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.

Network15.0.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
15.0.0.0
Broadcast address
15.7.255.255
First usable
15.0.0.1
Last usable
15.7.255.254
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 0F000000 · Integer 251658240 to 252182527
Reverse DNS zones
0.15.in-addr.arpa
1.15.in-addr.arpa
2.15.in-addr.arpa
3.15.in-addr.arpa
4.15.in-addr.arpa
5.15.in-addr.arpa
6.15.in-addr.arpa
7.15.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
Address00001111.00000000.00000000.0000000015.0.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network00001111.00000000.00000000.0000000015.0.0.0
Broadcast00001111.00000111.11111111.1111111115.7.255.255
Split into smaller subnets/24
/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)

15.0.0.0/13 makes 2,048 subnets of /24; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
115.0.0.0/2415.0.0.1 to 15.0.0.25415.0.0.255254
215.0.1.0/2415.0.1.1 to 15.0.1.25415.0.1.255254
315.0.2.0/2415.0.2.1 to 15.0.2.25415.0.2.255254
415.0.3.0/2415.0.3.1 to 15.0.3.25415.0.3.255254
515.0.4.0/2415.0.4.1 to 15.0.4.25415.0.4.255254
615.0.5.0/2415.0.5.1 to 15.0.5.25415.0.5.255254
715.0.6.0/2415.0.6.1 to 15.0.6.25415.0.6.255254
815.0.7.0/2415.0.7.1 to 15.0.7.25415.0.7.255254
915.0.8.0/2415.0.8.1 to 15.0.8.25415.0.8.255254
1015.0.9.0/2415.0.9.1 to 15.0.9.25415.0.9.255254
1115.0.10.0/2415.0.10.1 to 15.0.10.25415.0.10.255254
1215.0.11.0/2415.0.11.1 to 15.0.11.25415.0.11.255254
1315.0.12.0/2415.0.12.1 to 15.0.12.25415.0.12.255254
1415.0.13.0/2415.0.13.1 to 15.0.13.25415.0.13.255254
1515.0.14.0/2415.0.14.1 to 15.0.14.25415.0.14.255254
1615.0.15.0/2415.0.15.1 to 15.0.15.25415.0.15.255254
1715.0.16.0/2415.0.16.1 to 15.0.16.25415.0.16.255254
1815.0.17.0/2415.0.17.1 to 15.0.17.25415.0.17.255254
1915.0.18.0/2415.0.18.1 to 15.0.18.25415.0.18.255254
2015.0.19.0/2415.0.19.1 to 15.0.19.25415.0.19.255254
2115.0.20.0/2415.0.20.1 to 15.0.20.25415.0.20.255254
2215.0.21.0/2415.0.21.1 to 15.0.21.25415.0.21.255254
2315.0.22.0/2415.0.22.1 to 15.0.22.25415.0.22.255254
2415.0.23.0/2415.0.23.1 to 15.0.23.25415.0.23.255254
2515.0.24.0/2415.0.24.1 to 15.0.24.25415.0.24.255254
2615.0.25.0/2415.0.25.1 to 15.0.25.25415.0.25.255254
2715.0.26.0/2415.0.26.1 to 15.0.26.25415.0.26.255254
2815.0.27.0/2415.0.27.1 to 15.0.27.25415.0.27.255254
2915.0.28.0/2415.0.28.1 to 15.0.28.25415.0.28.255254
3015.0.29.0/2415.0.29.1 to 15.0.29.25415.0.29.255254
3115.0.30.0/2415.0.30.1 to 15.0.30.25415.0.30.255254
3215.0.31.0/2415.0.31.1 to 15.0.31.25415.0.31.255254
3315.0.32.0/2415.0.32.1 to 15.0.32.25415.0.32.255254
3415.0.33.0/2415.0.33.1 to 15.0.33.25415.0.33.255254
3515.0.34.0/2415.0.34.1 to 15.0.34.25415.0.34.255254
3615.0.35.0/2415.0.35.1 to 15.0.35.25415.0.35.255254
3715.0.36.0/2415.0.36.1 to 15.0.36.25415.0.36.255254
3815.0.37.0/2415.0.37.1 to 15.0.37.25415.0.37.255254
3915.0.38.0/2415.0.38.1 to 15.0.38.25415.0.38.255254
4015.0.39.0/2415.0.39.1 to 15.0.39.25415.0.39.255254
4115.0.40.0/2415.0.40.1 to 15.0.40.25415.0.40.255254
4215.0.41.0/2415.0.41.1 to 15.0.41.25415.0.41.255254
4315.0.42.0/2415.0.42.1 to 15.0.42.25415.0.42.255254
4415.0.43.0/2415.0.43.1 to 15.0.43.25415.0.43.255254
4515.0.44.0/2415.0.44.1 to 15.0.44.25415.0.44.255254
4615.0.45.0/2415.0.45.1 to 15.0.45.25415.0.45.255254
4715.0.46.0/2415.0.46.1 to 15.0.46.25415.0.46.255254
4815.0.47.0/2415.0.47.1 to 15.0.47.25415.0.47.255254
4915.0.48.0/2415.0.48.1 to 15.0.48.25415.0.48.255254
5015.0.49.0/2415.0.49.1 to 15.0.49.25415.0.49.255254
5115.0.50.0/2415.0.50.1 to 15.0.50.25415.0.50.255254
5215.0.51.0/2415.0.51.1 to 15.0.51.25415.0.51.255254
5315.0.52.0/2415.0.52.1 to 15.0.52.25415.0.52.255254
