Speed and call quality testMy IP addressIP subnet calculatorDNS reportWhoIs lookupRemote support

Internet and network

Speed and call quality testTest delay, jitter and speed, with a focus on phone calls.My IP addressYour public IPv4 and IPv6 addresses, provider and address range.WhoIs lookupWho owns a domain or IP address, when it expires, and its DNS.DNS reportEvery DNS record for a domain, with email setup checked.IP subnet calculatorWork out a network's range, mask and hosts, and split it into subnets.

Computers and devices

Update checkIs this computer, phone and browser up to date? With links to update.Camera and mic testCheck your webcam and microphone before a call.Test print pagePrint an A4 page to check a printer: edges, text, line art and colours.

Make and print

Clean textStrip hidden characters, smart quotes and odd spaces from pasted text.QR code makerMake a QR code for a link, contact or message. Nothing leaves your browser.Wi-Fi QR posterPrint an A4 poster that lets guests join your Wi-Fi by scanning.

Surftec support

Remote supportLet a Surftec engineer connect to your computer to help you.All workingA full-screen confirmation that everything is up and running.

Surftec

Surftec websiteServices, news and how to contact Surftec
Cloud Tools
Guest
GuestNot signed in

Surftec customers will be recognised automatically when they use these tools from their office network.

Customer sign-in is coming soon.

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.

Network80.0.0.0/4
Usable hosts268,435,454
Subnet mask240.0.0.0
Addresses268,435,456
Network address
80.0.0.0
Broadcast address
95.255.255.255
First usable
80.0.0.1
Last usable
95.255.255.254
Usable hosts
268,435,454 (268,435,456 less the network and broadcast addresses)
Subnet mask
240.0.0.0
Wildcard mask
15.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/4
Type
Public public
Old class
A (default /8)
As numbers
Hex 50000000 · Integer 1342177280 to 1610612735
Reverse DNS zones
80.in-addr.arpa
81.in-addr.arpa
82.in-addr.arpa
83.in-addr.arpa
84.in-addr.arpa
85.in-addr.arpa
86.in-addr.arpa
87.in-addr.arpa
88.in-addr.arpa
89.in-addr.arpa
90.in-addr.arpa
91.in-addr.arpa
92.in-addr.arpa
93.in-addr.arpa
94.in-addr.arpa
95.in-addr.arpa
/4 is not on a 8-bit boundary, so it takes 16 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01010000.00000000.00000000.0000000080.0.0.0
Subnet mask11110000.00000000.00000000.00000000240.0.0.0
Network01010000.00000000.00000000.0000000080.0.0.0
Broadcast01011111.11111111.11111111.1111111195.255.255.255
Split into smaller subnets/12
/5 (2)/6 (4)/7 (8)/8 (16)/9 (32)/10 (64)/11 (128)/12 (256)/13 (512)/14 (1,024)/15 (2,048)/16 (4,096)

