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.

Network13.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
13.0.0.0
Broadcast address
13.255.255.255
First usable
13.0.0.1
Last usable
13.255.255.254
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 0D000000 · Integer 218103808 to 234881023
Reverse DNS zone
13.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001101..00000000.00000000.0000000013.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network00001101..00000000.00000000.0000000013.0.0.0
Broadcast00001101..11111111.11111111.1111111113.255.255.255
Split into smaller subnets/18
/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)

13.0.0.0/8 makes 1,024 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
113.0.0.0/1813.0.0.1 to 13.0.63.25413.0.63.25516,382
213.0.64.0/1813.0.64.1 to 13.0.127.25413.0.127.25516,382
313.0.128.0/1813.0.128.1 to 13.0.191.25413.0.191.25516,382
413.0.192.0/1813.0.192.1 to 13.0.255.25413.0.255.25516,382
513.1.0.0/1813.1.0.1 to 13.1.63.25413.1.63.25516,382
613.1.64.0/1813.1.64.1 to 13.1.127.25413.1.127.25516,382
713.1.128.0/1813.1.128.1 to 13.1.191.25413.1.191.25516,382
813.1.192.0/1813.1.192.1 to 13.1.255.25413.1.255.25516,382
913.2.0.0/1813.2.0.1 to 13.2.63.25413.2.63.25516,382
1013.2.64.0/1813.2.64.1 to 13.2.127.25413.2.127.25516,382
1113.2.128.0/1813.2.128.1 to 13.2.191.25413.2.191.25516,382
1213.2.192.0/1813.2.192.1 to 13.2.255.25413.2.255.25516,382
1313.3.0.0/1813.3.0.1 to 13.3.63.25413.3.63.25516,382
1413.3.64.0/1813.3.64.1 to 13.3.127.25413.3.127.25516,382
1513.3.128.0/1813.3.128.1 to 13.3.191.25413.3.191.25516,382
1613.3.192.0/1813.3.192.1 to 13.3.255.25413.3.255.25516,382
1713.4.0.0/1813.4.0.1 to 13.4.63.25413.4.63.25516,382
1813.4.64.0/1813.4.64.1 to 13.4.127.25413.4.127.25516,382
1913.4.128.0/1813.4.128.1 to 13.4.191.25413.4.191.25516,382
2013.4.192.0/1813.4.192.1 to 13.4.255.25413.4.255.25516,382
2113.5.0.0/1813.5.0.1 to 13.5.63.25413.5.63.25516,382
2213.5.64.0/1813.5.64.1 to 13.5.127.25413.5.127.25516,382
2313.5.128.0/1813.5.128.1 to 13.5.191.25413.5.191.25516,382
2413.5.192.0/1813.5.192.1 to 13.5.255.25413.5.255.25516,382
2513.6.0.0/1813.6.0.1 to 13.6.63.25413.6.63.25516,382
2613.6.64.0/1813.6.64.1 to 13.6.127.25413.6.127.25516,382
2713.6.128.0/1813.6.128.1 to 13.6.191.25413.6.191.25516,382
2813.6.192.0/1813.6.192.1 to 13.6.255.25413.6.255.25516,382
2913.7.0.0/1813.7.0.1 to 13.7.63.25413.7.63.25516,382
3013.7.64.0/1813.7.64.1 to 13.7.127.25413.7.127.25516,382
3113.7.128.0/1813.7.128.1 to 13.7.191.25413.7.191.25516,382
3213.7.192.0/1813.7.192.1 to 13.7.255.25413.7.255.25516,382
3313.8.0.0/1813.8.0.1 to 13.8.63.25413.8.63.25516,382
3413.8.64.0/1813.8.64.1 to 13.8.127.25413.8.127.25516,382
3513.8.128.0/1813.8.128.1 to 13.8.191.25413.8.191.25516,382
