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.

Network16.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
16.0.0.0
Broadcast address
16.255.255.255
First usable
16.0.0.1
Last usable
16.255.255.254
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 10000000 · Integer 268435456 to 285212671
Reverse DNS zone
16.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010000..00000000.00000000.0000000016.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network00010000..00000000.00000000.0000000016.0.0.0
Broadcast00010000..11111111.11111111.1111111116.255.255.255
Split into smaller subnets/16
/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)

16.0.0.0/8 makes 256 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
116.0.0.0/1616.0.0.1 to 16.0.255.25416.0.255.25565,534
216.1.0.0/1616.1.0.1 to 16.1.255.25416.1.255.25565,534
316.2.0.0/1616.2.0.1 to 16.2.255.25416.2.255.25565,534
416.3.0.0/1616.3.0.1 to 16.3.255.25416.3.255.25565,534
516.4.0.0/1616.4.0.1 to 16.4.255.25416.4.255.25565,534
616.5.0.0/1616.5.0.1 to 16.5.255.25416.5.255.25565,534
716.6.0.0/1616.6.0.1 to 16.6.255.25416.6.255.25565,534
816.7.0.0/1616.7.0.1 to 16.7.255.25416.7.255.25565,534
916.8.0.0/1616.8.0.1 to 16.8.255.25416.8.255.25565,534
1016.9.0.0/1616.9.0.1 to 16.9.255.25416.9.255.25565,534
1116.10.0.0/1616.10.0.1 to 16.10.255.25416.10.255.25565,534
1216.11.0.0/1616.11.0.1 to 16.11.255.25416.11.255.25565,534
1316.12.0.0/1616.12.0.1 to 16.12.255.25416.12.255.25565,534
1416.13.0.0/1616.13.0.1 to 16.13.255.25416.13.255.25565,534
1516.14.0.0/1616.14.0.1 to 16.14.255.25416.14.255.25565,534
1616.15.0.0/1616.15.0.1 to 16.15.255.25416.15.255.25565,534
1716.16.0.0/1616.16.0.1 to 16.16.255.25416.16.255.25565,534
1816.17.0.0/1616.17.0.1 to 16.17.255.25416.17.255.25565,534
1916.18.0.0/1616.18.0.1 to 16.18.255.25416.18.255.25565,534
2016.19.0.0/1616.19.0.1 to 16.19.255.25416.19.255.25565,534
2116.20.0.0/1616.20.0.1 to 16.20.255.25416.20.255.25565,534
2216.21.0.0/1616.21.0.1 to 16.21.255.25416.21.255.25565,534
2316.22.0.0/1616.22.0.1 to 16.22.255.25416.22.255.25565,534
2416.23.0.0/1616.23.0.1 to 16.23.255.25416.23.255.25565,534
2516.24.0.0/1616.24.0.1 to 16.24.255.25416.24.255.25565,534
2616.25.0.0/1616.25.0.1 to 16.25.255.25416.25.255.25565,534
2716.26.0.0/1616.26.0.1 to 16.26.255.25416.26.255.25565,534
2816.27.0.0/1616.27.0.1 to 16.27.255.25416.27.255.25565,534
2916.28.0.0/1616.28.0.1 to 16.28.255.25416.28.255.25565,534
3016.29.0.0/1616.29.0.1 to 16.29.255.25416.29.255.25565,534
3116.30.0.0/1616.30.0.1 to 16.30.255.25416.30.255.25565,534
3216.31.0.0/1616.31.0.1 to 16.31.255.25416.31.255.25565,534
3316.32.0.0/1616.32.0.1 to 16.32.255.25416.32.255.25565,534
3416.33.0.0/1616.33.0.1 to 16.33.255.25416.33.255.25565,534
3516.34.0.0/1616.34.0.1 to 16.34.255.25416.34.255.25565,534
