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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/10
Addresses2^118
/64 networks2^54
Network
ff40::/10
First address
ff40::
Last address
ff7f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
332,306,998,946,228,968,225,951,765,070,086,144 (2^118)
/64 networks (LANs)
18,014,398,509,481,984 (2^54)
Full form
ff40:0000:0000:0000:0000:0000:0000:0000
Type
Multicast ff00::/8
One-to-many traffic; replaces broadcast
Reverse DNS zones
4.f.f.ip6.arpa
5.f.f.ip6.arpa
6.f.f.ip6.arpa
7.f.f.ip6.arpa
/10 is not on a 4-bit boundary, so it takes 4 /12 zones.
Split into smaller subnets/16
/11 (2)/12 (4)/13 (8)/14 (16)/16 (64)/20 (1,024)/24 (16,384)

ff40::/10 makes 64 subnets of /16.

Subnets
#SubnetLast address
1ff40::/16ff40:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2ff41::/16ff41:ffff:ffff:ffff:ffff:ffff:ffff:ffff
3ff42::/16ff42:ffff:ffff:ffff:ffff:ffff:ffff:ffff
4ff43::/16ff43:ffff:ffff:ffff:ffff:ffff:ffff:ffff
5ff44::/16ff44:ffff:ffff:ffff:ffff:ffff:ffff:ffff
6ff45::/16ff45:ffff:ffff:ffff:ffff:ffff:ffff:ffff
7ff46::/16ff46:ffff:ffff:ffff:ffff:ffff:ffff:ffff
8ff47::/16ff47:ffff:ffff:ffff:ffff:ffff:ffff:ffff
9ff48::/16ff48:ffff:ffff:ffff:ffff:ffff:ffff:ffff
10ff49::/16ff49:ffff:ffff:ffff:ffff:ffff:ffff:ffff
11ff4a::/16ff4a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
12ff4b::/16ff4b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
13ff4c::/16ff4c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
14ff4d::/16ff4d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
15ff4e::/16ff4e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
16ff4f::/16ff4f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
17ff50::/16ff50:ffff:ffff:ffff:ffff:ffff:ffff:ffff
18ff51::/16ff51:ffff:ffff:ffff:ffff:ffff:ffff:ffff
19ff52::/16ff52:ffff:ffff:ffff:ffff:ffff:ffff:ffff
20ff53::/16ff53:ffff:ffff:ffff:ffff:ffff:ffff:ffff
21ff54::/16ff54:ffff:ffff:ffff:ffff:ffff:ffff:ffff
22ff55::/16ff55:ffff:ffff:ffff:ffff:ffff:ffff:ffff
23ff56::/16ff56:ffff:ffff:ffff:ffff:ffff:ffff:ffff
24ff57::/16ff57:ffff:ffff:ffff:ffff:ffff:ffff:ffff
25ff58::/16ff58:ffff:ffff:ffff:ffff:ffff:ffff:ffff
26ff59::/16ff59:ffff:ffff:ffff:ffff:ffff:ffff:ffff
27ff5a::/16ff5a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
28ff5b::/16ff5b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
29ff5c::/16ff5c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
30ff5d::/16ff5d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
31ff5e::/16ff5e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
32ff5f::/16ff5f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
33ff60::/16ff60:ffff:ffff:ffff:ffff:ffff:ffff:ffff
34ff61::/16ff61:ffff:ffff:ffff:ffff:ffff:ffff:ffff
35ff62::/16ff62:ffff:ffff:ffff:ffff:ffff:ffff:ffff
36ff63::/16ff63:ffff:ffff:ffff:ffff:ffff:ffff:ffff
37ff64::/16ff64:ffff:ffff:ffff:ffff:ffff:ffff:ffff
38ff65::/16ff65:ffff:ffff:ffff:ffff:ffff:ffff:ffff
39ff66::/16ff66:ffff:ffff:ffff:ffff:ffff:ffff:ffff
40ff67::/16ff67:ffff:ffff:ffff:ffff:ffff:ffff:ffff
41ff68::/16ff68:ffff:ffff:ffff:ffff:ffff:ffff:ffff
42ff69::/16ff69:ffff:ffff:ffff:ffff:ffff:ffff:ffff
43ff6a::/16ff6a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
44ff6b::/16ff6b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
45ff6c::/16ff6c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
46ff6d::/16ff6d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
47ff6e::/16ff6e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
48ff6f::/16ff6f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
49ff70::/16ff70:ffff:ffff:ffff:ffff:ffff:ffff:ffff
50ff71::/16ff71:ffff:ffff:ffff:ffff:ffff:ffff:ffff
51ff72::/16ff72:ffff:ffff:ffff:ffff:ffff:ffff:ffff
52ff73::/16ff73:ffff:ffff:ffff:ffff:ffff:ffff:ffff
53ff74::/16ff74:ffff:ffff:ffff:ffff:ffff:ffff:ffff
54ff75::/16ff75:ffff:ffff:ffff:ffff:ffff:ffff:ffff
55ff76::/16ff76:ffff:ffff:ffff:ffff:ffff:ffff:ffff
56ff77::/16ff77:ffff:ffff:ffff:ffff:ffff:ffff:ffff
57ff78::/16ff78:ffff:ffff:ffff:ffff:ffff:ffff:ffff
58ff79::/16ff79:ffff:ffff:ffff:ffff:ffff:ffff:ffff
59ff7a::/16ff7a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
60ff7b::/16ff7b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
61ff7c::/16ff7c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
62ff7d::/16ff7d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
63ff7e::/16ff7e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
64ff7f::/16ff7f: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.