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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.

Network24.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
24.0.0.0
Broadcast address
25.255.255.255
First usable
24.0.0.1
Last usable
25.255.255.254
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 18000000 · Integer 402653184 to 436207615
Reverse DNS zones
24.in-addr.arpa
25.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
Address00011000.00000000.00000000.0000000024.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network00011000.00000000.00000000.0000000024.0.0.0
Broadcast00011001.11111111.11111111.1111111125.255.255.255
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)

24.0.0.0/7 makes 64 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
124.0.0.0/1324.0.0.1 to 24.7.255.25424.7.255.255524,286
224.8.0.0/1324.8.0.1 to 24.15.255.25424.15.255.255524,286
324.16.0.0/1324.16.0.1 to 24.23.255.25424.23.255.255524,286
424.24.0.0/1324.24.0.1 to 24.31.255.25424.31.255.255524,286
524.32.0.0/1324.32.0.1 to 24.39.255.25424.39.255.255524,286
624.40.0.0/1324.40.0.1 to 24.47.255.25424.47.255.255524,286
724.48.0.0/1324.48.0.1 to 24.55.255.25424.55.255.255524,286
824.56.0.0/1324.56.0.1 to 24.63.255.25424.63.255.255524,286
924.64.0.0/1324.64.0.1 to 24.71.255.25424.71.255.255524,286
1024.72.0.0/1324.72.0.1 to 24.79.255.25424.79.255.255524,286
1124.80.0.0/1324.80.0.1 to 24.87.255.25424.87.255.255524,286
1224.88.0.0/1324.88.0.1 to 24.95.255.25424.95.255.255524,286
1324.96.0.0/1324.96.0.1 to 24.103.255.25424.103.255.255524,286
1424.104.0.0/1324.104.0.1 to 24.111.255.25424.111.255.255524,286
1524.112.0.0/1324.112.0.1 to 24.119.255.25424.119.255.255524,286
1624.120.0.0/1324.120.0.1 to 24.127.255.25424.127.255.255524,286
1724.128.0.0/1324.128.0.1 to 24.135.255.25424.135.255.255524,286
1824.136.0.0/1324.136.0.1 to 24.143.255.25424.143.255.255524,286
1924.144.0.0/1324.144.0.1 to 24.151.255.25424.151.255.255524,286
2024.152.0.0/1324.152.0.1 to 24.159.255.25424.159.255.255524,286
2124.160.0.0/1324.160.0.1 to 24.167.255.25424.167.255.255524,286
2224.168.0.0/1324.168.0.1 to 24.175.255.25424.175.255.255524,286
2324.176.0.0/1324.176.0.1 to 24.183.255.25424.183.255.255524,286
2424.184.0.0/1324.184.0.1 to 24.191.255.25424.191.255.255524,286
2524.192.0.0/1324.192.0.1 to 24.199.255.25424.199.255.255524,286
2624.200.0.0/1324.200.0.1 to 24.207.255.25424.207.255.255524,286
2724.208.0.0/1324.208.0.1 to 24.215.255.25424.215.255.255524,286
2824.216.0.0/1324.216.0.1 to 24.223.255.25424.223.255.255524,286
2924.224.0.0/1324.224.0.1 to 24.231.255.25424.231.255.255524,286
3024.232.0.0/1324.232.0.1 to 24.239.255.25424.239.255.255524,286
3124.240.0.0/1324.240.0.1 to 24.247.255.25424.247.255.255524,286
3224.248.0.0/1324.248.0.1 to 24.255.255.25424.255.255.255524,286
3325.0.0.0/1325.0.0.1 to 25.7.255.25425.7.255.255524,286
3425.8.0.0/1325.8.0.1 to 25.15.255.25425.15.255.255524,286
3525.16.0.0/1325.16.0.1 to 25.23.255.25425.23.255.255524,286
3625.24.0.0/1325.24.0.1 to 25.31.255.25425.31.255.255524,286
3725.32.0.0/1325.32.0.1 to 25.39.255.25425.39.255.255524,286
3825.40.0.0/1325.40.0.1 to 25.47.255.25425.47.255.255524,286
3925.48.0.0/1325.48.0.1 to 25.55.255.25425.55.255.255524,286
4025.56.0.0/1325.56.0.1 to 25.63.255.25425.63.255.255524,286
4125.64.0.0/1325.64.0.1 to 25.71.255.25425.71.255.255524,286
4225.72.0.0/1325.72.0.1 to 25.79.255.25425.79.255.255524,286
4325.80.0.0/1325.80.0.1 to 25.87.255.25425.87.255.255524,286
4425.88.0.0/1325.88.0.1 to 25.95.255.25425.95.255.255524,286
4525.96.0.0/1325.96.0.1 to 25.103.255.25425.103.255.255524,286
4625.104.0.0/1325.104.0.1 to 25.111.255.25425.111.255.255524,286
4725.112.0.0/1325.112.0.1 to 25.119.255.25425.119.255.255524,286
4825.120.0.0/1325.120.0.1 to 25.127.255.25425.127.255.255524,286
4925.128.0.0/1325.128.0.1 to 25.135.255.25425.135.255.255524,286
5025.136.0.0/1325.136.0.1 to 25.143.255.25425.143.255.255524,286
5125.144.0.0/1325.144.0.1 to 25.151.255.25425.151.255.255524,286
5225.152.0.0/1325.152.0.1 to 25.159.255.25425.159.255.255524,286
5325.160.0.0/1325.160.0.1 to 25.167.255.25425.167.255.255524,286
5425.168.0.0/1325.168.0.1 to 25.175.255.25425.175.255.255524,286
5525.176.0.0/1325.176.0.1 to 25.183.255.25425.183.255.255524,286
5625.184.0.0/1325.184.0.1 to 25.191.255.25425.191.255.255524,286
5725.192.0.0/1325.192.0.1 to 25.199.255.25425.199.255.255524,286
5825.200.0.0/1325.200.0.1 to 25.207.255.25425.207.255.255524,286
5925.208.0.0/1325.208.0.1 to 25.215.255.25425.215.255.255524,286
6025.216.0.0/1325.216.0.1 to 25.223.255.25425.223.255.255524,286
6125.224.0.0/1325.224.0.1 to 25.231.255.25425.231.255.255524,286
6225.232.0.0/1325.232.0.1 to 25.239.255.25425.239.255.255524,286
6325.240.0.0/1325.240.0.1 to 25.247.255.25425.247.255.255524,286
6425.248.0.0/1325.248.0.1 to 25.255.255.25425.255.255.255524,286

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.