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.

Network1.38.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
1.38.0.0
Broadcast address
1.39.255.255
First usable
1.38.0.1
Last usable
1.39.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
A (default /8)
As numbers
Hex 01260000 · Integer 19267584 to 19398655
Reverse DNS zones
38.1.in-addr.arpa
39.1.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00000001.00100110.00000000.000000001.38.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network00000001.00100110.00000000.000000001.38.0.0
Broadcast00000001.00100111.11111111.111111111.39.255.255
Split into smaller subnets/23
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

1.38.0.0/15 makes 256 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
11.38.0.0/231.38.0.1 to 1.38.1.2541.38.1.255510
21.38.2.0/231.38.2.1 to 1.38.3.2541.38.3.255510
31.38.4.0/231.38.4.1 to 1.38.5.2541.38.5.255510
41.38.6.0/231.38.6.1 to 1.38.7.2541.38.7.255510
51.38.8.0/231.38.8.1 to 1.38.9.2541.38.9.255510
61.38.10.0/231.38.10.1 to 1.38.11.2541.38.11.255510
71.38.12.0/231.38.12.1 to 1.38.13.2541.38.13.255510
81.38.14.0/231.38.14.1 to 1.38.15.2541.38.15.255510
91.38.16.0/231.38.16.1 to 1.38.17.2541.38.17.255510
101.38.18.0/231.38.18.1 to 1.38.19.2541.38.19.255510
111.38.20.0/231.38.20.1 to 1.38.21.2541.38.21.255510
121.38.22.0/231.38.22.1 to 1.38.23.2541.38.23.255510
131.38.24.0/231.38.24.1 to 1.38.25.2541.38.25.255510
141.38.26.0/231.38.26.1 to 1.38.27.2541.38.27.255510
151.38.28.0/231.38.28.1 to 1.38.29.2541.38.29.255510
161.38.30.0/231.38.30.1 to 1.38.31.2541.38.31.255510
171.38.32.0/231.38.32.1 to 1.38.33.2541.38.33.255510
181.38.34.0/231.38.34.1 to 1.38.35.2541.38.35.255510
191.38.36.0/231.38.36.1 to 1.38.37.2541.38.37.255510
201.38.38.0/231.38.38.1 to 1.38.39.2541.38.39.255510
211.38.40.0/231.38.40.1 to 1.38.41.2541.38.41.255510
221.38.42.0/231.38.42.1 to 1.38.43.2541.38.43.255510
231.38.44.0/231.38.44.1 to 1.38.45.2541.38.45.255510
241.38.46.0/231.38.46.1 to 1.38.47.2541.38.47.255510
251.38.48.0/231.38.48.1 to 1.38.49.2541.38.49.255510
261.38.50.0/231.38.50.1 to 1.38.51.2541.38.51.255510
271.38.52.0/231.38.52.1 to 1.38.53.2541.38.53.255510
281.38.54.0/231.38.54.1 to 1.38.55.2541.38.55.255510
291.38.56.0/231.38.56.1 to 1.38.57.2541.38.57.255510
301.38.58.0/231.38.58.1 to 1.38.59.2541.38.59.255510
311.38.60.0/231.38.60.1 to 1.38.61.2541.38.61.255510
321.38.62.0/231.38.62.1 to 1.38.63.2541.38.63.255510
331.38.64.0/231.38.64.1 to 1.38.65.2541.38.65.255510
341.38.66.0/231.38.66.1 to 1.38.67.2541.38.67.255510
351.38.68.0/231.38.68.1 to 1.38.69.2541.38.69.255510
361.38.70.0/231.38.70.1 to 1.38.71.2541.38.71.255510
371.38.72.0/231.38.72.1 to 1.38.73.2541.38.73.255510
381.38.74.0/231.38.74.1 to 1.38.75.2541.38.75.255510
391.38.76.0/231.38.76.1 to 1.38.77.2541.38.77.255510
401.38.78.0/231.38.78.1 to 1.38.79.2541.38.79.255510
411.38.80.0/231.38.80.1 to 1.38.81.2541.38.81.255510
421.38.82.0/231.38.82.1 to 1.38.83.2541.38.83.255510
431.38.84.0/231.38.84.1 to 1.38.85.2541.38.85.255510
