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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.

Network65.236.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
65.236.0.0
Broadcast address
65.237.255.255
First usable
65.236.0.1
Last usable
65.237.255.254
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 41EC0000 · Integer 1105985536 to 1106116607
Reverse DNS zones
236.65.in-addr.arpa
237.65.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
Address01000001.11101100.00000000.0000000065.236.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network01000001.11101100.00000000.0000000065.236.0.0
Broadcast01000001.11101101.11111111.1111111165.237.255.255
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)

65.236.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
165.236.0.0/2265.236.0.1 to 65.236.3.25465.236.3.2551,022
265.236.4.0/2265.236.4.1 to 65.236.7.25465.236.7.2551,022
365.236.8.0/2265.236.8.1 to 65.236.11.25465.236.11.2551,022
465.236.12.0/2265.236.12.1 to 65.236.15.25465.236.15.2551,022
565.236.16.0/2265.236.16.1 to 65.236.19.25465.236.19.2551,022
665.236.20.0/2265.236.20.1 to 65.236.23.25465.236.23.2551,022
765.236.24.0/2265.236.24.1 to 65.236.27.25465.236.27.2551,022
865.236.28.0/2265.236.28.1 to 65.236.31.25465.236.31.2551,022
965.236.32.0/2265.236.32.1 to 65.236.35.25465.236.35.2551,022
1065.236.36.0/2265.236.36.1 to 65.236.39.25465.236.39.2551,022
1165.236.40.0/2265.236.40.1 to 65.236.43.25465.236.43.2551,022
1265.236.44.0/2265.236.44.1 to 65.236.47.25465.236.47.2551,022
1365.236.48.0/2265.236.48.1 to 65.236.51.25465.236.51.2551,022
1465.236.52.0/2265.236.52.1 to 65.236.55.25465.236.55.2551,022
1565.236.56.0/2265.236.56.1 to 65.236.59.25465.236.59.2551,022
1665.236.60.0/2265.236.60.1 to 65.236.63.25465.236.63.2551,022
1765.236.64.0/2265.236.64.1 to 65.236.67.25465.236.67.2551,022
1865.236.68.0/2265.236.68.1 to 65.236.71.25465.236.71.2551,022
1965.236.72.0/2265.236.72.1 to 65.236.75.25465.236.75.2551,022
2065.236.76.0/2265.236.76.1 to 65.236.79.25465.236.79.2551,022
2165.236.80.0/2265.236.80.1 to 65.236.83.25465.236.83.2551,022
2265.236.84.0/2265.236.84.1 to 65.236.87.25465.236.87.2551,022
2365.236.88.0/2265.236.88.1 to 65.236.91.25465.236.91.2551,022
2465.236.92.0/2265.236.92.1 to 65.236.95.25465.236.95.2551,022
2565.236.96.0/2265.236.96.1 to 65.236.99.25465.236.99.2551,022
2665.236.100.0/2265.236.100.1 to 65.236.103.25465.236.103.2551,022
2765.236.104.0/2265.236.104.1 to 65.236.107.25465.236.107.2551,022
2865.236.108.0/2265.236.108.1 to 65.236.111.25465.236.111.2551,022
2965.236.112.0/2265.236.112.1 to 65.236.115.25465.236.115.2551,022
3065.236.116.0/2265.236.116.1 to 65.236.119.25465.236.119.2551,022
3165.236.120.0/2265.236.120.1 to 65.236.123.25465.236.123.2551,022
3265.236.124.0/2265.236.124.1 to 65.236.127.25465.236.127.2551,022
3365.236.128.0/2265.236.128.1 to 65.236.131.25465.236.131.2551,022
3465.236.132.0/2265.236.132.1 to 65.236.135.25465.236.135.2551,022
3565.236.136.0/2265.236.136.1 to 65.236.139.25465.236.139.2551,022
3665.236.140.0/2265.236.140.1 to 65.236.143.25465.236.143.2551,022