3616.35.0.0/1616.35.0.1 to 16.35.255.25416.35.255.25565,534
3716.36.0.0/1616.36.0.1 to 16.36.255.25416.36.255.25565,534
3816.37.0.0/1616.37.0.1 to 16.37.255.25416.37.255.25565,534
3916.38.0.0/1616.38.0.1 to 16.38.255.25416.38.255.25565,534
4016.39.0.0/1616.39.0.1 to 16.39.255.25416.39.255.25565,534
4116.40.0.0/1616.40.0.1 to 16.40.255.25416.40.255.25565,534
4216.41.0.0/1616.41.0.1 to 16.41.255.25416.41.255.25565,534
4316.42.0.0/1616.42.0.1 to 16.42.255.25416.42.255.25565,534
4416.43.0.0/1616.43.0.1 to 16.43.255.25416.43.255.25565,534
4516.44.0.0/1616.44.0.1 to 16.44.255.25416.44.255.25565,534
4616.45.0.0/1616.45.0.1 to 16.45.255.25416.45.255.25565,534
4716.46.0.0/1616.46.0.1 to 16.46.255.25416.46.255.25565,534
4816.47.0.0/1616.47.0.1 to 16.47.255.25416.47.255.25565,534
4916.48.0.0/1616.48.0.1 to 16.48.255.25416.48.255.25565,534
5016.49.0.0/1616.49.0.1 to 16.49.255.25416.49.255.25565,534
5116.50.0.0/1616.50.0.1 to 16.50.255.25416.50.255.25565,534
5216.51.0.0/1616.51.0.1 to 16.51.255.25416.51.255.25565,534
5316.52.0.0/1616.52.0.1 to 16.52.255.25416.52.255.25565,534
5416.53.0.0/1616.53.0.1 to 16.53.255.25416.53.255.25565,534
5516.54.0.0/1616.54.0.1 to 16.54.255.25416.54.255.25565,534
5616.55.0.0/1616.55.0.1 to 16.55.255.25416.55.255.25565,534
5716.56.0.0/1616.56.0.1 to 16.56.255.25416.56.255.25565,534
5816.57.0.0/1616.57.0.1 to 16.57.255.25416.57.255.25565,534
5916.58.0.0/1616.58.0.1 to 16.58.255.25416.58.255.25565,534
6016.59.0.0/1616.59.0.1 to 16.59.255.25416.59.255.25565,534
6116.60.0.0/1616.60.0.1 to 16.60.255.25416.60.255.25565,534
6216.61.0.0/1616.61.0.1 to 16.61.255.25416.61.255.25565,534
6316.62.0.0/1616.62.0.1 to 16.62.255.25416.62.255.25565,534
6416.63.0.0/1616.63.0.1 to 16.63.255.25416.63.255.25565,534
6516.64.0.0/1616.64.0.1 to 16.64.255.25416.64.255.25565,534
6616.65.0.0/1616.65.0.1 to 16.65.255.25416.65.255.25565,534
6716.66.0.0/1616.66.0.1 to 16.66.255.25416.66.255.25565,534
6816.67.0.0/1616.67.0.1 to 16.67.255.25416.67.255.25565,534
6916.68.0.0/1616.68.0.1 to 16.68.255.25416.68.255.25565,534
7016.69.0.0/1616.69.0.1 to 16.69.255.25416.69.255.25565,534
7116.70.0.0/1616.70.0.1 to 16.70.255.25416.70.255.25565,534
7216.71.0.0/1616.71.0.1 to 16.71.255.25416.71.255.25565,534
7316.72.0.0/1616.72.0.1 to 16.72.255.25416.72.255.25565,534
7416.73.0.0/1616.73.0.1 to 16.73.255.25416.73.255.25565,534
7516.74.0.0/1616.74.0.1 to 16.74.255.25416.74.255.25565,534
7616.75.0.0/1616.75.0.1 to 16.75.255.25416.75.255.25565,534
7716.76.0.0/1616.76.0.1 to 16.76.255.25416.76.255.25565,534
7816.77.0.0/1616.77.0.1 to 16.77.255.25416.77.255.25565,534
7916.78.0.0/1616.78.0.1 to 16.78.255.25416.78.255.25565,534
8016.79.0.0/1616.79.0.1 to 16.79.255.25416.79.255.25565,534
8116.80.0.0/1616.80.0.1 to 16.80.255.25416.80.255.25565,534
8216.81.0.0/1616.81.0.1 to 16.81.255.25416.81.255.25565,534
