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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.

Network24.16.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
24.16.0.0
Broadcast address
24.31.255.255
First usable
24.16.0.1
Last usable
24.31.255.254
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 18100000 · Integer 403701760 to 404750335
Reverse DNS zones
16.24.in-addr.arpa
17.24.in-addr.arpa
18.24.in-addr.arpa
19.24.in-addr.arpa
20.24.in-addr.arpa
21.24.in-addr.arpa
22.24.in-addr.arpa
23.24.in-addr.arpa
24.24.in-addr.arpa
25.24.in-addr.arpa
26.24.in-addr.arpa
27.24.in-addr.arpa
28.24.in-addr.arpa
29.24.in-addr.arpa
30.24.in-addr.arpa
31.24.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
Address00011000.00010000.00000000.0000000024.16.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00011000.00010000.00000000.0000000024.16.0.0
Broadcast00011000.00011111.11111111.1111111124.31.255.255
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)

24.16.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
124.16.0.0/1924.16.0.1 to 24.16.31.25424.16.31.2558,190
224.16.32.0/1924.16.32.1 to 24.16.63.25424.16.63.2558,190
324.16.64.0/1924.16.64.1 to 24.16.95.25424.16.95.2558,190
424.16.96.0/1924.16.96.1 to 24.16.127.25424.16.127.2558,190
524.16.128.0/1924.16.128.1 to 24.16.159.25424.16.159.2558,190
624.16.160.0/1924.16.160.1 to 24.16.191.25424.16.191.2558,190
724.16.192.0/1924.16.192.1 to 24.16.223.25424.16.223.2558,190
824.16.224.0/1924.16.224.1 to 24.16.255.25424.16.255.2558,190
924.17.0.0/1924.17.0.1 to 24.17.31.25424.17.31.2558,190
1024.17.32.0/1924.17.32.1 to 24.17.63.25424.17.63.2558,190
1124.17.64.0/1924.17.64.1 to 24.17.95.25424.17.95.2558,190
1224.17.96.0/1924.17.96.1 to 24.17.127.25424.17.127.2558,190
1324.17.128.0/1924.17.128.1 to 24.17.159.25424.17.159.2558,190
1424.17.160.0/1924.17.160.1 to 24.17.191.25424.17.191.2558,190
1524.17.192.0/1924.17.192.1 to 24.17.223.25424.17.223.2558,190
1624.17.224.0/1924.17.224.1 to 24.17.255.25424.17.255.2558,190
1724.18.0.0/1924.18.0.1 to 24.18.31.25424.18.31.2558,190
1824.18.32.0/1924.18.32.1 to 24.18.63.25424.18.63.2558,190
1924.18.64.0/1924.18.64.1 to 24.18.95.25424.18.95.2558,190
2024.18.96.0/1924.18.96.1 to 24.18.127.25424.18.127.2558,190
2124.18.128.0/1924.18.128.1 to 24.18.159.25424.18.159.2558,190
2224.18.160.0/1924.18.160.1 to 24.18.191.25424.18.191.2558,190
2324.18.192.0/1924.18.192.1 to 24.18.223.25424.18.223.2558,190
2424.18.224.0/1924.18.224.1 to 24.18.255.25424.18.255.2558,190
2524.19.0.0/1924.19.0.1 to 24.19.31.25424.19.31.2558,190
2624.19.32.0/1924.19.32.1 to 24.19.63.25424.19.63.2558,190
2724.19.64.0/1924.19.64.1 to 24.19.95.25424.19.95.2558,190
2824.19.96.0/1924.19.96.1 to 24.19.127.25424.19.127.2558,190
2924.19.128.0/1924.19.128.1 to 24.19.159.25424.19.159.2558,190
3024.19.160.0/1924.19.160.1 to 24.19.191.25424.19.191.2558,190
3124.19.192.0/1924.19.192.1 to 24.19.223.25424.19.223.2558,190
3224.19.224.0/1924.19.224.1 to 24.19.255.25424.19.255.2558,190
