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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.

Network33.32.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
33.32.0.0
Broadcast address
33.47.255.255
First usable
33.32.0.1
Last usable
33.47.255.254
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
Public public
Old class
A (default /8)
As numbers
Hex 21200000 · Integer 555745280 to 556793855
Reverse DNS zones
32.33.in-addr.arpa
33.33.in-addr.arpa
34.33.in-addr.arpa
35.33.in-addr.arpa
36.33.in-addr.arpa
37.33.in-addr.arpa
38.33.in-addr.arpa
39.33.in-addr.arpa
40.33.in-addr.arpa
41.33.in-addr.arpa
42.33.in-addr.arpa
43.33.in-addr.arpa
44.33.in-addr.arpa
45.33.in-addr.arpa
46.33.in-addr.arpa
47.33.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
Address00100001.00100000.00000000.0000000033.32.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00100001.00100000.00000000.0000000033.32.0.0
Broadcast00100001.00101111.11111111.1111111133.47.255.255
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)

33.32.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
133.32.0.0/1933.32.0.1 to 33.32.31.25433.32.31.2558,190
233.32.32.0/1933.32.32.1 to 33.32.63.25433.32.63.2558,190
333.32.64.0/1933.32.64.1 to 33.32.95.25433.32.95.2558,190
433.32.96.0/1933.32.96.1 to 33.32.127.25433.32.127.2558,190
533.32.128.0/1933.32.128.1 to 33.32.159.25433.32.159.2558,190
633.32.160.0/1933.32.160.1 to 33.32.191.25433.32.191.2558,190
733.32.192.0/1933.32.192.1 to 33.32.223.25433.32.223.2558,190
833.32.224.0/1933.32.224.1 to 33.32.255.25433.32.255.2558,190
933.33.0.0/1933.33.0.1 to 33.33.31.25433.33.31.2558,190
1033.33.32.0/1933.33.32.1 to 33.33.63.25433.33.63.2558,190
1133.33.64.0/1933.33.64.1 to 33.33.95.25433.33.95.2558,190
1233.33.96.0/1933.33.96.1 to 33.33.127.25433.33.127.2558,190
1333.33.128.0/1933.33.128.1 to 33.33.159.25433.33.159.2558,190
1433.33.160.0/1933.33.160.1 to 33.33.191.25433.33.191.2558,190
1533.33.192.0/1933.33.192.1 to 33.33.223.25433.33.223.2558,190
1633.33.224.0/1933.33.224.1 to 33.33.255.25433.33.255.2558,190
1733.34.0.0/1933.34.0.1 to 33.34.31.25433.34.31.2558,190
1833.34.32.0/1933.34.32.1 to 33.34.63.25433.34.63.2558,190
1933.34.64.0/1933.34.64.1 to 33.34.95.25433.34.95.2558,190
2033.34.96.0/1933.34.96.1 to 33.34.127.25433.34.127.2558,190
2133.34.128.0/1933.34.128.1 to 33.34.159.25433.34.159.2558,190
2233.34.160.0/1933.34.160.1 to 33.34.191.25433.34.191.2558,190
2333.34.192.0/1933.34.192.1 to 33.34.223.25433.34.223.2558,190
2433.34.224.0/1933.34.224.1 to 33.34.255.25433.34.255.2558,190
2533.35.0.0/1933.35.0.1 to 33.35.31.25433.35.31.2558,190
2633.35.32.0/1933.35.32.1 to 33.35.63.25433.35.63.2558,190
2733.35.64.0/1933.35.64.1 to 33.35.95.25433.35.95.2558,190
2833.35.96.0/1933.35.96.1 to 33.35.127.25433.35.127.2558,190
2933.35.128.0/1933.35.128.1 to 33.35.159.25433.35.159.2558,190
3033.35.160.0/1933.35.160.1 to 33.35.191.25433.35.191.2558,190
3133.35.192.0/1933.35.192.1 to 33.35.223.25433.35.223.2558,190
