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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.

Network243.2.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
243.2.0.0
Broadcast address
243.3.255.255
First usable
243.2.0.1
Last usable
243.3.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F3020000 · Integer 4076994560 to 4077125631
Reverse DNS zones
2.243.in-addr.arpa
3.243.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
Address11110011.00000010.00000000.00000000243.2.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network11110011.00000010.00000000.00000000243.2.0.0
Broadcast11110011.00000011.11111111.11111111243.3.255.255
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)

243.2.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1243.2.0.0/22243.2.0.1 to 243.2.3.254243.2.3.2551,022
2243.2.4.0/22243.2.4.1 to 243.2.7.254243.2.7.2551,022
3243.2.8.0/22243.2.8.1 to 243.2.11.254243.2.11.2551,022
4243.2.12.0/22243.2.12.1 to 243.2.15.254243.2.15.2551,022
5243.2.16.0/22243.2.16.1 to 243.2.19.254243.2.19.2551,022
6243.2.20.0/22243.2.20.1 to 243.2.23.254243.2.23.2551,022
7243.2.24.0/22243.2.24.1 to 243.2.27.254243.2.27.2551,022
8243.2.28.0/22243.2.28.1 to 243.2.31.254243.2.31.2551,022
9243.2.32.0/22243.2.32.1 to 243.2.35.254243.2.35.2551,022
10243.2.36.0/22243.2.36.1 to 243.2.39.254243.2.39.2551,022
11243.2.40.0/22243.2.40.1 to 243.2.43.254243.2.43.2551,022
12243.2.44.0/22243.2.44.1 to 243.2.47.254243.2.47.2551,022
13243.2.48.0/22243.2.48.1 to 243.2.51.254243.2.51.2551,022
14243.2.52.0/22243.2.52.1 to 243.2.55.254243.2.55.2551,022
15243.2.56.0/22243.2.56.1 to 243.2.59.254243.2.59.2551,022
16243.2.60.0/22243.2.60.1 to 243.2.63.254243.2.63.2551,022
17243.2.64.0/22243.2.64.1 to 243.2.67.254243.2.67.2551,022
18243.2.68.0/22243.2.68.1 to 243.2.71.254243.2.71.2551,022
19243.2.72.0/22243.2.72.1 to 243.2.75.254243.2.75.2551,022
20243.2.76.0/22243.2.76.1 to 243.2.79.254243.2.79.2551,022
21243.2.80.0/22243.2.80.1 to 243.2.83.254243.2.83.2551,022
22243.2.84.0/22243.2.84.1 to 243.2.87.254243.2.87.2551,022
23243.2.88.0/22243.2.88.1 to 243.2.91.254243.2.91.2551,022
24243.2.92.0/22243.2.92.1 to 243.2.95.254243.2.95.2551,022
25243.2.96.0/22243.2.96.1 to 243.2.99.254243.2.99.2551,022
26243.2.100.0/22243.2.100.1 to 243.2.103.254243.2.103.2551,022
27243.2.104.0/22243.2.104.1 to 243.2.107.254243.2.107.2551,022
28243.2.108.0/22243.2.108.1 to 243.2.111.254243.2.111.2551,022
29243.2.112.0/22243.2.112.1 to 243.2.115.254243.2.115.2551,022
30243.2.116.0/22243.2.116.1 to 243.2.119.254243.2.119.2551,022
31243.2.120.0/22243.2.120.1 to 243.2.123.254243.2.123.2551,022
32243.2.124.0/22243.2.124.1 to 243.2.127.254243.2.127.2551,022
33243.2.128.0/22243.2.128.1 to 243.2.131.254243.2.131.2551,022
34243.2.132.0/22243.2.132.1 to 243.2.135.254243.2.135.2551,022
35243.2.136.0/22243.2.136.1 to 243.2.139.254243.2.139.2551,022
36243.2.140.0/22243.2.140.1 to 243.2.143.254243.2.143.2551,022