80.0.0.0/4 makes 256 subnets of /12.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
180.0.0.0/1280.0.0.1 to 80.15.255.25480.15.255.2551,048,574
280.16.0.0/1280.16.0.1 to 80.31.255.25480.31.255.2551,048,574
380.32.0.0/1280.32.0.1 to 80.47.255.25480.47.255.2551,048,574
480.48.0.0/1280.48.0.1 to 80.63.255.25480.63.255.2551,048,574
580.64.0.0/1280.64.0.1 to 80.79.255.25480.79.255.2551,048,574
680.80.0.0/1280.80.0.1 to 80.95.255.25480.95.255.2551,048,574
780.96.0.0/1280.96.0.1 to 80.111.255.25480.111.255.2551,048,574
880.112.0.0/1280.112.0.1 to 80.127.255.25480.127.255.2551,048,574
980.128.0.0/1280.128.0.1 to 80.143.255.25480.143.255.2551,048,574
1080.144.0.0/1280.144.0.1 to 80.159.255.25480.159.255.2551,048,574
1180.160.0.0/1280.160.0.1 to 80.175.255.25480.175.255.2551,048,574
1280.176.0.0/1280.176.0.1 to 80.191.255.25480.191.255.2551,048,574
1380.192.0.0/1280.192.0.1 to 80.207.255.25480.207.255.2551,048,574
1480.208.0.0/1280.208.0.1 to 80.223.255.25480.223.255.2551,048,574
1580.224.0.0/1280.224.0.1 to 80.239.255.25480.239.255.2551,048,574
1680.240.0.0/1280.240.0.1 to 80.255.255.25480.255.255.2551,048,574
1781.0.0.0/1281.0.0.1 to 81.15.255.25481.15.255.2551,048,574
1881.16.0.0/1281.16.0.1 to 81.31.255.25481.31.255.2551,048,574
1981.32.0.0/1281.32.0.1 to 81.47.255.25481.47.255.2551,048,574
2081.48.0.0/1281.48.0.1 to 81.63.255.25481.63.255.2551,048,574
2181.64.0.0/1281.64.0.1 to 81.79.255.25481.79.255.2551,048,574
2281.80.0.0/1281.80.0.1 to 81.95.255.25481.95.255.2551,048,574
2381.96.0.0/1281.96.0.1 to 81.111.255.25481.111.255.2551,048,574
2481.112.0.0/1281.112.0.1 to 81.127.255.25481.127.255.2551,048,574
2581.128.0.0/1281.128.0.1 to 81.143.255.25481.143.255.2551,048,574
2681.144.0.0/1281.144.0.1 to 81.159.255.25481.159.255.2551,048,574
2781.160.0.0/1281.160.0.1 to 81.175.255.25481.175.255.2551,048,574
2881.176.0.0/1281.176.0.1 to 81.191.255.25481.191.255.2551,048,574
2981.192.0.0/1281.192.0.1 to 81.207.255.25481.207.255.2551,048,574
3081.208.0.0/1281.208.0.1 to 81.223.255.25481.223.255.2551,048,574
3181.224.0.0/1281.224.0.1 to 81.239.255.25481.239.255.2551,048,574
3281.240.0.0/1281.240.0.1 to 81.255.255.25481.255.255.2551,048,574
3382.0.0.0/1282.0.0.1 to 82.15.255.25482.15.255.2551,048,574
3482.16.0.0/1282.16.0.1 to 82.31.255.25482.31.255.2551,048,574
3582.32.0.0/1282.32.0.1 to 82.47.255.25482.47.255.2551,048,574
3682.48.0.0/1282.48.0.1 to 82.63.255.25482.63.255.2551,048,574
3782.64.0.0/1282.64.0.1 to 82.79.255.25482.79.255.2551,048,574
3882.80.0.0/1282.80.0.1 to 82.95.255.25482.95.255.2551,048,574
3982.96.0.0/1282.96.0.1 to 82.111.255.25482.111.255.2551,048,574
4082.112.0.0/1282.112.0.1 to 82.127.255.25482.127.255.2551,048,574
4182.128.0.0/1282.128.0.1 to 82.143.255.25482.143.255.2551,048,574
4282.144.0.0/1282.144.0.1 to 82.159.255.25482.159.255.2551,048,574