441.38.86.0/231.38.86.1 to 1.38.87.2541.38.87.255510
451.38.88.0/231.38.88.1 to 1.38.89.2541.38.89.255510
461.38.90.0/231.38.90.1 to 1.38.91.2541.38.91.255510
471.38.92.0/231.38.92.1 to 1.38.93.2541.38.93.255510
481.38.94.0/231.38.94.1 to 1.38.95.2541.38.95.255510
491.38.96.0/231.38.96.1 to 1.38.97.2541.38.97.255510
501.38.98.0/231.38.98.1 to 1.38.99.2541.38.99.255510
511.38.100.0/231.38.100.1 to 1.38.101.2541.38.101.255510
521.38.102.0/231.38.102.1 to 1.38.103.2541.38.103.255510
531.38.104.0/231.38.104.1 to 1.38.105.2541.38.105.255510
541.38.106.0/231.38.106.1 to 1.38.107.2541.38.107.255510
551.38.108.0/231.38.108.1 to 1.38.109.2541.38.109.255510
561.38.110.0/231.38.110.1 to 1.38.111.2541.38.111.255510
571.38.112.0/231.38.112.1 to 1.38.113.2541.38.113.255510
581.38.114.0/231.38.114.1 to 1.38.115.2541.38.115.255510
591.38.116.0/231.38.116.1 to 1.38.117.2541.38.117.255510
601.38.118.0/231.38.118.1 to 1.38.119.2541.38.119.255510
611.38.120.0/231.38.120.1 to 1.38.121.2541.38.121.255510
621.38.122.0/231.38.122.1 to 1.38.123.2541.38.123.255510
631.38.124.0/231.38.124.1 to 1.38.125.2541.38.125.255510
641.38.126.0/231.38.126.1 to 1.38.127.2541.38.127.255510
651.38.128.0/231.38.128.1 to 1.38.129.2541.38.129.255510
661.38.130.0/231.38.130.1 to 1.38.131.2541.38.131.255510
671.38.132.0/231.38.132.1 to 1.38.133.2541.38.133.255510
681.38.134.0/231.38.134.1 to 1.38.135.2541.38.135.255510
691.38.136.0/231.38.136.1 to 1.38.137.2541.38.137.255510
701.38.138.0/231.38.138.1 to 1.38.139.2541.38.139.255510
711.38.140.0/231.38.140.1 to 1.38.141.2541.38.141.255510
721.38.142.0/231.38.142.1 to 1.38.143.2541.38.143.255510
731.38.144.0/231.38.144.1 to 1.38.145.2541.38.145.255510
741.38.146.0/231.38.146.1 to 1.38.147.2541.38.147.255510
751.38.148.0/231.38.148.1 to 1.38.149.2541.38.149.255510
761.38.150.0/231.38.150.1 to 1.38.151.2541.38.151.255510
771.38.152.0/231.38.152.1 to 1.38.153.2541.38.153.255510
781.38.154.0/231.38.154.1 to 1.38.155.2541.38.155.255510
791.38.156.0/231.38.156.1 to 1.38.157.2541.38.157.255510
801.38.158.0/231.38.158.1 to 1.38.159.2541.38.159.255510
811.38.160.0/231.38.160.1 to 1.38.161.2541.38.161.255510
821.38.162.0/231.38.162.1 to 1.38.163.2541.38.163.255510
831.38.164.0/231.38.164.1 to 1.38.165.2541.38.165.255510
841.38.166.0/231.38.166.1 to 1.38.167.2541.38.167.255510
851.38.168.0/231.38.168.1 to 1.38.169.2541.38.169.255510
861.38.170.0/231.38.170.1 to 1.38.171.2541.38.171.255510
871.38.172.0/231.38.172.1 to 1.38.173.2541.38.173.255510
881.38.174.0/231.38.174.1 to 1.38.175.2541.38.175.255510
891.38.176.0/231.38.176.1 to 1.38.177.2541.38.177.255510
901.38.178.0/231.38.178.1 to 1.38.179.2541.38.179.255510
911.38.180.0/231.38.180.1 to 1.38.181.2541.38.181.255510
921.38.182.0/231.38.182.1 to 1.38.183.2541.38.183.255510
931.38.184.0/231.38.184.1 to 1.38.185.2541.38.185.255510
941.38.186.0/231.38.186.1 to 1.38.187.2541.38.187.255510
951.38.188.0/231.38.188.1 to 1.38.189.2541.38.189.255510
961.38.190.0/231.38.190.1 to 1.38.191.2541.38.191.255510
971.38.192.0/231.38.192.1 to 1.38.193.2541.38.193.255510
