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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.

Network225.64.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
225.64.0.0
Broadcast address
225.79.255.255
First usable
225.64.0.1
Last usable
225.79.255.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E1400000 · Integer 3779067904 to 3780116479
Reverse DNS zones
64.225.in-addr.arpa
65.225.in-addr.arpa
66.225.in-addr.arpa
67.225.in-addr.arpa
68.225.in-addr.arpa
69.225.in-addr.arpa
70.225.in-addr.arpa
71.225.in-addr.arpa
72.225.in-addr.arpa
73.225.in-addr.arpa
74.225.in-addr.arpa
75.225.in-addr.arpa
76.225.in-addr.arpa
77.225.in-addr.arpa
78.225.in-addr.arpa
79.225.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
Address11100001.01000000.00000000.00000000225.64.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11100001.01000000.00000000.00000000225.64.0.0
Broadcast11100001.01001111.11111111.11111111225.79.255.255
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)

225.64.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1225.64.0.0/19225.64.0.1 to 225.64.31.254225.64.31.2558,190
2225.64.32.0/19225.64.32.1 to 225.64.63.254225.64.63.2558,190
3225.64.64.0/19225.64.64.1 to 225.64.95.254225.64.95.2558,190
4225.64.96.0/19225.64.96.1 to 225.64.127.254225.64.127.2558,190
5225.64.128.0/19225.64.128.1 to 225.64.159.254225.64.159.2558,190
6225.64.160.0/19225.64.160.1 to 225.64.191.254225.64.191.2558,190
7225.64.192.0/19225.64.192.1 to 225.64.223.254225.64.223.2558,190
8225.64.224.0/19225.64.224.1 to 225.64.255.254225.64.255.2558,190
9225.65.0.0/19225.65.0.1 to 225.65.31.254225.65.31.2558,190
10225.65.32.0/19225.65.32.1 to 225.65.63.254225.65.63.2558,190
11225.65.64.0/19225.65.64.1 to 225.65.95.254225.65.95.2558,190
12225.65.96.0/19225.65.96.1 to 225.65.127.254225.65.127.2558,190
13225.65.128.0/19225.65.128.1 to 225.65.159.254225.65.159.2558,190
14225.65.160.0/19225.65.160.1 to 225.65.191.254225.65.191.2558,190
15225.65.192.0/19225.65.192.1 to 225.65.223.254225.65.223.2558,190
16225.65.224.0/19225.65.224.1 to 225.65.255.254225.65.255.2558,190
17225.66.0.0/19225.66.0.1 to 225.66.31.254225.66.31.2558,190
18225.66.32.0/19225.66.32.1 to 225.66.63.254225.66.63.2558,190
19225.66.64.0/19225.66.64.1 to 225.66.95.254225.66.95.2558,190
20225.66.96.0/19225.66.96.1 to 225.66.127.254225.66.127.2558,190
21225.66.128.0/19225.66.128.1 to 225.66.159.254225.66.159.2558,190
22225.66.160.0/19225.66.160.1 to 225.66.191.254225.66.191.2558,190
23225.66.192.0/19225.66.192.1 to 225.66.223.254225.66.223.2558,190
24225.66.224.0/19225.66.224.1 to 225.66.255.254225.66.255.2558,190
25225.67.0.0/19225.67.0.1 to 225.67.31.254225.67.31.2558,190
26225.67.32.0/19225.67.32.1 to 225.67.63.254225.67.63.2558,190
27225.67.64.0/19225.67.64.1 to 225.67.95.254225.67.95.2558,190
28225.67.96.0/19225.67.96.1 to 225.67.127.254225.67.127.2558,190
29225.67.128.0/19225.67.128.1 to 225.67.159.254225.67.159.2558,190
30225.67.160.0/19225.67.160.1 to 225.67.191.254225.67.191.2558,190
31225.67.192.0/19225.67.192.1 to 225.67.223.254225.67.223.2558,190
32225.67.224.0/19225.67.224.1 to 225.67.255.254225.67.255.2558,190
