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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.

Network240.80.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
240.80.0.0
Broadcast address
240.95.255.255
First usable
240.80.0.1
Last usable
240.95.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F0500000 · Integer 4031774720 to 4032823295
Reverse DNS zones
80.240.in-addr.arpa
81.240.in-addr.arpa
82.240.in-addr.arpa
83.240.in-addr.arpa
84.240.in-addr.arpa
85.240.in-addr.arpa
86.240.in-addr.arpa
87.240.in-addr.arpa
88.240.in-addr.arpa
89.240.in-addr.arpa
90.240.in-addr.arpa
91.240.in-addr.arpa
92.240.in-addr.arpa
93.240.in-addr.arpa
94.240.in-addr.arpa
95.240.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110000.01010000.00000000.00000000240.80.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11110000.01010000.00000000.00000000240.80.0.0
Broadcast11110000.01011111.11111111.11111111240.95.255.255
Split into smaller subnets/19
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

240.80.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1240.80.0.0/19240.80.0.1 to 240.80.31.254240.80.31.2558,190
2240.80.32.0/19240.80.32.1 to 240.80.63.254240.80.63.2558,190
3240.80.64.0/19240.80.64.1 to 240.80.95.254240.80.95.2558,190
4240.80.96.0/19240.80.96.1 to 240.80.127.254240.80.127.2558,190
5240.80.128.0/19240.80.128.1 to 240.80.159.254240.80.159.2558,190
6240.80.160.0/19240.80.160.1 to 240.80.191.254240.80.191.2558,190
7240.80.192.0/19240.80.192.1 to 240.80.223.254240.80.223.2558,190
8240.80.224.0/19240.80.224.1 to 240.80.255.254240.80.255.2558,190
9240.81.0.0/19240.81.0.1 to 240.81.31.254240.81.31.2558,190
10240.81.32.0/19240.81.32.1 to 240.81.63.254240.81.63.2558,190
11240.81.64.0/19240.81.64.1 to 240.81.95.254240.81.95.2558,190
12240.81.96.0/19240.81.96.1 to 240.81.127.254240.81.127.2558,190
13240.81.128.0/19240.81.128.1 to 240.81.159.254240.81.159.2558,190
14240.81.160.0/19240.81.160.1 to 240.81.191.254240.81.191.2558,190
15240.81.192.0/19240.81.192.1 to 240.81.223.254240.81.223.2558,190
16240.81.224.0/19240.81.224.1 to 240.81.255.254240.81.255.2558,190
17240.82.0.0/19240.82.0.1 to 240.82.31.254240.82.31.2558,190
18240.82.32.0/19240.82.32.1 to 240.82.63.254240.82.63.2558,190
19240.82.64.0/19240.82.64.1 to 240.82.95.254240.82.95.2558,190
20240.82.96.0/19240.82.96.1 to 240.82.127.254240.82.127.2558,190
21240.82.128.0/19240.82.128.1 to 240.82.159.254240.82.159.2558,190
22240.82.160.0/19240.82.160.1 to 240.82.191.254240.82.191.2558,190
23240.82.192.0/19240.82.192.1 to 240.82.223.254240.82.223.2558,190
24240.82.224.0/19240.82.224.1 to 240.82.255.254240.82.255.2558,190
25240.83.0.0/19240.83.0.1 to 240.83.31.254240.83.31.2558,190
26240.83.32.0/19240.83.32.1 to 240.83.63.254240.83.63.2558,190
27240.83.64.0/19240.83.64.1 to 240.83.95.254240.83.95.2558,190
28240.83.96.0/19240.83.96.1 to 240.83.127.254240.83.127.2558,190
29240.83.128.0/19240.83.128.1 to 240.83.159.254240.83.159.2558,190
30240.83.160.0/19240.83.160.1 to 240.83.191.254240.83.191.2558,190
31240.83.192.0/19240.83.192.1 to 240.83.223.254240.83.223.2558,190
32240.83.224.0/19240.83.224.1 to 240.83.255.254240.83.255.2558,190
