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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.

Network241.64.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
241.64.0.0
Broadcast address
241.79.255.255
First usable
241.64.0.1
Last usable
241.79.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F1400000 · Integer 4047503360 to 4048551935
Reverse DNS zones
64.241.in-addr.arpa
65.241.in-addr.arpa
66.241.in-addr.arpa
67.241.in-addr.arpa
68.241.in-addr.arpa
69.241.in-addr.arpa
70.241.in-addr.arpa
71.241.in-addr.arpa
72.241.in-addr.arpa
73.241.in-addr.arpa
74.241.in-addr.arpa
75.241.in-addr.arpa
76.241.in-addr.arpa
77.241.in-addr.arpa
78.241.in-addr.arpa
79.241.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
Address11110001.01000000.00000000.00000000241.64.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11110001.01000000.00000000.00000000241.64.0.0
Broadcast11110001.01001111.11111111.11111111241.79.255.255
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)

241.64.0.0/12 makes 64 subnets of /18.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1241.64.0.0/18241.64.0.1 to 241.64.63.254241.64.63.25516,382
2241.64.64.0/18241.64.64.1 to 241.64.127.254241.64.127.25516,382
3241.64.128.0/18241.64.128.1 to 241.64.191.254241.64.191.25516,382
4241.64.192.0/18241.64.192.1 to 241.64.255.254241.64.255.25516,382
5241.65.0.0/18241.65.0.1 to 241.65.63.254241.65.63.25516,382
6241.65.64.0/18241.65.64.1 to 241.65.127.254241.65.127.25516,382
7241.65.128.0/18241.65.128.1 to 241.65.191.254241.65.191.25516,382
8241.65.192.0/18241.65.192.1 to 241.65.255.254241.65.255.25516,382
9241.66.0.0/18241.66.0.1 to 241.66.63.254241.66.63.25516,382
10241.66.64.0/18241.66.64.1 to 241.66.127.254241.66.127.25516,382
11241.66.128.0/18241.66.128.1 to 241.66.191.254241.66.191.25516,382
12241.66.192.0/18241.66.192.1 to 241.66.255.254241.66.255.25516,382
13241.67.0.0/18241.67.0.1 to 241.67.63.254241.67.63.25516,382
14241.67.64.0/18241.67.64.1 to 241.67.127.254241.67.127.25516,382
15241.67.128.0/18241.67.128.1 to 241.67.191.254241.67.191.25516,382
16241.67.192.0/18241.67.192.1 to 241.67.255.254241.67.255.25516,382
17241.68.0.0/18241.68.0.1 to 241.68.63.254241.68.63.25516,382
18241.68.64.0/18241.68.64.1 to 241.68.127.254241.68.127.25516,382
19241.68.128.0/18241.68.128.1 to 241.68.191.254241.68.191.25516,382
20241.68.192.0/18241.68.192.1 to 241.68.255.254241.68.255.25516,382
21241.69.0.0/18241.69.0.1 to 241.69.63.254241.69.63.25516,382
22241.69.64.0/18241.69.64.1 to 241.69.127.254241.69.127.25516,382
23241.69.128.0/18241.69.128.1 to 241.69.191.254241.69.191.25516,382
24241.69.192.0/18241.69.192.1 to 241.69.255.254241.69.255.25516,382
25241.70.0.0/18241.70.0.1 to 241.70.63.254241.70.63.25516,382
26241.70.64.0/18241.70.64.1 to 241.70.127.254241.70.127.25516,382
27241.70.128.0/18241.70.128.1 to 241.70.191.254241.70.191.25516,382
28241.70.192.0/18241.70.192.1 to 241.70.255.254241.70.255.25516,382
29241.71.0.0/18241.71.0.1 to 241.71.63.254241.71.63.25516,382
30241.71.64.0/18241.71.64.1 to 241.71.127.254241.71.127.25516,382
31241.71.128.0/18241.71.128.1 to 241.71.191.254241.71.191.25516,382
32241.71.192.0/18241.71.192.1 to 241.71.255.254241.71.255.25516,382
33241.72.0.0/18241.72.0.1 to 241.72.63.254241.72.63.25516,382
34241.72.64.0/18241.72.64.1 to 241.72.127.254241.72.127.25516,382
35241.72.128.0/18241.72.128.1 to 241.72.191.254241.72.191.25516,382
36241.72.192.0/18241.72.192.1 to 241.72.255.254241.72.255.25516,382
37241.73.0.0/18241.73.0.1 to 241.73.63.254241.73.63.25516,382
38241.73.64.0/18241.73.64.1 to 241.73.127.254241.73.127.25516,382
39241.73.128.0/18241.73.128.1 to 241.73.191.254241.73.191.25516,382
40241.73.192.0/18241.73.192.1 to 241.73.255.254241.73.255.25516,382
41241.74.0.0/18241.74.0.1 to 241.74.63.254241.74.63.25516,382
42241.74.64.0/18241.74.64.1 to 241.74.127.254241.74.127.25516,382
43241.74.128.0/18241.74.128.1 to 241.74.191.254241.74.191.25516,382
44241.74.192.0/18241.74.192.1 to 241.74.255.254241.74.255.25516,382
45241.75.0.0/18241.75.0.1 to 241.75.63.254241.75.63.25516,382
46241.75.64.0/18241.75.64.1 to 241.75.127.254241.75.127.25516,382
47241.75.128.0/18241.75.128.1 to 241.75.191.254241.75.191.25516,382
48241.75.192.0/18241.75.192.1 to 241.75.255.254241.75.255.25516,382
49241.76.0.0/18241.76.0.1 to 241.76.63.254241.76.63.25516,382
50241.76.64.0/18241.76.64.1 to 241.76.127.254241.76.127.25516,382
51241.76.128.0/18241.76.128.1 to 241.76.191.254241.76.191.25516,382
52241.76.192.0/18241.76.192.1 to 241.76.255.254241.76.255.25516,382
53241.77.0.0/18241.77.0.1 to 241.77.63.254241.77.63.25516,382
54241.77.64.0/18241.77.64.1 to 241.77.127.254241.77.127.25516,382
55241.77.128.0/18241.77.128.1 to 241.77.191.254241.77.191.25516,382
56241.77.192.0/18241.77.192.1 to 241.77.255.254241.77.255.25516,382
57241.78.0.0/18241.78.0.1 to 241.78.63.254241.78.63.25516,382
58241.78.64.0/18241.78.64.1 to 241.78.127.254241.78.127.25516,382
59241.78.128.0/18241.78.128.1 to 241.78.191.254241.78.191.25516,382
60241.78.192.0/18241.78.192.1 to 241.78.255.254241.78.255.25516,382
61241.79.0.0/18241.79.0.1 to 241.79.63.254241.79.63.25516,382
62241.79.64.0/18241.79.64.1 to 241.79.127.254241.79.127.25516,382
63241.79.128.0/18241.79.128.1 to 241.79.191.254241.79.191.25516,382
64241.79.192.0/18241.79.192.1 to 241.79.255.254241.79.255.25516,382

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.