3324.20.0.0/1924.20.0.1 to 24.20.31.25424.20.31.2558,190
3424.20.32.0/1924.20.32.1 to 24.20.63.25424.20.63.2558,190
3524.20.64.0/1924.20.64.1 to 24.20.95.25424.20.95.2558,190
3624.20.96.0/1924.20.96.1 to 24.20.127.25424.20.127.2558,190
3724.20.128.0/1924.20.128.1 to 24.20.159.25424.20.159.2558,190
3824.20.160.0/1924.20.160.1 to 24.20.191.25424.20.191.2558,190
3924.20.192.0/1924.20.192.1 to 24.20.223.25424.20.223.2558,190
4024.20.224.0/1924.20.224.1 to 24.20.255.25424.20.255.2558,190
4124.21.0.0/1924.21.0.1 to 24.21.31.25424.21.31.2558,190
4224.21.32.0/1924.21.32.1 to 24.21.63.25424.21.63.2558,190
4324.21.64.0/1924.21.64.1 to 24.21.95.25424.21.95.2558,190
4424.21.96.0/1924.21.96.1 to 24.21.127.25424.21.127.2558,190
4524.21.128.0/1924.21.128.1 to 24.21.159.25424.21.159.2558,190
4624.21.160.0/1924.21.160.1 to 24.21.191.25424.21.191.2558,190
4724.21.192.0/1924.21.192.1 to 24.21.223.25424.21.223.2558,190
4824.21.224.0/1924.21.224.1 to 24.21.255.25424.21.255.2558,190
4924.22.0.0/1924.22.0.1 to 24.22.31.25424.22.31.2558,190
5024.22.32.0/1924.22.32.1 to 24.22.63.25424.22.63.2558,190
5124.22.64.0/1924.22.64.1 to 24.22.95.25424.22.95.2558,190
5224.22.96.0/1924.22.96.1 to 24.22.127.25424.22.127.2558,190
5324.22.128.0/1924.22.128.1 to 24.22.159.25424.22.159.2558,190
5424.22.160.0/1924.22.160.1 to 24.22.191.25424.22.191.2558,190
5524.22.192.0/1924.22.192.1 to 24.22.223.25424.22.223.2558,190
5624.22.224.0/1924.22.224.1 to 24.22.255.25424.22.255.2558,190
5724.23.0.0/1924.23.0.1 to 24.23.31.25424.23.31.2558,190
5824.23.32.0/1924.23.32.1 to 24.23.63.25424.23.63.2558,190
5924.23.64.0/1924.23.64.1 to 24.23.95.25424.23.95.2558,190
6024.23.96.0/1924.23.96.1 to 24.23.127.25424.23.127.2558,190
6124.23.128.0/1924.23.128.1 to 24.23.159.25424.23.159.2558,190
6224.23.160.0/1924.23.160.1 to 24.23.191.25424.23.191.2558,190
6324.23.192.0/1924.23.192.1 to 24.23.223.25424.23.223.2558,190
6424.23.224.0/1924.23.224.1 to 24.23.255.25424.23.255.2558,190
6524.24.0.0/1924.24.0.1 to 24.24.31.25424.24.31.2558,190
6624.24.32.0/1924.24.32.1 to 24.24.63.25424.24.63.2558,190
6724.24.64.0/1924.24.64.1 to 24.24.95.25424.24.95.2558,190
6824.24.96.0/1924.24.96.1 to 24.24.127.25424.24.127.2558,190
6924.24.128.0/1924.24.128.1 to 24.24.159.25424.24.159.2558,190
7024.24.160.0/1924.24.160.1 to 24.24.191.25424.24.191.2558,190
7124.24.192.0/1924.24.192.1 to 24.24.223.25424.24.223.2558,190
7224.24.224.0/1924.24.224.1 to 24.24.255.25424.24.255.2558,190
7324.25.0.0/1924.25.0.1 to 24.25.31.25424.25.31.2558,190
7424.25.32.0/1924.25.32.1 to 24.25.63.25424.25.63.2558,190
7524.25.64.0/1924.25.64.1 to 24.25.95.25424.25.95.2558,190
7624.25.96.0/1924.25.96.1 to 24.25.127.25424.25.127.2558,190
7724.25.128.0/1924.25.128.1 to 24.25.159.25424.25.159.2558,190
7824.25.160.0/1924.25.160.1 to 24.25.191.25424.25.191.2558,190
7924.25.192.0/1924.25.192.1 to 24.25.223.25424.25.223.2558,190
8024.25.224.0/1924.25.224.1 to 24.25.255.25424.25.255.2558,190
8124.26.0.0/1924.26.0.1 to 24.26.31.25424.26.31.2558,190
