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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.

Network25.4.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
25.4.0.0
Broadcast address
25.5.255.255
First usable
25.4.0.1
Last usable
25.5.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
A (default /8)
As numbers
Hex 19040000 · Integer 419692544 to 419823615
Reverse DNS zones
4.25.in-addr.arpa
5.25.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011001.00000100.00000000.0000000025.4.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network00011001.00000100.00000000.0000000025.4.0.0
Broadcast00011001.00000101.11111111.1111111125.5.255.255
Split into smaller subnets/22
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

25.4.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
125.4.0.0/2225.4.0.1 to 25.4.3.25425.4.3.2551,022
225.4.4.0/2225.4.4.1 to 25.4.7.25425.4.7.2551,022
325.4.8.0/2225.4.8.1 to 25.4.11.25425.4.11.2551,022
425.4.12.0/2225.4.12.1 to 25.4.15.25425.4.15.2551,022
525.4.16.0/2225.4.16.1 to 25.4.19.25425.4.19.2551,022
625.4.20.0/2225.4.20.1 to 25.4.23.25425.4.23.2551,022
725.4.24.0/2225.4.24.1 to 25.4.27.25425.4.27.2551,022
825.4.28.0/2225.4.28.1 to 25.4.31.25425.4.31.2551,022
925.4.32.0/2225.4.32.1 to 25.4.35.25425.4.35.2551,022
1025.4.36.0/2225.4.36.1 to 25.4.39.25425.4.39.2551,022
1125.4.40.0/2225.4.40.1 to 25.4.43.25425.4.43.2551,022
1225.4.44.0/2225.4.44.1 to 25.4.47.25425.4.47.2551,022
1325.4.48.0/2225.4.48.1 to 25.4.51.25425.4.51.2551,022
1425.4.52.0/2225.4.52.1 to 25.4.55.25425.4.55.2551,022
1525.4.56.0/2225.4.56.1 to 25.4.59.25425.4.59.2551,022
1625.4.60.0/2225.4.60.1 to 25.4.63.25425.4.63.2551,022
1725.4.64.0/2225.4.64.1 to 25.4.67.25425.4.67.2551,022
1825.4.68.0/2225.4.68.1 to 25.4.71.25425.4.71.2551,022
1925.4.72.0/2225.4.72.1 to 25.4.75.25425.4.75.2551,022
2025.4.76.0/2225.4.76.1 to 25.4.79.25425.4.79.2551,022
2125.4.80.0/2225.4.80.1 to 25.4.83.25425.4.83.2551,022
2225.4.84.0/2225.4.84.1 to 25.4.87.25425.4.87.2551,022
2325.4.88.0/2225.4.88.1 to 25.4.91.25425.4.91.2551,022
2425.4.92.0/2225.4.92.1 to 25.4.95.25425.4.95.2551,022
2525.4.96.0/2225.4.96.1 to 25.4.99.25425.4.99.2551,022
2625.4.100.0/2225.4.100.1 to 25.4.103.25425.4.103.2551,022
2725.4.104.0/2225.4.104.1 to 25.4.107.25425.4.107.2551,022
2825.4.108.0/2225.4.108.1 to 25.4.111.25425.4.111.2551,022
2925.4.112.0/2225.4.112.1 to 25.4.115.25425.4.115.2551,022
3025.4.116.0/2225.4.116.1 to 25.4.119.25425.4.119.2551,022
3125.4.120.0/2225.4.120.1 to 25.4.123.25425.4.123.2551,022
3225.4.124.0/2225.4.124.1 to 25.4.127.25425.4.127.2551,022
3325.4.128.0/2225.4.128.1 to 25.4.131.25425.4.131.2551,022
3425.4.132.0/2225.4.132.1 to 25.4.135.25425.4.135.2551,022
3525.4.136.0/2225.4.136.1 to 25.4.139.25425.4.139.2551,022