8316.82.0.0/1616.82.0.1 to 16.82.255.25416.82.255.25565,534
8416.83.0.0/1616.83.0.1 to 16.83.255.25416.83.255.25565,534
8516.84.0.0/1616.84.0.1 to 16.84.255.25416.84.255.25565,534
8616.85.0.0/1616.85.0.1 to 16.85.255.25416.85.255.25565,534
8716.86.0.0/1616.86.0.1 to 16.86.255.25416.86.255.25565,534
8816.87.0.0/1616.87.0.1 to 16.87.255.25416.87.255.25565,534
8916.88.0.0/1616.88.0.1 to 16.88.255.25416.88.255.25565,534
9016.89.0.0/1616.89.0.1 to 16.89.255.25416.89.255.25565,534
9116.90.0.0/1616.90.0.1 to 16.90.255.25416.90.255.25565,534
9216.91.0.0/1616.91.0.1 to 16.91.255.25416.91.255.25565,534
9316.92.0.0/1616.92.0.1 to 16.92.255.25416.92.255.25565,534
9416.93.0.0/1616.93.0.1 to 16.93.255.25416.93.255.25565,534
9516.94.0.0/1616.94.0.1 to 16.94.255.25416.94.255.25565,534
9616.95.0.0/1616.95.0.1 to 16.95.255.25416.95.255.25565,534
9716.96.0.0/1616.96.0.1 to 16.96.255.25416.96.255.25565,534
9816.97.0.0/1616.97.0.1 to 16.97.255.25416.97.255.25565,534
9916.98.0.0/1616.98.0.1 to 16.98.255.25416.98.255.25565,534
10016.99.0.0/1616.99.0.1 to 16.99.255.25416.99.255.25565,534
10116.100.0.0/1616.100.0.1 to 16.100.255.25416.100.255.25565,534
10216.101.0.0/1616.101.0.1 to 16.101.255.25416.101.255.25565,534
10316.102.0.0/1616.102.0.1 to 16.102.255.25416.102.255.25565,534
10416.103.0.0/1616.103.0.1 to 16.103.255.25416.103.255.25565,534
10516.104.0.0/1616.104.0.1 to 16.104.255.25416.104.255.25565,534
10616.105.0.0/1616.105.0.1 to 16.105.255.25416.105.255.25565,534
10716.106.0.0/1616.106.0.1 to 16.106.255.25416.106.255.25565,534
10816.107.0.0/1616.107.0.1 to 16.107.255.25416.107.255.25565,534
10916.108.0.0/1616.108.0.1 to 16.108.255.25416.108.255.25565,534
11016.109.0.0/1616.109.0.1 to 16.109.255.25416.109.255.25565,534
11116.110.0.0/1616.110.0.1 to 16.110.255.25416.110.255.25565,534
11216.111.0.0/1616.111.0.1 to 16.111.255.25416.111.255.25565,534
11316.112.0.0/1616.112.0.1 to 16.112.255.25416.112.255.25565,534
11416.113.0.0/1616.113.0.1 to 16.113.255.25416.113.255.25565,534
11516.114.0.0/1616.114.0.1 to 16.114.255.25416.114.255.25565,534
11616.115.0.0/1616.115.0.1 to 16.115.255.25416.115.255.25565,534
11716.116.0.0/1616.116.0.1 to 16.116.255.25416.116.255.25565,534
11816.117.0.0/1616.117.0.1 to 16.117.255.25416.117.255.25565,534
11916.118.0.0/1616.118.0.1 to 16.118.255.25416.118.255.25565,534
12016.119.0.0/1616.119.0.1 to 16.119.255.25416.119.255.25565,534
12116.120.0.0/1616.120.0.1 to 16.120.255.25416.120.255.25565,534
12216.121.0.0/1616.121.0.1 to 16.121.255.25416.121.255.25565,534
12316.122.0.0/1616.122.0.1 to 16.122.255.25416.122.255.25565,534
12416.123.0.0/1616.123.0.1 to 16.123.255.25416.123.255.25565,534
12516.124.0.0/1616.124.0.1 to 16.124.255.25416.124.255.25565,534
12616.125.0.0/1616.125.0.1 to 16.125.255.25416.125.255.25565,534
12716.126.0.0/1616.126.0.1 to 16.126.255.25416.126.255.25565,534
