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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.

Network102.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
102.0.0.0
Broadcast address
103.255.255.255
First usable
102.0.0.1
Last usable
103.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
A (default /8)
As numbers
Hex 66000000 · Integer 1711276032 to 1744830463
Reverse DNS zones
102.in-addr.arpa
103.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01100110.00000000.00000000.00000000102.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network01100110.00000000.00000000.00000000102.0.0.0
Broadcast01100111.11111111.11111111.11111111103.255.255.255
Split into smaller subnets/13
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

102.0.0.0/7 makes 64 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1102.0.0.0/13102.0.0.1 to 102.7.255.254102.7.255.255524,286
2102.8.0.0/13102.8.0.1 to 102.15.255.254102.15.255.255524,286
3102.16.0.0/13102.16.0.1 to 102.23.255.254102.23.255.255524,286
4102.24.0.0/13102.24.0.1 to 102.31.255.254102.31.255.255524,286
5102.32.0.0/13102.32.0.1 to 102.39.255.254102.39.255.255524,286
6102.40.0.0/13102.40.0.1 to 102.47.255.254102.47.255.255524,286
7102.48.0.0/13102.48.0.1 to 102.55.255.254102.55.255.255524,286
8102.56.0.0/13102.56.0.1 to 102.63.255.254102.63.255.255524,286
9102.64.0.0/13102.64.0.1 to 102.71.255.254102.71.255.255524,286
10102.72.0.0/13102.72.0.1 to 102.79.255.254102.79.255.255524,286
11102.80.0.0/13102.80.0.1 to 102.87.255.254102.87.255.255524,286
12102.88.0.0/13102.88.0.1 to 102.95.255.254102.95.255.255524,286
13102.96.0.0/13102.96.0.1 to 102.103.255.254102.103.255.255524,286
14102.104.0.0/13102.104.0.1 to 102.111.255.254102.111.255.255524,286
15102.112.0.0/13102.112.0.1 to 102.119.255.254102.119.255.255524,286
16102.120.0.0/13102.120.0.1 to 102.127.255.254102.127.255.255524,286
17102.128.0.0/13102.128.0.1 to 102.135.255.254102.135.255.255524,286
18102.136.0.0/13102.136.0.1 to 102.143.255.254102.143.255.255524,286
19102.144.0.0/13102.144.0.1 to 102.151.255.254102.151.255.255524,286
20102.152.0.0/13102.152.0.1 to 102.159.255.254102.159.255.255524,286
21102.160.0.0/13102.160.0.1 to 102.167.255.254102.167.255.255524,286
22102.168.0.0/13102.168.0.1 to 102.175.255.254102.175.255.255524,286
23102.176.0.0/13102.176.0.1 to 102.183.255.254102.183.255.255524,286
24102.184.0.0/13102.184.0.1 to 102.191.255.254102.191.255.255524,286
25102.192.0.0/13102.192.0.1 to 102.199.255.254102.199.255.255524,286
26102.200.0.0/13102.200.0.1 to 102.207.255.254102.207.255.255524,286
27102.208.0.0/13102.208.0.1 to 102.215.255.254102.215.255.255524,286
28102.216.0.0/13102.216.0.1 to 102.223.255.254102.223.255.255524,286
29102.224.0.0/13102.224.0.1 to 102.231.255.254102.231.255.255524,286
30102.232.0.0/13102.232.0.1 to 102.239.255.254102.239.255.255524,286
31102.240.0.0/13102.240.0.1 to 102.247.255.254102.247.255.255524,286
32102.248.0.0/13102.248.0.1 to 102.255.255.254102.255.255.255524,286
33103.0.0.0/13103.0.0.1 to 103.7.255.254103.7.255.255524,286
34103.8.0.0/13103.8.0.1 to 103.15.255.254103.15.255.255524,286
35103.16.0.0/13103.16.0.1 to 103.23.255.254103.23.255.255524,286
36103.24.0.0/13103.24.0.1 to 103.31.255.254103.31.255.255524,286
37103.32.0.0/13103.32.0.1 to 103.39.255.254103.39.255.255524,286
38103.40.0.0/13103.40.0.1 to 103.47.255.254103.47.255.255524,286
39103.48.0.0/13103.48.0.1 to 103.55.255.254103.55.255.255524,286
40103.56.0.0/13103.56.0.1 to 103.63.255.254103.63.255.255524,286
41103.64.0.0/13103.64.0.1 to 103.71.255.254103.71.255.255524,286
42103.72.0.0/13103.72.0.1 to 103.79.255.254103.79.255.255524,286
43103.80.0.0/13103.80.0.1 to 103.87.255.254103.87.255.255524,286
44103.88.0.0/13103.88.0.1 to 103.95.255.254103.95.255.255524,286
45103.96.0.0/13103.96.0.1 to 103.103.255.254103.103.255.255524,286
46103.104.0.0/13103.104.0.1 to 103.111.255.254103.111.255.255524,286
47103.112.0.0/13103.112.0.1 to 103.119.255.254103.119.255.255524,286
48103.120.0.0/13103.120.0.1 to 103.127.255.254103.127.255.255524,286
49103.128.0.0/13103.128.0.1 to 103.135.255.254103.135.255.255524,286
50103.136.0.0/13103.136.0.1 to 103.143.255.254103.143.255.255524,286
51103.144.0.0/13103.144.0.1 to 103.151.255.254103.151.255.255524,286
52103.152.0.0/13103.152.0.1 to 103.159.255.254103.159.255.255524,286
53103.160.0.0/13103.160.0.1 to 103.167.255.254103.167.255.255524,286
54103.168.0.0/13103.168.0.1 to 103.175.255.254103.175.255.255524,286
55103.176.0.0/13103.176.0.1 to 103.183.255.254103.183.255.255524,286
56103.184.0.0/13103.184.0.1 to 103.191.255.254103.191.255.255524,286
57103.192.0.0/13103.192.0.1 to 103.199.255.254103.199.255.255524,286
58103.200.0.0/13103.200.0.1 to 103.207.255.254103.207.255.255524,286
59103.208.0.0/13103.208.0.1 to 103.215.255.254103.215.255.255524,286
60103.216.0.0/13103.216.0.1 to 103.223.255.254103.223.255.255524,286
61103.224.0.0/13103.224.0.1 to 103.231.255.254103.231.255.255524,286
62103.232.0.0/13103.232.0.1 to 103.239.255.254103.239.255.255524,286
63103.240.0.0/13103.240.0.1 to 103.247.255.254103.247.255.255524,286
64103.248.0.0/13103.248.0.1 to 103.255.255.254103.255.255.255524,286

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.