4382.160.0.0/1282.160.0.1 to 82.175.255.25482.175.255.2551,048,574
4482.176.0.0/1282.176.0.1 to 82.191.255.25482.191.255.2551,048,574
4582.192.0.0/1282.192.0.1 to 82.207.255.25482.207.255.2551,048,574
4682.208.0.0/1282.208.0.1 to 82.223.255.25482.223.255.2551,048,574
4782.224.0.0/1282.224.0.1 to 82.239.255.25482.239.255.2551,048,574
4882.240.0.0/1282.240.0.1 to 82.255.255.25482.255.255.2551,048,574
4983.0.0.0/1283.0.0.1 to 83.15.255.25483.15.255.2551,048,574
5083.16.0.0/1283.16.0.1 to 83.31.255.25483.31.255.2551,048,574
5183.32.0.0/1283.32.0.1 to 83.47.255.25483.47.255.2551,048,574
5283.48.0.0/1283.48.0.1 to 83.63.255.25483.63.255.2551,048,574
5383.64.0.0/1283.64.0.1 to 83.79.255.25483.79.255.2551,048,574
5483.80.0.0/1283.80.0.1 to 83.95.255.25483.95.255.2551,048,574
5583.96.0.0/1283.96.0.1 to 83.111.255.25483.111.255.2551,048,574
5683.112.0.0/1283.112.0.1 to 83.127.255.25483.127.255.2551,048,574
5783.128.0.0/1283.128.0.1 to 83.143.255.25483.143.255.2551,048,574
5883.144.0.0/1283.144.0.1 to 83.159.255.25483.159.255.2551,048,574
5983.160.0.0/1283.160.0.1 to 83.175.255.25483.175.255.2551,048,574
6083.176.0.0/1283.176.0.1 to 83.191.255.25483.191.255.2551,048,574
6183.192.0.0/1283.192.0.1 to 83.207.255.25483.207.255.2551,048,574
6283.208.0.0/1283.208.0.1 to 83.223.255.25483.223.255.2551,048,574
6383.224.0.0/1283.224.0.1 to 83.239.255.25483.239.255.2551,048,574
6483.240.0.0/1283.240.0.1 to 83.255.255.25483.255.255.2551,048,574
6584.0.0.0/1284.0.0.1 to 84.15.255.25484.15.255.2551,048,574
6684.16.0.0/1284.16.0.1 to 84.31.255.25484.31.255.2551,048,574
6784.32.0.0/1284.32.0.1 to 84.47.255.25484.47.255.2551,048,574
6884.48.0.0/1284.48.0.1 to 84.63.255.25484.63.255.2551,048,574
6984.64.0.0/1284.64.0.1 to 84.79.255.25484.79.255.2551,048,574
7084.80.0.0/1284.80.0.1 to 84.95.255.25484.95.255.2551,048,574
7184.96.0.0/1284.96.0.1 to 84.111.255.25484.111.255.2551,048,574
7284.112.0.0/1284.112.0.1 to 84.127.255.25484.127.255.2551,048,574
7384.128.0.0/1284.128.0.1 to 84.143.255.25484.143.255.2551,048,574
7484.144.0.0/1284.144.0.1 to 84.159.255.25484.159.255.2551,048,574
7584.160.0.0/1284.160.0.1 to 84.175.255.25484.175.255.2551,048,574
7684.176.0.0/1284.176.0.1 to 84.191.255.25484.191.255.2551,048,574
7784.192.0.0/1284.192.0.1 to 84.207.255.25484.207.255.2551,048,574
7884.208.0.0/1284.208.0.1 to 84.223.255.25484.223.255.2551,048,574
7984.224.0.0/1284.224.0.1 to 84.239.255.25484.239.255.2551,048,574
8084.240.0.0/1284.240.0.1 to 84.255.255.25484.255.255.2551,048,574
8185.0.0.0/1285.0.0.1 to 85.15.255.25485.15.255.2551,048,574
8285.16.0.0/1285.16.0.1 to 85.31.255.25485.31.255.2551,048,574
8385.32.0.0/1285.32.0.1 to 85.47.255.25485.47.255.2551,048,574
8485.48.0.0/1285.48.0.1 to 85.63.255.25485.63.255.2551,048,574
8585.64.0.0/1285.64.0.1 to 85.79.255.25485.79.255.2551,048,574
8685.80.0.0/1285.80.0.1 to 85.95.255.25485.95.255.2551,048,574