3625.4.140.0/2225.4.140.1 to 25.4.143.25425.4.143.2551,022
3725.4.144.0/2225.4.144.1 to 25.4.147.25425.4.147.2551,022
3825.4.148.0/2225.4.148.1 to 25.4.151.25425.4.151.2551,022
3925.4.152.0/2225.4.152.1 to 25.4.155.25425.4.155.2551,022
4025.4.156.0/2225.4.156.1 to 25.4.159.25425.4.159.2551,022
4125.4.160.0/2225.4.160.1 to 25.4.163.25425.4.163.2551,022
4225.4.164.0/2225.4.164.1 to 25.4.167.25425.4.167.2551,022
4325.4.168.0/2225.4.168.1 to 25.4.171.25425.4.171.2551,022
4425.4.172.0/2225.4.172.1 to 25.4.175.25425.4.175.2551,022
4525.4.176.0/2225.4.176.1 to 25.4.179.25425.4.179.2551,022
4625.4.180.0/2225.4.180.1 to 25.4.183.25425.4.183.2551,022
4725.4.184.0/2225.4.184.1 to 25.4.187.25425.4.187.2551,022
4825.4.188.0/2225.4.188.1 to 25.4.191.25425.4.191.2551,022
4925.4.192.0/2225.4.192.1 to 25.4.195.25425.4.195.2551,022
5025.4.196.0/2225.4.196.1 to 25.4.199.25425.4.199.2551,022
5125.4.200.0/2225.4.200.1 to 25.4.203.25425.4.203.2551,022
5225.4.204.0/2225.4.204.1 to 25.4.207.25425.4.207.2551,022
5325.4.208.0/2225.4.208.1 to 25.4.211.25425.4.211.2551,022
5425.4.212.0/2225.4.212.1 to 25.4.215.25425.4.215.2551,022
5525.4.216.0/2225.4.216.1 to 25.4.219.25425.4.219.2551,022
5625.4.220.0/2225.4.220.1 to 25.4.223.25425.4.223.2551,022
5725.4.224.0/2225.4.224.1 to 25.4.227.25425.4.227.2551,022
5825.4.228.0/2225.4.228.1 to 25.4.231.25425.4.231.2551,022
5925.4.232.0/2225.4.232.1 to 25.4.235.25425.4.235.2551,022
6025.4.236.0/2225.4.236.1 to 25.4.239.25425.4.239.2551,022
6125.4.240.0/2225.4.240.1 to 25.4.243.25425.4.243.2551,022
6225.4.244.0/2225.4.244.1 to 25.4.247.25425.4.247.2551,022
6325.4.248.0/2225.4.248.1 to 25.4.251.25425.4.251.2551,022
6425.4.252.0/2225.4.252.1 to 25.4.255.25425.4.255.2551,022
6525.5.0.0/2225.5.0.1 to 25.5.3.25425.5.3.2551,022
6625.5.4.0/2225.5.4.1 to 25.5.7.25425.5.7.2551,022
6725.5.8.0/2225.5.8.1 to 25.5.11.25425.5.11.2551,022
6825.5.12.0/2225.5.12.1 to 25.5.15.25425.5.15.2551,022
6925.5.16.0/2225.5.16.1 to 25.5.19.25425.5.19.2551,022
7025.5.20.0/2225.5.20.1 to 25.5.23.25425.5.23.2551,022
7125.5.24.0/2225.5.24.1 to 25.5.27.25425.5.27.2551,022
7225.5.28.0/2225.5.28.1 to 25.5.31.25425.5.31.2551,022
7325.5.32.0/2225.5.32.1 to 25.5.35.25425.5.35.2551,022
7425.5.36.0/2225.5.36.1 to 25.5.39.25425.5.39.2551,022
7525.5.40.0/2225.5.40.1 to 25.5.43.25425.5.43.2551,022
7625.5.44.0/2225.5.44.1 to 25.5.47.25425.5.47.2551,022
7725.5.48.0/2225.5.48.1 to 25.5.51.25425.5.51.2551,022
7825.5.52.0/2225.5.52.1 to 25.5.55.25425.5.55.2551,022
7925.5.56.0/2225.5.56.1 to 25.5.59.25425.5.59.2551,022
8025.5.60.0/2225.5.60.1 to 25.5.63.25425.5.63.2551,022
8125.5.64.0/2225.5.64.1 to 25.5.67.25425.5.67.2551,022
8225.5.68.0/2225.5.68.1 to 25.5.71.25425.5.71.2551,022
8325.5.72.0/2225.5.72.1 to 25.5.75.25425.5.75.2551,022
