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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.

Network245.32.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
245.32.0.0
Broadcast address
245.47.255.255
First usable
245.32.0.1
Last usable
245.47.255.254
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 F5200000 · Integer 4112515072 to 4113563647
Reverse DNS zones
32.245.in-addr.arpa
33.245.in-addr.arpa
34.245.in-addr.arpa
35.245.in-addr.arpa
36.245.in-addr.arpa
37.245.in-addr.arpa
38.245.in-addr.arpa
39.245.in-addr.arpa
40.245.in-addr.arpa
41.245.in-addr.arpa
42.245.in-addr.arpa
43.245.in-addr.arpa
44.245.in-addr.arpa
45.245.in-addr.arpa
46.245.in-addr.arpa
47.245.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
Address11110101.00100000.00000000.00000000245.32.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11110101.00100000.00000000.00000000245.32.0.0
Broadcast11110101.00101111.11111111.11111111245.47.255.255
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)

245.32.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1245.32.0.0/19245.32.0.1 to 245.32.31.254245.32.31.2558,190
2245.32.32.0/19245.32.32.1 to 245.32.63.254245.32.63.2558,190
3245.32.64.0/19245.32.64.1 to 245.32.95.254245.32.95.2558,190
4245.32.96.0/19245.32.96.1 to 245.32.127.254245.32.127.2558,190
5245.32.128.0/19245.32.128.1 to 245.32.159.254245.32.159.2558,190
6245.32.160.0/19245.32.160.1 to 245.32.191.254245.32.191.2558,190
7245.32.192.0/19245.32.192.1 to 245.32.223.254245.32.223.2558,190
8245.32.224.0/19245.32.224.1 to 245.32.255.254245.32.255.2558,190
9245.33.0.0/19245.33.0.1 to 245.33.31.254245.33.31.2558,190
10245.33.32.0/19245.33.32.1 to 245.33.63.254245.33.63.2558,190
11245.33.64.0/19245.33.64.1 to 245.33.95.254245.33.95.2558,190
12245.33.96.0/19245.33.96.1 to 245.33.127.254245.33.127.2558,190
13245.33.128.0/19245.33.128.1 to 245.33.159.254245.33.159.2558,190
14245.33.160.0/19245.33.160.1 to 245.33.191.254245.33.191.2558,190
15245.33.192.0/19245.33.192.1 to 245.33.223.254245.33.223.2558,190
16245.33.224.0/19245.33.224.1 to 245.33.255.254245.33.255.2558,190
17245.34.0.0/19245.34.0.1 to 245.34.31.254245.34.31.2558,190
18245.34.32.0/19245.34.32.1 to 245.34.63.254245.34.63.2558,190
19245.34.64.0/19245.34.64.1 to 245.34.95.254245.34.95.2558,190
20245.34.96.0/19245.34.96.1 to 245.34.127.254245.34.127.2558,190
21245.34.128.0/19245.34.128.1 to 245.34.159.254245.34.159.2558,190
22245.34.160.0/19245.34.160.1 to 245.34.191.254245.34.191.2558,190
23245.34.192.0/19245.34.192.1 to 245.34.223.254245.34.223.2558,190
24245.34.224.0/19245.34.224.1 to 245.34.255.254245.34.255.2558,190
25245.35.0.0/19245.35.0.1 to 245.35.31.254245.35.31.2558,190
26245.35.32.0/19245.35.32.1 to 245.35.63.254245.35.63.2558,190
27245.35.64.0/19245.35.64.1 to 245.35.95.254245.35.95.2558,190
28245.35.96.0/19245.35.96.1 to 245.35.127.254245.35.127.2558,190
29245.35.128.0/19245.35.128.1 to 245.35.159.254245.35.159.2558,190
30245.35.160.0/19245.35.160.1 to 245.35.191.254245.35.191.2558,190
31245.35.192.0/19245.35.192.1 to 245.35.223.254245.35.223.2558,190
32245.35.224.0/19245.35.224.1 to 245.35.255.254245.35.255.2558,190