981.38.194.0/231.38.194.1 to 1.38.195.2541.38.195.255510
991.38.196.0/231.38.196.1 to 1.38.197.2541.38.197.255510
1001.38.198.0/231.38.198.1 to 1.38.199.2541.38.199.255510
1011.38.200.0/231.38.200.1 to 1.38.201.2541.38.201.255510
1021.38.202.0/231.38.202.1 to 1.38.203.2541.38.203.255510
1031.38.204.0/231.38.204.1 to 1.38.205.2541.38.205.255510
1041.38.206.0/231.38.206.1 to 1.38.207.2541.38.207.255510
1051.38.208.0/231.38.208.1 to 1.38.209.2541.38.209.255510
1061.38.210.0/231.38.210.1 to 1.38.211.2541.38.211.255510
1071.38.212.0/231.38.212.1 to 1.38.213.2541.38.213.255510
1081.38.214.0/231.38.214.1 to 1.38.215.2541.38.215.255510
1091.38.216.0/231.38.216.1 to 1.38.217.2541.38.217.255510
1101.38.218.0/231.38.218.1 to 1.38.219.2541.38.219.255510
1111.38.220.0/231.38.220.1 to 1.38.221.2541.38.221.255510
1121.38.222.0/231.38.222.1 to 1.38.223.2541.38.223.255510
1131.38.224.0/231.38.224.1 to 1.38.225.2541.38.225.255510
1141.38.226.0/231.38.226.1 to 1.38.227.2541.38.227.255510
1151.38.228.0/231.38.228.1 to 1.38.229.2541.38.229.255510
1161.38.230.0/231.38.230.1 to 1.38.231.2541.38.231.255510
1171.38.232.0/231.38.232.1 to 1.38.233.2541.38.233.255510
1181.38.234.0/231.38.234.1 to 1.38.235.2541.38.235.255510
1191.38.236.0/231.38.236.1 to 1.38.237.2541.38.237.255510
1201.38.238.0/231.38.238.1 to 1.38.239.2541.38.239.255510
1211.38.240.0/231.38.240.1 to 1.38.241.2541.38.241.255510
1221.38.242.0/231.38.242.1 to 1.38.243.2541.38.243.255510
1231.38.244.0/231.38.244.1 to 1.38.245.2541.38.245.255510
1241.38.246.0/231.38.246.1 to 1.38.247.2541.38.247.255510
1251.38.248.0/231.38.248.1 to 1.38.249.2541.38.249.255510
1261.38.250.0/231.38.250.1 to 1.38.251.2541.38.251.255510
1271.38.252.0/231.38.252.1 to 1.38.253.2541.38.253.255510
1281.38.254.0/231.38.254.1 to 1.38.255.2541.38.255.255510
1291.39.0.0/231.39.0.1 to 1.39.1.2541.39.1.255510
1301.39.2.0/231.39.2.1 to 1.39.3.2541.39.3.255510
1311.39.4.0/231.39.4.1 to 1.39.5.2541.39.5.255510
1321.39.6.0/231.39.6.1 to 1.39.7.2541.39.7.255510
1331.39.8.0/231.39.8.1 to 1.39.9.2541.39.9.255510
1341.39.10.0/231.39.10.1 to 1.39.11.2541.39.11.255510
1351.39.12.0/231.39.12.1 to 1.39.13.2541.39.13.255510
1361.39.14.0/231.39.14.1 to 1.39.15.2541.39.15.255510
1371.39.16.0/231.39.16.1 to 1.39.17.2541.39.17.255510
1381.39.18.0/231.39.18.1 to 1.39.19.2541.39.19.255510
1391.39.20.0/231.39.20.1 to 1.39.21.2541.39.21.255510
1401.39.22.0/231.39.22.1 to 1.39.23.2541.39.23.255510
1411.39.24.0/231.39.24.1 to 1.39.25.2541.39.25.255510
1421.39.26.0/231.39.26.1 to 1.39.27.2541.39.27.255510
1431.39.28.0/231.39.28.1 to 1.39.29.2541.39.29.255510
1441.39.30.0/231.39.30.1 to 1.39.31.2541.39.31.255510
1451.39.32.0/231.39.32.1 to 1.39.33.2541.39.33.255510
1461.39.34.0/231.39.34.1 to 1.39.35.2541.39.35.255510
1471.39.36.0/231.39.36.1 to 1.39.37.2541.39.37.255510
1481.39.38.0/231.39.38.1 to 1.39.39.2541.39.39.255510
1491.39.40.0/231.39.40.1 to 1.39.41.2541.39.41.255510
1501.39.42.0/231.39.42.1 to 1.39.43.2541.39.43.255510
1511.39.44.0/231.39.44.1 to 1.39.45.2541.39.45.255510
