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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.

Network23.166.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
23.166.0.0
Broadcast address
23.167.255.255
First usable
23.166.0.1
Last usable
23.167.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
A (default /8)
As numbers
Hex 17A60000 · Integer 396754944 to 396886015
Reverse DNS zones
166.23.in-addr.arpa
167.23.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010111.10100110.00000000.0000000023.166.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network00010111.10100110.00000000.0000000023.166.0.0
Broadcast00010111.10100111.11111111.1111111123.167.255.255
Split into smaller subnets/22
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

23.166.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
123.166.0.0/2223.166.0.1 to 23.166.3.25423.166.3.2551,022
223.166.4.0/2223.166.4.1 to 23.166.7.25423.166.7.2551,022
323.166.8.0/2223.166.8.1 to 23.166.11.25423.166.11.2551,022
423.166.12.0/2223.166.12.1 to 23.166.15.25423.166.15.2551,022
523.166.16.0/2223.166.16.1 to 23.166.19.25423.166.19.2551,022
623.166.20.0/2223.166.20.1 to 23.166.23.25423.166.23.2551,022
723.166.24.0/2223.166.24.1 to 23.166.27.25423.166.27.2551,022
823.166.28.0/2223.166.28.1 to 23.166.31.25423.166.31.2551,022
923.166.32.0/2223.166.32.1 to 23.166.35.25423.166.35.2551,022
1023.166.36.0/2223.166.36.1 to 23.166.39.25423.166.39.2551,022
1123.166.40.0/2223.166.40.1 to 23.166.43.25423.166.43.2551,022
1223.166.44.0/2223.166.44.1 to 23.166.47.25423.166.47.2551,022
1323.166.48.0/2223.166.48.1 to 23.166.51.25423.166.51.2551,022
1423.166.52.0/2223.166.52.1 to 23.166.55.25423.166.55.2551,022
1523.166.56.0/2223.166.56.1 to 23.166.59.25423.166.59.2551,022
1623.166.60.0/2223.166.60.1 to 23.166.63.25423.166.63.2551,022
1723.166.64.0/2223.166.64.1 to 23.166.67.25423.166.67.2551,022
1823.166.68.0/2223.166.68.1 to 23.166.71.25423.166.71.2551,022
1923.166.72.0/2223.166.72.1 to 23.166.75.25423.166.75.2551,022
2023.166.76.0/2223.166.76.1 to 23.166.79.25423.166.79.2551,022
2123.166.80.0/2223.166.80.1 to 23.166.83.25423.166.83.2551,022
2223.166.84.0/2223.166.84.1 to 23.166.87.25423.166.87.2551,022
2323.166.88.0/2223.166.88.1 to 23.166.91.25423.166.91.2551,022
2423.166.92.0/2223.166.92.1 to 23.166.95.25423.166.95.2551,022
2523.166.96.0/2223.166.96.1 to 23.166.99.25423.166.99.2551,022
2623.166.100.0/2223.166.100.1 to 23.166.103.25423.166.103.2551,022
2723.166.104.0/2223.166.104.1 to 23.166.107.25423.166.107.2551,022
2823.166.108.0/2223.166.108.1 to 23.166.111.25423.166.111.2551,022
2923.166.112.0/2223.166.112.1 to 23.166.115.25423.166.115.2551,022
3023.166.116.0/2223.166.116.1 to 23.166.119.25423.166.119.2551,022
3123.166.120.0/2223.166.120.1 to 23.166.123.25423.166.123.2551,022
3223.166.124.0/2223.166.124.1 to 23.166.127.25423.166.127.2551,022
3323.166.128.0/2223.166.128.1 to 23.166.131.25423.166.131.2551,022
3423.166.132.0/2223.166.132.1 to 23.166.135.25423.166.135.2551,022
3523.166.136.0/2223.166.136.1 to 23.166.139.25423.166.139.2551,022
