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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.

Network25.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
25.0.0.0
Broadcast address
25.255.255.255
First usable
25.0.0.1
Last usable
25.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
A (default /8)
As numbers
Hex 19000000 · Integer 419430400 to 436207615
Reverse DNS zone
25.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011001..00000000.00000000.0000000025.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network00011001..00000000.00000000.0000000025.0.0.0
Broadcast00011001..11111111.11111111.1111111125.255.255.255
Split into smaller subnets/15
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

25.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
125.0.0.0/1525.0.0.1 to 25.1.255.25425.1.255.255131,070
225.2.0.0/1525.2.0.1 to 25.3.255.25425.3.255.255131,070
325.4.0.0/1525.4.0.1 to 25.5.255.25425.5.255.255131,070
425.6.0.0/1525.6.0.1 to 25.7.255.25425.7.255.255131,070
525.8.0.0/1525.8.0.1 to 25.9.255.25425.9.255.255131,070
625.10.0.0/1525.10.0.1 to 25.11.255.25425.11.255.255131,070
725.12.0.0/1525.12.0.1 to 25.13.255.25425.13.255.255131,070
825.14.0.0/1525.14.0.1 to 25.15.255.25425.15.255.255131,070
925.16.0.0/1525.16.0.1 to 25.17.255.25425.17.255.255131,070
1025.18.0.0/1525.18.0.1 to 25.19.255.25425.19.255.255131,070
1125.20.0.0/1525.20.0.1 to 25.21.255.25425.21.255.255131,070
1225.22.0.0/1525.22.0.1 to 25.23.255.25425.23.255.255131,070
1325.24.0.0/1525.24.0.1 to 25.25.255.25425.25.255.255131,070
1425.26.0.0/1525.26.0.1 to 25.27.255.25425.27.255.255131,070
1525.28.0.0/1525.28.0.1 to 25.29.255.25425.29.255.255131,070
1625.30.0.0/1525.30.0.1 to 25.31.255.25425.31.255.255131,070
1725.32.0.0/1525.32.0.1 to 25.33.255.25425.33.255.255131,070
1825.34.0.0/1525.34.0.1 to 25.35.255.25425.35.255.255131,070
1925.36.0.0/1525.36.0.1 to 25.37.255.25425.37.255.255131,070
2025.38.0.0/1525.38.0.1 to 25.39.255.25425.39.255.255131,070
2125.40.0.0/1525.40.0.1 to 25.41.255.25425.41.255.255131,070
2225.42.0.0/1525.42.0.1 to 25.43.255.25425.43.255.255131,070
2325.44.0.0/1525.44.0.1 to 25.45.255.25425.45.255.255131,070
2425.46.0.0/1525.46.0.1 to 25.47.255.25425.47.255.255131,070
2525.48.0.0/1525.48.0.1 to 25.49.255.25425.49.255.255131,070
2625.50.0.0/1525.50.0.1 to 25.51.255.25425.51.255.255131,070
2725.52.0.0/1525.52.0.1 to 25.53.255.25425.53.255.255131,070
2825.54.0.0/1525.54.0.1 to 25.55.255.25425.55.255.255131,070
2925.56.0.0/1525.56.0.1 to 25.57.255.25425.57.255.255131,070
3025.58.0.0/1525.58.0.1 to 25.59.255.25425.59.255.255131,070
3125.60.0.0/1525.60.0.1 to 25.61.255.25425.61.255.255131,070
3225.62.0.0/1525.62.0.1 to 25.63.255.25425.63.255.255131,070
3325.64.0.0/1525.64.0.1 to 25.65.255.25425.65.255.255131,070
3425.66.0.0/1525.66.0.1 to 25.67.255.25425.67.255.255131,070
3525.68.0.0/1525.68.0.1 to 25.69.255.25425.69.255.255131,070
3625.70.0.0/1525.70.0.1 to 25.71.255.25425.71.255.255131,070