33245.36.0.0/19245.36.0.1 to 245.36.31.254245.36.31.2558,190
34245.36.32.0/19245.36.32.1 to 245.36.63.254245.36.63.2558,190
35245.36.64.0/19245.36.64.1 to 245.36.95.254245.36.95.2558,190
36245.36.96.0/19245.36.96.1 to 245.36.127.254245.36.127.2558,190
37245.36.128.0/19245.36.128.1 to 245.36.159.254245.36.159.2558,190
38245.36.160.0/19245.36.160.1 to 245.36.191.254245.36.191.2558,190
39245.36.192.0/19245.36.192.1 to 245.36.223.254245.36.223.2558,190
40245.36.224.0/19245.36.224.1 to 245.36.255.254245.36.255.2558,190
41245.37.0.0/19245.37.0.1 to 245.37.31.254245.37.31.2558,190
42245.37.32.0/19245.37.32.1 to 245.37.63.254245.37.63.2558,190
43245.37.64.0/19245.37.64.1 to 245.37.95.254245.37.95.2558,190
44245.37.96.0/19245.37.96.1 to 245.37.127.254245.37.127.2558,190
45245.37.128.0/19245.37.128.1 to 245.37.159.254245.37.159.2558,190
46245.37.160.0/19245.37.160.1 to 245.37.191.254245.37.191.2558,190
47245.37.192.0/19245.37.192.1 to 245.37.223.254245.37.223.2558,190
48245.37.224.0/19245.37.224.1 to 245.37.255.254245.37.255.2558,190
49245.38.0.0/19245.38.0.1 to 245.38.31.254245.38.31.2558,190
50245.38.32.0/19245.38.32.1 to 245.38.63.254245.38.63.2558,190
51245.38.64.0/19245.38.64.1 to 245.38.95.254245.38.95.2558,190
52245.38.96.0/19245.38.96.1 to 245.38.127.254245.38.127.2558,190
53245.38.128.0/19245.38.128.1 to 245.38.159.254245.38.159.2558,190
54245.38.160.0/19245.38.160.1 to 245.38.191.254245.38.191.2558,190
55245.38.192.0/19245.38.192.1 to 245.38.223.254245.38.223.2558,190
56245.38.224.0/19245.38.224.1 to 245.38.255.254245.38.255.2558,190
57245.39.0.0/19245.39.0.1 to 245.39.31.254245.39.31.2558,190
58245.39.32.0/19245.39.32.1 to 245.39.63.254245.39.63.2558,190
59245.39.64.0/19245.39.64.1 to 245.39.95.254245.39.95.2558,190
60245.39.96.0/19245.39.96.1 to 245.39.127.254245.39.127.2558,190
61245.39.128.0/19245.39.128.1 to 245.39.159.254245.39.159.2558,190
62245.39.160.0/19245.39.160.1 to 245.39.191.254245.39.191.2558,190
63245.39.192.0/19245.39.192.1 to 245.39.223.254245.39.223.2558,190
64245.39.224.0/19245.39.224.1 to 245.39.255.254245.39.255.2558,190
65245.40.0.0/19245.40.0.1 to 245.40.31.254245.40.31.2558,190
66245.40.32.0/19245.40.32.1 to 245.40.63.254245.40.63.2558,190
67245.40.64.0/19245.40.64.1 to 245.40.95.254245.40.95.2558,190
68245.40.96.0/19245.40.96.1 to 245.40.127.254245.40.127.2558,190
69245.40.128.0/19245.40.128.1 to 245.40.159.254245.40.159.2558,190
70245.40.160.0/19245.40.160.1 to 245.40.191.254245.40.191.2558,190
71245.40.192.0/19245.40.192.1 to 245.40.223.254245.40.223.2558,190
72245.40.224.0/19245.40.224.1 to 245.40.255.254245.40.255.2558,190
73245.41.0.0/19245.41.0.1 to 245.41.31.254245.41.31.2558,190
74245.41.32.0/19245.41.32.1 to 245.41.63.254245.41.63.2558,190
75245.41.64.0/19245.41.64.1 to 245.41.95.254245.41.95.2558,190
76245.41.96.0/19245.41.96.1 to 245.41.127.254245.41.127.2558,190
77245.41.128.0/19245.41.128.1 to 245.41.159.254245.41.159.2558,190
78245.41.160.0/19245.41.160.1 to 245.41.191.254245.41.191.2558,190
79245.41.192.0/19245.41.192.1 to 245.41.223.254245.41.223.2558,190
80245.41.224.0/19245.41.224.1 to 245.41.255.254245.41.255.2558,190
81245.42.0.0/19245.42.0.1 to 245.42.31.254245.42.31.2558,190
