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.

Network13.8.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
13.8.0.0
Broadcast address
13.15.255.255
First usable
13.8.0.1
Last usable
13.15.255.254
Usable hosts
524,286 (524,288 less the network and broadcast addresses)
Subnet mask
255.248.0.0
Wildcard mask
0.7.255.255 (Cisco ACLs, OSPF)
Prefix length
/13
Type
Public public
Old class
A (default /8)
As numbers
Hex 0D080000 · Integer 218628096 to 219152383
Reverse DNS zones
8.13.in-addr.arpa
9.13.in-addr.arpa
10.13.in-addr.arpa
11.13.in-addr.arpa
12.13.in-addr.arpa
13.13.in-addr.arpa
14.13.in-addr.arpa
15.13.in-addr.arpa
/13 is not on a 8-bit boundary, so it takes 8 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001101.00001000.00000000.0000000013.8.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network00001101.00001000.00000000.0000000013.8.0.0
Broadcast00001101.00001111.11111111.1111111113.15.255.255
Split into smaller subnets/23
/14 (2)/15 (4)/16 (8)/17 (16)/18 (32)/19 (64)/20 (128)/21 (256)/22 (512)/23 (1,024)/24 (2,048)/25 (4,096)

13.8.0.0/13 makes 1,024 subnets of /23; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
113.8.0.0/2313.8.0.1 to 13.8.1.25413.8.1.255510
213.8.2.0/2313.8.2.1 to 13.8.3.25413.8.3.255510
313.8.4.0/2313.8.4.1 to 13.8.5.25413.8.5.255510
413.8.6.0/2313.8.6.1 to 13.8.7.25413.8.7.255510
513.8.8.0/2313.8.8.1 to 13.8.9.25413.8.9.255510
613.8.10.0/2313.8.10.1 to 13.8.11.25413.8.11.255510
713.8.12.0/2313.8.12.1 to 13.8.13.25413.8.13.255510
813.8.14.0/2313.8.14.1 to 13.8.15.25413.8.15.255510
913.8.16.0/2313.8.16.1 to 13.8.17.25413.8.17.255510
1013.8.18.0/2313.8.18.1 to 13.8.19.25413.8.19.255510
1113.8.20.0/2313.8.20.1 to 13.8.21.25413.8.21.255510
1213.8.22.0/2313.8.22.1 to 13.8.23.25413.8.23.255510
1313.8.24.0/2313.8.24.1 to 13.8.25.25413.8.25.255510
1413.8.26.0/2313.8.26.1 to 13.8.27.25413.8.27.255510
1513.8.28.0/2313.8.28.1 to 13.8.29.25413.8.29.255510
1613.8.30.0/2313.8.30.1 to 13.8.31.25413.8.31.255510
1713.8.32.0/2313.8.32.1 to 13.8.33.25413.8.33.255510
1813.8.34.0/2313.8.34.1 to 13.8.35.25413.8.35.255510
1913.8.36.0/2313.8.36.1 to 13.8.37.25413.8.37.255510
2013.8.38.0/2313.8.38.1 to 13.8.39.25413.8.39.255510
2113.8.40.0/2313.8.40.1 to 13.8.41.25413.8.41.255510
2213.8.42.0/2313.8.42.1 to 13.8.43.25413.8.43.255510
2313.8.44.0/2313.8.44.1 to 13.8.45.25413.8.45.255510
2413.8.46.0/2313.8.46.1 to 13.8.47.25413.8.47.255510
2513.8.48.0/2313.8.48.1 to 13.8.49.25413.8.49.255510
2613.8.50.0/2313.8.50.1 to 13.8.51.25413.8.51.255510
2713.8.52.0/2313.8.52.1 to 13.8.53.25413.8.53.255510