3765.236.144.0/2265.236.144.1 to 65.236.147.25465.236.147.2551,022
3865.236.148.0/2265.236.148.1 to 65.236.151.25465.236.151.2551,022
3965.236.152.0/2265.236.152.1 to 65.236.155.25465.236.155.2551,022
4065.236.156.0/2265.236.156.1 to 65.236.159.25465.236.159.2551,022
4165.236.160.0/2265.236.160.1 to 65.236.163.25465.236.163.2551,022
4265.236.164.0/2265.236.164.1 to 65.236.167.25465.236.167.2551,022
4365.236.168.0/2265.236.168.1 to 65.236.171.25465.236.171.2551,022
4465.236.172.0/2265.236.172.1 to 65.236.175.25465.236.175.2551,022
4565.236.176.0/2265.236.176.1 to 65.236.179.25465.236.179.2551,022
4665.236.180.0/2265.236.180.1 to 65.236.183.25465.236.183.2551,022
4765.236.184.0/2265.236.184.1 to 65.236.187.25465.236.187.2551,022
4865.236.188.0/2265.236.188.1 to 65.236.191.25465.236.191.2551,022
4965.236.192.0/2265.236.192.1 to 65.236.195.25465.236.195.2551,022
5065.236.196.0/2265.236.196.1 to 65.236.199.25465.236.199.2551,022
5165.236.200.0/2265.236.200.1 to 65.236.203.25465.236.203.2551,022
5265.236.204.0/2265.236.204.1 to 65.236.207.25465.236.207.2551,022
5365.236.208.0/2265.236.208.1 to 65.236.211.25465.236.211.2551,022
5465.236.212.0/2265.236.212.1 to 65.236.215.25465.236.215.2551,022
5565.236.216.0/2265.236.216.1 to 65.236.219.25465.236.219.2551,022
5665.236.220.0/2265.236.220.1 to 65.236.223.25465.236.223.2551,022
5765.236.224.0/2265.236.224.1 to 65.236.227.25465.236.227.2551,022
5865.236.228.0/2265.236.228.1 to 65.236.231.25465.236.231.2551,022
5965.236.232.0/2265.236.232.1 to 65.236.235.25465.236.235.2551,022
6065.236.236.0/2265.236.236.1 to 65.236.239.25465.236.239.2551,022
6165.236.240.0/2265.236.240.1 to 65.236.243.25465.236.243.2551,022
6265.236.244.0/2265.236.244.1 to 65.236.247.25465.236.247.2551,022
6365.236.248.0/2265.236.248.1 to 65.236.251.25465.236.251.2551,022
6465.236.252.0/2265.236.252.1 to 65.236.255.25465.236.255.2551,022
6565.237.0.0/2265.237.0.1 to 65.237.3.25465.237.3.2551,022
6665.237.4.0/2265.237.4.1 to 65.237.7.25465.237.7.2551,022
6765.237.8.0/2265.237.8.1 to 65.237.11.25465.237.11.2551,022
6865.237.12.0/2265.237.12.1 to 65.237.15.25465.237.15.2551,022
6965.237.16.0/2265.237.16.1 to 65.237.19.25465.237.19.2551,022
7065.237.20.0/2265.237.20.1 to 65.237.23.25465.237.23.2551,022
7165.237.24.0/2265.237.24.1 to 65.237.27.25465.237.27.2551,022
7265.237.28.0/2265.237.28.1 to 65.237.31.25465.237.31.2551,022
7365.237.32.0/2265.237.32.1 to 65.237.35.25465.237.35.2551,022
7465.237.36.0/2265.237.36.1 to 65.237.39.25465.237.39.2551,022
7565.237.40.0/2265.237.40.1 to 65.237.43.25465.237.43.2551,022
7665.237.44.0/2265.237.44.1 to 65.237.47.25465.237.47.2551,022
7765.237.48.0/2265.237.48.1 to 65.237.51.25465.237.51.2551,022
7865.237.52.0/2265.237.52.1 to 65.237.55.25465.237.55.2551,022
7965.237.56.0/2265.237.56.1 to 65.237.59.25465.237.59.2551,022
8065.237.60.0/2265.237.60.1 to 65.237.63.25465.237.63.2551,022
8165.237.64.0/2265.237.64.1 to 65.237.67.25465.237.67.2551,022
8265.237.68.0/2265.237.68.1 to 65.237.71.25465.237.71.2551,022
8365.237.72.0/2265.237.72.1 to 65.237.75.25465.237.75.2551,022