3233.35.224.0/1933.35.224.1 to 33.35.255.25433.35.255.2558,190
3333.36.0.0/1933.36.0.1 to 33.36.31.25433.36.31.2558,190
3433.36.32.0/1933.36.32.1 to 33.36.63.25433.36.63.2558,190
3533.36.64.0/1933.36.64.1 to 33.36.95.25433.36.95.2558,190
3633.36.96.0/1933.36.96.1 to 33.36.127.25433.36.127.2558,190
3733.36.128.0/1933.36.128.1 to 33.36.159.25433.36.159.2558,190
3833.36.160.0/1933.36.160.1 to 33.36.191.25433.36.191.2558,190
3933.36.192.0/1933.36.192.1 to 33.36.223.25433.36.223.2558,190
4033.36.224.0/1933.36.224.1 to 33.36.255.25433.36.255.2558,190
4133.37.0.0/1933.37.0.1 to 33.37.31.25433.37.31.2558,190
4233.37.32.0/1933.37.32.1 to 33.37.63.25433.37.63.2558,190
4333.37.64.0/1933.37.64.1 to 33.37.95.25433.37.95.2558,190
4433.37.96.0/1933.37.96.1 to 33.37.127.25433.37.127.2558,190
4533.37.128.0/1933.37.128.1 to 33.37.159.25433.37.159.2558,190
4633.37.160.0/1933.37.160.1 to 33.37.191.25433.37.191.2558,190
4733.37.192.0/1933.37.192.1 to 33.37.223.25433.37.223.2558,190
4833.37.224.0/1933.37.224.1 to 33.37.255.25433.37.255.2558,190
4933.38.0.0/1933.38.0.1 to 33.38.31.25433.38.31.2558,190
5033.38.32.0/1933.38.32.1 to 33.38.63.25433.38.63.2558,190
5133.38.64.0/1933.38.64.1 to 33.38.95.25433.38.95.2558,190
5233.38.96.0/1933.38.96.1 to 33.38.127.25433.38.127.2558,190
5333.38.128.0/1933.38.128.1 to 33.38.159.25433.38.159.2558,190
5433.38.160.0/1933.38.160.1 to 33.38.191.25433.38.191.2558,190
5533.38.192.0/1933.38.192.1 to 33.38.223.25433.38.223.2558,190
5633.38.224.0/1933.38.224.1 to 33.38.255.25433.38.255.2558,190
5733.39.0.0/1933.39.0.1 to 33.39.31.25433.39.31.2558,190
5833.39.32.0/1933.39.32.1 to 33.39.63.25433.39.63.2558,190
5933.39.64.0/1933.39.64.1 to 33.39.95.25433.39.95.2558,190
6033.39.96.0/1933.39.96.1 to 33.39.127.25433.39.127.2558,190
6133.39.128.0/1933.39.128.1 to 33.39.159.25433.39.159.2558,190
6233.39.160.0/1933.39.160.1 to 33.39.191.25433.39.191.2558,190
6333.39.192.0/1933.39.192.1 to 33.39.223.25433.39.223.2558,190
6433.39.224.0/1933.39.224.1 to 33.39.255.25433.39.255.2558,190
6533.40.0.0/1933.40.0.1 to 33.40.31.25433.40.31.2558,190
6633.40.32.0/1933.40.32.1 to 33.40.63.25433.40.63.2558,190
6733.40.64.0/1933.40.64.1 to 33.40.95.25433.40.95.2558,190
6833.40.96.0/1933.40.96.1 to 33.40.127.25433.40.127.2558,190
6933.40.128.0/1933.40.128.1 to 33.40.159.25433.40.159.2558,190
7033.40.160.0/1933.40.160.1 to 33.40.191.25433.40.191.2558,190
7133.40.192.0/1933.40.192.1 to 33.40.223.25433.40.223.2558,190
7233.40.224.0/1933.40.224.1 to 33.40.255.25433.40.255.2558,190
7333.41.0.0/1933.41.0.1 to 33.41.31.25433.41.31.2558,190
7433.41.32.0/1933.41.32.1 to 33.41.63.25433.41.63.2558,190
7533.41.64.0/1933.41.64.1 to 33.41.95.25433.41.95.2558,190
7633.41.96.0/1933.41.96.1 to 33.41.127.25433.41.127.2558,190
7733.41.128.0/1933.41.128.1 to 33.41.159.25433.41.159.2558,190
7833.41.160.0/1933.41.160.1 to 33.41.191.25433.41.191.2558,190
7933.41.192.0/1933.41.192.1 to 33.41.223.25433.41.223.2558,190
8033.41.224.0/1933.41.224.1 to 33.41.255.25433.41.255.2558,190
