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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.

Network240.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
240.0.0.0
Broadcast address
243.255.255.255
First usable
240.0.0.1
Last usable
243.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F0000000 · Integer 4026531840 to 4093640703
Reverse DNS zones
240.in-addr.arpa
241.in-addr.arpa
242.in-addr.arpa
243.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110000.00000000.00000000.00000000240.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network11110000.00000000.00000000.00000000240.0.0.0
Broadcast11110011.11111111.11111111.11111111243.255.255.255
Split into smaller subnets/13
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

240.0.0.0/6 makes 128 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1240.0.0.0/13240.0.0.1 to 240.7.255.254240.7.255.255524,286
2240.8.0.0/13240.8.0.1 to 240.15.255.254240.15.255.255524,286
3240.16.0.0/13240.16.0.1 to 240.23.255.254240.23.255.255524,286
4240.24.0.0/13240.24.0.1 to 240.31.255.254240.31.255.255524,286
5240.32.0.0/13240.32.0.1 to 240.39.255.254240.39.255.255524,286
6240.40.0.0/13240.40.0.1 to 240.47.255.254240.47.255.255524,286
7240.48.0.0/13240.48.0.1 to 240.55.255.254240.55.255.255524,286
8240.56.0.0/13240.56.0.1 to 240.63.255.254240.63.255.255524,286
9240.64.0.0/13240.64.0.1 to 240.71.255.254240.71.255.255524,286
10240.72.0.0/13240.72.0.1 to 240.79.255.254240.79.255.255524,286
11240.80.0.0/13240.80.0.1 to 240.87.255.254240.87.255.255524,286
12240.88.0.0/13240.88.0.1 to 240.95.255.254240.95.255.255524,286
13240.96.0.0/13240.96.0.1 to 240.103.255.254240.103.255.255524,286
14240.104.0.0/13240.104.0.1 to 240.111.255.254240.111.255.255524,286
15240.112.0.0/13240.112.0.1 to 240.119.255.254240.119.255.255524,286
16240.120.0.0/13240.120.0.1 to 240.127.255.254240.127.255.255524,286
17240.128.0.0/13240.128.0.1 to 240.135.255.254240.135.255.255524,286
18240.136.0.0/13240.136.0.1 to 240.143.255.254240.143.255.255524,286
19240.144.0.0/13240.144.0.1 to 240.151.255.254240.151.255.255524,286
20240.152.0.0/13240.152.0.1 to 240.159.255.254240.159.255.255524,286
21240.160.0.0/13240.160.0.1 to 240.167.255.254240.167.255.255524,286
22240.168.0.0/13240.168.0.1 to 240.175.255.254240.175.255.255524,286
23240.176.0.0/13240.176.0.1 to 240.183.255.254240.183.255.255524,286
24240.184.0.0/13240.184.0.1 to 240.191.255.254240.191.255.255524,286
25240.192.0.0/13240.192.0.1 to 240.199.255.254240.199.255.255524,286
26240.200.0.0/13240.200.0.1 to 240.207.255.254240.207.255.255524,286
27240.208.0.0/13240.208.0.1 to 240.215.255.254240.215.255.255524,286
28240.216.0.0/13240.216.0.1 to 240.223.255.254240.223.255.255524,286
29240.224.0.0/13240.224.0.1 to 240.231.255.254240.231.255.255524,286
30240.232.0.0/13240.232.0.1 to 240.239.255.254240.239.255.255524,286
31240.240.0.0/13240.240.0.1 to 240.247.255.254240.247.255.255524,286
32240.248.0.0/13240.248.0.1 to 240.255.255.254240.255.255.255524,286
33241.0.0.0/13241.0.0.1 to 241.7.255.254241.7.255.255524,286
34241.8.0.0/13241.8.0.1 to 241.15.255.254241.15.255.255524,286
35241.16.0.0/13241.16.0.1 to 241.23.255.254241.23.255.255524,286