8465.237.76.0/2265.237.76.1 to 65.237.79.25465.237.79.2551,022
8565.237.80.0/2265.237.80.1 to 65.237.83.25465.237.83.2551,022
8665.237.84.0/2265.237.84.1 to 65.237.87.25465.237.87.2551,022
8765.237.88.0/2265.237.88.1 to 65.237.91.25465.237.91.2551,022
8865.237.92.0/2265.237.92.1 to 65.237.95.25465.237.95.2551,022
8965.237.96.0/2265.237.96.1 to 65.237.99.25465.237.99.2551,022
9065.237.100.0/2265.237.100.1 to 65.237.103.25465.237.103.2551,022
9165.237.104.0/2265.237.104.1 to 65.237.107.25465.237.107.2551,022
9265.237.108.0/2265.237.108.1 to 65.237.111.25465.237.111.2551,022
9365.237.112.0/2265.237.112.1 to 65.237.115.25465.237.115.2551,022
9465.237.116.0/2265.237.116.1 to 65.237.119.25465.237.119.2551,022
9565.237.120.0/2265.237.120.1 to 65.237.123.25465.237.123.2551,022
9665.237.124.0/2265.237.124.1 to 65.237.127.25465.237.127.2551,022
9765.237.128.0/2265.237.128.1 to 65.237.131.25465.237.131.2551,022
9865.237.132.0/2265.237.132.1 to 65.237.135.25465.237.135.2551,022
9965.237.136.0/2265.237.136.1 to 65.237.139.25465.237.139.2551,022
10065.237.140.0/2265.237.140.1 to 65.237.143.25465.237.143.2551,022
10165.237.144.0/2265.237.144.1 to 65.237.147.25465.237.147.2551,022
10265.237.148.0/2265.237.148.1 to 65.237.151.25465.237.151.2551,022
10365.237.152.0/2265.237.152.1 to 65.237.155.25465.237.155.2551,022
10465.237.156.0/2265.237.156.1 to 65.237.159.25465.237.159.2551,022
10565.237.160.0/2265.237.160.1 to 65.237.163.25465.237.163.2551,022
10665.237.164.0/2265.237.164.1 to 65.237.167.25465.237.167.2551,022
10765.237.168.0/2265.237.168.1 to 65.237.171.25465.237.171.2551,022
10865.237.172.0/2265.237.172.1 to 65.237.175.25465.237.175.2551,022
10965.237.176.0/2265.237.176.1 to 65.237.179.25465.237.179.2551,022
11065.237.180.0/2265.237.180.1 to 65.237.183.25465.237.183.2551,022
11165.237.184.0/2265.237.184.1 to 65.237.187.25465.237.187.2551,022
11265.237.188.0/2265.237.188.1 to 65.237.191.25465.237.191.2551,022
11365.237.192.0/2265.237.192.1 to 65.237.195.25465.237.195.2551,022
11465.237.196.0/2265.237.196.1 to 65.237.199.25465.237.199.2551,022
11565.237.200.0/2265.237.200.1 to 65.237.203.25465.237.203.2551,022
11665.237.204.0/2265.237.204.1 to 65.237.207.25465.237.207.2551,022
11765.237.208.0/2265.237.208.1 to 65.237.211.25465.237.211.2551,022
11865.237.212.0/2265.237.212.1 to 65.237.215.25465.237.215.2551,022
11965.237.216.0/2265.237.216.1 to 65.237.219.25465.237.219.2551,022
12065.237.220.0/2265.237.220.1 to 65.237.223.25465.237.223.2551,022
12165.237.224.0/2265.237.224.1 to 65.237.227.25465.237.227.2551,022
12265.237.228.0/2265.237.228.1 to 65.237.231.25465.237.231.2551,022
12365.237.232.0/2265.237.232.1 to 65.237.235.25465.237.235.2551,022
12465.237.236.0/2265.237.236.1 to 65.237.239.25465.237.239.2551,022
12565.237.240.0/2265.237.240.1 to 65.237.243.25465.237.243.2551,022
12665.237.244.0/2265.237.244.1 to 65.237.247.25465.237.247.2551,022
12765.237.248.0/2265.237.248.1 to 65.237.251.25465.237.251.2551,022
12865.237.252.0/2265.237.252.1 to 65.237.255.25465.237.255.2551,022

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.