523.2.121.1 to 23.2.121.12623.2.121.127126
11623.2.121.128/2523.2.121.129 to 23.2.121.25423.2.121.255126
11723.2.122.0/2523.2.122.1 to 23.2.122.12623.2.122.127126
11823.2.122.128/2523.2.122.129 to 23.2.122.25423.2.122.255126
11923.2.123.0/2523.2.123.1 to 23.2.123.12623.2.123.127126
12023.2.123.128/2523.2.123.129 to 23.2.123.25423.2.123.255126
12123.2.124.0/2523.2.124.1 to 23.2.124.12623.2.124.127126
12223.2.124.128/2523.2.124.129 to 23.2.124.25423.2.124.255126
12323.2.125.0/2523.2.125.1 to 23.2.125.12623.2.125.127126
12423.2.125.128/2523.2.125.129 to 23.2.125.25423.2.125.255126
12523.2.126.0/2523.2.126.1 to 23.2.126.12623.2.126.127126
12623.2.126.128/2523.2.126.129 to 23.2.126.25423.2.126.255126
12723.2.127.0/2523.2.127.1 to 23.2.127.12623.2.127.127126
12823.2.127.128/2523.2.127.129 to 23.2.127.25423.2.127.255126

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.