37243.2.144.0/22243.2.144.1 to 243.2.147.254243.2.147.2551,022
38243.2.148.0/22243.2.148.1 to 243.2.151.254243.2.151.2551,022
39243.2.152.0/22243.2.152.1 to 243.2.155.254243.2.155.2551,022
40243.2.156.0/22243.2.156.1 to 243.2.159.254243.2.159.2551,022
41243.2.160.0/22243.2.160.1 to 243.2.163.254243.2.163.2551,022
42243.2.164.0/22243.2.164.1 to 243.2.167.254243.2.167.2551,022
43243.2.168.0/22243.2.168.1 to 243.2.171.254243.2.171.2551,022
44243.2.172.0/22243.2.172.1 to 243.2.175.254243.2.175.2551,022
45243.2.176.0/22243.2.176.1 to 243.2.179.254243.2.179.2551,022
46243.2.180.0/22243.2.180.1 to 243.2.183.254243.2.183.2551,022
47243.2.184.0/22243.2.184.1 to 243.2.187.254243.2.187.2551,022
48243.2.188.0/22243.2.188.1 to 243.2.191.254243.2.191.2551,022
49243.2.192.0/22243.2.192.1 to 243.2.195.254243.2.195.2551,022
50243.2.196.0/22243.2.196.1 to 243.2.199.254243.2.199.2551,022
51243.2.200.0/22243.2.200.1 to 243.2.203.254243.2.203.2551,022
52243.2.204.0/22243.2.204.1 to 243.2.207.254243.2.207.2551,022
53243.2.208.0/22243.2.208.1 to 243.2.211.254243.2.211.2551,022
54243.2.212.0/22243.2.212.1 to 243.2.215.254243.2.215.2551,022
55243.2.216.0/22243.2.216.1 to 243.2.219.254243.2.219.2551,022
56243.2.220.0/22243.2.220.1 to 243.2.223.254243.2.223.2551,022
57243.2.224.0/22243.2.224.1 to 243.2.227.254243.2.227.2551,022
58243.2.228.0/22243.2.228.1 to 243.2.231.254243.2.231.2551,022
59243.2.232.0/22243.2.232.1 to 243.2.235.254243.2.235.2551,022
60243.2.236.0/22243.2.236.1 to 243.2.239.254243.2.239.2551,022
61243.2.240.0/22243.2.240.1 to 243.2.243.254243.2.243.2551,022
62243.2.244.0/22243.2.244.1 to 243.2.247.254243.2.247.2551,022
63243.2.248.0/22243.2.248.1 to 243.2.251.254243.2.251.2551,022
64243.2.252.0/22243.2.252.1 to 243.2.255.254243.2.255.2551,022
65243.3.0.0/22243.3.0.1 to 243.3.3.254243.3.3.2551,022
66243.3.4.0/22243.3.4.1 to 243.3.7.254243.3.7.2551,022
67243.3.8.0/22243.3.8.1 to 243.3.11.254243.3.11.2551,022
68243.3.12.0/22243.3.12.1 to 243.3.15.254243.3.15.2551,022
69243.3.16.0/22243.3.16.1 to 243.3.19.254243.3.19.2551,022
70243.3.20.0/22243.3.20.1 to 243.3.23.254243.3.23.2551,022
71243.3.24.0/22243.3.24.1 to 243.3.27.254243.3.27.2551,022
72243.3.28.0/22243.3.28.1 to 243.3.31.254243.3.31.2551,022
73243.3.32.0/22243.3.32.1 to 243.3.35.254243.3.35.2551,022
74243.3.36.0/22243.3.36.1 to 243.3.39.254243.3.39.2551,022
75243.3.40.0/22243.3.40.1 to 243.3.43.254243.3.43.2551,022
76243.3.44.0/22243.3.44.1 to 243.3.47.254243.3.47.2551,022
77243.3.48.0/22243.3.48.1 to 243.3.51.254243.3.51.2551,022
78243.3.52.0/22243.3.52.1 to 243.3.55.254243.3.55.2551,022
79243.3.56.0/22243.3.56.1 to 243.3.59.254243.3.59.2551,022
80243.3.60.0/22243.3.60.1 to 243.3.63.254243.3.63.2551,022
81243.3.64.0/22243.3.64.1 to 243.3.67.254243.3.67.2551,022
82243.3.68.0/22243.3.68.1 to 243.3.71.254243.3.71.2551,022
83243.3.72.0/22243.3.72.1 to 243.3.75.254243.3.75.2551,022