33240.84.0.0/19240.84.0.1 to 240.84.31.254240.84.31.2558,190
34240.84.32.0/19240.84.32.1 to 240.84.63.254240.84.63.2558,190
35240.84.64.0/19240.84.64.1 to 240.84.95.254240.84.95.2558,190
36240.84.96.0/19240.84.96.1 to 240.84.127.254240.84.127.2558,190
37240.84.128.0/19240.84.128.1 to 240.84.159.254240.84.159.2558,190
38240.84.160.0/19240.84.160.1 to 240.84.191.254240.84.191.2558,190
39240.84.192.0/19240.84.192.1 to 240.84.223.254240.84.223.2558,190
40240.84.224.0/19240.84.224.1 to 240.84.255.254240.84.255.2558,190
41240.85.0.0/19240.85.0.1 to 240.85.31.254240.85.31.2558,190
42240.85.32.0/19240.85.32.1 to 240.85.63.254240.85.63.2558,190
43240.85.64.0/19240.85.64.1 to 240.85.95.254240.85.95.2558,190
44240.85.96.0/19240.85.96.1 to 240.85.127.254240.85.127.2558,190
45240.85.128.0/19240.85.128.1 to 240.85.159.254240.85.159.2558,190
46240.85.160.0/19240.85.160.1 to 240.85.191.254240.85.191.2558,190
47240.85.192.0/19240.85.192.1 to 240.85.223.254240.85.223.2558,190
48240.85.224.0/19240.85.224.1 to 240.85.255.254240.85.255.2558,190
49240.86.0.0/19240.86.0.1 to 240.86.31.254240.86.31.2558,190
50240.86.32.0/19240.86.32.1 to 240.86.63.254240.86.63.2558,190
51240.86.64.0/19240.86.64.1 to 240.86.95.254240.86.95.2558,190
52240.86.96.0/19240.86.96.1 to 240.86.127.254240.86.127.2558,190
53240.86.128.0/19240.86.128.1 to 240.86.159.254240.86.159.2558,190
54240.86.160.0/19240.86.160.1 to 240.86.191.254240.86.191.2558,190
55240.86.192.0/19240.86.192.1 to 240.86.223.254240.86.223.2558,190
56240.86.224.0/19240.86.224.1 to 240.86.255.254240.86.255.2558,190
57240.87.0.0/19240.87.0.1 to 240.87.31.254240.87.31.2558,190
58240.87.32.0/19240.87.32.1 to 240.87.63.254240.87.63.2558,190
59240.87.64.0/19240.87.64.1 to 240.87.95.254240.87.95.2558,190
60240.87.96.0/19240.87.96.1 to 240.87.127.254240.87.127.2558,190
61240.87.128.0/19240.87.128.1 to 240.87.159.254240.87.159.2558,190
62240.87.160.0/19240.87.160.1 to 240.87.191.254240.87.191.2558,190
63240.87.192.0/19240.87.192.1 to 240.87.223.254240.87.223.2558,190
64240.87.224.0/19240.87.224.1 to 240.87.255.254240.87.255.2558,190
65240.88.0.0/19240.88.0.1 to 240.88.31.254240.88.31.2558,190
66240.88.32.0/19240.88.32.1 to 240.88.63.254240.88.63.2558,190
67240.88.64.0/19240.88.64.1 to 240.88.95.254240.88.95.2558,190
68240.88.96.0/19240.88.96.1 to 240.88.127.254240.88.127.2558,190
69240.88.128.0/19240.88.128.1 to 240.88.159.254240.88.159.2558,190
70240.88.160.0/19240.88.160.1 to 240.88.191.254240.88.191.2558,190
71240.88.192.0/19240.88.192.1 to 240.88.223.254240.88.223.2558,190
72240.88.224.0/19240.88.224.1 to 240.88.255.254240.88.255.2558,190
73240.89.0.0/19240.89.0.1 to 240.89.31.254240.89.31.2558,190
74240.89.32.0/19240.89.32.1 to 240.89.63.254240.89.63.2558,190
75240.89.64.0/19240.89.64.1 to 240.89.95.254240.89.95.2558,190
76240.89.96.0/19240.89.96.1 to 240.89.127.254240.89.127.2558,190
77240.89.128.0/19240.89.128.1 to 240.89.159.254240.89.159.2558,190
78240.89.160.0/19240.89.160.1 to 240.89.191.254240.89.191.2558,190
79240.89.192.0/19240.89.192.1 to 240.89.223.254240.89.223.2558,190
80240.89.224.0/19240.89.224.1 to 240.89.255.254240.89.255.2558,190
81240.90.0.0/19240.90.0.1 to 240.90.31.254240.90.31.2558,190
