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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.

Network57.2.192.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
57.2.192.0
Broadcast address
57.2.255.255
First usable
57.2.192.1
Last usable
57.2.255.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
A (default /8)
As numbers
Hex 3902C000 · Integer 956481536 to 956497919
Reverse DNS zones
192.2.57.in-addr.arpa
193.2.57.in-addr.arpa
194.2.57.in-addr.arpa
195.2.57.in-addr.arpa
196.2.57.in-addr.arpa
197.2.57.in-addr.arpa
198.2.57.in-addr.arpa
199.2.57.in-addr.arpa
200.2.57.in-addr.arpa
201.2.57.in-addr.arpa
202.2.57.in-addr.arpa
203.2.57.in-addr.arpa
204.2.57.in-addr.arpa
205.2.57.in-addr.arpa
206.2.57.in-addr.arpa
207.2.57.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00111001.00000010.11000000.0000000057.2.192.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network00111001.00000010.11000000.0000000057.2.192.0
Broadcast00111001.00000010.11111111.1111111157.2.255.255
Split into smaller subnets/25
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

57.2.192.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
157.2.192.0/2557.2.192.1 to 57.2.192.12657.2.192.127126
257.2.192.128/2557.2.192.129 to 57.2.192.25457.2.192.255126
357.2.193.0/2557.2.193.1 to 57.2.193.12657.2.193.127126
457.2.193.128/2557.2.193.129 to 57.2.193.25457.2.193.255126
557.2.194.0/2557.2.194.1 to 57.2.194.12657.2.194.127126
657.2.194.128/2557.2.194.129 to 57.2.194.25457.2.194.255126
757.2.195.0/2557.2.195.1 to 57.2.195.12657.2.195.127126
857.2.195.128/2557.2.195.129 to 57.2.195.25457.2.195.255126
957.2.196.0/2557.2.196.1 to 57.2.196.12657.2.196.127126
1057.2.196.128/2557.2.196.129 to 57.2.196.25457.2.196.255126
1157.2.197.0/2557.2.197.1 to 57.2.197.12657.2.197.127126
1257.2.197.128/2557.2.197.129 to 57.2.197.25457.2.197.255126
1357.2.198.0/2557.2.198.1 to 57.2.198.12657.2.198.127126
1457.2.198.128/2557.2.198.129 to 57.2.198.25457.2.198.255126
1557.2.199.0/2557.2.199.1 to 57.2.199.12657.2.199.127126
1657.2.199.128/2557.2.199.129 to 57.2.199.25457.2.199.255126
1757.2.200.0/2557.2.200.1 to 57.2.200.12657.2.200.127126
1857.2.200.128/2557.2.200.129 to 57.2.200.25457.2.200.255126
1957.2.201.0/2557.2.201.1 to 57.2.201.12657.2.201.127126
2057.2.201.128/2557.2.201.129 to 57.2.201.25457.2.201.255126
2157.2.202.0/2557.2.202.1 to 57.2.202.12657.2.202.127126
2257.2.202.128/2557.2.202.129 to 57.2.202.25457.2.202.255126
2357.2.203.0/2557.2.203.1 to 57.2.203.12657.2.203.127126
2457.2.203.128/2557.2.203.129 to 57.2.203.25457.2.203.255126
2557.2.204.0/2557.2.204.1 to 57.2.204.12657.2.204.127126
2657.2.204.128/2557.2.204.129 to 57.2.204.25457.2.204.255126
2757.2.205.0/2557.2.205.1 to 57.2.205.12657.2.205.127126
2857.2.205.128/2557.2.205.129 to 57.2.205.25457.2.205.255126
2957.2.206.0/2557.2.206.1 to 57.2.206.12657.2.206.127126
3057.2.206.128/2557.2.206.129 to 57.2.206.25457.2.206.255126