2813.8.54.0/2313.8.54.1 to 13.8.55.25413.8.55.255510
2913.8.56.0/2313.8.56.1 to 13.8.57.25413.8.57.255510
3013.8.58.0/2313.8.58.1 to 13.8.59.25413.8.59.255510
3113.8.60.0/2313.8.60.1 to 13.8.61.25413.8.61.255510
3213.8.62.0/2313.8.62.1 to 13.8.63.25413.8.63.255510
3313.8.64.0/2313.8.64.1 to 13.8.65.25413.8.65.255510
3413.8.66.0/2313.8.66.1 to 13.8.67.25413.8.67.255510
3513.8.68.0/2313.8.68.1 to 13.8.69.25413.8.69.255510
3613.8.70.0/2313.8.70.1 to 13.8.71.25413.8.71.255510
3713.8.72.0/2313.8.72.1 to 13.8.73.25413.8.73.255510
3813.8.74.0/2313.8.74.1 to 13.8.75.25413.8.75.255510
3913.8.76.0/2313.8.76.1 to 13.8.77.25413.8.77.255510
4013.8.78.0/2313.8.78.1 to 13.8.79.25413.8.79.255510
4113.8.80.0/2313.8.80.1 to 13.8.81.25413.8.81.255510
4213.8.82.0/2313.8.82.1 to 13.8.83.25413.8.83.255510
4313.8.84.0/2313.8.84.1 to 13.8.85.25413.8.85.255510
4413.8.86.0/2313.8.86.1 to 13.8.87.25413.8.87.255510
4513.8.88.0/2313.8.88.1 to 13.8.89.25413.8.89.255510
4613.8.90.0/2313.8.90.1 to 13.8.91.25413.8.91.255510
4713.8.92.0/2313.8.92.1 to 13.8.93.25413.8.93.255510
4813.8.94.0/2313.8.94.1 to 13.8.95.25413.8.95.255510
4913.8.96.0/2313.8.96.1 to 13.8.97.25413.8.97.255510
5013.8.98.0/2313.8.98.1 to 13.8.99.25413.8.99.255510
5113.8.100.0/2313.8.100.1 to 13.8.101.25413.8.101.255510
5213.8.102.0/2313.8.102.1 to 13.8.103.25413.8.103.255510
5313.8.104.0/2313.8.104.1 to 13.8.105.25413.8.105.255510
5413.8.106.0/2313.8.106.1 to 13.8.107.25413.8.107.255510
5513.8.108.0/2313.8.108.1 to 13.8.109.25413.8.109.255510
5613.8.110.0/2313.8.110.1 to 13.8.111.25413.8.111.255510
5713.8.112.0/2313.8.112.1 to 13.8.113.25413.8.113.255510
5813.8.114.0/2313.8.114.1 to 13.8.115.25413.8.115.255510
5913.8.116.0/2313.8.116.1 to 13.8.117.25413.8.117.255510
6013.8.118.0/2313.8.118.1 to 13.8.119.25413.8.119.255510
6113.8.120.0/2313.8.120.1 to 13.8.121.25413.8.121.255510
6213.8.122.0/2313.8.122.1 to 13.8.123.25413.8.123.255510
6313.8.124.0/2313.8.124.1 to 13.8.125.25413.8.125.255510
6413.8.126.0/2313.8.126.1 to 13.8.127.25413.8.127.255510
6513.8.128.0/2313.8.128.1 to 13.8.129.25413.8.129.255510
6613.8.130.0/2313.8.130.1 to 13.8.131.25413.8.131.255510
6713.8.132.0/2313.8.132.1 to 13.8.133.25413.8.133.255510
6813.8.134.0/2313.8.134.1 to 13.8.135.25413.8.135.255510
6913.8.136.0/2313.8.136.1 to 13.8.137.25413.8.137.255510
7013.8.138.0/2313.8.138.1 to 13.8.139.25413.8.139.255510
7113.8.140.0/2313.8.140.1 to 13.8.141.25413.8.141.255510
7213.8.142.0/2313.8.142.1 to 13.8.143.25413.8.143.255510
7313.8.144.0/2313.8.144.1 to 13.8.145.25413.8.145.255510
7413.8.146.0/2313.8.146.1 to 13.8.147.25413.8.147.255510
