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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.

Network58.64.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
58.64.0.0
Broadcast address
58.79.255.255
First usable
58.64.0.1
Last usable
58.79.255.254
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
Public public
Old class
A (default /8)
As numbers
Hex 3A400000 · Integer 977272832 to 978321407
Reverse DNS zones
64.58.in-addr.arpa
65.58.in-addr.arpa
66.58.in-addr.arpa
67.58.in-addr.arpa
68.58.in-addr.arpa
69.58.in-addr.arpa
70.58.in-addr.arpa
71.58.in-addr.arpa
72.58.in-addr.arpa
73.58.in-addr.arpa
74.58.in-addr.arpa
75.58.in-addr.arpa
76.58.in-addr.arpa
77.58.in-addr.arpa
78.58.in-addr.arpa
79.58.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
Address00111010.01000000.00000000.0000000058.64.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00111010.01000000.00000000.0000000058.64.0.0
Broadcast00111010.01001111.11111111.1111111158.79.255.255
Split into smaller subnets/18
/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)

58.64.0.0/12 makes 64 subnets of /18.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
158.64.0.0/1858.64.0.1 to 58.64.63.25458.64.63.25516,382
258.64.64.0/1858.64.64.1 to 58.64.127.25458.64.127.25516,382
358.64.128.0/1858.64.128.1 to 58.64.191.25458.64.191.25516,382
458.64.192.0/1858.64.192.1 to 58.64.255.25458.64.255.25516,382
558.65.0.0/1858.65.0.1 to 58.65.63.25458.65.63.25516,382
658.65.64.0/1858.65.64.1 to 58.65.127.25458.65.127.25516,382
758.65.128.0/1858.65.128.1 to 58.65.191.25458.65.191.25516,382
858.65.192.0/1858.65.192.1 to 58.65.255.25458.65.255.25516,382
958.66.0.0/1858.66.0.1 to 58.66.63.25458.66.63.25516,382
1058.66.64.0/1858.66.64.1 to 58.66.127.25458.66.127.25516,382
1158.66.128.0/1858.66.128.1 to 58.66.191.25458.66.191.25516,382
1258.66.192.0/1858.66.192.1 to 58.66.255.25458.66.255.25516,382
1358.67.0.0/1858.67.0.1 to 58.67.63.25458.67.63.25516,382
1458.67.64.0/1858.67.64.1 to 58.67.127.25458.67.127.25516,382
1558.67.128.0/1858.67.128.1 to 58.67.191.25458.67.191.25516,382
1658.67.192.0/1858.67.192.1 to 58.67.255.25458.67.255.25516,382
1758.68.0.0/1858.68.0.1 to 58.68.63.25458.68.63.25516,382
1858.68.64.0/1858.68.64.1 to 58.68.127.25458.68.127.25516,382
1958.68.128.0/1858.68.128.1 to 58.68.191.25458.68.191.25516,382
2058.68.192.0/1858.68.192.1 to 58.68.255.25458.68.255.25516,382
2158.69.0.0/1858.69.0.1 to 58.69.63.25458.69.63.25516,382
2258.69.64.0/1858.69.64.1 to 58.69.127.25458.69.127.25516,382
2358.69.128.0/1858.69.128.1 to 58.69.191.25458.69.191.25516,382
2458.69.192.0/1858.69.192.1 to 58.69.255.25458.69.255.25516,382
2558.70.0.0/1858.70.0.1 to 58.70.63.25458.70.63.25516,382
2658.70.64.0/1858.70.64.1 to 58.70.127.25458.70.127.25516,382
2758.70.128.0/1858.70.128.1 to 58.70.191.25458.70.191.25516,382
2858.70.192.0/1858.70.192.1 to 58.70.255.25458.70.255.25516,382
2958.71.0.0/1858.71.0.1 to 58.71.63.25458.71.63.25516,382
3058.71.64.0/1858.71.64.1 to 58.71.127.25458.71.127.25516,382
3158.71.128.0/1858.71.128.1 to 58.71.191.25458.71.191.25516,382
3258.71.192.0/1858.71.192.1 to 58.71.255.25458.71.255.25516,382
3358.72.0.0/1858.72.0.1 to 58.72.63.25458.72.63.25516,382
3458.72.64.0/1858.72.64.1 to 58.72.127.25458.72.127.25516,382
3558.72.128.0/1858.72.128.1 to 58.72.191.25458.72.191.25516,382
3658.72.192.0/1858.72.192.1 to 58.72.255.25458.72.255.25516,382
3758.73.0.0/1858.73.0.1 to 58.73.63.25458.73.63.25516,382
3858.73.64.0/1858.73.64.1 to 58.73.127.25458.73.127.25516,382
3958.73.128.0/1858.73.128.1 to 58.73.191.25458.73.191.25516,382
4058.73.192.0/1858.73.192.1 to 58.73.255.25458.73.255.25516,382
4158.74.0.0/1858.74.0.1 to 58.74.63.25458.74.63.25516,382
4258.74.64.0/1858.74.64.1 to 58.74.127.25458.74.127.25516,382
4358.74.128.0/1858.74.128.1 to 58.74.191.25458.74.191.25516,382
4458.74.192.0/1858.74.192.1 to 58.74.255.25458.74.255.25516,382
4558.75.0.0/1858.75.0.1 to 58.75.63.25458.75.63.25516,382
4658.75.64.0/1858.75.64.1 to 58.75.127.25458.75.127.25516,382
4758.75.128.0/1858.75.128.1 to 58.75.191.25458.75.191.25516,382
4858.75.192.0/1858.75.192.1 to 58.75.255.25458.75.255.25516,382
4958.76.0.0/1858.76.0.1 to 58.76.63.25458.76.63.25516,382
5058.76.64.0/1858.76.64.1 to 58.76.127.25458.76.127.25516,382
5158.76.128.0/1858.76.128.1 to 58.76.191.25458.76.191.25516,382
5258.76.192.0/1858.76.192.1 to 58.76.255.25458.76.255.25516,382
5358.77.0.0/1858.77.0.1 to 58.77.63.25458.77.63.25516,382
5458.77.64.0/1858.77.64.1 to 58.77.127.25458.77.127.25516,382
5558.77.128.0/1858.77.128.1 to 58.77.191.25458.77.191.25516,382
5658.77.192.0/1858.77.192.1 to 58.77.255.25458.77.255.25516,382
5758.78.0.0/1858.78.0.1 to 58.78.63.25458.78.63.25516,382
5858.78.64.0/1858.78.64.1 to 58.78.127.25458.78.127.25516,382
5958.78.128.0/1858.78.128.1 to 58.78.191.25458.78.191.25516,382
6058.78.192.0/1858.78.192.1 to 58.78.255.25458.78.255.25516,382
6158.79.0.0/1858.79.0.1 to 58.79.63.25458.79.63.25516,382
6258.79.64.0/1858.79.64.1 to 58.79.127.25458.79.127.25516,382
6358.79.128.0/1858.79.128.1 to 58.79.191.25458.79.191.25516,382
6458.79.192.0/1858.79.192.1 to 58.79.255.25458.79.255.25516,382

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.