3157.2.207.0/2557.2.207.1 to 57.2.207.12657.2.207.127126
3257.2.207.128/2557.2.207.129 to 57.2.207.25457.2.207.255126
3357.2.208.0/2557.2.208.1 to 57.2.208.12657.2.208.127126
3457.2.208.128/2557.2.208.129 to 57.2.208.25457.2.208.255126
3557.2.209.0/2557.2.209.1 to 57.2.209.12657.2.209.127126
3657.2.209.128/2557.2.209.129 to 57.2.209.25457.2.209.255126
3757.2.210.0/2557.2.210.1 to 57.2.210.12657.2.210.127126
3857.2.210.128/2557.2.210.129 to 57.2.210.25457.2.210.255126
3957.2.211.0/2557.2.211.1 to 57.2.211.12657.2.211.127126
4057.2.211.128/2557.2.211.129 to 57.2.211.25457.2.211.255126
4157.2.212.0/2557.2.212.1 to 57.2.212.12657.2.212.127126
4257.2.212.128/2557.2.212.129 to 57.2.212.25457.2.212.255126
4357.2.213.0/2557.2.213.1 to 57.2.213.12657.2.213.127126
4457.2.213.128/2557.2.213.129 to 57.2.213.25457.2.213.255126
4557.2.214.0/2557.2.214.1 to 57.2.214.12657.2.214.127126
4657.2.214.128/2557.2.214.129 to 57.2.214.25457.2.214.255126
4757.2.215.0/2557.2.215.1 to 57.2.215.12657.2.215.127126
4857.2.215.128/2557.2.215.129 to 57.2.215.25457.2.215.255126
4957.2.216.0/2557.2.216.1 to 57.2.216.12657.2.216.127126
5057.2.216.128/2557.2.216.129 to 57.2.216.25457.2.216.255126
5157.2.217.0/2557.2.217.1 to 57.2.217.12657.2.217.127126
5257.2.217.128/2557.2.217.129 to 57.2.217.25457.2.217.255126
5357.2.218.0/2557.2.218.1 to 57.2.218.12657.2.218.127126
5457.2.218.128/2557.2.218.129 to 57.2.218.25457.2.218.255126
5557.2.219.0/2557.2.219.1 to 57.2.219.12657.2.219.127126
5657.2.219.128/2557.2.219.129 to 57.2.219.25457.2.219.255126
5757.2.220.0/2557.2.220.1 to 57.2.220.12657.2.220.127126
5857.2.220.128/2557.2.220.129 to 57.2.220.25457.2.220.255126
5957.2.221.0/2557.2.221.1 to 57.2.221.12657.2.221.127126
6057.2.221.128/2557.2.221.129 to 57.2.221.25457.2.221.255126
6157.2.222.0/2557.2.222.1 to 57.2.222.12657.2.222.127126
6257.2.222.128/2557.2.222.129 to 57.2.222.25457.2.222.255126
6357.2.223.0/2557.2.223.1 to 57.2.223.12657.2.223.127126
6457.2.223.128/2557.2.223.129 to 57.2.223.25457.2.223.255126
6557.2.224.0/2557.2.224.1 to 57.2.224.12657.2.224.127126
6657.2.224.128/2557.2.224.129 to 57.2.224.25457.2.224.255126
6757.2.225.0/2557.2.225.1 to 57.2.225.12657.2.225.127126
6857.2.225.128/2557.2.225.129 to 57.2.225.25457.2.225.255126
6957.2.226.0/2557.2.226.1 to 57.2.226.12657.2.226.127126
7057.2.226.128/2557.2.226.129 to 57.2.226.25457.2.226.255126
7157.2.227.0/2557.2.227.1 to 57.2.227.12657.2.227.127126
7257.2.227.128/2557.2.227.129 to 57.2.227.25457.2.227.255126
7357.2.228.0/2557.2.228.1 to 57.2.228.12657.2.228.127126
7457.2.228.128/2557.2.228.129 to 57.2.228.25457.2.228.255126
7557.2.229.0/2557.2.229.1 to 57.2.229.12657.2.229.127126
7657.2.229.128/2557.2.229.129 to 57.2.229.25457.2.229.255126
7757.2.230.0/2557.2.230.1 to 57.2.230.12657.2.230.127126
7857.2.230.128/2557.2.230.129 to 57.2.230.25457.2.230.255126
7957.2.231.0/2557.2.231.1 to 57.2.231.12657.2.231.127126
8057.2.231.128/2557.2.231.129 to 57.2.231.25457.2.231.255126