3613.8.192.0/1813.8.192.1 to 13.8.255.25413.8.255.25516,382
3713.9.0.0/1813.9.0.1 to 13.9.63.25413.9.63.25516,382
3813.9.64.0/1813.9.64.1 to 13.9.127.25413.9.127.25516,382
3913.9.128.0/1813.9.128.1 to 13.9.191.25413.9.191.25516,382
4013.9.192.0/1813.9.192.1 to 13.9.255.25413.9.255.25516,382
4113.10.0.0/1813.10.0.1 to 13.10.63.25413.10.63.25516,382
4213.10.64.0/1813.10.64.1 to 13.10.127.25413.10.127.25516,382
4313.10.128.0/1813.10.128.1 to 13.10.191.25413.10.191.25516,382
4413.10.192.0/1813.10.192.1 to 13.10.255.25413.10.255.25516,382
4513.11.0.0/1813.11.0.1 to 13.11.63.25413.11.63.25516,382
4613.11.64.0/1813.11.64.1 to 13.11.127.25413.11.127.25516,382
4713.11.128.0/1813.11.128.1 to 13.11.191.25413.11.191.25516,382
4813.11.192.0/1813.11.192.1 to 13.11.255.25413.11.255.25516,382
4913.12.0.0/1813.12.0.1 to 13.12.63.25413.12.63.25516,382
5013.12.64.0/1813.12.64.1 to 13.12.127.25413.12.127.25516,382
5113.12.128.0/1813.12.128.1 to 13.12.191.25413.12.191.25516,382
5213.12.192.0/1813.12.192.1 to 13.12.255.25413.12.255.25516,382
5313.13.0.0/1813.13.0.1 to 13.13.63.25413.13.63.25516,382
5413.13.64.0/1813.13.64.1 to 13.13.127.25413.13.127.25516,382
5513.13.128.0/1813.13.128.1 to 13.13.191.25413.13.191.25516,382
5613.13.192.0/1813.13.192.1 to 13.13.255.25413.13.255.25516,382
5713.14.0.0/1813.14.0.1 to 13.14.63.25413.14.63.25516,382
5813.14.64.0/1813.14.64.1 to 13.14.127.25413.14.127.25516,382
5913.14.128.0/1813.14.128.1 to 13.14.191.25413.14.191.25516,382
6013.14.192.0/1813.14.192.1 to 13.14.255.25413.14.255.25516,382
6113.15.0.0/1813.15.0.1 to 13.15.63.25413.15.63.25516,382
6213.15.64.0/1813.15.64.1 to 13.15.127.25413.15.127.25516,382
6313.15.128.0/1813.15.128.1 to 13.15.191.25413.15.191.25516,382
6413.15.192.0/1813.15.192.1 to 13.15.255.25413.15.255.25516,382
6513.16.0.0/1813.16.0.1 to 13.16.63.25413.16.63.25516,382
6613.16.64.0/1813.16.64.1 to 13.16.127.25413.16.127.25516,382
6713.16.128.0/1813.16.128.1 to 13.16.191.25413.16.191.25516,382
6813.16.192.0/1813.16.192.1 to 13.16.255.25413.16.255.25516,382
6913.17.0.0/1813.17.0.1 to 13.17.63.25413.17.63.25516,382
7013.17.64.0/1813.17.64.1 to 13.17.127.25413.17.127.25516,382
7113.17.128.0/1813.17.128.1 to 13.17.191.25413.17.191.25516,382
7213.17.192.0/1813.17.192.1 to 13.17.255.25413.17.255.25516,382
7313.18.0.0/1813.18.0.1 to 13.18.63.25413.18.63.25516,382
7413.18.64.0/1813.18.64.1 to 13.18.127.25413.18.127.25516,382
7513.18.128.0/1813.18.128.1 to 13.18.191.25413.18.191.25516,382
7613.18.192.0/1813.18.192.1 to 13.18.255.25413.18.255.25516,382
7713.19.0.0/1813.19.0.1 to 13.19.63.25413.19.63.25516,382
7813.19.64.0/1813.19.64.1 to 13.19.127.25413.19.127.25516,382
7913.19.128.0/1813.19.128.1 to 13.19.191.25413.19.191.25516,382
8013.19.192.0/1813.19.192.1 to 13.19.255.25413.19.255.25516,382
