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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.

Network38.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
38.0.0.0
Broadcast address
39.255.255.255
First usable
38.0.0.1
Last usable
39.255.255.254
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 26000000 · Integer 637534208 to 671088639
Reverse DNS zones
38.in-addr.arpa
39.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
Address00100110.00000000.00000000.0000000038.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network00100110.00000000.00000000.0000000038.0.0.0
Broadcast00100111.11111111.11111111.1111111139.255.255.255
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)

38.0.0.0/7 makes 64 subnets of /13.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
138.0.0.0/1338.0.0.1 to 38.7.255.25438.7.255.255524,286
238.8.0.0/1338.8.0.1 to 38.15.255.25438.15.255.255524,286
338.16.0.0/1338.16.0.1 to 38.23.255.25438.23.255.255524,286
438.24.0.0/1338.24.0.1 to 38.31.255.25438.31.255.255524,286
538.32.0.0/1338.32.0.1 to 38.39.255.25438.39.255.255524,286
638.40.0.0/1338.40.0.1 to 38.47.255.25438.47.255.255524,286
738.48.0.0/1338.48.0.1 to 38.55.255.25438.55.255.255524,286
838.56.0.0/1338.56.0.1 to 38.63.255.25438.63.255.255524,286
938.64.0.0/1338.64.0.1 to 38.71.255.25438.71.255.255524,286
1038.72.0.0/1338.72.0.1 to 38.79.255.25438.79.255.255524,286
1138.80.0.0/1338.80.0.1 to 38.87.255.25438.87.255.255524,286
1238.88.0.0/1338.88.0.1 to 38.95.255.25438.95.255.255524,286
1338.96.0.0/1338.96.0.1 to 38.103.255.25438.103.255.255524,286
1438.104.0.0/1338.104.0.1 to 38.111.255.25438.111.255.255524,286
1538.112.0.0/1338.112.0.1 to 38.119.255.25438.119.255.255524,286
1638.120.0.0/1338.120.0.1 to 38.127.255.25438.127.255.255524,286
1738.128.0.0/1338.128.0.1 to 38.135.255.25438.135.255.255524,286
1838.136.0.0/1338.136.0.1 to 38.143.255.25438.143.255.255524,286
1938.144.0.0/1338.144.0.1 to 38.151.255.25438.151.255.255524,286
2038.152.0.0/1338.152.0.1 to 38.159.255.25438.159.255.255524,286
2138.160.0.0/1338.160.0.1 to 38.167.255.25438.167.255.255524,286
2238.168.0.0/1338.168.0.1 to 38.175.255.25438.175.255.255524,286
2338.176.0.0/1338.176.0.1 to 38.183.255.25438.183.255.255524,286
2438.184.0.0/1338.184.0.1 to 38.191.255.25438.191.255.255524,286
2538.192.0.0/1338.192.0.1 to 38.199.255.25438.199.255.255524,286
2638.200.0.0/1338.200.0.1 to 38.207.255.25438.207.255.255524,286
2738.208.0.0/1338.208.0.1 to 38.215.255.25438.215.255.255524,286
2838.216.0.0/1338.216.0.1 to 38.223.255.25438.223.255.255524,286
2938.224.0.0/1338.224.0.1 to 38.231.255.25438.231.255.255524,286
3038.232.0.0/1338.232.0.1 to 38.239.255.25438.239.255.255524,286
3138.240.0.0/1338.240.0.1 to 38.247.255.25438.247.255.255524,286
3238.248.0.0/1338.248.0.1 to 38.255.255.25438.255.255.255524,286
3339.0.0.0/1339.0.0.1 to 39.7.255.25439.7.255.255524,286
3439.8.0.0/1339.8.0.1 to 39.15.255.25439.15.255.255524,286
3539.16.0.0/1339.16.0.1 to 39.23.255.25439.23.255.255524,286
3639.24.0.0/1339.24.0.1 to 39.31.255.25439.31.255.255524,286
3739.32.0.0/1339.32.0.1 to 39.39.255.25439.39.255.255524,286
3839.40.0.0/1339.40.0.1 to 39.47.255.25439.47.255.255524,286
3939.48.0.0/1339.48.0.1 to 39.55.255.25439.55.255.255524,286
4039.56.0.0/1339.56.0.1 to 39.63.255.25439.63.255.255524,286
4139.64.0.0/1339.64.0.1 to 39.71.255.25439.71.255.255524,286
4239.72.0.0/1339.72.0.1 to 39.79.255.25439.79.255.255524,286
4339.80.0.0/1339.80.0.1 to 39.87.255.25439.87.255.255524,286
4439.88.0.0/1339.88.0.1 to 39.95.255.25439.95.255.255524,286
4539.96.0.0/1339.96.0.1 to 39.103.255.25439.103.255.255524,286
4639.104.0.0/1339.104.0.1 to 39.111.255.25439.111.255.255524,286
4739.112.0.0/1339.112.0.1 to 39.119.255.25439.119.255.255524,286
4839.120.0.0/1339.120.0.1 to 39.127.255.25439.127.255.255524,286
4939.128.0.0/1339.128.0.1 to 39.135.255.25439.135.255.255524,286
5039.136.0.0/1339.136.0.1 to 39.143.255.25439.143.255.255524,286
5139.144.0.0/1339.144.0.1 to 39.151.255.25439.151.255.255524,286
5239.152.0.0/1339.152.0.1 to 39.159.255.25439.159.255.255524,286
5339.160.0.0/1339.160.0.1 to 39.167.255.25439.167.255.255524,286
5439.168.0.0/1339.168.0.1 to 39.175.255.25439.175.255.255524,286
5539.176.0.0/1339.176.0.1 to 39.183.255.25439.183.255.255524,286
5639.184.0.0/1339.184.0.1 to 39.191.255.25439.191.255.255524,286
5739.192.0.0/1339.192.0.1 to 39.199.255.25439.199.255.255524,286
5839.200.0.0/1339.200.0.1 to 39.207.255.25439.207.255.255524,286
5939.208.0.0/1339.208.0.1 to 39.215.255.25439.215.255.255524,286
6039.216.0.0/1339.216.0.1 to 39.223.255.25439.223.255.255524,286
6139.224.0.0/1339.224.0.1 to 39.231.255.25439.231.255.255524,286
6239.232.0.0/1339.232.0.1 to 39.239.255.25439.239.255.255524,286
6339.240.0.0/1339.240.0.1 to 39.247.255.25439.247.255.255524,286
6439.248.0.0/1339.248.0.1 to 39.255.255.25439.255.255.255524,286

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.