3623.166.140.0/2223.166.140.1 to 23.166.143.25423.166.143.2551,022
3723.166.144.0/2223.166.144.1 to 23.166.147.25423.166.147.2551,022
3823.166.148.0/2223.166.148.1 to 23.166.151.25423.166.151.2551,022
3923.166.152.0/2223.166.152.1 to 23.166.155.25423.166.155.2551,022
4023.166.156.0/2223.166.156.1 to 23.166.159.25423.166.159.2551,022
4123.166.160.0/2223.166.160.1 to 23.166.163.25423.166.163.2551,022
4223.166.164.0/2223.166.164.1 to 23.166.167.25423.166.167.2551,022
4323.166.168.0/2223.166.168.1 to 23.166.171.25423.166.171.2551,022
4423.166.172.0/2223.166.172.1 to 23.166.175.25423.166.175.2551,022
4523.166.176.0/2223.166.176.1 to 23.166.179.25423.166.179.2551,022
4623.166.180.0/2223.166.180.1 to 23.166.183.25423.166.183.2551,022
4723.166.184.0/2223.166.184.1 to 23.166.187.25423.166.187.2551,022
4823.166.188.0/2223.166.188.1 to 23.166.191.25423.166.191.2551,022
4923.166.192.0/2223.166.192.1 to 23.166.195.25423.166.195.2551,022
5023.166.196.0/2223.166.196.1 to 23.166.199.25423.166.199.2551,022
5123.166.200.0/2223.166.200.1 to 23.166.203.25423.166.203.2551,022
5223.166.204.0/2223.166.204.1 to 23.166.207.25423.166.207.2551,022
5323.166.208.0/2223.166.208.1 to 23.166.211.25423.166.211.2551,022
5423.166.212.0/2223.166.212.1 to 23.166.215.25423.166.215.2551,022
5523.166.216.0/2223.166.216.1 to 23.166.219.25423.166.219.2551,022
5623.166.220.0/2223.166.220.1 to 23.166.223.25423.166.223.2551,022
5723.166.224.0/2223.166.224.1 to 23.166.227.25423.166.227.2551,022
5823.166.228.0/2223.166.228.1 to 23.166.231.25423.166.231.2551,022
5923.166.232.0/2223.166.232.1 to 23.166.235.25423.166.235.2551,022
6023.166.236.0/2223.166.236.1 to 23.166.239.25423.166.239.2551,022
6123.166.240.0/2223.166.240.1 to 23.166.243.25423.166.243.2551,022
6223.166.244.0/2223.166.244.1 to 23.166.247.25423.166.247.2551,022
6323.166.248.0/2223.166.248.1 to 23.166.251.25423.166.251.2551,022
6423.166.252.0/2223.166.252.1 to 23.166.255.25423.166.255.2551,022
6523.167.0.0/2223.167.0.1 to 23.167.3.25423.167.3.2551,022
6623.167.4.0/2223.167.4.1 to 23.167.7.25423.167.7.2551,022
6723.167.8.0/2223.167.8.1 to 23.167.11.25423.167.11.2551,022
6823.167.12.0/2223.167.12.1 to 23.167.15.25423.167.15.2551,022
6923.167.16.0/2223.167.16.1 to 23.167.19.25423.167.19.2551,022
7023.167.20.0/2223.167.20.1 to 23.167.23.25423.167.23.2551,022
7123.167.24.0/2223.167.24.1 to 23.167.27.25423.167.27.2551,022
7223.167.28.0/2223.167.28.1 to 23.167.31.25423.167.31.2551,022
7323.167.32.0/2223.167.32.1 to 23.167.35.25423.167.35.2551,022
7423.167.36.0/2223.167.36.1 to 23.167.39.25423.167.39.2551,022
7523.167.40.0/2223.167.40.1 to 23.167.43.25423.167.43.2551,022
7623.167.44.0/2223.167.44.1 to 23.167.47.25423.167.47.2551,022
7723.167.48.0/2223.167.48.1 to 23.167.51.25423.167.51.2551,022
7823.167.52.0/2223.167.52.1 to 23.167.55.25423.167.55.2551,022
7923.167.56.0/2223.167.56.1 to 23.167.59.25423.167.59.2551,022
8023.167.60.0/2223.167.60.1 to 23.167.63.25423.167.63.2551,022
8123.167.64.0/2223.167.64.1 to 23.167.67.25423.167.67.2551,022
8223.167.68.0/2223.167.68.1 to 23.167.71.25423.167.71.2551,022
8323.167.72.0/2223.167.72.1 to 23.167.75.25423.167.75.2551,022
