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.

Network80.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
80.0.0.0
Broadcast address
81.255.255.255
First usable
80.0.0.1
Last usable
81.255.255.254
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 50000000 · Integer 1342177280 to 1375731711
Reverse DNS zones
80.in-addr.arpa
81.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
Address01010000.00000000.00000000.0000000080.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network01010000.00000000.00000000.0000000080.0.0.0
Broadcast01010001.11111111.11111111.1111111181.255.255.255
Split into smaller subnets/15
/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)

80.0.0.0/7 makes 256 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
180.0.0.0/1580.0.0.1 to 80.1.255.25480.1.255.255131,070
280.2.0.0/1580.2.0.1 to 80.3.255.25480.3.255.255131,070
380.4.0.0/1580.4.0.1 to 80.5.255.25480.5.255.255131,070
480.6.0.0/1580.6.0.1 to 80.7.255.25480.7.255.255131,070
580.8.0.0/1580.8.0.1 to 80.9.255.25480.9.255.255131,070
680.10.0.0/1580.10.0.1 to 80.11.255.25480.11.255.255131,070
780.12.0.0/1580.12.0.1 to 80.13.255.25480.13.255.255131,070
880.14.0.0/1580.14.0.1 to 80.15.255.25480.15.255.255131,070
980.16.0.0/1580.16.0.1 to 80.17.255.25480.17.255.255131,070
1080.18.0.0/1580.18.0.1 to 80.19.255.25480.19.255.255131,070
1180.20.0.0/1580.20.0.1 to 80.21.255.25480.21.255.255131,070
1280.22.0.0/1580.22.0.1 to 80.23.255.25480.23.255.255131,070
1380.24.0.0/1580.24.0.1 to 80.25.255.25480.25.255.255131,070
1480.26.0.0/1580.26.0.1 to 80.27.255.25480.27.255.255131,070
1580.28.0.0/1580.28.0.1 to 80.29.255.25480.29.255.255131,070
1680.30.0.0/1580.30.0.1 to 80.31.255.25480.31.255.255131,070
1780.32.0.0/1580.32.0.1 to 80.33.255.25480.33.255.255131,070
1880.34.0.0/1580.34.0.1 to 80.35.255.25480.35.255.255131,070
1980.36.0.0/1580.36.0.1 to 80.37.255.25480.37.255.255131,070
2080.38.0.0/1580.38.0.1 to 80.39.255.25480.39.255.255131,070
2180.40.0.0/1580.40.0.1 to 80.41.255.25480.41.255.255131,070
2280.42.0.0/1580.42.0.1 to 80.43.255.25480.43.255.255131,070
2380.44.0.0/1580.44.0.1 to 80.45.255.25480.45.255.255131,070
2480.46.0.0/1580.46.0.1 to 80.47.255.25480.47.255.255131,070
2580.48.0.0/1580.48.0.1 to 80.49.255.25480.49.255.255131,070
2680.50.0.0/1580.50.0.1 to 80.51.255.25480.51.255.255131,070
2780.52.0.0/1580.52.0.1 to 80.53.255.25480.53.255.255131,070
2880.54.0.0/1580.54.0.1 to 80.55.255.25480.55.255.255131,070
2980.56.0.0/1580.56.0.1 to 80.57.255.25480.57.255.255131,070
3080.58.0.0/1580.58.0.1 to 80.59.255.25480.59.255.255131,070
3180.60.0.0/1580.60.0.1 to 80.61.255.25480.61.255.255131,070
3280.62.0.0/1580.62.0.1 to 80.63.255.25480.63.255.255131,070
3380.64.0.0/1580.64.0.1 to 80.65.255.25480.65.255.255131,070
3480.66.0.0/1580.66.0.1 to 80.67.255.25480.67.255.255131,070
3580.68.0.0/1580.68.0.1 to 80.69.255.25480.69.255.255131,070