8113.20.0.0/1813.20.0.1 to 13.20.63.25413.20.63.25516,382
8213.20.64.0/1813.20.64.1 to 13.20.127.25413.20.127.25516,382
8313.20.128.0/1813.20.128.1 to 13.20.191.25413.20.191.25516,382
8413.20.192.0/1813.20.192.1 to 13.20.255.25413.20.255.25516,382
8513.21.0.0/1813.21.0.1 to 13.21.63.25413.21.63.25516,382
8613.21.64.0/1813.21.64.1 to 13.21.127.25413.21.127.25516,382
8713.21.128.0/1813.21.128.1 to 13.21.191.25413.21.191.25516,382
8813.21.192.0/1813.21.192.1 to 13.21.255.25413.21.255.25516,382
8913.22.0.0/1813.22.0.1 to 13.22.63.25413.22.63.25516,382
9013.22.64.0/1813.22.64.1 to 13.22.127.25413.22.127.25516,382
9113.22.128.0/1813.22.128.1 to 13.22.191.25413.22.191.25516,382
9213.22.192.0/1813.22.192.1 to 13.22.255.25413.22.255.25516,382
9313.23.0.0/1813.23.0.1 to 13.23.63.25413.23.63.25516,382
9413.23.64.0/1813.23.64.1 to 13.23.127.25413.23.127.25516,382
9513.23.128.0/1813.23.128.1 to 13.23.191.25413.23.191.25516,382
9613.23.192.0/1813.23.192.1 to 13.23.255.25413.23.255.25516,382
9713.24.0.0/1813.24.0.1 to 13.24.63.25413.24.63.25516,382
9813.24.64.0/1813.24.64.1 to 13.24.127.25413.24.127.25516,382
9913.24.128.0/1813.24.128.1 to 13.24.191.25413.24.191.25516,382
10013.24.192.0/1813.24.192.1 to 13.24.255.25413.24.255.25516,382
10113.25.0.0/1813.25.0.1 to 13.25.63.25413.25.63.25516,382
10213.25.64.0/1813.25.64.1 to 13.25.127.25413.25.127.25516,382
10313.25.128.0/1813.25.128.1 to 13.25.191.25413.25.191.25516,382
10413.25.192.0/1813.25.192.1 to 13.25.255.25413.25.255.25516,382
10513.26.0.0/1813.26.0.1 to 13.26.63.25413.26.63.25516,382
10613.26.64.0/1813.26.64.1 to 13.26.127.25413.26.127.25516,382
10713.26.128.0/1813.26.128.1 to 13.26.191.25413.26.191.25516,382
10813.26.192.0/1813.26.192.1 to 13.26.255.25413.26.255.25516,382
10913.27.0.0/1813.27.0.1 to 13.27.63.25413.27.63.25516,382
11013.27.64.0/1813.27.64.1 to 13.27.127.25413.27.127.25516,382
11113.27.128.0/1813.27.128.1 to 13.27.191.25413.27.191.25516,382
11213.27.192.0/1813.27.192.1 to 13.27.255.25413.27.255.25516,382
11313.28.0.0/1813.28.0.1 to 13.28.63.25413.28.63.25516,382
11413.28.64.0/1813.28.64.1 to 13.28.127.25413.28.127.25516,382
11513.28.128.0/1813.28.128.1 to 13.28.191.25413.28.191.25516,382
11613.28.192.0/1813.28.192.1 to 13.28.255.25413.28.255.25516,382
11713.29.0.0/1813.29.0.1 to 13.29.63.25413.29.63.25516,382
11813.29.64.0/1813.29.64.1 to 13.29.127.25413.29.127.25516,382
11913.29.128.0/1813.29.128.1 to 13.29.191.25413.29.191.25516,382
12013.29.192.0/1813.29.192.1 to 13.29.255.25413.29.255.25516,382
12113.30.0.0/1813.30.0.1 to 13.30.63.25413.30.63.25516,382
12213.30.64.0/1813.30.64.1 to 13.30.127.25413.30.127.25516,382
12313.30.128.0/1813.30.128.1 to 13.30.191.25413.30.191.25516,382
12413.30.192.0/1813.30.192.1 to 13.30.255.25413.30.255.25516,382
12513.31.0.0/1813.31.0.1 to 13.31.63.25413.31.63.25516,382