8423.167.76.0/2223.167.76.1 to 23.167.79.25423.167.79.2551,022
8523.167.80.0/2223.167.80.1 to 23.167.83.25423.167.83.2551,022
8623.167.84.0/2223.167.84.1 to 23.167.87.25423.167.87.2551,022
8723.167.88.0/2223.167.88.1 to 23.167.91.25423.167.91.2551,022
8823.167.92.0/2223.167.92.1 to 23.167.95.25423.167.95.2551,022
8923.167.96.0/2223.167.96.1 to 23.167.99.25423.167.99.2551,022
9023.167.100.0/2223.167.100.1 to 23.167.103.25423.167.103.2551,022
9123.167.104.0/2223.167.104.1 to 23.167.107.25423.167.107.2551,022
9223.167.108.0/2223.167.108.1 to 23.167.111.25423.167.111.2551,022
9323.167.112.0/2223.167.112.1 to 23.167.115.25423.167.115.2551,022
9423.167.116.0/2223.167.116.1 to 23.167.119.25423.167.119.2551,022
9523.167.120.0/2223.167.120.1 to 23.167.123.25423.167.123.2551,022
9623.167.124.0/2223.167.124.1 to 23.167.127.25423.167.127.2551,022
9723.167.128.0/2223.167.128.1 to 23.167.131.25423.167.131.2551,022
9823.167.132.0/2223.167.132.1 to 23.167.135.25423.167.135.2551,022
9923.167.136.0/2223.167.136.1 to 23.167.139.25423.167.139.2551,022
10023.167.140.0/2223.167.140.1 to 23.167.143.25423.167.143.2551,022
10123.167.144.0/2223.167.144.1 to 23.167.147.25423.167.147.2551,022
10223.167.148.0/2223.167.148.1 to 23.167.151.25423.167.151.2551,022
10323.167.152.0/2223.167.152.1 to 23.167.155.25423.167.155.2551,022
10423.167.156.0/2223.167.156.1 to 23.167.159.25423.167.159.2551,022
10523.167.160.0/2223.167.160.1 to 23.167.163.25423.167.163.2551,022
10623.167.164.0/2223.167.164.1 to 23.167.167.25423.167.167.2551,022
10723.167.168.0/2223.167.168.1 to 23.167.171.25423.167.171.2551,022
10823.167.172.0/2223.167.172.1 to 23.167.175.25423.167.175.2551,022
10923.167.176.0/2223.167.176.1 to 23.167.179.25423.167.179.2551,022
11023.167.180.0/2223.167.180.1 to 23.167.183.25423.167.183.2551,022
11123.167.184.0/2223.167.184.1 to 23.167.187.25423.167.187.2551,022
11223.167.188.0/2223.167.188.1 to 23.167.191.25423.167.191.2551,022
11323.167.192.0/2223.167.192.1 to 23.167.195.25423.167.195.2551,022
11423.167.196.0/2223.167.196.1 to 23.167.199.25423.167.199.2551,022
11523.167.200.0/2223.167.200.1 to 23.167.203.25423.167.203.2551,022
11623.167.204.0/2223.167.204.1 to 23.167.207.25423.167.207.2551,022
11723.167.208.0/2223.167.208.1 to 23.167.211.25423.167.211.2551,022
11823.167.212.0/2223.167.212.1 to 23.167.215.25423.167.215.2551,022
11923.167.216.0/2223.167.216.1 to 23.167.219.25423.167.219.2551,022
12023.167.220.0/2223.167.220.1 to 23.167.223.25423.167.223.2551,022
12123.167.224.0/2223.167.224.1 to 23.167.227.25423.167.227.2551,022
12223.167.228.0/2223.167.228.1 to 23.167.231.25423.167.231.2551,022
12323.167.232.0/2223.167.232.1 to 23.167.235.25423.167.235.2551,022
12423.167.236.0/2223.167.236.1 to 23.167.239.25423.167.239.2551,022
12523.167.240.0/2223.167.240.1 to 23.167.243.25423.167.243.2551,022
12623.167.244.0/2223.167.244.1 to 23.167.247.25423.167.247.2551,022
12723.167.248.0/2223.167.248.1 to 23.167.251.25423.167.251.2551,022
12823.167.252.0/2223.167.252.1 to 23.167.255.25423.167.255.2551,022

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.