12816.127.0.0/1616.127.0.1 to 16.127.255.25416.127.255.25565,534
12916.128.0.0/1616.128.0.1 to 16.128.255.25416.128.255.25565,534
13016.129.0.0/1616.129.0.1 to 16.129.255.25416.129.255.25565,534
13116.130.0.0/1616.130.0.1 to 16.130.255.25416.130.255.25565,534
13216.131.0.0/1616.131.0.1 to 16.131.255.25416.131.255.25565,534
13316.132.0.0/1616.132.0.1 to 16.132.255.25416.132.255.25565,534
13416.133.0.0/1616.133.0.1 to 16.133.255.25416.133.255.25565,534
13516.134.0.0/1616.134.0.1 to 16.134.255.25416.134.255.25565,534
13616.135.0.0/1616.135.0.1 to 16.135.255.25416.135.255.25565,534
13716.136.0.0/1616.136.0.1 to 16.136.255.25416.136.255.25565,534
13816.137.0.0/1616.137.0.1 to 16.137.255.25416.137.255.25565,534
13916.138.0.0/1616.138.0.1 to 16.138.255.25416.138.255.25565,534
14016.139.0.0/1616.139.0.1 to 16.139.255.25416.139.255.25565,534
14116.140.0.0/1616.140.0.1 to 16.140.255.25416.140.255.25565,534
14216.141.0.0/1616.141.0.1 to 16.141.255.25416.141.255.25565,534
14316.142.0.0/1616.142.0.1 to 16.142.255.25416.142.255.25565,534
14416.143.0.0/1616.143.0.1 to 16.143.255.25416.143.255.25565,534
14516.144.0.0/1616.144.0.1 to 16.144.255.25416.144.255.25565,534
14616.145.0.0/1616.145.0.1 to 16.145.255.25416.145.255.25565,534
14716.146.0.0/1616.146.0.1 to 16.146.255.25416.146.255.25565,534
14816.147.0.0/1616.147.0.1 to 16.147.255.25416.147.255.25565,534
14916.148.0.0/1616.148.0.1 to 16.148.255.25416.148.255.25565,534
15016.149.0.0/1616.149.0.1 to 16.149.255.25416.149.255.25565,534
15116.150.0.0/1616.150.0.1 to 16.150.255.25416.150.255.25565,534
15216.151.0.0/1616.151.0.1 to 16.151.255.25416.151.255.25565,534
15316.152.0.0/1616.152.0.1 to 16.152.255.25416.152.255.25565,534
15416.153.0.0/1616.153.0.1 to 16.153.255.25416.153.255.25565,534
15516.154.0.0/1616.154.0.1 to 16.154.255.25416.154.255.25565,534
15616.155.0.0/1616.155.0.1 to 16.155.255.25416.155.255.25565,534
15716.156.0.0/1616.156.0.1 to 16.156.255.25416.156.255.25565,534
15816.157.0.0/1616.157.0.1 to 16.157.255.25416.157.255.25565,534
15916.158.0.0/1616.158.0.1 to 16.158.255.25416.158.255.25565,534
16016.159.0.0/1616.159.0.1 to 16.159.255.25416.159.255.25565,534
16116.160.0.0/1616.160.0.1 to 16.160.255.25416.160.255.25565,534
16216.161.0.0/1616.161.0.1 to 16.161.255.25416.161.255.25565,534
16316.162.0.0/1616.162.0.1 to 16.162.255.25416.162.255.25565,534
16416.163.0.0/1616.163.0.1 to 16.163.255.25416.163.255.25565,534
16516.164.0.0/1616.164.0.1 to 16.164.255.25416.164.255.25565,534
16616.165.0.0/1616.165.0.1 to 16.165.255.25416.165.255.25565,534
16716.166.0.0/1616.166.0.1 to 16.166.255.25416.166.255.25565,534
16816.167.0.0/1616.167.0.1 to 16.167.255.25416.167.255.25565,534
16916.168.0.0/1616.168.0.1 to 16.168.255.25416.168.255.25565,534
17016.169.0.0/1616.169.0.1 to 16.169.255.25416.169.255.25565,534