1521.39.46.0/231.39.46.1 to 1.39.47.2541.39.47.255510
1531.39.48.0/231.39.48.1 to 1.39.49.2541.39.49.255510
1541.39.50.0/231.39.50.1 to 1.39.51.2541.39.51.255510
1551.39.52.0/231.39.52.1 to 1.39.53.2541.39.53.255510
1561.39.54.0/231.39.54.1 to 1.39.55.2541.39.55.255510
1571.39.56.0/231.39.56.1 to 1.39.57.2541.39.57.255510
1581.39.58.0/231.39.58.1 to 1.39.59.2541.39.59.255510
1591.39.60.0/231.39.60.1 to 1.39.61.2541.39.61.255510
1601.39.62.0/231.39.62.1 to 1.39.63.2541.39.63.255510
1611.39.64.0/231.39.64.1 to 1.39.65.2541.39.65.255510
1621.39.66.0/231.39.66.1 to 1.39.67.2541.39.67.255510
1631.39.68.0/231.39.68.1 to 1.39.69.2541.39.69.255510
1641.39.70.0/231.39.70.1 to 1.39.71.2541.39.71.255510
1651.39.72.0/231.39.72.1 to 1.39.73.2541.39.73.255510
1661.39.74.0/231.39.74.1 to 1.39.75.2541.39.75.255510
1671.39.76.0/231.39.76.1 to 1.39.77.2541.39.77.255510
1681.39.78.0/231.39.78.1 to 1.39.79.2541.39.79.255510
1691.39.80.0/231.39.80.1 to 1.39.81.2541.39.81.255510
1701.39.82.0/231.39.82.1 to 1.39.83.2541.39.83.255510
1711.39.84.0/231.39.84.1 to 1.39.85.2541.39.85.255510
1721.39.86.0/231.39.86.1 to 1.39.87.2541.39.87.255510
1731.39.88.0/231.39.88.1 to 1.39.89.2541.39.89.255510
1741.39.90.0/231.39.90.1 to 1.39.91.2541.39.91.255510
1751.39.92.0/231.39.92.1 to 1.39.93.2541.39.93.255510
1761.39.94.0/231.39.94.1 to 1.39.95.2541.39.95.255510
1771.39.96.0/231.39.96.1 to 1.39.97.2541.39.97.255510
1781.39.98.0/231.39.98.1 to 1.39.99.2541.39.99.255510
1791.39.100.0/231.39.100.1 to 1.39.101.2541.39.101.255510
1801.39.102.0/231.39.102.1 to 1.39.103.2541.39.103.255510
1811.39.104.0/231.39.104.1 to 1.39.105.2541.39.105.255510
1821.39.106.0/231.39.106.1 to 1.39.107.2541.39.107.255510
1831.39.108.0/231.39.108.1 to 1.39.109.2541.39.109.255510
1841.39.110.0/231.39.110.1 to 1.39.111.2541.39.111.255510
1851.39.112.0/231.39.112.1 to 1.39.113.2541.39.113.255510
1861.39.114.0/231.39.114.1 to 1.39.115.2541.39.115.255510
1871.39.116.0/231.39.116.1 to 1.39.117.2541.39.117.255510
1881.39.118.0/231.39.118.1 to 1.39.119.2541.39.119.255510
1891.39.120.0/231.39.120.1 to 1.39.121.2541.39.121.255510
1901.39.122.0/231.39.122.1 to 1.39.123.2541.39.123.255510
1911.39.124.0/231.39.124.1 to 1.39.125.2541.39.125.255510
1921.39.126.0/231.39.126.1 to 1.39.127.2541.39.127.255510
1931.39.128.0/231.39.128.1 to 1.39.129.2541.39.129.255510
1941.39.130.0/231.39.130.1 to 1.39.131.2541.39.131.255510
1951.39.132.0/231.39.132.1 to 1.39.133.2541.39.133.255510
1961.39.134.0/231.39.134.1 to 1.39.135.2541.39.135.255510
1971.39.136.0/231.39.136.1 to 1.39.137.2541.39.137.255510
1981.39.138.0/231.39.138.1 to 1.39.139.2541.39.139.255510
1991.39.140.0/231.39.140.1 to 1.39.141.2541.39.141.255510
2001.39.142.0/231.39.142.1 to 1.39.143.2541.39.143.255510
2011.39.144.0/231.39.144.1 to 1.39.145.2541.39.145.255510
2021.39.146.0/231.39.146.1 to 1.39.147.2541.39.147.255510
2031.39.148.0/231.39.148.1 to 1.39.149.2541.39.149.255510
2041.39.150.0/231.39.150.1 to 1.39.151.2541.39.151.255510
2051.39.152.0/231.39.152.1 to 1.39.153.2541.39.153.255510