8157.2.232.0/2557.2.232.1 to 57.2.232.12657.2.232.127126
8257.2.232.128/2557.2.232.129 to 57.2.232.25457.2.232.255126
8357.2.233.0/2557.2.233.1 to 57.2.233.12657.2.233.127126
8457.2.233.128/2557.2.233.129 to 57.2.233.25457.2.233.255126
8557.2.234.0/2557.2.234.1 to 57.2.234.12657.2.234.127126
8657.2.234.128/2557.2.234.129 to 57.2.234.25457.2.234.255126
8757.2.235.0/2557.2.235.1 to 57.2.235.12657.2.235.127126
8857.2.235.128/2557.2.235.129 to 57.2.235.25457.2.235.255126
8957.2.236.0/2557.2.236.1 to 57.2.236.12657.2.236.127126
9057.2.236.128/2557.2.236.129 to 57.2.236.25457.2.236.255126
9157.2.237.0/2557.2.237.1 to 57.2.237.12657.2.237.127126
9257.2.237.128/2557.2.237.129 to 57.2.237.25457.2.237.255126
9357.2.238.0/2557.2.238.1 to 57.2.238.12657.2.238.127126
9457.2.238.128/2557.2.238.129 to 57.2.238.25457.2.238.255126
9557.2.239.0/2557.2.239.1 to 57.2.239.12657.2.239.127126
9657.2.239.128/2557.2.239.129 to 57.2.239.25457.2.239.255126
9757.2.240.0/2557.2.240.1 to 57.2.240.12657.2.240.127126
9857.2.240.128/2557.2.240.129 to 57.2.240.25457.2.240.255126
9957.2.241.0/2557.2.241.1 to 57.2.241.12657.2.241.127126
10057.2.241.128/2557.2.241.129 to 57.2.241.25457.2.241.255126
10157.2.242.0/2557.2.242.1 to 57.2.242.12657.2.242.127126
10257.2.242.128/2557.2.242.129 to 57.2.242.25457.2.242.255126
10357.2.243.0/2557.2.243.1 to 57.2.243.12657.2.243.127126
10457.2.243.128/2557.2.243.129 to 57.2.243.25457.2.243.255126
10557.2.244.0/2557.2.244.1 to 57.2.244.12657.2.244.127126
10657.2.244.128/2557.2.244.129 to 57.2.244.25457.2.244.255126
10757.2.245.0/2557.2.245.1 to 57.2.245.12657.2.245.127126
10857.2.245.128/2557.2.245.129 to 57.2.245.25457.2.245.255126
10957.2.246.0/2557.2.246.1 to 57.2.246.12657.2.246.127126
11057.2.246.128/2557.2.246.129 to 57.2.246.25457.2.246.255126
11157.2.247.0/2557.2.247.1 to 57.2.247.12657.2.247.127126
11257.2.247.128/2557.2.247.129 to 57.2.247.25457.2.247.255126
11357.2.248.0/2557.2.248.1 to 57.2.248.12657.2.248.127126
11457.2.248.128/2557.2.248.129 to 57.2.248.25457.2.248.255126
11557.2.249.0/2557.2.249.1 to 57.2.249.12657.2.249.127126
11657.2.249.128/2557.2.249.129 to 57.2.249.25457.2.249.255126
11757.2.250.0/2557.2.250.1 to 57.2.250.12657.2.250.127126
11857.2.250.128/2557.2.250.129 to 57.2.250.25457.2.250.255126
11957.2.251.0/2557.2.251.1 to 57.2.251.12657.2.251.127126
12057.2.251.128/2557.2.251.129 to 57.2.251.25457.2.251.255126
12157.2.252.0/2557.2.252.1 to 57.2.252.12657.2.252.127126
12257.2.252.128/2557.2.252.129 to 57.2.252.25457.2.252.255126
12357.2.253.0/2557.2.253.1 to 57.2.253.12657.2.253.127126
12457.2.253.128/2557.2.253.129 to 57.2.253.25457.2.253.255126
12557.2.254.0/2557.2.254.1 to 57.2.254.12657.2.254.127126
12657.2.254.128/2557.2.254.129 to 57.2.254.25457.2.254.255126
12757.2.255.0/2557.2.255.1 to 57.2.255.12657.2.255.127126
12857.2.255.128/2557.2.255.129 to 57.2.255.25457.2.255.255126

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.