17116.170.0.0/1616.170.0.1 to 16.170.255.25416.170.255.25565,534
17216.171.0.0/1616.171.0.1 to 16.171.255.25416.171.255.25565,534
17316.172.0.0/1616.172.0.1 to 16.172.255.25416.172.255.25565,534
17416.173.0.0/1616.173.0.1 to 16.173.255.25416.173.255.25565,534
17516.174.0.0/1616.174.0.1 to 16.174.255.25416.174.255.25565,534
17616.175.0.0/1616.175.0.1 to 16.175.255.25416.175.255.25565,534
17716.176.0.0/1616.176.0.1 to 16.176.255.25416.176.255.25565,534
17816.177.0.0/1616.177.0.1 to 16.177.255.25416.177.255.25565,534
17916.178.0.0/1616.178.0.1 to 16.178.255.25416.178.255.25565,534
18016.179.0.0/1616.179.0.1 to 16.179.255.25416.179.255.25565,534
18116.180.0.0/1616.180.0.1 to 16.180.255.25416.180.255.25565,534
18216.181.0.0/1616.181.0.1 to 16.181.255.25416.181.255.25565,534
18316.182.0.0/1616.182.0.1 to 16.182.255.25416.182.255.25565,534
18416.183.0.0/1616.183.0.1 to 16.183.255.25416.183.255.25565,534
18516.184.0.0/1616.184.0.1 to 16.184.255.25416.184.255.25565,534
18616.185.0.0/1616.185.0.1 to 16.185.255.25416.185.255.25565,534
18716.186.0.0/1616.186.0.1 to 16.186.255.25416.186.255.25565,534
18816.187.0.0/1616.187.0.1 to 16.187.255.25416.187.255.25565,534
18916.188.0.0/1616.188.0.1 to 16.188.255.25416.188.255.25565,534
19016.189.0.0/1616.189.0.1 to 16.189.255.25416.189.255.25565,534
19116.190.0.0/1616.190.0.1 to 16.190.255.25416.190.255.25565,534
19216.191.0.0/1616.191.0.1 to 16.191.255.25416.191.255.25565,534
19316.192.0.0/1616.192.0.1 to 16.192.255.25416.192.255.25565,534
19416.193.0.0/1616.193.0.1 to 16.193.255.25416.193.255.25565,534
19516.194.0.0/1616.194.0.1 to 16.194.255.25416.194.255.25565,534
19616.195.0.0/1616.195.0.1 to 16.195.255.25416.195.255.25565,534
19716.196.0.0/1616.196.0.1 to 16.196.255.25416.196.255.25565,534
19816.197.0.0/1616.197.0.1 to 16.197.255.25416.197.255.25565,534
19916.198.0.0/1616.198.0.1 to 16.198.255.25416.198.255.25565,534
20016.199.0.0/1616.199.0.1 to 16.199.255.25416.199.255.25565,534
20116.200.0.0/1616.200.0.1 to 16.200.255.25416.200.255.25565,534
20216.201.0.0/1616.201.0.1 to 16.201.255.25416.201.255.25565,534
20316.202.0.0/1616.202.0.1 to 16.202.255.25416.202.255.25565,534
20416.203.0.0/1616.203.0.1 to 16.203.255.25416.203.255.25565,534
20516.204.0.0/1616.204.0.1 to 16.204.255.25416.204.255.25565,534
20616.205.0.0/1616.205.0.1 to 16.205.255.25416.205.255.25565,534
20716.206.0.0/1616.206.0.1 to 16.206.255.25416.206.255.25565,534
20816.207.0.0/1616.207.0.1 to 16.207.255.25416.207.255.25565,534
20916.208.0.0/1616.208.0.1 to 16.208.255.25416.208.255.25565,534
21016.209.0.0/1616.209.0.1 to 16.209.255.25416.209.255.25565,534
21116.210.0.0/1616.210.0.1 to 16.210.255.25416.210.255.25565,534
21216.211.0.0/1616.211.0.1 to 16.211.255.25416.211.255.25565,534
21316.212.0.0/1616.212.0.1 to 16.212.255.25416.212.255.25565,534
21416.213.0.0/1616.213.0.1 to 16.213.255.25416.213.255.25565,534