8224.26.32.0/1924.26.32.1 to 24.26.63.25424.26.63.2558,190
8324.26.64.0/1924.26.64.1 to 24.26.95.25424.26.95.2558,190
8424.26.96.0/1924.26.96.1 to 24.26.127.25424.26.127.2558,190
8524.26.128.0/1924.26.128.1 to 24.26.159.25424.26.159.2558,190
8624.26.160.0/1924.26.160.1 to 24.26.191.25424.26.191.2558,190
8724.26.192.0/1924.26.192.1 to 24.26.223.25424.26.223.2558,190
8824.26.224.0/1924.26.224.1 to 24.26.255.25424.26.255.2558,190
8924.27.0.0/1924.27.0.1 to 24.27.31.25424.27.31.2558,190
9024.27.32.0/1924.27.32.1 to 24.27.63.25424.27.63.2558,190
9124.27.64.0/1924.27.64.1 to 24.27.95.25424.27.95.2558,190
9224.27.96.0/1924.27.96.1 to 24.27.127.25424.27.127.2558,190
9324.27.128.0/1924.27.128.1 to 24.27.159.25424.27.159.2558,190
9424.27.160.0/1924.27.160.1 to 24.27.191.25424.27.191.2558,190
9524.27.192.0/1924.27.192.1 to 24.27.223.25424.27.223.2558,190
9624.27.224.0/1924.27.224.1 to 24.27.255.25424.27.255.2558,190
9724.28.0.0/1924.28.0.1 to 24.28.31.25424.28.31.2558,190
9824.28.32.0/1924.28.32.1 to 24.28.63.25424.28.63.2558,190
9924.28.64.0/1924.28.64.1 to 24.28.95.25424.28.95.2558,190
10024.28.96.0/1924.28.96.1 to 24.28.127.25424.28.127.2558,190
10124.28.128.0/1924.28.128.1 to 24.28.159.25424.28.159.2558,190
10224.28.160.0/1924.28.160.1 to 24.28.191.25424.28.191.2558,190
10324.28.192.0/1924.28.192.1 to 24.28.223.25424.28.223.2558,190
10424.28.224.0/1924.28.224.1 to 24.28.255.25424.28.255.2558,190
10524.29.0.0/1924.29.0.1 to 24.29.31.25424.29.31.2558,190
10624.29.32.0/1924.29.32.1 to 24.29.63.25424.29.63.2558,190
10724.29.64.0/1924.29.64.1 to 24.29.95.25424.29.95.2558,190
10824.29.96.0/1924.29.96.1 to 24.29.127.25424.29.127.2558,190
10924.29.128.0/1924.29.128.1 to 24.29.159.25424.29.159.2558,190
11024.29.160.0/1924.29.160.1 to 24.29.191.25424.29.191.2558,190
11124.29.192.0/1924.29.192.1 to 24.29.223.25424.29.223.2558,190
11224.29.224.0/1924.29.224.1 to 24.29.255.25424.29.255.2558,190
11324.30.0.0/1924.30.0.1 to 24.30.31.25424.30.31.2558,190
11424.30.32.0/1924.30.32.1 to 24.30.63.25424.30.63.2558,190
11524.30.64.0/1924.30.64.1 to 24.30.95.25424.30.95.2558,190
11624.30.96.0/1924.30.96.1 to 24.30.127.25424.30.127.2558,190
11724.30.128.0/1924.30.128.1 to 24.30.159.25424.30.159.2558,190
11824.30.160.0/1924.30.160.1 to 24.30.191.25424.30.191.2558,190
11924.30.192.0/1924.30.192.1 to 24.30.223.25424.30.223.2558,190
12024.30.224.0/1924.30.224.1 to 24.30.255.25424.30.255.2558,190
12124.31.0.0/1924.31.0.1 to 24.31.31.25424.31.31.2558,190
12224.31.32.0/1924.31.32.1 to 24.31.63.25424.31.63.2558,190
12324.31.64.0/1924.31.64.1 to 24.31.95.25424.31.95.2558,190
12424.31.96.0/1924.31.96.1 to 24.31.127.25424.31.127.2558,190
12524.31.128.0/1924.31.128.1 to 24.31.159.25424.31.159.2558,190
12624.31.160.0/1924.31.160.1 to 24.31.191.25424.31.191.2558,190
12724.31.192.0/1924.31.192.1 to 24.31.223.25424.31.223.2558,190
12824.31.224.0/1924.31.224.1 to 24.31.255.25424.31.255.2558,190

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.