82240.90.32.0/19240.90.32.1 to 240.90.63.254240.90.63.2558,190
83240.90.64.0/19240.90.64.1 to 240.90.95.254240.90.95.2558,190
84240.90.96.0/19240.90.96.1 to 240.90.127.254240.90.127.2558,190
85240.90.128.0/19240.90.128.1 to 240.90.159.254240.90.159.2558,190
86240.90.160.0/19240.90.160.1 to 240.90.191.254240.90.191.2558,190
87240.90.192.0/19240.90.192.1 to 240.90.223.254240.90.223.2558,190
88240.90.224.0/19240.90.224.1 to 240.90.255.254240.90.255.2558,190
89240.91.0.0/19240.91.0.1 to 240.91.31.254240.91.31.2558,190
90240.91.32.0/19240.91.32.1 to 240.91.63.254240.91.63.2558,190
91240.91.64.0/19240.91.64.1 to 240.91.95.254240.91.95.2558,190
92240.91.96.0/19240.91.96.1 to 240.91.127.254240.91.127.2558,190
93240.91.128.0/19240.91.128.1 to 240.91.159.254240.91.159.2558,190
94240.91.160.0/19240.91.160.1 to 240.91.191.254240.91.191.2558,190
95240.91.192.0/19240.91.192.1 to 240.91.223.254240.91.223.2558,190
96240.91.224.0/19240.91.224.1 to 240.91.255.254240.91.255.2558,190
97240.92.0.0/19240.92.0.1 to 240.92.31.254240.92.31.2558,190
98240.92.32.0/19240.92.32.1 to 240.92.63.254240.92.63.2558,190
99240.92.64.0/19240.92.64.1 to 240.92.95.254240.92.95.2558,190
100240.92.96.0/19240.92.96.1 to 240.92.127.254240.92.127.2558,190
101240.92.128.0/19240.92.128.1 to 240.92.159.254240.92.159.2558,190
102240.92.160.0/19240.92.160.1 to 240.92.191.254240.92.191.2558,190
103240.92.192.0/19240.92.192.1 to 240.92.223.254240.92.223.2558,190
104240.92.224.0/19240.92.224.1 to 240.92.255.254240.92.255.2558,190
105240.93.0.0/19240.93.0.1 to 240.93.31.254240.93.31.2558,190
106240.93.32.0/19240.93.32.1 to 240.93.63.254240.93.63.2558,190
107240.93.64.0/19240.93.64.1 to 240.93.95.254240.93.95.2558,190
108240.93.96.0/19240.93.96.1 to 240.93.127.254240.93.127.2558,190
109240.93.128.0/19240.93.128.1 to 240.93.159.254240.93.159.2558,190
110240.93.160.0/19240.93.160.1 to 240.93.191.254240.93.191.2558,190
111240.93.192.0/19240.93.192.1 to 240.93.223.254240.93.223.2558,190
112240.93.224.0/19240.93.224.1 to 240.93.255.254240.93.255.2558,190
113240.94.0.0/19240.94.0.1 to 240.94.31.254240.94.31.2558,190
114240.94.32.0/19240.94.32.1 to 240.94.63.254240.94.63.2558,190
115240.94.64.0/19240.94.64.1 to 240.94.95.254240.94.95.2558,190
116240.94.96.0/19240.94.96.1 to 240.94.127.254240.94.127.2558,190
117240.94.128.0/19240.94.128.1 to 240.94.159.254240.94.159.2558,190
118240.94.160.0/19240.94.160.1 to 240.94.191.254240.94.191.2558,190
119240.94.192.0/19240.94.192.1 to 240.94.223.254240.94.223.2558,190
120240.94.224.0/19240.94.224.1 to 240.94.255.254240.94.255.2558,190
121240.95.0.0/19240.95.0.1 to 240.95.31.254240.95.31.2558,190
122240.95.32.0/19240.95.32.1 to 240.95.63.254240.95.63.2558,190
123240.95.64.0/19240.95.64.1 to 240.95.95.254240.95.95.2558,190
124240.95.96.0/19240.95.96.1 to 240.95.127.254240.95.127.2558,190
125240.95.128.0/19240.95.128.1 to 240.95.159.254240.95.159.2558,190
126240.95.160.0/19240.95.160.1 to 240.95.191.254240.95.191.2558,190
127240.95.192.0/19240.95.192.1 to 240.95.223.254240.95.223.2558,190
128240.95.224.0/19240.95.224.1 to 240.95.255.254240.95.255.2558,190

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.