84243.3.76.0/22243.3.76.1 to 243.3.79.254243.3.79.2551,022
85243.3.80.0/22243.3.80.1 to 243.3.83.254243.3.83.2551,022
86243.3.84.0/22243.3.84.1 to 243.3.87.254243.3.87.2551,022
87243.3.88.0/22243.3.88.1 to 243.3.91.254243.3.91.2551,022
88243.3.92.0/22243.3.92.1 to 243.3.95.254243.3.95.2551,022
89243.3.96.0/22243.3.96.1 to 243.3.99.254243.3.99.2551,022
90243.3.100.0/22243.3.100.1 to 243.3.103.254243.3.103.2551,022
91243.3.104.0/22243.3.104.1 to 243.3.107.254243.3.107.2551,022
92243.3.108.0/22243.3.108.1 to 243.3.111.254243.3.111.2551,022
93243.3.112.0/22243.3.112.1 to 243.3.115.254243.3.115.2551,022
94243.3.116.0/22243.3.116.1 to 243.3.119.254243.3.119.2551,022
95243.3.120.0/22243.3.120.1 to 243.3.123.254243.3.123.2551,022
96243.3.124.0/22243.3.124.1 to 243.3.127.254243.3.127.2551,022
97243.3.128.0/22243.3.128.1 to 243.3.131.254243.3.131.2551,022
98243.3.132.0/22243.3.132.1 to 243.3.135.254243.3.135.2551,022
99243.3.136.0/22243.3.136.1 to 243.3.139.254243.3.139.2551,022
100243.3.140.0/22243.3.140.1 to 243.3.143.254243.3.143.2551,022
101243.3.144.0/22243.3.144.1 to 243.3.147.254243.3.147.2551,022
102243.3.148.0/22243.3.148.1 to 243.3.151.254243.3.151.2551,022
103243.3.152.0/22243.3.152.1 to 243.3.155.254243.3.155.2551,022
104243.3.156.0/22243.3.156.1 to 243.3.159.254243.3.159.2551,022
105243.3.160.0/22243.3.160.1 to 243.3.163.254243.3.163.2551,022
106243.3.164.0/22243.3.164.1 to 243.3.167.254243.3.167.2551,022
107243.3.168.0/22243.3.168.1 to 243.3.171.254243.3.171.2551,022
108243.3.172.0/22243.3.172.1 to 243.3.175.254243.3.175.2551,022
109243.3.176.0/22243.3.176.1 to 243.3.179.254243.3.179.2551,022
110243.3.180.0/22243.3.180.1 to 243.3.183.254243.3.183.2551,022
111243.3.184.0/22243.3.184.1 to 243.3.187.254243.3.187.2551,022
112243.3.188.0/22243.3.188.1 to 243.3.191.254243.3.191.2551,022
113243.3.192.0/22243.3.192.1 to 243.3.195.254243.3.195.2551,022
114243.3.196.0/22243.3.196.1 to 243.3.199.254243.3.199.2551,022
115243.3.200.0/22243.3.200.1 to 243.3.203.254243.3.203.2551,022
116243.3.204.0/22243.3.204.1 to 243.3.207.254243.3.207.2551,022
117243.3.208.0/22243.3.208.1 to 243.3.211.254243.3.211.2551,022
118243.3.212.0/22243.3.212.1 to 243.3.215.254243.3.215.2551,022
119243.3.216.0/22243.3.216.1 to 243.3.219.254243.3.219.2551,022
120243.3.220.0/22243.3.220.1 to 243.3.223.254243.3.223.2551,022
121243.3.224.0/22243.3.224.1 to 243.3.227.254243.3.227.2551,022
122243.3.228.0/22243.3.228.1 to 243.3.231.254243.3.231.2551,022
123243.3.232.0/22243.3.232.1 to 243.3.235.254243.3.235.2551,022
124243.3.236.0/22243.3.236.1 to 243.3.239.254243.3.239.2551,022
125243.3.240.0/22243.3.240.1 to 243.3.243.254243.3.243.2551,022
126243.3.244.0/22243.3.244.1 to 243.3.247.254243.3.247.2551,022
127243.3.248.0/22243.3.248.1 to 243.3.251.254243.3.251.2551,022
128243.3.252.0/22243.3.252.1 to 243.3.255.254243.3.255.2551,022

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.