33225.68.0.0/19225.68.0.1 to 225.68.31.254225.68.31.2558,190
34225.68.32.0/19225.68.32.1 to 225.68.63.254225.68.63.2558,190
35225.68.64.0/19225.68.64.1 to 225.68.95.254225.68.95.2558,190
36225.68.96.0/19225.68.96.1 to 225.68.127.254225.68.127.2558,190
37225.68.128.0/19225.68.128.1 to 225.68.159.254225.68.159.2558,190
38225.68.160.0/19225.68.160.1 to 225.68.191.254225.68.191.2558,190
39225.68.192.0/19225.68.192.1 to 225.68.223.254225.68.223.2558,190
40225.68.224.0/19225.68.224.1 to 225.68.255.254225.68.255.2558,190
41225.69.0.0/19225.69.0.1 to 225.69.31.254225.69.31.2558,190
42225.69.32.0/19225.69.32.1 to 225.69.63.254225.69.63.2558,190
43225.69.64.0/19225.69.64.1 to 225.69.95.254225.69.95.2558,190
44225.69.96.0/19225.69.96.1 to 225.69.127.254225.69.127.2558,190
45225.69.128.0/19225.69.128.1 to 225.69.159.254225.69.159.2558,190
46225.69.160.0/19225.69.160.1 to 225.69.191.254225.69.191.2558,190
47225.69.192.0/19225.69.192.1 to 225.69.223.254225.69.223.2558,190
48225.69.224.0/19225.69.224.1 to 225.69.255.254225.69.255.2558,190
49225.70.0.0/19225.70.0.1 to 225.70.31.254225.70.31.2558,190
50225.70.32.0/19225.70.32.1 to 225.70.63.254225.70.63.2558,190
51225.70.64.0/19225.70.64.1 to 225.70.95.254225.70.95.2558,190
52225.70.96.0/19225.70.96.1 to 225.70.127.254225.70.127.2558,190
53225.70.128.0/19225.70.128.1 to 225.70.159.254225.70.159.2558,190
54225.70.160.0/19225.70.160.1 to 225.70.191.254225.70.191.2558,190
55225.70.192.0/19225.70.192.1 to 225.70.223.254225.70.223.2558,190
56225.70.224.0/19225.70.224.1 to 225.70.255.254225.70.255.2558,190
57225.71.0.0/19225.71.0.1 to 225.71.31.254225.71.31.2558,190
58225.71.32.0/19225.71.32.1 to 225.71.63.254225.71.63.2558,190
59225.71.64.0/19225.71.64.1 to 225.71.95.254225.71.95.2558,190
60225.71.96.0/19225.71.96.1 to 225.71.127.254225.71.127.2558,190
61225.71.128.0/19225.71.128.1 to 225.71.159.254225.71.159.2558,190
62225.71.160.0/19225.71.160.1 to 225.71.191.254225.71.191.2558,190
63225.71.192.0/19225.71.192.1 to 225.71.223.254225.71.223.2558,190
64225.71.224.0/19225.71.224.1 to 225.71.255.254225.71.255.2558,190
65225.72.0.0/19225.72.0.1 to 225.72.31.254225.72.31.2558,190
66225.72.32.0/19225.72.32.1 to 225.72.63.254225.72.63.2558,190
67225.72.64.0/19225.72.64.1 to 225.72.95.254225.72.95.2558,190
68225.72.96.0/19225.72.96.1 to 225.72.127.254225.72.127.2558,190
69225.72.128.0/19225.72.128.1 to 225.72.159.254225.72.159.2558,190
70225.72.160.0/19225.72.160.1 to 225.72.191.254225.72.191.2558,190
71225.72.192.0/19225.72.192.1 to 225.72.223.254225.72.223.2558,190
72225.72.224.0/19225.72.224.1 to 225.72.255.254225.72.255.2558,190
73225.73.0.0/19225.73.0.1 to 225.73.31.254225.73.31.2558,190
74225.73.32.0/19225.73.32.1 to 225.73.63.254225.73.63.2558,190
75225.73.64.0/19225.73.64.1 to 225.73.95.254225.73.95.2558,190
76225.73.96.0/19225.73.96.1 to 225.73.127.254225.73.127.2558,190
77225.73.128.0/19225.73.128.1 to 225.73.159.254225.73.159.2558,190
78225.73.160.0/19225.73.160.1 to 225.73.191.254225.73.191.2558,190
79225.73.192.0/19225.73.192.1 to 225.73.223.254225.73.223.2558,190
80225.73.224.0/19225.73.224.1 to 225.73.255.254225.73.255.2558,190
81225.74.0.0/19225.74.0.1 to 225.74.31.254225.74.31.2558,190