36241.24.0.0/13241.24.0.1 to 241.31.255.254241.31.255.255524,286
37241.32.0.0/13241.32.0.1 to 241.39.255.254241.39.255.255524,286
38241.40.0.0/13241.40.0.1 to 241.47.255.254241.47.255.255524,286
39241.48.0.0/13241.48.0.1 to 241.55.255.254241.55.255.255524,286
40241.56.0.0/13241.56.0.1 to 241.63.255.254241.63.255.255524,286
41241.64.0.0/13241.64.0.1 to 241.71.255.254241.71.255.255524,286
42241.72.0.0/13241.72.0.1 to 241.79.255.254241.79.255.255524,286
43241.80.0.0/13241.80.0.1 to 241.87.255.254241.87.255.255524,286
44241.88.0.0/13241.88.0.1 to 241.95.255.254241.95.255.255524,286
45241.96.0.0/13241.96.0.1 to 241.103.255.254241.103.255.255524,286
46241.104.0.0/13241.104.0.1 to 241.111.255.254241.111.255.255524,286
47241.112.0.0/13241.112.0.1 to 241.119.255.254241.119.255.255524,286
48241.120.0.0/13241.120.0.1 to 241.127.255.254241.127.255.255524,286
49241.128.0.0/13241.128.0.1 to 241.135.255.254241.135.255.255524,286
50241.136.0.0/13241.136.0.1 to 241.143.255.254241.143.255.255524,286
51241.144.0.0/13241.144.0.1 to 241.151.255.254241.151.255.255524,286
52241.152.0.0/13241.152.0.1 to 241.159.255.254241.159.255.255524,286
53241.160.0.0/13241.160.0.1 to 241.167.255.254241.167.255.255524,286
54241.168.0.0/13241.168.0.1 to 241.175.255.254241.175.255.255524,286
55241.176.0.0/13241.176.0.1 to 241.183.255.254241.183.255.255524,286
56241.184.0.0/13241.184.0.1 to 241.191.255.254241.191.255.255524,286
57241.192.0.0/13241.192.0.1 to 241.199.255.254241.199.255.255524,286
58241.200.0.0/13241.200.0.1 to 241.207.255.254241.207.255.255524,286
59241.208.0.0/13241.208.0.1 to 241.215.255.254241.215.255.255524,286
60241.216.0.0/13241.216.0.1 to 241.223.255.254241.223.255.255524,286
61241.224.0.0/13241.224.0.1 to 241.231.255.254241.231.255.255524,286
62241.232.0.0/13241.232.0.1 to 241.239.255.254241.239.255.255524,286
63241.240.0.0/13241.240.0.1 to 241.247.255.254241.247.255.255524,286
64241.248.0.0/13241.248.0.1 to 241.255.255.254241.255.255.255524,286
65242.0.0.0/13242.0.0.1 to 242.7.255.254242.7.255.255524,286
66242.8.0.0/13242.8.0.1 to 242.15.255.254242.15.255.255524,286
67242.16.0.0/13242.16.0.1 to 242.23.255.254242.23.255.255524,286
68242.24.0.0/13242.24.0.1 to 242.31.255.254242.31.255.255524,286
69242.32.0.0/13242.32.0.1 to 242.39.255.254242.39.255.255524,286
70242.40.0.0/13242.40.0.1 to 242.47.255.254242.47.255.255524,286
71242.48.0.0/13242.48.0.1 to 242.55.255.254242.55.255.255524,286
72242.56.0.0/13242.56.0.1 to 242.63.255.254242.63.255.255524,286
73242.64.0.0/13242.64.0.1 to 242.71.255.254242.71.255.255524,286
74242.72.0.0/13242.72.0.1 to 242.79.255.254242.79.255.255524,286
75242.80.0.0/13242.80.0.1 to 242.87.255.254242.87.255.255524,286
76242.88.0.0/13242.88.0.1 to 242.95.255.254242.95.255.255524,286
77242.96.0.0/13242.96.0.1 to 242.103.255.254242.103.255.255524,286
78242.104.0.0/13242.104.0.1 to 242.111.255.254242.111.255.255524,286
79242.112.0.0/13242.112.0.1 to 242.119.255.254242.119.255.255524,286
80242.120.0.0/13242.120.0.1 to 242.127.255.254242.127.255.255524,286
81242.128.0.0/13242.128.0.1 to 242.135.255.254242.135.255.255524,286
82242.136.0.0/13242.136.0.1 to 242.143.255.254242.143.255.255524,286