12613.31.64.0/1813.31.64.1 to 13.31.127.25413.31.127.25516,382
12713.31.128.0/1813.31.128.1 to 13.31.191.25413.31.191.25516,382
12813.31.192.0/1813.31.192.1 to 13.31.255.25413.31.255.25516,382
12913.32.0.0/1813.32.0.1 to 13.32.63.25413.32.63.25516,382
13013.32.64.0/1813.32.64.1 to 13.32.127.25413.32.127.25516,382
13113.32.128.0/1813.32.128.1 to 13.32.191.25413.32.191.25516,382
13213.32.192.0/1813.32.192.1 to 13.32.255.25413.32.255.25516,382
13313.33.0.0/1813.33.0.1 to 13.33.63.25413.33.63.25516,382
13413.33.64.0/1813.33.64.1 to 13.33.127.25413.33.127.25516,382
13513.33.128.0/1813.33.128.1 to 13.33.191.25413.33.191.25516,382
13613.33.192.0/1813.33.192.1 to 13.33.255.25413.33.255.25516,382
13713.34.0.0/1813.34.0.1 to 13.34.63.25413.34.63.25516,382
13813.34.64.0/1813.34.64.1 to 13.34.127.25413.34.127.25516,382
13913.34.128.0/1813.34.128.1 to 13.34.191.25413.34.191.25516,382
14013.34.192.0/1813.34.192.1 to 13.34.255.25413.34.255.25516,382
14113.35.0.0/1813.35.0.1 to 13.35.63.25413.35.63.25516,382
14213.35.64.0/1813.35.64.1 to 13.35.127.25413.35.127.25516,382
14313.35.128.0/1813.35.128.1 to 13.35.191.25413.35.191.25516,382
14413.35.192.0/1813.35.192.1 to 13.35.255.25413.35.255.25516,382
14513.36.0.0/1813.36.0.1 to 13.36.63.25413.36.63.25516,382
14613.36.64.0/1813.36.64.1 to 13.36.127.25413.36.127.25516,382
14713.36.128.0/1813.36.128.1 to 13.36.191.25413.36.191.25516,382
14813.36.192.0/1813.36.192.1 to 13.36.255.25413.36.255.25516,382
14913.37.0.0/1813.37.0.1 to 13.37.63.25413.37.63.25516,382
15013.37.64.0/1813.37.64.1 to 13.37.127.25413.37.127.25516,382
15113.37.128.0/1813.37.128.1 to 13.37.191.25413.37.191.25516,382
15213.37.192.0/1813.37.192.1 to 13.37.255.25413.37.255.25516,382
15313.38.0.0/1813.38.0.1 to 13.38.63.25413.38.63.25516,382
15413.38.64.0/1813.38.64.1 to 13.38.127.25413.38.127.25516,382
15513.38.128.0/1813.38.128.1 to 13.38.191.25413.38.191.25516,382
15613.38.192.0/1813.38.192.1 to 13.38.255.25413.38.255.25516,382
15713.39.0.0/1813.39.0.1 to 13.39.63.25413.39.63.25516,382
15813.39.64.0/1813.39.64.1 to 13.39.127.25413.39.127.25516,382
15913.39.128.0/1813.39.128.1 to 13.39.191.25413.39.191.25516,382
16013.39.192.0/1813.39.192.1 to 13.39.255.25413.39.255.25516,382
16113.40.0.0/1813.40.0.1 to 13.40.63.25413.40.63.25516,382
16213.40.64.0/1813.40.64.1 to 13.40.127.25413.40.127.25516,382
16313.40.128.0/1813.40.128.1 to 13.40.191.25413.40.191.25516,382
16413.40.192.0/1813.40.192.1 to 13.40.255.25413.40.255.25516,382
16513.41.0.0/1813.41.0.1 to 13.41.63.25413.41.63.25516,382
16613.41.64.0/1813.41.64.1 to 13.41.127.25413.41.127.25516,382
16713.41.128.0/1813.41.128.1 to 13.41.191.25413.41.191.25516,382
16813.41.192.0/1813.41.192.1 to 13.41.255.25413.41.255.25516,382
16913.42.0.0/1813.42.0.1 to 13.42.63.25413.42.63.25516,382