8785.96.0.0/1285.96.0.1 to 85.111.255.25485.111.255.2551,048,574
8885.112.0.0/1285.112.0.1 to 85.127.255.25485.127.255.2551,048,574
8985.128.0.0/1285.128.0.1 to 85.143.255.25485.143.255.2551,048,574
9085.144.0.0/1285.144.0.1 to 85.159.255.25485.159.255.2551,048,574
9185.160.0.0/1285.160.0.1 to 85.175.255.25485.175.255.2551,048,574
9285.176.0.0/1285.176.0.1 to 85.191.255.25485.191.255.2551,048,574
9385.192.0.0/1285.192.0.1 to 85.207.255.25485.207.255.2551,048,574
9485.208.0.0/1285.208.0.1 to 85.223.255.25485.223.255.2551,048,574
9585.224.0.0/1285.224.0.1 to 85.239.255.25485.239.255.2551,048,574
9685.240.0.0/1285.240.0.1 to 85.255.255.25485.255.255.2551,048,574
9786.0.0.0/1286.0.0.1 to 86.15.255.25486.15.255.2551,048,574
9886.16.0.0/1286.16.0.1 to 86.31.255.25486.31.255.2551,048,574
9986.32.0.0/1286.32.0.1 to 86.47.255.25486.47.255.2551,048,574
10086.48.0.0/1286.48.0.1 to 86.63.255.25486.63.255.2551,048,574
10186.64.0.0/1286.64.0.1 to 86.79.255.25486.79.255.2551,048,574
10286.80.0.0/1286.80.0.1 to 86.95.255.25486.95.255.2551,048,574
10386.96.0.0/1286.96.0.1 to 86.111.255.25486.111.255.2551,048,574
10486.112.0.0/1286.112.0.1 to 86.127.255.25486.127.255.2551,048,574
10586.128.0.0/1286.128.0.1 to 86.143.255.25486.143.255.2551,048,574
10686.144.0.0/1286.144.0.1 to 86.159.255.25486.159.255.2551,048,574
10786.160.0.0/1286.160.0.1 to 86.175.255.25486.175.255.2551,048,574
10886.176.0.0/1286.176.0.1 to 86.191.255.25486.191.255.2551,048,574
10986.192.0.0/1286.192.0.1 to 86.207.255.25486.207.255.2551,048,574
11086.208.0.0/1286.208.0.1 to 86.223.255.25486.223.255.2551,048,574
11186.224.0.0/1286.224.0.1 to 86.239.255.25486.239.255.2551,048,574
11286.240.0.0/1286.240.0.1 to 86.255.255.25486.255.255.2551,048,574
11387.0.0.0/1287.0.0.1 to 87.15.255.25487.15.255.2551,048,574
11487.16.0.0/1287.16.0.1 to 87.31.255.25487.31.255.2551,048,574
11587.32.0.0/1287.32.0.1 to 87.47.255.25487.47.255.2551,048,574
11687.48.0.0/1287.48.0.1 to 87.63.255.25487.63.255.2551,048,574
11787.64.0.0/1287.64.0.1 to 87.79.255.25487.79.255.2551,048,574
11887.80.0.0/1287.80.0.1 to 87.95.255.25487.95.255.2551,048,574
11987.96.0.0/1287.96.0.1 to 87.111.255.25487.111.255.2551,048,574
12087.112.0.0/1287.112.0.1 to 87.127.255.25487.127.255.2551,048,574
12187.128.0.0/1287.128.0.1 to 87.143.255.25487.143.255.2551,048,574
12287.144.0.0/1287.144.0.1 to 87.159.255.25487.159.255.2551,048,574
12387.160.0.0/1287.160.0.1 to 87.175.255.25487.175.255.2551,048,574
12487.176.0.0/1287.176.0.1 to 87.191.255.25487.191.255.2551,048,574
12587.192.0.0/1287.192.0.1 to 87.207.255.25487.207.255.2551,048,574
12687.208.0.0/1287.208.0.1 to 87.223.255.25487.223.255.2551,048,574
12787.224.0.0/1287.224.0.1 to 87.239.255.25487.239.255.2551,048,574
12887.240.0.0/1287.240.0.1 to 87.255.255.25487.255.255.2551,048,574
12988.0.0.0/1288.0.0.1 to 88.15.255.25488.15.255.2551,048,574
