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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.

Network246.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
246.0.0.0
Broadcast address
247.255.255.255
First usable
246.0.0.1
Last usable
247.255.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F6000000 · Integer 4127195136 to 4160749567
Reverse DNS zones
246.in-addr.arpa
247.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
Address11110110.00000000.00000000.00000000246.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network11110110.00000000.00000000.00000000246.0.0.0
Broadcast11110111.11111111.11111111.11111111247.255.255.255
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)

246.0.0.0/7 makes 64 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1246.0.0.0/13246.0.0.1 to 246.7.255.254246.7.255.255524,286
2246.8.0.0/13246.8.0.1 to 246.15.255.254246.15.255.255524,286
3246.16.0.0/13246.16.0.1 to 246.23.255.254246.23.255.255524,286
4246.24.0.0/13246.24.0.1 to 246.31.255.254246.31.255.255524,286
5246.32.0.0/13246.32.0.1 to 246.39.255.254246.39.255.255524,286
6246.40.0.0/13246.40.0.1 to 246.47.255.254246.47.255.255524,286
7246.48.0.0/13246.48.0.1 to 246.55.255.254246.55.255.255524,286
8246.56.0.0/13246.56.0.1 to 246.63.255.254246.63.255.255524,286
9246.64.0.0/13246.64.0.1 to 246.71.255.254246.71.255.255524,286
10246.72.0.0/13246.72.0.1 to 246.79.255.254246.79.255.255524,286
11246.80.0.0/13246.80.0.1 to 246.87.255.254246.87.255.255524,286
12246.88.0.0/13246.88.0.1 to 246.95.255.254246.95.255.255524,286
13246.96.0.0/13246.96.0.1 to 246.103.255.254246.103.255.255524,286
14246.104.0.0/13246.104.0.1 to 246.111.255.254246.111.255.255524,286
15246.112.0.0/13246.112.0.1 to 246.119.255.254246.119.255.255524,286
16246.120.0.0/13246.120.0.1 to 246.127.255.254246.127.255.255524,286
17246.128.0.0/13246.128.0.1 to 246.135.255.254246.135.255.255524,286
18246.136.0.0/13246.136.0.1 to 246.143.255.254246.143.255.255524,286
19246.144.0.0/13246.144.0.1 to 246.151.255.254246.151.255.255524,286
20246.152.0.0/13246.152.0.1 to 246.159.255.254246.159.255.255524,286
21246.160.0.0/13246.160.0.1 to 246.167.255.254246.167.255.255524,286
22246.168.0.0/13246.168.0.1 to 246.175.255.254246.175.255.255524,286
23246.176.0.0/13246.176.0.1 to 246.183.255.254246.183.255.255524,286
24246.184.0.0/13246.184.0.1 to 246.191.255.254246.191.255.255524,286
25246.192.0.0/13246.192.0.1 to 246.199.255.254246.199.255.255524,286
26246.200.0.0/13246.200.0.1 to 246.207.255.254246.207.255.255524,286
27246.208.0.0/13246.208.0.1 to 246.215.255.254246.215.255.255524,286
28246.216.0.0/13246.216.0.1 to 246.223.255.254246.223.255.255524,286
29246.224.0.0/13246.224.0.1 to 246.231.255.254246.231.255.255524,286
30246.232.0.0/13246.232.0.1 to 246.239.255.254246.239.255.255524,286
31246.240.0.0/13246.240.0.1 to 246.247.255.254246.247.255.255524,286
32246.248.0.0/13246.248.0.1 to 246.255.255.254246.255.255.255524,286
33247.0.0.0/13247.0.0.1 to 247.7.255.254247.7.255.255524,286
34247.8.0.0/13247.8.0.1 to 247.15.255.254247.15.255.255524,286
35247.16.0.0/13247.16.0.1 to 247.23.255.254247.23.255.255524,286
36247.24.0.0/13247.24.0.1 to 247.31.255.254247.31.255.255524,286
37247.32.0.0/13247.32.0.1 to 247.39.255.254247.39.255.255524,286
38247.40.0.0/13247.40.0.1 to 247.47.255.254247.47.255.255524,286
39247.48.0.0/13247.48.0.1 to 247.55.255.254247.55.255.255524,286
40247.56.0.0/13247.56.0.1 to 247.63.255.254247.63.255.255524,286
41247.64.0.0/13247.64.0.1 to 247.71.255.254247.71.255.255524,286
42247.72.0.0/13247.72.0.1 to 247.79.255.254247.79.255.255524,286
43247.80.0.0/13247.80.0.1 to 247.87.255.254247.87.255.255524,286
44247.88.0.0/13247.88.0.1 to 247.95.255.254247.95.255.255524,286
45247.96.0.0/13247.96.0.1 to 247.103.255.254247.103.255.255524,286
46247.104.0.0/13247.104.0.1 to 247.111.255.254247.111.255.255524,286
47247.112.0.0/13247.112.0.1 to 247.119.255.254247.119.255.255524,286
48247.120.0.0/13247.120.0.1 to 247.127.255.254247.127.255.255524,286
49247.128.0.0/13247.128.0.1 to 247.135.255.254247.135.255.255524,286
50247.136.0.0/13247.136.0.1 to 247.143.255.254247.143.255.255524,286
51247.144.0.0/13247.144.0.1 to 247.151.255.254247.151.255.255524,286
52247.152.0.0/13247.152.0.1 to 247.159.255.254247.159.255.255524,286
53247.160.0.0/13247.160.0.1 to 247.167.255.254247.167.255.255524,286
54247.168.0.0/13247.168.0.1 to 247.175.255.254247.175.255.255524,286
55247.176.0.0/13247.176.0.1 to 247.183.255.254247.183.255.255524,286
56247.184.0.0/13247.184.0.1 to 247.191.255.254247.191.255.255524,286
57247.192.0.0/13247.192.0.1 to 247.199.255.254247.199.255.255524,286
58247.200.0.0/13247.200.0.1 to 247.207.255.254247.207.255.255524,286
59247.208.0.0/13247.208.0.1 to 247.215.255.254247.215.255.255524,286
60247.216.0.0/13247.216.0.1 to 247.223.255.254247.223.255.255524,286
61247.224.0.0/13247.224.0.1 to 247.231.255.254247.231.255.255524,286
62247.232.0.0/13247.232.0.1 to 247.239.255.254247.239.255.255524,286
63247.240.0.0/13247.240.0.1 to 247.247.255.254247.247.255.255524,286
64247.248.0.0/13247.248.0.1 to 247.255.255.254247.255.255.255524,286

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.