17013.42.64.0/1813.42.64.1 to 13.42.127.25413.42.127.25516,382
17113.42.128.0/1813.42.128.1 to 13.42.191.25413.42.191.25516,382
17213.42.192.0/1813.42.192.1 to 13.42.255.25413.42.255.25516,382
17313.43.0.0/1813.43.0.1 to 13.43.63.25413.43.63.25516,382
17413.43.64.0/1813.43.64.1 to 13.43.127.25413.43.127.25516,382
17513.43.128.0/1813.43.128.1 to 13.43.191.25413.43.191.25516,382
17613.43.192.0/1813.43.192.1 to 13.43.255.25413.43.255.25516,382
17713.44.0.0/1813.44.0.1 to 13.44.63.25413.44.63.25516,382
17813.44.64.0/1813.44.64.1 to 13.44.127.25413.44.127.25516,382
17913.44.128.0/1813.44.128.1 to 13.44.191.25413.44.191.25516,382
18013.44.192.0/1813.44.192.1 to 13.44.255.25413.44.255.25516,382
18113.45.0.0/1813.45.0.1 to 13.45.63.25413.45.63.25516,382
18213.45.64.0/1813.45.64.1 to 13.45.127.25413.45.127.25516,382
18313.45.128.0/1813.45.128.1 to 13.45.191.25413.45.191.25516,382
18413.45.192.0/1813.45.192.1 to 13.45.255.25413.45.255.25516,382
18513.46.0.0/1813.46.0.1 to 13.46.63.25413.46.63.25516,382
18613.46.64.0/1813.46.64.1 to 13.46.127.25413.46.127.25516,382
18713.46.128.0/1813.46.128.1 to 13.46.191.25413.46.191.25516,382
18813.46.192.0/1813.46.192.1 to 13.46.255.25413.46.255.25516,382
18913.47.0.0/1813.47.0.1 to 13.47.63.25413.47.63.25516,382
19013.47.64.0/1813.47.64.1 to 13.47.127.25413.47.127.25516,382
19113.47.128.0/1813.47.128.1 to 13.47.191.25413.47.191.25516,382
19213.47.192.0/1813.47.192.1 to 13.47.255.25413.47.255.25516,382
19313.48.0.0/1813.48.0.1 to 13.48.63.25413.48.63.25516,382
19413.48.64.0/1813.48.64.1 to 13.48.127.25413.48.127.25516,382
19513.48.128.0/1813.48.128.1 to 13.48.191.25413.48.191.25516,382
19613.48.192.0/1813.48.192.1 to 13.48.255.25413.48.255.25516,382
19713.49.0.0/1813.49.0.1 to 13.49.63.25413.49.63.25516,382
19813.49.64.0/1813.49.64.1 to 13.49.127.25413.49.127.25516,382
19913.49.128.0/1813.49.128.1 to 13.49.191.25413.49.191.25516,382
20013.49.192.0/1813.49.192.1 to 13.49.255.25413.49.255.25516,382
20113.50.0.0/1813.50.0.1 to 13.50.63.25413.50.63.25516,382
20213.50.64.0/1813.50.64.1 to 13.50.127.25413.50.127.25516,382
20313.50.128.0/1813.50.128.1 to 13.50.191.25413.50.191.25516,382
20413.50.192.0/1813.50.192.1 to 13.50.255.25413.50.255.25516,382
20513.51.0.0/1813.51.0.1 to 13.51.63.25413.51.63.25516,382
20613.51.64.0/1813.51.64.1 to 13.51.127.25413.51.127.25516,382
20713.51.128.0/1813.51.128.1 to 13.51.191.25413.51.191.25516,382
20813.51.192.0/1813.51.192.1 to 13.51.255.25413.51.255.25516,382
20913.52.0.0/1813.52.0.1 to 13.52.63.25413.52.63.25516,382
21013.52.64.0/1813.52.64.1 to 13.52.127.25413.52.127.25516,382
21113.52.128.0/1813.52.128.1 to 13.52.191.25413.52.191.25516,382
21213.52.192.0/1813.52.192.1 to 13.52.255.25413.52.255.25516,382
21313.53.0.0/1813.53.0.1 to 13.53.63.25413.53.63.25516,382