3680.70.0.0/1580.70.0.1 to 80.71.255.25480.71.255.255131,070
3780.72.0.0/1580.72.0.1 to 80.73.255.25480.73.255.255131,070
3880.74.0.0/1580.74.0.1 to 80.75.255.25480.75.255.255131,070
3980.76.0.0/1580.76.0.1 to 80.77.255.25480.77.255.255131,070
4080.78.0.0/1580.78.0.1 to 80.79.255.25480.79.255.255131,070
4180.80.0.0/1580.80.0.1 to 80.81.255.25480.81.255.255131,070
4280.82.0.0/1580.82.0.1 to 80.83.255.25480.83.255.255131,070
4380.84.0.0/1580.84.0.1 to 80.85.255.25480.85.255.255131,070
4480.86.0.0/1580.86.0.1 to 80.87.255.25480.87.255.255131,070
4580.88.0.0/1580.88.0.1 to 80.89.255.25480.89.255.255131,070
4680.90.0.0/1580.90.0.1 to 80.91.255.25480.91.255.255131,070
4780.92.0.0/1580.92.0.1 to 80.93.255.25480.93.255.255131,070
4880.94.0.0/1580.94.0.1 to 80.95.255.25480.95.255.255131,070
4980.96.0.0/1580.96.0.1 to 80.97.255.25480.97.255.255131,070
5080.98.0.0/1580.98.0.1 to 80.99.255.25480.99.255.255131,070
5180.100.0.0/1580.100.0.1 to 80.101.255.25480.101.255.255131,070
5280.102.0.0/1580.102.0.1 to 80.103.255.25480.103.255.255131,070
5380.104.0.0/1580.104.0.1 to 80.105.255.25480.105.255.255131,070
5480.106.0.0/1580.106.0.1 to 80.107.255.25480.107.255.255131,070
5580.108.0.0/1580.108.0.1 to 80.109.255.25480.109.255.255131,070
5680.110.0.0/1580.110.0.1 to 80.111.255.25480.111.255.255131,070
5780.112.0.0/1580.112.0.1 to 80.113.255.25480.113.255.255131,070
5880.114.0.0/1580.114.0.1 to 80.115.255.25480.115.255.255131,070
5980.116.0.0/1580.116.0.1 to 80.117.255.25480.117.255.255131,070
6080.118.0.0/1580.118.0.1 to 80.119.255.25480.119.255.255131,070
6180.120.0.0/1580.120.0.1 to 80.121.255.25480.121.255.255131,070
6280.122.0.0/1580.122.0.1 to 80.123.255.25480.123.255.255131,070
6380.124.0.0/1580.124.0.1 to 80.125.255.25480.125.255.255131,070
6480.126.0.0/1580.126.0.1 to 80.127.255.25480.127.255.255131,070
6580.128.0.0/1580.128.0.1 to 80.129.255.25480.129.255.255131,070
6680.130.0.0/1580.130.0.1 to 80.131.255.25480.131.255.255131,070
6780.132.0.0/1580.132.0.1 to 80.133.255.25480.133.255.255131,070
6880.134.0.0/1580.134.0.1 to 80.135.255.25480.135.255.255131,070
6980.136.0.0/1580.136.0.1 to 80.137.255.25480.137.255.255131,070
7080.138.0.0/1580.138.0.1 to 80.139.255.25480.139.255.255131,070
7180.140.0.0/1580.140.0.1 to 80.141.255.25480.141.255.255131,070
7280.142.0.0/1580.142.0.1 to 80.143.255.25480.143.255.255131,070
7380.144.0.0/1580.144.0.1 to 80.145.255.25480.145.255.255131,070
7480.146.0.0/1580.146.0.1 to 80.147.255.25480.147.255.255131,070
7580.148.0.0/1580.148.0.1 to 80.149.255.25480.149.255.255131,070
7680.150.0.0/1580.150.0.1 to 80.151.255.25480.151.255.255131,070
7780.152.0.0/1580.152.0.1 to 80.153.255.25480.153.255.255131,070
7880.154.0.0/1580.154.0.1 to 80.155.255.25480.155.255.255131,070
7980.156.0.0/1580.156.0.1 to 80.157.255.25480.157.255.255131,070
8080.158.0.0/1580.158.0.1 to 80.159.255.25480.159.255.255131,070