13088.16.0.0/1288.16.0.1 to 88.31.255.25488.31.255.2551,048,574
13188.32.0.0/1288.32.0.1 to 88.47.255.25488.47.255.2551,048,574
13288.48.0.0/1288.48.0.1 to 88.63.255.25488.63.255.2551,048,574
13388.64.0.0/1288.64.0.1 to 88.79.255.25488.79.255.2551,048,574
13488.80.0.0/1288.80.0.1 to 88.95.255.25488.95.255.2551,048,574
13588.96.0.0/1288.96.0.1 to 88.111.255.25488.111.255.2551,048,574
13688.112.0.0/1288.112.0.1 to 88.127.255.25488.127.255.2551,048,574
13788.128.0.0/1288.128.0.1 to 88.143.255.25488.143.255.2551,048,574
13888.144.0.0/1288.144.0.1 to 88.159.255.25488.159.255.2551,048,574
13988.160.0.0/1288.160.0.1 to 88.175.255.25488.175.255.2551,048,574
14088.176.0.0/1288.176.0.1 to 88.191.255.25488.191.255.2551,048,574
14188.192.0.0/1288.192.0.1 to 88.207.255.25488.207.255.2551,048,574
14288.208.0.0/1288.208.0.1 to 88.223.255.25488.223.255.2551,048,574
14388.224.0.0/1288.224.0.1 to 88.239.255.25488.239.255.2551,048,574
14488.240.0.0/1288.240.0.1 to 88.255.255.25488.255.255.2551,048,574
14589.0.0.0/1289.0.0.1 to 89.15.255.25489.15.255.2551,048,574
14689.16.0.0/1289.16.0.1 to 89.31.255.25489.31.255.2551,048,574
14789.32.0.0/1289.32.0.1 to 89.47.255.25489.47.255.2551,048,574
14889.48.0.0/1289.48.0.1 to 89.63.255.25489.63.255.2551,048,574
14989.64.0.0/1289.64.0.1 to 89.79.255.25489.79.255.2551,048,574
15089.80.0.0/1289.80.0.1 to 89.95.255.25489.95.255.2551,048,574
15189.96.0.0/1289.96.0.1 to 89.111.255.25489.111.255.2551,048,574
15289.112.0.0/1289.112.0.1 to 89.127.255.25489.127.255.2551,048,574
15389.128.0.0/1289.128.0.1 to 89.143.255.25489.143.255.2551,048,574
15489.144.0.0/1289.144.0.1 to 89.159.255.25489.159.255.2551,048,574
15589.160.0.0/1289.160.0.1 to 89.175.255.25489.175.255.2551,048,574
15689.176.0.0/1289.176.0.1 to 89.191.255.25489.191.255.2551,048,574
15789.192.0.0/1289.192.0.1 to 89.207.255.25489.207.255.2551,048,574
15889.208.0.0/1289.208.0.1 to 89.223.255.25489.223.255.2551,048,574
15989.224.0.0/1289.224.0.1 to 89.239.255.25489.239.255.2551,048,574
16089.240.0.0/1289.240.0.1 to 89.255.255.25489.255.255.2551,048,574
16190.0.0.0/1290.0.0.1 to 90.15.255.25490.15.255.2551,048,574
16290.16.0.0/1290.16.0.1 to 90.31.255.25490.31.255.2551,048,574
16390.32.0.0/1290.32.0.1 to 90.47.255.25490.47.255.2551,048,574
16490.48.0.0/1290.48.0.1 to 90.63.255.25490.63.255.2551,048,574
16590.64.0.0/1290.64.0.1 to 90.79.255.25490.79.255.2551,048,574
16690.80.0.0/1290.80.0.1 to 90.95.255.25490.95.255.2551,048,574
16790.96.0.0/1290.96.0.1 to 90.111.255.25490.111.255.2551,048,574
16890.112.0.0/1290.112.0.1 to 90.127.255.25490.127.255.2551,048,574
16990.128.0.0/1290.128.0.1 to 90.143.255.25490.143.255.2551,048,574
17090.144.0.0/1290.144.0.1 to 90.159.255.25490.159.255.2551,048,574
17190.160.0.0/1290.160.0.1 to 90.175.255.25490.175.255.2551,048,574