82245.42.32.0/19245.42.32.1 to 245.42.63.254245.42.63.2558,190
83245.42.64.0/19245.42.64.1 to 245.42.95.254245.42.95.2558,190
84245.42.96.0/19245.42.96.1 to 245.42.127.254245.42.127.2558,190
85245.42.128.0/19245.42.128.1 to 245.42.159.254245.42.159.2558,190
86245.42.160.0/19245.42.160.1 to 245.42.191.254245.42.191.2558,190
87245.42.192.0/19245.42.192.1 to 245.42.223.254245.42.223.2558,190
88245.42.224.0/19245.42.224.1 to 245.42.255.254245.42.255.2558,190
89245.43.0.0/19245.43.0.1 to 245.43.31.254245.43.31.2558,190
90245.43.32.0/19245.43.32.1 to 245.43.63.254245.43.63.2558,190
91245.43.64.0/19245.43.64.1 to 245.43.95.254245.43.95.2558,190
92245.43.96.0/19245.43.96.1 to 245.43.127.254245.43.127.2558,190
93245.43.128.0/19245.43.128.1 to 245.43.159.254245.43.159.2558,190
94245.43.160.0/19245.43.160.1 to 245.43.191.254245.43.191.2558,190
95245.43.192.0/19245.43.192.1 to 245.43.223.254245.43.223.2558,190
96245.43.224.0/19245.43.224.1 to 245.43.255.254245.43.255.2558,190
97245.44.0.0/19245.44.0.1 to 245.44.31.254245.44.31.2558,190
98245.44.32.0/19245.44.32.1 to 245.44.63.254245.44.63.2558,190
99245.44.64.0/19245.44.64.1 to 245.44.95.254245.44.95.2558,190
100245.44.96.0/19245.44.96.1 to 245.44.127.254245.44.127.2558,190
101245.44.128.0/19245.44.128.1 to 245.44.159.254245.44.159.2558,190
102245.44.160.0/19245.44.160.1 to 245.44.191.254245.44.191.2558,190
103245.44.192.0/19245.44.192.1 to 245.44.223.254245.44.223.2558,190
104245.44.224.0/19245.44.224.1 to 245.44.255.254245.44.255.2558,190
105245.45.0.0/19245.45.0.1 to 245.45.31.254245.45.31.2558,190
106245.45.32.0/19245.45.32.1 to 245.45.63.254245.45.63.2558,190
107245.45.64.0/19245.45.64.1 to 245.45.95.254245.45.95.2558,190
108245.45.96.0/19245.45.96.1 to 245.45.127.254245.45.127.2558,190
109245.45.128.0/19245.45.128.1 to 245.45.159.254245.45.159.2558,190
110245.45.160.0/19245.45.160.1 to 245.45.191.254245.45.191.2558,190
111245.45.192.0/19245.45.192.1 to 245.45.223.254245.45.223.2558,190
112245.45.224.0/19245.45.224.1 to 245.45.255.254245.45.255.2558,190
113245.46.0.0/19245.46.0.1 to 245.46.31.254245.46.31.2558,190
114245.46.32.0/19245.46.32.1 to 245.46.63.254245.46.63.2558,190
115245.46.64.0/19245.46.64.1 to 245.46.95.254245.46.95.2558,190
116245.46.96.0/19245.46.96.1 to 245.46.127.254245.46.127.2558,190
117245.46.128.0/19245.46.128.1 to 245.46.159.254245.46.159.2558,190
118245.46.160.0/19245.46.160.1 to 245.46.191.254245.46.191.2558,190
119245.46.192.0/19245.46.192.1 to 245.46.223.254245.46.223.2558,190
120245.46.224.0/19245.46.224.1 to 245.46.255.254245.46.255.2558,190
121245.47.0.0/19245.47.0.1 to 245.47.31.254245.47.31.2558,190
122245.47.32.0/19245.47.32.1 to 245.47.63.254245.47.63.2558,190
123245.47.64.0/19245.47.64.1 to 245.47.95.254245.47.95.2558,190
124245.47.96.0/19245.47.96.1 to 245.47.127.254245.47.127.2558,190
125245.47.128.0/19245.47.128.1 to 245.47.159.254245.47.159.2558,190
126245.47.160.0/19245.47.160.1 to 245.47.191.254245.47.191.2558,190
127245.47.192.0/19245.47.192.1 to 245.47.223.254245.47.223.2558,190
128245.47.224.0/19245.47.224.1 to 245.47.255.254245.47.255.2558,190

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.