7513.8.148.0/2313.8.148.1 to 13.8.149.25413.8.149.255510
7613.8.150.0/2313.8.150.1 to 13.8.151.25413.8.151.255510
7713.8.152.0/2313.8.152.1 to 13.8.153.25413.8.153.255510
7813.8.154.0/2313.8.154.1 to 13.8.155.25413.8.155.255510
7913.8.156.0/2313.8.156.1 to 13.8.157.25413.8.157.255510
8013.8.158.0/2313.8.158.1 to 13.8.159.25413.8.159.255510
8113.8.160.0/2313.8.160.1 to 13.8.161.25413.8.161.255510
8213.8.162.0/2313.8.162.1 to 13.8.163.25413.8.163.255510
8313.8.164.0/2313.8.164.1 to 13.8.165.25413.8.165.255510
8413.8.166.0/2313.8.166.1 to 13.8.167.25413.8.167.255510
8513.8.168.0/2313.8.168.1 to 13.8.169.25413.8.169.255510
8613.8.170.0/2313.8.170.1 to 13.8.171.25413.8.171.255510
8713.8.172.0/2313.8.172.1 to 13.8.173.25413.8.173.255510
8813.8.174.0/2313.8.174.1 to 13.8.175.25413.8.175.255510
8913.8.176.0/2313.8.176.1 to 13.8.177.25413.8.177.255510
9013.8.178.0/2313.8.178.1 to 13.8.179.25413.8.179.255510
9113.8.180.0/2313.8.180.1 to 13.8.181.25413.8.181.255510
9213.8.182.0/2313.8.182.1 to 13.8.183.25413.8.183.255510
9313.8.184.0/2313.8.184.1 to 13.8.185.25413.8.185.255510
9413.8.186.0/2313.8.186.1 to 13.8.187.25413.8.187.255510
9513.8.188.0/2313.8.188.1 to 13.8.189.25413.8.189.255510
9613.8.190.0/2313.8.190.1 to 13.8.191.25413.8.191.255510
9713.8.192.0/2313.8.192.1 to 13.8.193.25413.8.193.255510
9813.8.194.0/2313.8.194.1 to 13.8.195.25413.8.195.255510
9913.8.196.0/2313.8.196.1 to 13.8.197.25413.8.197.255510
10013.8.198.0/2313.8.198.1 to 13.8.199.25413.8.199.255510
10113.8.200.0/2313.8.200.1 to 13.8.201.25413.8.201.255510
10213.8.202.0/2313.8.202.1 to 13.8.203.25413.8.203.255510
10313.8.204.0/2313.8.204.1 to 13.8.205.25413.8.205.255510
10413.8.206.0/2313.8.206.1 to 13.8.207.25413.8.207.255510
10513.8.208.0/2313.8.208.1 to 13.8.209.25413.8.209.255510
10613.8.210.0/2313.8.210.1 to 13.8.211.25413.8.211.255510
10713.8.212.0/2313.8.212.1 to 13.8.213.25413.8.213.255510
10813.8.214.0/2313.8.214.1 to 13.8.215.25413.8.215.255510
10913.8.216.0/2313.8.216.1 to 13.8.217.25413.8.217.255510
11013.8.218.0/2313.8.218.1 to 13.8.219.25413.8.219.255510
11113.8.220.0/2313.8.220.1 to 13.8.221.25413.8.221.255510
11213.8.222.0/2313.8.222.1 to 13.8.223.25413.8.223.255510
11313.8.224.0/2313.8.224.1 to 13.8.225.25413.8.225.255510
11413.8.226.0/2313.8.226.1 to 13.8.227.25413.8.227.255510
11513.8.228.0/2313.8.228.1 to 13.8.229.25413.8.229.255510
11613.8.230.0/2313.8.230.1 to 13.8.231.25413.8.231.255510
11713.8.232.0/2313.8.232.1 to 13.8.233.25413.8.233.255510
11813.8.234.0/2313.8.234.1 to 13.8.235.25413.8.235.255510
11913.8.236.0/2313.8.236.1 to 13.8.237.25413.8.237.255510