3725.72.0.0/1525.72.0.1 to 25.73.255.25425.73.255.255131,070
3825.74.0.0/1525.74.0.1 to 25.75.255.25425.75.255.255131,070
3925.76.0.0/1525.76.0.1 to 25.77.255.25425.77.255.255131,070
4025.78.0.0/1525.78.0.1 to 25.79.255.25425.79.255.255131,070
4125.80.0.0/1525.80.0.1 to 25.81.255.25425.81.255.255131,070
4225.82.0.0/1525.82.0.1 to 25.83.255.25425.83.255.255131,070
4325.84.0.0/1525.84.0.1 to 25.85.255.25425.85.255.255131,070
4425.86.0.0/1525.86.0.1 to 25.87.255.25425.87.255.255131,070
4525.88.0.0/1525.88.0.1 to 25.89.255.25425.89.255.255131,070
4625.90.0.0/1525.90.0.1 to 25.91.255.25425.91.255.255131,070
4725.92.0.0/1525.92.0.1 to 25.93.255.25425.93.255.255131,070
4825.94.0.0/1525.94.0.1 to 25.95.255.25425.95.255.255131,070
4925.96.0.0/1525.96.0.1 to 25.97.255.25425.97.255.255131,070
5025.98.0.0/1525.98.0.1 to 25.99.255.25425.99.255.255131,070
5125.100.0.0/1525.100.0.1 to 25.101.255.25425.101.255.255131,070
5225.102.0.0/1525.102.0.1 to 25.103.255.25425.103.255.255131,070
5325.104.0.0/1525.104.0.1 to 25.105.255.25425.105.255.255131,070
5425.106.0.0/1525.106.0.1 to 25.107.255.25425.107.255.255131,070
5525.108.0.0/1525.108.0.1 to 25.109.255.25425.109.255.255131,070
5625.110.0.0/1525.110.0.1 to 25.111.255.25425.111.255.255131,070
5725.112.0.0/1525.112.0.1 to 25.113.255.25425.113.255.255131,070
5825.114.0.0/1525.114.0.1 to 25.115.255.25425.115.255.255131,070
5925.116.0.0/1525.116.0.1 to 25.117.255.25425.117.255.255131,070
6025.118.0.0/1525.118.0.1 to 25.119.255.25425.119.255.255131,070
6125.120.0.0/1525.120.0.1 to 25.121.255.25425.121.255.255131,070
6225.122.0.0/1525.122.0.1 to 25.123.255.25425.123.255.255131,070
6325.124.0.0/1525.124.0.1 to 25.125.255.25425.125.255.255131,070
6425.126.0.0/1525.126.0.1 to 25.127.255.25425.127.255.255131,070
6525.128.0.0/1525.128.0.1 to 25.129.255.25425.129.255.255131,070
6625.130.0.0/1525.130.0.1 to 25.131.255.25425.131.255.255131,070
6725.132.0.0/1525.132.0.1 to 25.133.255.25425.133.255.255131,070
6825.134.0.0/1525.134.0.1 to 25.135.255.25425.135.255.255131,070
6925.136.0.0/1525.136.0.1 to 25.137.255.25425.137.255.255131,070
7025.138.0.0/1525.138.0.1 to 25.139.255.25425.139.255.255131,070
7125.140.0.0/1525.140.0.1 to 25.141.255.25425.141.255.255131,070
7225.142.0.0/1525.142.0.1 to 25.143.255.25425.143.255.255131,070
7325.144.0.0/1525.144.0.1 to 25.145.255.25425.145.255.255131,070
7425.146.0.0/1525.146.0.1 to 25.147.255.25425.147.255.255131,070
7525.148.0.0/1525.148.0.1 to 25.149.255.25425.149.255.255131,070
7625.150.0.0/1525.150.0.1 to 25.151.255.25425.151.255.255131,070
7725.152.0.0/1525.152.0.1 to 25.153.255.25425.153.255.255131,070
7825.154.0.0/1525.154.0.1 to 25.155.255.25425.155.255.255131,070
7925.156.0.0/1525.156.0.1 to 25.157.255.25425.157.255.255131,070
8025.158.0.0/1525.158.0.1 to 25.159.255.25425.159.255.255131,070
8125.160.0.0/1525.160.0.1 to 25.161.255.25425.161.255.255131,070
8225.162.0.0/1525.162.0.1 to 25.163.255.25425.163.255.255131,070
8325.164.0.0/1525.164.0.1 to 25.165.255.25425.165.255.255131,070
