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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.

Prefix/14
Addresses2^114
/64 networks2^50
Network
fc00::/14
First address
fc00::
Last address
fc03:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
20,769,187,434,139,310,514,121,985,316,880,384 (2^114)
/64 networks (LANs)
1,125,899,906,842,624 (2^50)
Full form
fc00:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zones
0.0.c.f.ip6.arpa
1.0.c.f.ip6.arpa
2.0.c.f.ip6.arpa
3.0.c.f.ip6.arpa
/14 is not on a 4-bit boundary, so it takes 4 /16 zones.
Split into smaller subnets/20
/15 (2)/16 (4)/17 (8)/18 (16)/20 (64)/24 (1,024)/28 (16,384)

fc00::/14 makes 64 subnets of /20.

Subnets
#SubnetLast address
1fc00::/20fc00:fff:ffff:ffff:ffff:ffff:ffff:ffff
2fc00:1000::/20fc00:1fff:ffff:ffff:ffff:ffff:ffff:ffff
3fc00:2000::/20fc00:2fff:ffff:ffff:ffff:ffff:ffff:ffff
4fc00:3000::/20fc00:3fff:ffff:ffff:ffff:ffff:ffff:ffff
5fc00:4000::/20fc00:4fff:ffff:ffff:ffff:ffff:ffff:ffff
6fc00:5000::/20fc00:5fff:ffff:ffff:ffff:ffff:ffff:ffff
7fc00:6000::/20fc00:6fff:ffff:ffff:ffff:ffff:ffff:ffff
8fc00:7000::/20fc00:7fff:ffff:ffff:ffff:ffff:ffff:ffff
9fc00:8000::/20fc00:8fff:ffff:ffff:ffff:ffff:ffff:ffff
10fc00:9000::/20fc00:9fff:ffff:ffff:ffff:ffff:ffff:ffff
11fc00:a000::/20fc00:afff:ffff:ffff:ffff:ffff:ffff:ffff
12fc00:b000::/20fc00:bfff:ffff:ffff:ffff:ffff:ffff:ffff
13fc00:c000::/20fc00:cfff:ffff:ffff:ffff:ffff:ffff:ffff
14fc00:d000::/20fc00:dfff:ffff:ffff:ffff:ffff:ffff:ffff
15fc00:e000::/20fc00:efff:ffff:ffff:ffff:ffff:ffff:ffff
16fc00:f000::/20fc00:ffff:ffff:ffff:ffff:ffff:ffff:ffff
17fc01::/20fc01:fff:ffff:ffff:ffff:ffff:ffff:ffff
18fc01:1000::/20fc01:1fff:ffff:ffff:ffff:ffff:ffff:ffff
19fc01:2000::/20fc01:2fff:ffff:ffff:ffff:ffff:ffff:ffff
20fc01:3000::/20fc01:3fff:ffff:ffff:ffff:ffff:ffff:ffff
21fc01:4000::/20fc01:4fff:ffff:ffff:ffff:ffff:ffff:ffff
22fc01:5000::/20fc01:5fff:ffff:ffff:ffff:ffff:ffff:ffff
23fc01:6000::/20fc01:6fff:ffff:ffff:ffff:ffff:ffff:ffff
24fc01:7000::/20fc01:7fff:ffff:ffff:ffff:ffff:ffff:ffff
25fc01:8000::/20fc01:8fff:ffff:ffff:ffff:ffff:ffff:ffff
26fc01:9000::/20fc01:9fff:ffff:ffff:ffff:ffff:ffff:ffff
27fc01:a000::/20fc01:afff:ffff:ffff:ffff:ffff:ffff:ffff
28fc01:b000::/20fc01:bfff:ffff:ffff:ffff:ffff:ffff:ffff
29fc01:c000::/20fc01:cfff:ffff:ffff:ffff:ffff:ffff:ffff
30fc01:d000::/20fc01:dfff:ffff:ffff:ffff:ffff:ffff:ffff
31fc01:e000::/20fc01:efff:ffff:ffff:ffff:ffff:ffff:ffff
32fc01:f000::/20fc01:ffff:ffff:ffff:ffff:ffff:ffff:ffff
33fc02::/20fc02:fff:ffff:ffff:ffff:ffff:ffff:ffff
34fc02:1000::/20fc02:1fff:ffff:ffff:ffff:ffff:ffff:ffff
35fc02:2000::/20fc02:2fff:ffff:ffff:ffff:ffff:ffff:ffff
36fc02:3000::/20fc02:3fff:ffff:ffff:ffff:ffff:ffff:ffff
37fc02:4000::/20fc02:4fff:ffff:ffff:ffff:ffff:ffff:ffff
38fc02:5000::/20fc02:5fff:ffff:ffff:ffff:ffff:ffff:ffff
39fc02:6000::/20fc02:6fff:ffff:ffff:ffff:ffff:ffff:ffff
40fc02:7000::/20fc02:7fff:ffff:ffff:ffff:ffff:ffff:ffff
41fc02:8000::/20fc02:8fff:ffff:ffff:ffff:ffff:ffff:ffff
42fc02:9000::/20fc02:9fff:ffff:ffff:ffff:ffff:ffff:ffff
43fc02:a000::/20fc02:afff:ffff:ffff:ffff:ffff:ffff:ffff
44fc02:b000::/20fc02:bfff:ffff:ffff:ffff:ffff:ffff:ffff
45fc02:c000::/20fc02:cfff:ffff:ffff:ffff:ffff:ffff:ffff
46fc02:d000::/20fc02:dfff:ffff:ffff:ffff:ffff:ffff:ffff
47fc02:e000::/20fc02:efff:ffff:ffff:ffff:ffff:ffff:ffff
48fc02:f000::/20fc02:ffff:ffff:ffff:ffff:ffff:ffff:ffff
49fc03::/20fc03:fff:ffff:ffff:ffff:ffff:ffff:ffff
50fc03:1000::/20fc03:1fff:ffff:ffff:ffff:ffff:ffff:ffff
51fc03:2000::/20fc03:2fff:ffff:ffff:ffff:ffff:ffff:ffff
52fc03:3000::/20fc03:3fff:ffff:ffff:ffff:ffff:ffff:ffff
53fc03:4000::/20fc03:4fff:ffff:ffff:ffff:ffff:ffff:ffff
54fc03:5000::/20fc03:5fff:ffff:ffff:ffff:ffff:ffff:ffff
55fc03:6000::/20fc03:6fff:ffff:ffff:ffff:ffff:ffff:ffff
56fc03:7000::/20fc03:7fff:ffff:ffff:ffff:ffff:ffff:ffff
57fc03:8000::/20fc03:8fff:ffff:ffff:ffff:ffff:ffff:ffff
58fc03:9000::/20fc03:9fff:ffff:ffff:ffff:ffff:ffff:ffff
59fc03:a000::/20fc03:afff:ffff:ffff:ffff:ffff:ffff:ffff
60fc03:b000::/20fc03:bfff:ffff:ffff:ffff:ffff:ffff:ffff
61fc03:c000::/20fc03:cfff:ffff:ffff:ffff:ffff:ffff:ffff
62fc03:d000::/20fc03:dfff:ffff:ffff:ffff:ffff:ffff:ffff
63fc03:e000::/20fc03:efff:ffff:ffff:ffff:ffff:ffff:ffff
64fc03:f000::/20fc03:ffff:ffff:ffff:ffff:ffff:ffff:ffff

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.