8180.160.0.0/1580.160.0.1 to 80.161.255.25480.161.255.255131,070
8280.162.0.0/1580.162.0.1 to 80.163.255.25480.163.255.255131,070
8380.164.0.0/1580.164.0.1 to 80.165.255.25480.165.255.255131,070
8480.166.0.0/1580.166.0.1 to 80.167.255.25480.167.255.255131,070
8580.168.0.0/1580.168.0.1 to 80.169.255.25480.169.255.255131,070
8680.170.0.0/1580.170.0.1 to 80.171.255.25480.171.255.255131,070
8780.172.0.0/1580.172.0.1 to 80.173.255.25480.173.255.255131,070
8880.174.0.0/1580.174.0.1 to 80.175.255.25480.175.255.255131,070
8980.176.0.0/1580.176.0.1 to 80.177.255.25480.177.255.255131,070
9080.178.0.0/1580.178.0.1 to 80.179.255.25480.179.255.255131,070
9180.180.0.0/1580.180.0.1 to 80.181.255.25480.181.255.255131,070
9280.182.0.0/1580.182.0.1 to 80.183.255.25480.183.255.255131,070
9380.184.0.0/1580.184.0.1 to 80.185.255.25480.185.255.255131,070
9480.186.0.0/1580.186.0.1 to 80.187.255.25480.187.255.255131,070
9580.188.0.0/1580.188.0.1 to 80.189.255.25480.189.255.255131,070
9680.190.0.0/1580.190.0.1 to 80.191.255.25480.191.255.255131,070
9780.192.0.0/1580.192.0.1 to 80.193.255.25480.193.255.255131,070
9880.194.0.0/1580.194.0.1 to 80.195.255.25480.195.255.255131,070
9980.196.0.0/1580.196.0.1 to 80.197.255.25480.197.255.255131,070
10080.198.0.0/1580.198.0.1 to 80.199.255.25480.199.255.255131,070
10180.200.0.0/1580.200.0.1 to 80.201.255.25480.201.255.255131,070
10280.202.0.0/1580.202.0.1 to 80.203.255.25480.203.255.255131,070
10380.204.0.0/1580.204.0.1 to 80.205.255.25480.205.255.255131,070
10480.206.0.0/1580.206.0.1 to 80.207.255.25480.207.255.255131,070
10580.208.0.0/1580.208.0.1 to 80.209.255.25480.209.255.255131,070
10680.210.0.0/1580.210.0.1 to 80.211.255.25480.211.255.255131,070
10780.212.0.0/1580.212.0.1 to 80.213.255.25480.213.255.255131,070
10880.214.0.0/1580.214.0.1 to 80.215.255.25480.215.255.255131,070
10980.216.0.0/1580.216.0.1 to 80.217.255.25480.217.255.255131,070
11080.218.0.0/1580.218.0.1 to 80.219.255.25480.219.255.255131,070
11180.220.0.0/1580.220.0.1 to 80.221.255.25480.221.255.255131,070
11280.222.0.0/1580.222.0.1 to 80.223.255.25480.223.255.255131,070
11380.224.0.0/1580.224.0.1 to 80.225.255.25480.225.255.255131,070
11480.226.0.0/1580.226.0.1 to 80.227.255.25480.227.255.255131,070
11580.228.0.0/1580.228.0.1 to 80.229.255.25480.229.255.255131,070
11680.230.0.0/1580.230.0.1 to 80.231.255.25480.231.255.255131,070
11780.232.0.0/1580.232.0.1 to 80.233.255.25480.233.255.255131,070
11880.234.0.0/1580.234.0.1 to 80.235.255.25480.235.255.255131,070
11980.236.0.0/1580.236.0.1 to 80.237.255.25480.237.255.255131,070
12080.238.0.0/1580.238.0.1 to 80.239.255.25480.239.255.255131,070
12180.240.0.0/1580.240.0.1 to 80.241.255.25480.241.255.255131,070
12280.242.0.0/1580.242.0.1 to 80.243.255.25480.243.255.255131,070
12380.244.0.0/1580.244.0.1 to 80.245.255.25480.245.255.255131,070