8425.166.0.0/1525.166.0.1 to 25.167.255.25425.167.255.255131,070
8525.168.0.0/1525.168.0.1 to 25.169.255.25425.169.255.255131,070
8625.170.0.0/1525.170.0.1 to 25.171.255.25425.171.255.255131,070
8725.172.0.0/1525.172.0.1 to 25.173.255.25425.173.255.255131,070
8825.174.0.0/1525.174.0.1 to 25.175.255.25425.175.255.255131,070
8925.176.0.0/1525.176.0.1 to 25.177.255.25425.177.255.255131,070
9025.178.0.0/1525.178.0.1 to 25.179.255.25425.179.255.255131,070
9125.180.0.0/1525.180.0.1 to 25.181.255.25425.181.255.255131,070
9225.182.0.0/1525.182.0.1 to 25.183.255.25425.183.255.255131,070
9325.184.0.0/1525.184.0.1 to 25.185.255.25425.185.255.255131,070
9425.186.0.0/1525.186.0.1 to 25.187.255.25425.187.255.255131,070
9525.188.0.0/1525.188.0.1 to 25.189.255.25425.189.255.255131,070
9625.190.0.0/1525.190.0.1 to 25.191.255.25425.191.255.255131,070
9725.192.0.0/1525.192.0.1 to 25.193.255.25425.193.255.255131,070
9825.194.0.0/1525.194.0.1 to 25.195.255.25425.195.255.255131,070
9925.196.0.0/1525.196.0.1 to 25.197.255.25425.197.255.255131,070
10025.198.0.0/1525.198.0.1 to 25.199.255.25425.199.255.255131,070
10125.200.0.0/1525.200.0.1 to 25.201.255.25425.201.255.255131,070
10225.202.0.0/1525.202.0.1 to 25.203.255.25425.203.255.255131,070
10325.204.0.0/1525.204.0.1 to 25.205.255.25425.205.255.255131,070
10425.206.0.0/1525.206.0.1 to 25.207.255.25425.207.255.255131,070
10525.208.0.0/1525.208.0.1 to 25.209.255.25425.209.255.255131,070
10625.210.0.0/1525.210.0.1 to 25.211.255.25425.211.255.255131,070
10725.212.0.0/1525.212.0.1 to 25.213.255.25425.213.255.255131,070
10825.214.0.0/1525.214.0.1 to 25.215.255.25425.215.255.255131,070
10925.216.0.0/1525.216.0.1 to 25.217.255.25425.217.255.255131,070
11025.218.0.0/1525.218.0.1 to 25.219.255.25425.219.255.255131,070
11125.220.0.0/1525.220.0.1 to 25.221.255.25425.221.255.255131,070
11225.222.0.0/1525.222.0.1 to 25.223.255.25425.223.255.255131,070
11325.224.0.0/1525.224.0.1 to 25.225.255.25425.225.255.255131,070
11425.226.0.0/1525.226.0.1 to 25.227.255.25425.227.255.255131,070
11525.228.0.0/1525.228.0.1 to 25.229.255.25425.229.255.255131,070
11625.230.0.0/1525.230.0.1 to 25.231.255.25425.231.255.255131,070
11725.232.0.0/1525.232.0.1 to 25.233.255.25425.233.255.255131,070
11825.234.0.0/1525.234.0.1 to 25.235.255.25425.235.255.255131,070
11925.236.0.0/1525.236.0.1 to 25.237.255.25425.237.255.255131,070
12025.238.0.0/1525.238.0.1 to 25.239.255.25425.239.255.255131,070
12125.240.0.0/1525.240.0.1 to 25.241.255.25425.241.255.255131,070
12225.242.0.0/1525.242.0.1 to 25.243.255.25425.243.255.255131,070
12325.244.0.0/1525.244.0.1 to 25.245.255.25425.245.255.255131,070
12425.246.0.0/1525.246.0.1 to 25.247.255.25425.247.255.255131,070
12525.248.0.0/1525.248.0.1 to 25.249.255.25425.249.255.255131,070
12625.250.0.0/1525.250.0.1 to 25.251.255.25425.251.255.255131,070
12725.252.0.0/1525.252.0.1 to 25.253.255.25425.253.255.255131,070
12825.254.0.0/1525.254.0.1 to 25.255.255.25425.255.255.255131,070

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.