8425.5.76.0/2225.5.76.1 to 25.5.79.25425.5.79.2551,022
8525.5.80.0/2225.5.80.1 to 25.5.83.25425.5.83.2551,022
8625.5.84.0/2225.5.84.1 to 25.5.87.25425.5.87.2551,022
8725.5.88.0/2225.5.88.1 to 25.5.91.25425.5.91.2551,022
8825.5.92.0/2225.5.92.1 to 25.5.95.25425.5.95.2551,022
8925.5.96.0/2225.5.96.1 to 25.5.99.25425.5.99.2551,022
9025.5.100.0/2225.5.100.1 to 25.5.103.25425.5.103.2551,022
9125.5.104.0/2225.5.104.1 to 25.5.107.25425.5.107.2551,022
9225.5.108.0/2225.5.108.1 to 25.5.111.25425.5.111.2551,022
9325.5.112.0/2225.5.112.1 to 25.5.115.25425.5.115.2551,022
9425.5.116.0/2225.5.116.1 to 25.5.119.25425.5.119.2551,022
9525.5.120.0/2225.5.120.1 to 25.5.123.25425.5.123.2551,022
9625.5.124.0/2225.5.124.1 to 25.5.127.25425.5.127.2551,022
9725.5.128.0/2225.5.128.1 to 25.5.131.25425.5.131.2551,022
9825.5.132.0/2225.5.132.1 to 25.5.135.25425.5.135.2551,022
9925.5.136.0/2225.5.136.1 to 25.5.139.25425.5.139.2551,022
10025.5.140.0/2225.5.140.1 to 25.5.143.25425.5.143.2551,022
10125.5.144.0/2225.5.144.1 to 25.5.147.25425.5.147.2551,022
10225.5.148.0/2225.5.148.1 to 25.5.151.25425.5.151.2551,022
10325.5.152.0/2225.5.152.1 to 25.5.155.25425.5.155.2551,022
10425.5.156.0/2225.5.156.1 to 25.5.159.25425.5.159.2551,022
10525.5.160.0/2225.5.160.1 to 25.5.163.25425.5.163.2551,022
10625.5.164.0/2225.5.164.1 to 25.5.167.25425.5.167.2551,022
10725.5.168.0/2225.5.168.1 to 25.5.171.25425.5.171.2551,022
10825.5.172.0/2225.5.172.1 to 25.5.175.25425.5.175.2551,022
10925.5.176.0/2225.5.176.1 to 25.5.179.25425.5.179.2551,022
11025.5.180.0/2225.5.180.1 to 25.5.183.25425.5.183.2551,022
11125.5.184.0/2225.5.184.1 to 25.5.187.25425.5.187.2551,022
11225.5.188.0/2225.5.188.1 to 25.5.191.25425.5.191.2551,022
11325.5.192.0/2225.5.192.1 to 25.5.195.25425.5.195.2551,022
11425.5.196.0/2225.5.196.1 to 25.5.199.25425.5.199.2551,022
11525.5.200.0/2225.5.200.1 to 25.5.203.25425.5.203.2551,022
11625.5.204.0/2225.5.204.1 to 25.5.207.25425.5.207.2551,022
11725.5.208.0/2225.5.208.1 to 25.5.211.25425.5.211.2551,022
11825.5.212.0/2225.5.212.1 to 25.5.215.25425.5.215.2551,022
11925.5.216.0/2225.5.216.1 to 25.5.219.25425.5.219.2551,022
12025.5.220.0/2225.5.220.1 to 25.5.223.25425.5.223.2551,022
12125.5.224.0/2225.5.224.1 to 25.5.227.25425.5.227.2551,022
12225.5.228.0/2225.5.228.1 to 25.5.231.25425.5.231.2551,022
12325.5.232.0/2225.5.232.1 to 25.5.235.25425.5.235.2551,022
12425.5.236.0/2225.5.236.1 to 25.5.239.25425.5.239.2551,022
12525.5.240.0/2225.5.240.1 to 25.5.243.25425.5.243.2551,022
12625.5.244.0/2225.5.244.1 to 25.5.247.25425.5.247.2551,022
12725.5.248.0/2225.5.248.1 to 25.5.251.25425.5.251.2551,022
12825.5.252.0/2225.5.252.1 to 25.5.255.25425.5.255.2551,022

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.