12480.246.0.0/1580.246.0.1 to 80.247.255.25480.247.255.255131,070
12580.248.0.0/1580.248.0.1 to 80.249.255.25480.249.255.255131,070
12680.250.0.0/1580.250.0.1 to 80.251.255.25480.251.255.255131,070
12780.252.0.0/1580.252.0.1 to 80.253.255.25480.253.255.255131,070
12880.254.0.0/1580.254.0.1 to 80.255.255.25480.255.255.255131,070
12981.0.0.0/1581.0.0.1 to 81.1.255.25481.1.255.255131,070
13081.2.0.0/1581.2.0.1 to 81.3.255.25481.3.255.255131,070
13181.4.0.0/1581.4.0.1 to 81.5.255.25481.5.255.255131,070
13281.6.0.0/1581.6.0.1 to 81.7.255.25481.7.255.255131,070
13381.8.0.0/1581.8.0.1 to 81.9.255.25481.9.255.255131,070
13481.10.0.0/1581.10.0.1 to 81.11.255.25481.11.255.255131,070
13581.12.0.0/1581.12.0.1 to 81.13.255.25481.13.255.255131,070
13681.14.0.0/1581.14.0.1 to 81.15.255.25481.15.255.255131,070
13781.16.0.0/1581.16.0.1 to 81.17.255.25481.17.255.255131,070
13881.18.0.0/1581.18.0.1 to 81.19.255.25481.19.255.255131,070
13981.20.0.0/1581.20.0.1 to 81.21.255.25481.21.255.255131,070
14081.22.0.0/1581.22.0.1 to 81.23.255.25481.23.255.255131,070
14181.24.0.0/1581.24.0.1 to 81.25.255.25481.25.255.255131,070
14281.26.0.0/1581.26.0.1 to 81.27.255.25481.27.255.255131,070
14381.28.0.0/1581.28.0.1 to 81.29.255.25481.29.255.255131,070
14481.30.0.0/1581.30.0.1 to 81.31.255.25481.31.255.255131,070
14581.32.0.0/1581.32.0.1 to 81.33.255.25481.33.255.255131,070
14681.34.0.0/1581.34.0.1 to 81.35.255.25481.35.255.255131,070
14781.36.0.0/1581.36.0.1 to 81.37.255.25481.37.255.255131,070
14881.38.0.0/1581.38.0.1 to 81.39.255.25481.39.255.255131,070
14981.40.0.0/1581.40.0.1 to 81.41.255.25481.41.255.255131,070
15081.42.0.0/1581.42.0.1 to 81.43.255.25481.43.255.255131,070
15181.44.0.0/1581.44.0.1 to 81.45.255.25481.45.255.255131,070
15281.46.0.0/1581.46.0.1 to 81.47.255.25481.47.255.255131,070
15381.48.0.0/1581.48.0.1 to 81.49.255.25481.49.255.255131,070
15481.50.0.0/1581.50.0.1 to 81.51.255.25481.51.255.255131,070
15581.52.0.0/1581.52.0.1 to 81.53.255.25481.53.255.255131,070
15681.54.0.0/1581.54.0.1 to 81.55.255.25481.55.255.255131,070
15781.56.0.0/1581.56.0.1 to 81.57.255.25481.57.255.255131,070
15881.58.0.0/1581.58.0.1 to 81.59.255.25481.59.255.255131,070
15981.60.0.0/1581.60.0.1 to 81.61.255.25481.61.255.255131,070
16081.62.0.0/1581.62.0.1 to 81.63.255.25481.63.255.255131,070
16181.64.0.0/1581.64.0.1 to 81.65.255.25481.65.255.255131,070
16281.66.0.0/1581.66.0.1 to 81.67.255.25481.67.255.255131,070
16381.68.0.0/1581.68.0.1 to 81.69.255.25481.69.255.255131,070
16481.70.0.0/1581.70.0.1 to 81.71.255.25481.71.255.255131,070
16581.72.0.0/1581.72.0.1 to 81.73.255.25481.73.255.255131,070
16681.74.0.0/1581.74.0.1 to 81.75.255.25481.75.255.255131,070
16781.76.0.0/1581.76.0.1 to 81.77.255.25481.77.255.255131,070
16881.78.0.0/1581.78.0.1 to 81.79.255.25481.79.255.255131,070
16981.80.0.0/1581.80.0.1 to 81.81.255.25481.81.255.255131,070
17081.82.0.0/1581.82.0.1 to 81.83.255.25481.83.255.255131,070