2061.39.154.0/231.39.154.1 to 1.39.155.2541.39.155.255510
2071.39.156.0/231.39.156.1 to 1.39.157.2541.39.157.255510
2081.39.158.0/231.39.158.1 to 1.39.159.2541.39.159.255510
2091.39.160.0/231.39.160.1 to 1.39.161.2541.39.161.255510
2101.39.162.0/231.39.162.1 to 1.39.163.2541.39.163.255510
2111.39.164.0/231.39.164.1 to 1.39.165.2541.39.165.255510
2121.39.166.0/231.39.166.1 to 1.39.167.2541.39.167.255510
2131.39.168.0/231.39.168.1 to 1.39.169.2541.39.169.255510
2141.39.170.0/231.39.170.1 to 1.39.171.2541.39.171.255510
2151.39.172.0/231.39.172.1 to 1.39.173.2541.39.173.255510
2161.39.174.0/231.39.174.1 to 1.39.175.2541.39.175.255510
2171.39.176.0/231.39.176.1 to 1.39.177.2541.39.177.255510
2181.39.178.0/231.39.178.1 to 1.39.179.2541.39.179.255510
2191.39.180.0/231.39.180.1 to 1.39.181.2541.39.181.255510
2201.39.182.0/231.39.182.1 to 1.39.183.2541.39.183.255510
2211.39.184.0/231.39.184.1 to 1.39.185.2541.39.185.255510
2221.39.186.0/231.39.186.1 to 1.39.187.2541.39.187.255510
2231.39.188.0/231.39.188.1 to 1.39.189.2541.39.189.255510
2241.39.190.0/231.39.190.1 to 1.39.191.2541.39.191.255510
2251.39.192.0/231.39.192.1 to 1.39.193.2541.39.193.255510
2261.39.194.0/231.39.194.1 to 1.39.195.2541.39.195.255510
2271.39.196.0/231.39.196.1 to 1.39.197.2541.39.197.255510
2281.39.198.0/231.39.198.1 to 1.39.199.2541.39.199.255510
2291.39.200.0/231.39.200.1 to 1.39.201.2541.39.201.255510
2301.39.202.0/231.39.202.1 to 1.39.203.2541.39.203.255510
2311.39.204.0/231.39.204.1 to 1.39.205.2541.39.205.255510
2321.39.206.0/231.39.206.1 to 1.39.207.2541.39.207.255510
2331.39.208.0/231.39.208.1 to 1.39.209.2541.39.209.255510
2341.39.210.0/231.39.210.1 to 1.39.211.2541.39.211.255510
2351.39.212.0/231.39.212.1 to 1.39.213.2541.39.213.255510
2361.39.214.0/231.39.214.1 to 1.39.215.2541.39.215.255510
2371.39.216.0/231.39.216.1 to 1.39.217.2541.39.217.255510
2381.39.218.0/231.39.218.1 to 1.39.219.2541.39.219.255510
2391.39.220.0/231.39.220.1 to 1.39.221.2541.39.221.255510
2401.39.222.0/231.39.222.1 to 1.39.223.2541.39.223.255510
2411.39.224.0/231.39.224.1 to 1.39.225.2541.39.225.255510
2421.39.226.0/231.39.226.1 to 1.39.227.2541.39.227.255510
2431.39.228.0/231.39.228.1 to 1.39.229.2541.39.229.255510
2441.39.230.0/231.39.230.1 to 1.39.231.2541.39.231.255510
2451.39.232.0/231.39.232.1 to 1.39.233.2541.39.233.255510
2461.39.234.0/231.39.234.1 to 1.39.235.2541.39.235.255510
2471.39.236.0/231.39.236.1 to 1.39.237.2541.39.237.255510
2481.39.238.0/231.39.238.1 to 1.39.239.2541.39.239.255510
2491.39.240.0/231.39.240.1 to 1.39.241.2541.39.241.255510
2501.39.242.0/231.39.242.1 to 1.39.243.2541.39.243.255510
2511.39.244.0/231.39.244.1 to 1.39.245.2541.39.245.255510
2521.39.246.0/231.39.246.1 to 1.39.247.2541.39.247.255510
2531.39.248.0/231.39.248.1 to 1.39.249.2541.39.249.255510
2541.39.250.0/231.39.250.1 to 1.39.251.2541.39.251.255510
2551.39.252.0/231.39.252.1 to 1.39.253.2541.39.253.255510
2561.39.254.0/231.39.254.1 to 1.39.255.2541.39.255.255510

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.