83242.144.0.0/13242.144.0.1 to 242.151.255.254242.151.255.255524,286
84242.152.0.0/13242.152.0.1 to 242.159.255.254242.159.255.255524,286
85242.160.0.0/13242.160.0.1 to 242.167.255.254242.167.255.255524,286
86242.168.0.0/13242.168.0.1 to 242.175.255.254242.175.255.255524,286
87242.176.0.0/13242.176.0.1 to 242.183.255.254242.183.255.255524,286
88242.184.0.0/13242.184.0.1 to 242.191.255.254242.191.255.255524,286
89242.192.0.0/13242.192.0.1 to 242.199.255.254242.199.255.255524,286
90242.200.0.0/13242.200.0.1 to 242.207.255.254242.207.255.255524,286
91242.208.0.0/13242.208.0.1 to 242.215.255.254242.215.255.255524,286
92242.216.0.0/13242.216.0.1 to 242.223.255.254242.223.255.255524,286
93242.224.0.0/13242.224.0.1 to 242.231.255.254242.231.255.255524,286
94242.232.0.0/13242.232.0.1 to 242.239.255.254242.239.255.255524,286
95242.240.0.0/13242.240.0.1 to 242.247.255.254242.247.255.255524,286
96242.248.0.0/13242.248.0.1 to 242.255.255.254242.255.255.255524,286
97243.0.0.0/13243.0.0.1 to 243.7.255.254243.7.255.255524,286
98243.8.0.0/13243.8.0.1 to 243.15.255.254243.15.255.255524,286
99243.16.0.0/13243.16.0.1 to 243.23.255.254243.23.255.255524,286
100243.24.0.0/13243.24.0.1 to 243.31.255.254243.31.255.255524,286
101243.32.0.0/13243.32.0.1 to 243.39.255.254243.39.255.255524,286
102243.40.0.0/13243.40.0.1 to 243.47.255.254243.47.255.255524,286
103243.48.0.0/13243.48.0.1 to 243.55.255.254243.55.255.255524,286
104243.56.0.0/13243.56.0.1 to 243.63.255.254243.63.255.255524,286
105243.64.0.0/13243.64.0.1 to 243.71.255.254243.71.255.255524,286
106243.72.0.0/13243.72.0.1 to 243.79.255.254243.79.255.255524,286
107243.80.0.0/13243.80.0.1 to 243.87.255.254243.87.255.255524,286
108243.88.0.0/13243.88.0.1 to 243.95.255.254243.95.255.255524,286
109243.96.0.0/13243.96.0.1 to 243.103.255.254243.103.255.255524,286
110243.104.0.0/13243.104.0.1 to 243.111.255.254243.111.255.255524,286
111243.112.0.0/13243.112.0.1 to 243.119.255.254243.119.255.255524,286
112243.120.0.0/13243.120.0.1 to 243.127.255.254243.127.255.255524,286
113243.128.0.0/13243.128.0.1 to 243.135.255.254243.135.255.255524,286
114243.136.0.0/13243.136.0.1 to 243.143.255.254243.143.255.255524,286
115243.144.0.0/13243.144.0.1 to 243.151.255.254243.151.255.255524,286
116243.152.0.0/13243.152.0.1 to 243.159.255.254243.159.255.255524,286
117243.160.0.0/13243.160.0.1 to 243.167.255.254243.167.255.255524,286
118243.168.0.0/13243.168.0.1 to 243.175.255.254243.175.255.255524,286
119243.176.0.0/13243.176.0.1 to 243.183.255.254243.183.255.255524,286
120243.184.0.0/13243.184.0.1 to 243.191.255.254243.191.255.255524,286
121243.192.0.0/13243.192.0.1 to 243.199.255.254243.199.255.255524,286
122243.200.0.0/13243.200.0.1 to 243.207.255.254243.207.255.255524,286
123243.208.0.0/13243.208.0.1 to 243.215.255.254243.215.255.255524,286
124243.216.0.0/13243.216.0.1 to 243.223.255.254243.223.255.255524,286
125243.224.0.0/13243.224.0.1 to 243.231.255.254243.231.255.255524,286
126243.232.0.0/13243.232.0.1 to 243.239.255.254243.239.255.255524,286
127243.240.0.0/13243.240.0.1 to 243.247.255.254243.247.255.255524,286
128243.248.0.0/13243.248.0.1 to 243.255.255.254243.255.255.255524,286

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.