17181.84.0.0/1581.84.0.1 to 81.85.255.25481.85.255.255131,070
17281.86.0.0/1581.86.0.1 to 81.87.255.25481.87.255.255131,070
17381.88.0.0/1581.88.0.1 to 81.89.255.25481.89.255.255131,070
17481.90.0.0/1581.90.0.1 to 81.91.255.25481.91.255.255131,070
17581.92.0.0/1581.92.0.1 to 81.93.255.25481.93.255.255131,070
17681.94.0.0/1581.94.0.1 to 81.95.255.25481.95.255.255131,070
17781.96.0.0/1581.96.0.1 to 81.97.255.25481.97.255.255131,070
17881.98.0.0/1581.98.0.1 to 81.99.255.25481.99.255.255131,070
17981.100.0.0/1581.100.0.1 to 81.101.255.25481.101.255.255131,070
18081.102.0.0/1581.102.0.1 to 81.103.255.25481.103.255.255131,070
18181.104.0.0/1581.104.0.1 to 81.105.255.25481.105.255.255131,070
18281.106.0.0/1581.106.0.1 to 81.107.255.25481.107.255.255131,070
18381.108.0.0/1581.108.0.1 to 81.109.255.25481.109.255.255131,070
18481.110.0.0/1581.110.0.1 to 81.111.255.25481.111.255.255131,070
18581.112.0.0/1581.112.0.1 to 81.113.255.25481.113.255.255131,070
18681.114.0.0/1581.114.0.1 to 81.115.255.25481.115.255.255131,070
18781.116.0.0/1581.116.0.1 to 81.117.255.25481.117.255.255131,070
18881.118.0.0/1581.118.0.1 to 81.119.255.25481.119.255.255131,070
18981.120.0.0/1581.120.0.1 to 81.121.255.25481.121.255.255131,070
19081.122.0.0/1581.122.0.1 to 81.123.255.25481.123.255.255131,070
19181.124.0.0/1581.124.0.1 to 81.125.255.25481.125.255.255131,070
19281.126.0.0/1581.126.0.1 to 81.127.255.25481.127.255.255131,070
19381.128.0.0/1581.128.0.1 to 81.129.255.25481.129.255.255131,070
19481.130.0.0/1581.130.0.1 to 81.131.255.25481.131.255.255131,070
19581.132.0.0/1581.132.0.1 to 81.133.255.25481.133.255.255131,070
19681.134.0.0/1581.134.0.1 to 81.135.255.25481.135.255.255131,070
19781.136.0.0/1581.136.0.1 to 81.137.255.25481.137.255.255131,070
19881.138.0.0/1581.138.0.1 to 81.139.255.25481.139.255.255131,070
19981.140.0.0/1581.140.0.1 to 81.141.255.25481.141.255.255131,070
20081.142.0.0/1581.142.0.1 to 81.143.255.25481.143.255.255131,070
20181.144.0.0/1581.144.0.1 to 81.145.255.25481.145.255.255131,070
20281.146.0.0/1581.146.0.1 to 81.147.255.25481.147.255.255131,070
20381.148.0.0/1581.148.0.1 to 81.149.255.25481.149.255.255131,070
20481.150.0.0/1581.150.0.1 to 81.151.255.25481.151.255.255131,070
20581.152.0.0/1581.152.0.1 to 81.153.255.25481.153.255.255131,070
20681.154.0.0/1581.154.0.1 to 81.155.255.25481.155.255.255131,070
20781.156.0.0/1581.156.0.1 to 81.157.255.25481.157.255.255131,070
20881.158.0.0/1581.158.0.1 to 81.159.255.25481.159.255.255131,070
20981.160.0.0/1581.160.0.1 to 81.161.255.25481.161.255.255131,070
21081.162.0.0/1581.162.0.1 to 81.163.255.25481.163.255.255131,070
21181.164.0.0/1581.164.0.1 to 81.165.255.25481.165.255.255131,070
21281.166.0.0/1581.166.0.1 to 81.167.255.25481.167.255.255131,070
21381.168.0.0/1581.168.0.1 to 81.169.255.25481.169.255.255131,070