12013.8.238.0/2313.8.238.1 to 13.8.239.25413.8.239.255510
12113.8.240.0/2313.8.240.1 to 13.8.241.25413.8.241.255510
12213.8.242.0/2313.8.242.1 to 13.8.243.25413.8.243.255510
12313.8.244.0/2313.8.244.1 to 13.8.245.25413.8.245.255510
12413.8.246.0/2313.8.246.1 to 13.8.247.25413.8.247.255510
12513.8.248.0/2313.8.248.1 to 13.8.249.25413.8.249.255510
12613.8.250.0/2313.8.250.1 to 13.8.251.25413.8.251.255510
12713.8.252.0/2313.8.252.1 to 13.8.253.25413.8.253.255510
12813.8.254.0/2313.8.254.1 to 13.8.255.25413.8.255.255510
12913.9.0.0/2313.9.0.1 to 13.9.1.25413.9.1.255510
13013.9.2.0/2313.9.2.1 to 13.9.3.25413.9.3.255510
13113.9.4.0/2313.9.4.1 to 13.9.5.25413.9.5.255510
13213.9.6.0/2313.9.6.1 to 13.9.7.25413.9.7.255510
13313.9.8.0/2313.9.8.1 to 13.9.9.25413.9.9.255510
13413.9.10.0/2313.9.10.1 to 13.9.11.25413.9.11.255510
13513.9.12.0/2313.9.12.1 to 13.9.13.25413.9.13.255510
13613.9.14.0/2313.9.14.1 to 13.9.15.25413.9.15.255510
13713.9.16.0/2313.9.16.1 to 13.9.17.25413.9.17.255510
13813.9.18.0/2313.9.18.1 to 13.9.19.25413.9.19.255510
13913.9.20.0/2313.9.20.1 to 13.9.21.25413.9.21.255510
14013.9.22.0/2313.9.22.1 to 13.9.23.25413.9.23.255510
14113.9.24.0/2313.9.24.1 to 13.9.25.25413.9.25.255510
14213.9.26.0/2313.9.26.1 to 13.9.27.25413.9.27.255510
14313.9.28.0/2313.9.28.1 to 13.9.29.25413.9.29.255510
14413.9.30.0/2313.9.30.1 to 13.9.31.25413.9.31.255510
14513.9.32.0/2313.9.32.1 to 13.9.33.25413.9.33.255510
14613.9.34.0/2313.9.34.1 to 13.9.35.25413.9.35.255510
14713.9.36.0/2313.9.36.1 to 13.9.37.25413.9.37.255510
14813.9.38.0/2313.9.38.1 to 13.9.39.25413.9.39.255510
14913.9.40.0/2313.9.40.1 to 13.9.41.25413.9.41.255510
15013.9.42.0/2313.9.42.1 to 13.9.43.25413.9.43.255510
15113.9.44.0/2313.9.44.1 to 13.9.45.25413.9.45.255510
15213.9.46.0/2313.9.46.1 to 13.9.47.25413.9.47.255510
15313.9.48.0/2313.9.48.1 to 13.9.49.25413.9.49.255510
15413.9.50.0/2313.9.50.1 to 13.9.51.25413.9.51.255510
15513.9.52.0/2313.9.52.1 to 13.9.53.25413.9.53.255510
15613.9.54.0/2313.9.54.1 to 13.9.55.25413.9.55.255510
15713.9.56.0/2313.9.56.1 to 13.9.57.25413.9.57.255510
15813.9.58.0/2313.9.58.1 to 13.9.59.25413.9.59.255510
15913.9.60.0/2313.9.60.1 to 13.9.61.25413.9.61.255510
16013.9.62.0/2313.9.62.1 to 13.9.63.25413.9.63.255510
16113.9.64.0/2313.9.64.1 to 13.9.65.25413.9.65.255510
16213.9.66.0/2313.9.66.1 to 13.9.67.25413.9.67.255510
16313.9.68.0/2313.9.68.1 to 13.9.69.25413.9.69.255510
16413.9.70.0/2313.9.70.1 to 13.9.71.25413.9.71.255510
16513.9.72.0/2313.9.72.1 to 13.9.73.25413.9.73.255510
16613.9.74.0/2313.9.74.1 to 13.9.75.25413.9.75.255510
16713.9.76.0/2313.9.76.1 to 13.9.77.25413.9.77.255510