21516.214.0.0/1616.214.0.1 to 16.214.255.25416.214.255.25565,534
21616.215.0.0/1616.215.0.1 to 16.215.255.25416.215.255.25565,534
21716.216.0.0/1616.216.0.1 to 16.216.255.25416.216.255.25565,534
21816.217.0.0/1616.217.0.1 to 16.217.255.25416.217.255.25565,534
21916.218.0.0/1616.218.0.1 to 16.218.255.25416.218.255.25565,534
22016.219.0.0/1616.219.0.1 to 16.219.255.25416.219.255.25565,534
22116.220.0.0/1616.220.0.1 to 16.220.255.25416.220.255.25565,534
22216.221.0.0/1616.221.0.1 to 16.221.255.25416.221.255.25565,534
22316.222.0.0/1616.222.0.1 to 16.222.255.25416.222.255.25565,534
22416.223.0.0/1616.223.0.1 to 16.223.255.25416.223.255.25565,534
22516.224.0.0/1616.224.0.1 to 16.224.255.25416.224.255.25565,534
22616.225.0.0/1616.225.0.1 to 16.225.255.25416.225.255.25565,534
22716.226.0.0/1616.226.0.1 to 16.226.255.25416.226.255.25565,534
22816.227.0.0/1616.227.0.1 to 16.227.255.25416.227.255.25565,534
22916.228.0.0/1616.228.0.1 to 16.228.255.25416.228.255.25565,534
23016.229.0.0/1616.229.0.1 to 16.229.255.25416.229.255.25565,534
23116.230.0.0/1616.230.0.1 to 16.230.255.25416.230.255.25565,534
23216.231.0.0/1616.231.0.1 to 16.231.255.25416.231.255.25565,534
23316.232.0.0/1616.232.0.1 to 16.232.255.25416.232.255.25565,534
23416.233.0.0/1616.233.0.1 to 16.233.255.25416.233.255.25565,534
23516.234.0.0/1616.234.0.1 to 16.234.255.25416.234.255.25565,534
23616.235.0.0/1616.235.0.1 to 16.235.255.25416.235.255.25565,534
23716.236.0.0/1616.236.0.1 to 16.236.255.25416.236.255.25565,534
23816.237.0.0/1616.237.0.1 to 16.237.255.25416.237.255.25565,534
23916.238.0.0/1616.238.0.1 to 16.238.255.25416.238.255.25565,534
24016.239.0.0/1616.239.0.1 to 16.239.255.25416.239.255.25565,534
24116.240.0.0/1616.240.0.1 to 16.240.255.25416.240.255.25565,534
24216.241.0.0/1616.241.0.1 to 16.241.255.25416.241.255.25565,534
24316.242.0.0/1616.242.0.1 to 16.242.255.25416.242.255.25565,534
24416.243.0.0/1616.243.0.1 to 16.243.255.25416.243.255.25565,534
24516.244.0.0/1616.244.0.1 to 16.244.255.25416.244.255.25565,534
24616.245.0.0/1616.245.0.1 to 16.245.255.25416.245.255.25565,534
24716.246.0.0/1616.246.0.1 to 16.246.255.25416.246.255.25565,534
24816.247.0.0/1616.247.0.1 to 16.247.255.25416.247.255.25565,534
24916.248.0.0/1616.248.0.1 to 16.248.255.25416.248.255.25565,534
25016.249.0.0/1616.249.0.1 to 16.249.255.25416.249.255.25565,534
25116.250.0.0/1616.250.0.1 to 16.250.255.25416.250.255.25565,534
25216.251.0.0/1616.251.0.1 to 16.251.255.25416.251.255.25565,534
25316.252.0.0/1616.252.0.1 to 16.252.255.25416.252.255.25565,534
25416.253.0.0/1616.253.0.1 to 16.253.255.25416.253.255.25565,534
25516.254.0.0/1616.254.0.1 to 16.254.255.25416.254.255.25565,534
25616.255.0.0/1616.255.0.1 to 16.255.255.25416.255.255.25565,534

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.