17290.176.0.0/1290.176.0.1 to 90.191.255.25490.191.255.2551,048,574
17390.192.0.0/1290.192.0.1 to 90.207.255.25490.207.255.2551,048,574
17490.208.0.0/1290.208.0.1 to 90.223.255.25490.223.255.2551,048,574
17590.224.0.0/1290.224.0.1 to 90.239.255.25490.239.255.2551,048,574
17690.240.0.0/1290.240.0.1 to 90.255.255.25490.255.255.2551,048,574
17791.0.0.0/1291.0.0.1 to 91.15.255.25491.15.255.2551,048,574
17891.16.0.0/1291.16.0.1 to 91.31.255.25491.31.255.2551,048,574
17991.32.0.0/1291.32.0.1 to 91.47.255.25491.47.255.2551,048,574
18091.48.0.0/1291.48.0.1 to 91.63.255.25491.63.255.2551,048,574
18191.64.0.0/1291.64.0.1 to 91.79.255.25491.79.255.2551,048,574
18291.80.0.0/1291.80.0.1 to 91.95.255.25491.95.255.2551,048,574
18391.96.0.0/1291.96.0.1 to 91.111.255.25491.111.255.2551,048,574
18491.112.0.0/1291.112.0.1 to 91.127.255.25491.127.255.2551,048,574
18591.128.0.0/1291.128.0.1 to 91.143.255.25491.143.255.2551,048,574
18691.144.0.0/1291.144.0.1 to 91.159.255.25491.159.255.2551,048,574
18791.160.0.0/1291.160.0.1 to 91.175.255.25491.175.255.2551,048,574
18891.176.0.0/1291.176.0.1 to 91.191.255.25491.191.255.2551,048,574
18991.192.0.0/1291.192.0.1 to 91.207.255.25491.207.255.2551,048,574
19091.208.0.0/1291.208.0.1 to 91.223.255.25491.223.255.2551,048,574
19191.224.0.0/1291.224.0.1 to 91.239.255.25491.239.255.2551,048,574
19291.240.0.0/1291.240.0.1 to 91.255.255.25491.255.255.2551,048,574
19392.0.0.0/1292.0.0.1 to 92.15.255.25492.15.255.2551,048,574
19492.16.0.0/1292.16.0.1 to 92.31.255.25492.31.255.2551,048,574
19592.32.0.0/1292.32.0.1 to 92.47.255.25492.47.255.2551,048,574
19692.48.0.0/1292.48.0.1 to 92.63.255.25492.63.255.2551,048,574
19792.64.0.0/1292.64.0.1 to 92.79.255.25492.79.255.2551,048,574
19892.80.0.0/1292.80.0.1 to 92.95.255.25492.95.255.2551,048,574
19992.96.0.0/1292.96.0.1 to 92.111.255.25492.111.255.2551,048,574
20092.112.0.0/1292.112.0.1 to 92.127.255.25492.127.255.2551,048,574
20192.128.0.0/1292.128.0.1 to 92.143.255.25492.143.255.2551,048,574
20292.144.0.0/1292.144.0.1 to 92.159.255.25492.159.255.2551,048,574
20392.160.0.0/1292.160.0.1 to 92.175.255.25492.175.255.2551,048,574
20492.176.0.0/1292.176.0.1 to 92.191.255.25492.191.255.2551,048,574
20592.192.0.0/1292.192.0.1 to 92.207.255.25492.207.255.2551,048,574
20692.208.0.0/1292.208.0.1 to 92.223.255.25492.223.255.2551,048,574
20792.224.0.0/1292.224.0.1 to 92.239.255.25492.239.255.2551,048,574
20892.240.0.0/1292.240.0.1 to 92.255.255.25492.255.255.2551,048,574
20993.0.0.0/1293.0.0.1 to 93.15.255.25493.15.255.2551,048,574
21093.16.0.0/1293.16.0.1 to 93.31.255.25493.31.255.2551,048,574
21193.32.0.0/1293.32.0.1 to 93.47.255.25493.47.255.2551,048,574
21293.48.0.0/1293.48.0.1 to 93.63.255.25493.63.255.2551,048,574
21393.64.0.0/1293.64.0.1 to 93.79.255.25493.79.255.2551,048,574
21493.80.0.0/1293.80.0.1 to 93.95.255.25493.95.255.2551,048,574