16813.9.78.0/2313.9.78.1 to 13.9.79.25413.9.79.255510
16913.9.80.0/2313.9.80.1 to 13.9.81.25413.9.81.255510
17013.9.82.0/2313.9.82.1 to 13.9.83.25413.9.83.255510
17113.9.84.0/2313.9.84.1 to 13.9.85.25413.9.85.255510
17213.9.86.0/2313.9.86.1 to 13.9.87.25413.9.87.255510
17313.9.88.0/2313.9.88.1 to 13.9.89.25413.9.89.255510
17413.9.90.0/2313.9.90.1 to 13.9.91.25413.9.91.255510
17513.9.92.0/2313.9.92.1 to 13.9.93.25413.9.93.255510
17613.9.94.0/2313.9.94.1 to 13.9.95.25413.9.95.255510
17713.9.96.0/2313.9.96.1 to 13.9.97.25413.9.97.255510
17813.9.98.0/2313.9.98.1 to 13.9.99.25413.9.99.255510
17913.9.100.0/2313.9.100.1 to 13.9.101.25413.9.101.255510
18013.9.102.0/2313.9.102.1 to 13.9.103.25413.9.103.255510
18113.9.104.0/2313.9.104.1 to 13.9.105.25413.9.105.255510
18213.9.106.0/2313.9.106.1 to 13.9.107.25413.9.107.255510
18313.9.108.0/2313.9.108.1 to 13.9.109.25413.9.109.255510
18413.9.110.0/2313.9.110.1 to 13.9.111.25413.9.111.255510
18513.9.112.0/2313.9.112.1 to 13.9.113.25413.9.113.255510
18613.9.114.0/2313.9.114.1 to 13.9.115.25413.9.115.255510
18713.9.116.0/2313.9.116.1 to 13.9.117.25413.9.117.255510
18813.9.118.0/2313.9.118.1 to 13.9.119.25413.9.119.255510
18913.9.120.0/2313.9.120.1 to 13.9.121.25413.9.121.255510
19013.9.122.0/2313.9.122.1 to 13.9.123.25413.9.123.255510
19113.9.124.0/2313.9.124.1 to 13.9.125.25413.9.125.255510
19213.9.126.0/2313.9.126.1 to 13.9.127.25413.9.127.255510
19313.9.128.0/2313.9.128.1 to 13.9.129.25413.9.129.255510
19413.9.130.0/2313.9.130.1 to 13.9.131.25413.9.131.255510
19513.9.132.0/2313.9.132.1 to 13.9.133.25413.9.133.255510
19613.9.134.0/2313.9.134.1 to 13.9.135.25413.9.135.255510
19713.9.136.0/2313.9.136.1 to 13.9.137.25413.9.137.255510
19813.9.138.0/2313.9.138.1 to 13.9.139.25413.9.139.255510
19913.9.140.0/2313.9.140.1 to 13.9.141.25413.9.141.255510
20013.9.142.0/2313.9.142.1 to 13.9.143.25413.9.143.255510
20113.9.144.0/2313.9.144.1 to 13.9.145.25413.9.145.255510
20213.9.146.0/2313.9.146.1 to 13.9.147.25413.9.147.255510
20313.9.148.0/2313.9.148.1 to 13.9.149.25413.9.149.255510
20413.9.150.0/2313.9.150.1 to 13.9.151.25413.9.151.255510
20513.9.152.0/2313.9.152.1 to 13.9.153.25413.9.153.255510
20613.9.154.0/2313.9.154.1 to 13.9.155.25413.9.155.255510
20713.9.156.0/2313.9.156.1 to 13.9.157.25413.9.157.255510
20813.9.158.0/2313.9.158.1 to 13.9.159.25413.9.159.255510
20913.9.160.0/2313.9.160.1 to 13.9.161.25413.9.161.255510
21013.9.162.0/2313.9.162.1 to 13.9.163.25413.9.163.255510
21113.9.164.0/2313.9.164.1 to 13.9.165.25413.9.165.255510
21213.9.166.0/2313.9.166.1 to 13.9.167.25413.9.167.255510