82225.74.32.0/19225.74.32.1 to 225.74.63.254225.74.63.2558,190
83225.74.64.0/19225.74.64.1 to 225.74.95.254225.74.95.2558,190
84225.74.96.0/19225.74.96.1 to 225.74.127.254225.74.127.2558,190
85225.74.128.0/19225.74.128.1 to 225.74.159.254225.74.159.2558,190
86225.74.160.0/19225.74.160.1 to 225.74.191.254225.74.191.2558,190
87225.74.192.0/19225.74.192.1 to 225.74.223.254225.74.223.2558,190
88225.74.224.0/19225.74.224.1 to 225.74.255.254225.74.255.2558,190
89225.75.0.0/19225.75.0.1 to 225.75.31.254225.75.31.2558,190
90225.75.32.0/19225.75.32.1 to 225.75.63.254225.75.63.2558,190
91225.75.64.0/19225.75.64.1 to 225.75.95.254225.75.95.2558,190
92225.75.96.0/19225.75.96.1 to 225.75.127.254225.75.127.2558,190
93225.75.128.0/19225.75.128.1 to 225.75.159.254225.75.159.2558,190
94225.75.160.0/19225.75.160.1 to 225.75.191.254225.75.191.2558,190
95225.75.192.0/19225.75.192.1 to 225.75.223.254225.75.223.2558,190
96225.75.224.0/19225.75.224.1 to 225.75.255.254225.75.255.2558,190
97225.76.0.0/19225.76.0.1 to 225.76.31.254225.76.31.2558,190
98225.76.32.0/19225.76.32.1 to 225.76.63.254225.76.63.2558,190
99225.76.64.0/19225.76.64.1 to 225.76.95.254225.76.95.2558,190
100225.76.96.0/19225.76.96.1 to 225.76.127.254225.76.127.2558,190
101225.76.128.0/19225.76.128.1 to 225.76.159.254225.76.159.2558,190
102225.76.160.0/19225.76.160.1 to 225.76.191.254225.76.191.2558,190
103225.76.192.0/19225.76.192.1 to 225.76.223.254225.76.223.2558,190
104225.76.224.0/19225.76.224.1 to 225.76.255.254225.76.255.2558,190
105225.77.0.0/19225.77.0.1 to 225.77.31.254225.77.31.2558,190
106225.77.32.0/19225.77.32.1 to 225.77.63.254225.77.63.2558,190
107225.77.64.0/19225.77.64.1 to 225.77.95.254225.77.95.2558,190
108225.77.96.0/19225.77.96.1 to 225.77.127.254225.77.127.2558,190
109225.77.128.0/19225.77.128.1 to 225.77.159.254225.77.159.2558,190
110225.77.160.0/19225.77.160.1 to 225.77.191.254225.77.191.2558,190
111225.77.192.0/19225.77.192.1 to 225.77.223.254225.77.223.2558,190
112225.77.224.0/19225.77.224.1 to 225.77.255.254225.77.255.2558,190
113225.78.0.0/19225.78.0.1 to 225.78.31.254225.78.31.2558,190
114225.78.32.0/19225.78.32.1 to 225.78.63.254225.78.63.2558,190
115225.78.64.0/19225.78.64.1 to 225.78.95.254225.78.95.2558,190
116225.78.96.0/19225.78.96.1 to 225.78.127.254225.78.127.2558,190
117225.78.128.0/19225.78.128.1 to 225.78.159.254225.78.159.2558,190
118225.78.160.0/19225.78.160.1 to 225.78.191.254225.78.191.2558,190
119225.78.192.0/19225.78.192.1 to 225.78.223.254225.78.223.2558,190
120225.78.224.0/19225.78.224.1 to 225.78.255.254225.78.255.2558,190
121225.79.0.0/19225.79.0.1 to 225.79.31.254225.79.31.2558,190
122225.79.32.0/19225.79.32.1 to 225.79.63.254225.79.63.2558,190
123225.79.64.0/19225.79.64.1 to 225.79.95.254225.79.95.2558,190
124225.79.96.0/19225.79.96.1 to 225.79.127.254225.79.127.2558,190
125225.79.128.0/19225.79.128.1 to 225.79.159.254225.79.159.2558,190
126225.79.160.0/19225.79.160.1 to 225.79.191.254225.79.191.2558,190
127225.79.192.0/19225.79.192.1 to 225.79.223.254225.79.223.2558,190
128225.79.224.0/19225.79.224.1 to 225.79.255.254225.79.255.2558,190

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.