8133.42.0.0/1933.42.0.1 to 33.42.31.25433.42.31.2558,190
8233.42.32.0/1933.42.32.1 to 33.42.63.25433.42.63.2558,190
8333.42.64.0/1933.42.64.1 to 33.42.95.25433.42.95.2558,190
8433.42.96.0/1933.42.96.1 to 33.42.127.25433.42.127.2558,190
8533.42.128.0/1933.42.128.1 to 33.42.159.25433.42.159.2558,190
8633.42.160.0/1933.42.160.1 to 33.42.191.25433.42.191.2558,190
8733.42.192.0/1933.42.192.1 to 33.42.223.25433.42.223.2558,190
8833.42.224.0/1933.42.224.1 to 33.42.255.25433.42.255.2558,190
8933.43.0.0/1933.43.0.1 to 33.43.31.25433.43.31.2558,190
9033.43.32.0/1933.43.32.1 to 33.43.63.25433.43.63.2558,190
9133.43.64.0/1933.43.64.1 to 33.43.95.25433.43.95.2558,190
9233.43.96.0/1933.43.96.1 to 33.43.127.25433.43.127.2558,190
9333.43.128.0/1933.43.128.1 to 33.43.159.25433.43.159.2558,190
9433.43.160.0/1933.43.160.1 to 33.43.191.25433.43.191.2558,190
9533.43.192.0/1933.43.192.1 to 33.43.223.25433.43.223.2558,190
9633.43.224.0/1933.43.224.1 to 33.43.255.25433.43.255.2558,190
9733.44.0.0/1933.44.0.1 to 33.44.31.25433.44.31.2558,190
9833.44.32.0/1933.44.32.1 to 33.44.63.25433.44.63.2558,190
9933.44.64.0/1933.44.64.1 to 33.44.95.25433.44.95.2558,190
10033.44.96.0/1933.44.96.1 to 33.44.127.25433.44.127.2558,190
10133.44.128.0/1933.44.128.1 to 33.44.159.25433.44.159.2558,190
10233.44.160.0/1933.44.160.1 to 33.44.191.25433.44.191.2558,190
10333.44.192.0/1933.44.192.1 to 33.44.223.25433.44.223.2558,190
10433.44.224.0/1933.44.224.1 to 33.44.255.25433.44.255.2558,190
10533.45.0.0/1933.45.0.1 to 33.45.31.25433.45.31.2558,190
10633.45.32.0/1933.45.32.1 to 33.45.63.25433.45.63.2558,190
10733.45.64.0/1933.45.64.1 to 33.45.95.25433.45.95.2558,190
10833.45.96.0/1933.45.96.1 to 33.45.127.25433.45.127.2558,190
10933.45.128.0/1933.45.128.1 to 33.45.159.25433.45.159.2558,190
11033.45.160.0/1933.45.160.1 to 33.45.191.25433.45.191.2558,190
11133.45.192.0/1933.45.192.1 to 33.45.223.25433.45.223.2558,190
11233.45.224.0/1933.45.224.1 to 33.45.255.25433.45.255.2558,190
11333.46.0.0/1933.46.0.1 to 33.46.31.25433.46.31.2558,190
11433.46.32.0/1933.46.32.1 to 33.46.63.25433.46.63.2558,190
11533.46.64.0/1933.46.64.1 to 33.46.95.25433.46.95.2558,190
11633.46.96.0/1933.46.96.1 to 33.46.127.25433.46.127.2558,190
11733.46.128.0/1933.46.128.1 to 33.46.159.25433.46.159.2558,190
11833.46.160.0/1933.46.160.1 to 33.46.191.25433.46.191.2558,190
11933.46.192.0/1933.46.192.1 to 33.46.223.25433.46.223.2558,190
12033.46.224.0/1933.46.224.1 to 33.46.255.25433.46.255.2558,190
12133.47.0.0/1933.47.0.1 to 33.47.31.25433.47.31.2558,190
12233.47.32.0/1933.47.32.1 to 33.47.63.25433.47.63.2558,190
12333.47.64.0/1933.47.64.1 to 33.47.95.25433.47.95.2558,190
12433.47.96.0/1933.47.96.1 to 33.47.127.25433.47.127.2558,190
12533.47.128.0/1933.47.128.1 to 33.47.159.25433.47.159.2558,190
12633.47.160.0/1933.47.160.1 to 33.47.191.25433.47.191.2558,190
12733.47.192.0/1933.47.192.1 to 33.47.223.25433.47.223.2558,190
12833.47.224.0/1933.47.224.1 to 33.47.255.25433.47.255.2558,190

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.