21313.9.168.0/2313.9.168.1 to 13.9.169.25413.9.169.255510
21413.9.170.0/2313.9.170.1 to 13.9.171.25413.9.171.255510
21513.9.172.0/2313.9.172.1 to 13.9.173.25413.9.173.255510
21613.9.174.0/2313.9.174.1 to 13.9.175.25413.9.175.255510
21713.9.176.0/2313.9.176.1 to 13.9.177.25413.9.177.255510
21813.9.178.0/2313.9.178.1 to 13.9.179.25413.9.179.255510
21913.9.180.0/2313.9.180.1 to 13.9.181.25413.9.181.255510
22013.9.182.0/2313.9.182.1 to 13.9.183.25413.9.183.255510
22113.9.184.0/2313.9.184.1 to 13.9.185.25413.9.185.255510
22213.9.186.0/2313.9.186.1 to 13.9.187.25413.9.187.255510
22313.9.188.0/2313.9.188.1 to 13.9.189.25413.9.189.255510
22413.9.190.0/2313.9.190.1 to 13.9.191.25413.9.191.255510
22513.9.192.0/2313.9.192.1 to 13.9.193.25413.9.193.255510
22613.9.194.0/2313.9.194.1 to 13.9.195.25413.9.195.255510
22713.9.196.0/2313.9.196.1 to 13.9.197.25413.9.197.255510
22813.9.198.0/2313.9.198.1 to 13.9.199.25413.9.199.255510
22913.9.200.0/2313.9.200.1 to 13.9.201.25413.9.201.255510
23013.9.202.0/2313.9.202.1 to 13.9.203.25413.9.203.255510
23113.9.204.0/2313.9.204.1 to 13.9.205.25413.9.205.255510
23213.9.206.0/2313.9.206.1 to 13.9.207.25413.9.207.255510
23313.9.208.0/2313.9.208.1 to 13.9.209.25413.9.209.255510
23413.9.210.0/2313.9.210.1 to 13.9.211.25413.9.211.255510
23513.9.212.0/2313.9.212.1 to 13.9.213.25413.9.213.255510
23613.9.214.0/2313.9.214.1 to 13.9.215.25413.9.215.255510
23713.9.216.0/2313.9.216.1 to 13.9.217.25413.9.217.255510
23813.9.218.0/2313.9.218.1 to 13.9.219.25413.9.219.255510
23913.9.220.0/2313.9.220.1 to 13.9.221.25413.9.221.255510
24013.9.222.0/2313.9.222.1 to 13.9.223.25413.9.223.255510
24113.9.224.0/2313.9.224.1 to 13.9.225.25413.9.225.255510
24213.9.226.0/2313.9.226.1 to 13.9.227.25413.9.227.255510
24313.9.228.0/2313.9.228.1 to 13.9.229.25413.9.229.255510
24413.9.230.0/2313.9.230.1 to 13.9.231.25413.9.231.255510
24513.9.232.0/2313.9.232.1 to 13.9.233.25413.9.233.255510
24613.9.234.0/2313.9.234.1 to 13.9.235.25413.9.235.255510
24713.9.236.0/2313.9.236.1 to 13.9.237.25413.9.237.255510
24813.9.238.0/2313.9.238.1 to 13.9.239.25413.9.239.255510
24913.9.240.0/2313.9.240.1 to 13.9.241.25413.9.241.255510
25013.9.242.0/2313.9.242.1 to 13.9.243.25413.9.243.255510
25113.9.244.0/2313.9.244.1 to 13.9.245.25413.9.245.255510
25213.9.246.0/2313.9.246.1 to 13.9.247.25413.9.247.255510
25313.9.248.0/2313.9.248.1 to 13.9.249.25413.9.249.255510
25413.9.250.0/2313.9.250.1 to 13.9.251.25413.9.251.255510
25513.9.252.0/2313.9.252.1 to 13.9.253.25413.9.253.255510
25613.9.254.0/2313.9.254.1 to 13.9.255.25413.9.255.255510

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.