21593.96.0.0/1293.96.0.1 to 93.111.255.25493.111.255.2551,048,574
21693.112.0.0/1293.112.0.1 to 93.127.255.25493.127.255.2551,048,574
21793.128.0.0/1293.128.0.1 to 93.143.255.25493.143.255.2551,048,574
21893.144.0.0/1293.144.0.1 to 93.159.255.25493.159.255.2551,048,574
21993.160.0.0/1293.160.0.1 to 93.175.255.25493.175.255.2551,048,574
22093.176.0.0/1293.176.0.1 to 93.191.255.25493.191.255.2551,048,574
22193.192.0.0/1293.192.0.1 to 93.207.255.25493.207.255.2551,048,574
22293.208.0.0/1293.208.0.1 to 93.223.255.25493.223.255.2551,048,574
22393.224.0.0/1293.224.0.1 to 93.239.255.25493.239.255.2551,048,574
22493.240.0.0/1293.240.0.1 to 93.255.255.25493.255.255.2551,048,574
22594.0.0.0/1294.0.0.1 to 94.15.255.25494.15.255.2551,048,574
22694.16.0.0/1294.16.0.1 to 94.31.255.25494.31.255.2551,048,574
22794.32.0.0/1294.32.0.1 to 94.47.255.25494.47.255.2551,048,574
22894.48.0.0/1294.48.0.1 to 94.63.255.25494.63.255.2551,048,574
22994.64.0.0/1294.64.0.1 to 94.79.255.25494.79.255.2551,048,574
23094.80.0.0/1294.80.0.1 to 94.95.255.25494.95.255.2551,048,574
23194.96.0.0/1294.96.0.1 to 94.111.255.25494.111.255.2551,048,574
23294.112.0.0/1294.112.0.1 to 94.127.255.25494.127.255.2551,048,574
23394.128.0.0/1294.128.0.1 to 94.143.255.25494.143.255.2551,048,574
23494.144.0.0/1294.144.0.1 to 94.159.255.25494.159.255.2551,048,574
23594.160.0.0/1294.160.0.1 to 94.175.255.25494.175.255.2551,048,574
23694.176.0.0/1294.176.0.1 to 94.191.255.25494.191.255.2551,048,574
23794.192.0.0/1294.192.0.1 to 94.207.255.25494.207.255.2551,048,574
23894.208.0.0/1294.208.0.1 to 94.223.255.25494.223.255.2551,048,574
23994.224.0.0/1294.224.0.1 to 94.239.255.25494.239.255.2551,048,574
24094.240.0.0/1294.240.0.1 to 94.255.255.25494.255.255.2551,048,574
24195.0.0.0/1295.0.0.1 to 95.15.255.25495.15.255.2551,048,574
24295.16.0.0/1295.16.0.1 to 95.31.255.25495.31.255.2551,048,574
24395.32.0.0/1295.32.0.1 to 95.47.255.25495.47.255.2551,048,574
24495.48.0.0/1295.48.0.1 to 95.63.255.25495.63.255.2551,048,574
24595.64.0.0/1295.64.0.1 to 95.79.255.25495.79.255.2551,048,574
24695.80.0.0/1295.80.0.1 to 95.95.255.25495.95.255.2551,048,574
24795.96.0.0/1295.96.0.1 to 95.111.255.25495.111.255.2551,048,574
24895.112.0.0/1295.112.0.1 to 95.127.255.25495.127.255.2551,048,574
24995.128.0.0/1295.128.0.1 to 95.143.255.25495.143.255.2551,048,574
25095.144.0.0/1295.144.0.1 to 95.159.255.25495.159.255.2551,048,574
25195.160.0.0/1295.160.0.1 to 95.175.255.25495.175.255.2551,048,574
25295.176.0.0/1295.176.0.1 to 95.191.255.25495.191.255.2551,048,574
25395.192.0.0/1295.192.0.1 to 95.207.255.25495.207.255.2551,048,574
25495.208.0.0/1295.208.0.1 to 95.223.255.25495.223.255.2551,048,574
25595.224.0.0/1295.224.0.1 to 95.239.255.25495.239.255.2551,048,574
25695.240.0.0/1295.240.0.1 to 95.255.255.25495.255.255.2551,048,574

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.