21413.53.64.0/1813.53.64.1 to 13.53.127.25413.53.127.25516,382
21513.53.128.0/1813.53.128.1 to 13.53.191.25413.53.191.25516,382
21613.53.192.0/1813.53.192.1 to 13.53.255.25413.53.255.25516,382
21713.54.0.0/1813.54.0.1 to 13.54.63.25413.54.63.25516,382
21813.54.64.0/1813.54.64.1 to 13.54.127.25413.54.127.25516,382
21913.54.128.0/1813.54.128.1 to 13.54.191.25413.54.191.25516,382
22013.54.192.0/1813.54.192.1 to 13.54.255.25413.54.255.25516,382
22113.55.0.0/1813.55.0.1 to 13.55.63.25413.55.63.25516,382
22213.55.64.0/1813.55.64.1 to 13.55.127.25413.55.127.25516,382
22313.55.128.0/1813.55.128.1 to 13.55.191.25413.55.191.25516,382
22413.55.192.0/1813.55.192.1 to 13.55.255.25413.55.255.25516,382
22513.56.0.0/1813.56.0.1 to 13.56.63.25413.56.63.25516,382
22613.56.64.0/1813.56.64.1 to 13.56.127.25413.56.127.25516,382
22713.56.128.0/1813.56.128.1 to 13.56.191.25413.56.191.25516,382
22813.56.192.0/1813.56.192.1 to 13.56.255.25413.56.255.25516,382
22913.57.0.0/1813.57.0.1 to 13.57.63.25413.57.63.25516,382
23013.57.64.0/1813.57.64.1 to 13.57.127.25413.57.127.25516,382
23113.57.128.0/1813.57.128.1 to 13.57.191.25413.57.191.25516,382
23213.57.192.0/1813.57.192.1 to 13.57.255.25413.57.255.25516,382
23313.58.0.0/1813.58.0.1 to 13.58.63.25413.58.63.25516,382
23413.58.64.0/1813.58.64.1 to 13.58.127.25413.58.127.25516,382
23513.58.128.0/1813.58.128.1 to 13.58.191.25413.58.191.25516,382
23613.58.192.0/1813.58.192.1 to 13.58.255.25413.58.255.25516,382
23713.59.0.0/1813.59.0.1 to 13.59.63.25413.59.63.25516,382
23813.59.64.0/1813.59.64.1 to 13.59.127.25413.59.127.25516,382
23913.59.128.0/1813.59.128.1 to 13.59.191.25413.59.191.25516,382
24013.59.192.0/1813.59.192.1 to 13.59.255.25413.59.255.25516,382
24113.60.0.0/1813.60.0.1 to 13.60.63.25413.60.63.25516,382
24213.60.64.0/1813.60.64.1 to 13.60.127.25413.60.127.25516,382
24313.60.128.0/1813.60.128.1 to 13.60.191.25413.60.191.25516,382
24413.60.192.0/1813.60.192.1 to 13.60.255.25413.60.255.25516,382
24513.61.0.0/1813.61.0.1 to 13.61.63.25413.61.63.25516,382
24613.61.64.0/1813.61.64.1 to 13.61.127.25413.61.127.25516,382
24713.61.128.0/1813.61.128.1 to 13.61.191.25413.61.191.25516,382
24813.61.192.0/1813.61.192.1 to 13.61.255.25413.61.255.25516,382
24913.62.0.0/1813.62.0.1 to 13.62.63.25413.62.63.25516,382
25013.62.64.0/1813.62.64.1 to 13.62.127.25413.62.127.25516,382
25113.62.128.0/1813.62.128.1 to 13.62.191.25413.62.191.25516,382
25213.62.192.0/1813.62.192.1 to 13.62.255.25413.62.255.25516,382
25313.63.0.0/1813.63.0.1 to 13.63.63.25413.63.63.25516,382
25413.63.64.0/1813.63.64.1 to 13.63.127.25413.63.127.25516,382
25513.63.128.0/1813.63.128.1 to 13.63.191.25413.63.191.25516,382
25613.63.192.0/1813.63.192.1 to 13.63.255.25413.63.255.25516,382

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.