21481.170.0.0/1581.170.0.1 to 81.171.255.25481.171.255.255131,070
21581.172.0.0/1581.172.0.1 to 81.173.255.25481.173.255.255131,070
21681.174.0.0/1581.174.0.1 to 81.175.255.25481.175.255.255131,070
21781.176.0.0/1581.176.0.1 to 81.177.255.25481.177.255.255131,070
21881.178.0.0/1581.178.0.1 to 81.179.255.25481.179.255.255131,070
21981.180.0.0/1581.180.0.1 to 81.181.255.25481.181.255.255131,070
22081.182.0.0/1581.182.0.1 to 81.183.255.25481.183.255.255131,070
22181.184.0.0/1581.184.0.1 to 81.185.255.25481.185.255.255131,070
22281.186.0.0/1581.186.0.1 to 81.187.255.25481.187.255.255131,070
22381.188.0.0/1581.188.0.1 to 81.189.255.25481.189.255.255131,070
22481.190.0.0/1581.190.0.1 to 81.191.255.25481.191.255.255131,070
22581.192.0.0/1581.192.0.1 to 81.193.255.25481.193.255.255131,070
22681.194.0.0/1581.194.0.1 to 81.195.255.25481.195.255.255131,070
22781.196.0.0/1581.196.0.1 to 81.197.255.25481.197.255.255131,070
22881.198.0.0/1581.198.0.1 to 81.199.255.25481.199.255.255131,070
22981.200.0.0/1581.200.0.1 to 81.201.255.25481.201.255.255131,070
23081.202.0.0/1581.202.0.1 to 81.203.255.25481.203.255.255131,070
23181.204.0.0/1581.204.0.1 to 81.205.255.25481.205.255.255131,070
23281.206.0.0/1581.206.0.1 to 81.207.255.25481.207.255.255131,070
23381.208.0.0/1581.208.0.1 to 81.209.255.25481.209.255.255131,070
23481.210.0.0/1581.210.0.1 to 81.211.255.25481.211.255.255131,070
23581.212.0.0/1581.212.0.1 to 81.213.255.25481.213.255.255131,070
23681.214.0.0/1581.214.0.1 to 81.215.255.25481.215.255.255131,070
23781.216.0.0/1581.216.0.1 to 81.217.255.25481.217.255.255131,070
23881.218.0.0/1581.218.0.1 to 81.219.255.25481.219.255.255131,070
23981.220.0.0/1581.220.0.1 to 81.221.255.25481.221.255.255131,070
24081.222.0.0/1581.222.0.1 to 81.223.255.25481.223.255.255131,070
24181.224.0.0/1581.224.0.1 to 81.225.255.25481.225.255.255131,070
24281.226.0.0/1581.226.0.1 to 81.227.255.25481.227.255.255131,070
24381.228.0.0/1581.228.0.1 to 81.229.255.25481.229.255.255131,070
24481.230.0.0/1581.230.0.1 to 81.231.255.25481.231.255.255131,070
24581.232.0.0/1581.232.0.1 to 81.233.255.25481.233.255.255131,070
24681.234.0.0/1581.234.0.1 to 81.235.255.25481.235.255.255131,070
24781.236.0.0/1581.236.0.1 to 81.237.255.25481.237.255.255131,070
24881.238.0.0/1581.238.0.1 to 81.239.255.25481.239.255.255131,070
24981.240.0.0/1581.240.0.1 to 81.241.255.25481.241.255.255131,070
25081.242.0.0/1581.242.0.1 to 81.243.255.25481.243.255.255131,070
25181.244.0.0/1581.244.0.1 to 81.245.255.25481.245.255.255131,070
25281.246.0.0/1581.246.0.1 to 81.247.255.25481.247.255.255131,070
25381.248.0.0/1581.248.0.1 to 81.249.255.25481.249.255.255131,070
25481.250.0.0/1581.250.0.1 to 81.251.255.25481.251.255.255131,070
25581.252.0.0/1581.252.0.1 to 81.253.255.25481.253.255.255131,070
25681.254.0.0/1581.254.0.1 to 81.255.255.25481.255.255.255131,070

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.