5415.0.53.0/2415.0.53.1 to 15.0.53.25415.0.53.255254
5515.0.54.0/2415.0.54.1 to 15.0.54.25415.0.54.255254
5615.0.55.0/2415.0.55.1 to 15.0.55.25415.0.55.255254
5715.0.56.0/2415.0.56.1 to 15.0.56.25415.0.56.255254
5815.0.57.0/2415.0.57.1 to 15.0.57.25415.0.57.255254
5915.0.58.0/2415.0.58.1 to 15.0.58.25415.0.58.255254
6015.0.59.0/2415.0.59.1 to 15.0.59.25415.0.59.255254
6115.0.60.0/2415.0.60.1 to 15.0.60.25415.0.60.255254
6215.0.61.0/2415.0.61.1 to 15.0.61.25415.0.61.255254
6315.0.62.0/2415.0.62.1 to 15.0.62.25415.0.62.255254
6415.0.63.0/2415.0.63.1 to 15.0.63.25415.0.63.255254
6515.0.64.0/2415.0.64.1 to 15.0.64.25415.0.64.255254
6615.0.65.0/2415.0.65.1 to 15.0.65.25415.0.65.255254
6715.0.66.0/2415.0.66.1 to 15.0.66.25415.0.66.255254
6815.0.67.0/2415.0.67.1 to 15.0.67.25415.0.67.255254
6915.0.68.0/2415.0.68.1 to 15.0.68.25415.0.68.255254
7015.0.69.0/2415.0.69.1 to 15.0.69.25415.0.69.255254
7115.0.70.0/2415.0.70.1 to 15.0.70.25415.0.70.255254
7215.0.71.0/2415.0.71.1 to 15.0.71.25415.0.71.255254
7315.0.72.0/2415.0.72.1 to 15.0.72.25415.0.72.255254
7415.0.73.0/2415.0.73.1 to 15.0.73.25415.0.73.255254
7515.0.74.0/2415.0.74.1 to 15.0.74.25415.0.74.255254
7615.0.75.0/2415.0.75.1 to 15.0.75.25415.0.75.255254
7715.0.76.0/2415.0.76.1 to 15.0.76.25415.0.76.255254
7815.0.77.0/2415.0.77.1 to 15.0.77.25415.0.77.255254
7915.0.78.0/2415.0.78.1 to 15.0.78.25415.0.78.255254
8015.0.79.0/2415.0.79.1 to 15.0.79.25415.0.79.255254
8115.0.80.0/2415.0.80.1 to 15.0.80.25415.0.80.255254
8215.0.81.0/2415.0.81.1 to 15.0.81.25415.0.81.255254
8315.0.82.0/2415.0.82.1 to 15.0.82.25415.0.82.255254
8415.0.83.0/2415.0.83.1 to 15.0.83.25415.0.83.255254
8515.0.84.0/2415.0.84.1 to 15.0.84.25415.0.84.255254
8615.0.85.0/2415.0.85.1 to 15.0.85.25415.0.85.255254
8715.0.86.0/2415.0.86.1 to 15.0.86.25415.0.86.255254
8815.0.87.0/2415.0.87.1 to 15.0.87.25415.0.87.255254
8915.0.88.0/2415.0.88.1 to 15.0.88.25415.0.88.255254
9015.0.89.0/2415.0.89.1 to 15.0.89.25415.0.89.255254
9115.0.90.0/2415.0.90.1 to 15.0.90.25415.0.90.255254
9215.0.91.0/2415.0.91.1 to 15.0.91.25415.0.91.255254
9315.0.92.0/2415.0.92.1 to 15.0.92.25415.0.92.255254
9415.0.93.0/2415.0.93.1 to 15.0.93.25415.0.93.255254
9515.0.94.0/2415.0.94.1 to 15.0.94.25415.0.94.255254
9615.0.95.0/2415.0.95.1 to 15.0.95.25415.0.95.255254
9715.0.96.0/2415.0.96.1 to 15.0.96.25415.0.96.255254
9815.0.97.0/2415.0.97.1 to 15.0.97.25415.0.97.255254
9915.0.98.0/2415.0.98.1 to 15.0.98.25415.0.98.255254
10015.0.99.0/2415.0.99.1 to 15.0.99.25415.0.99.255254
10115.0.100.0/2415.0.100.1 to 15.0.100.25415.0.100.255254
10215.0.101.0/2415.0.101.1 to 15.0.101.25415.0.101.255254
10315.0.102.0/2415.0.102.1 to 15.0.102.25415.0.102.255254
10415.0.103.0/2415.0.103.1 to 15.0.103.25415.0.103.255254
10515.0.104.0/2415.0.104.1 to 15.0.104.25415.0.104.255254
10615.0.105.0/2415.0.105.1 to 15.0.105.25415.0.105.255254
10715.0.106.0/2415.0.106.1 to 15.0.106.25415.0.106.255254
10815.0.107.0/2415.0.107.1 to 15.0.107.25415.0.107.255254
10915.0.108.0/2415.0.108.1 to 15.0.108.25415.0.108.255254
11015.0.109.0/2415.0.109.1 to 15.0.109.25415.0.109.255254
11115.0.110.0/2415.0.110.1 to 15.0.110.25415.0.110.255254
11215.0.111.0/2415.0.111.1 to 15.0.111.25415.0.111.255254
11315.0.112.0/2415.0.112.1 to 15.0.112.25415.0.112.255254
11415.0.113.0/2415.0.113.1 to 15.0.113.25415.0.113.255254
11515.0.114.0/2415.0.114.1 to 15.0.114.25415.0.114.255254
11615.0.115.0/2415.0.115.1 to 15.0.115.25415.0.115.255254
11715.0.116.0/2415.0.116.1 to 15.0.116.25415.0.116.255254
11815.0.117.0/2415.0.117.1 to 15.0.117.25415.0.117.255254
11915.0.118.0/2415.0.118.1 to 15.0.118.25415.0.118.255254
12015.0.119.0/2415.0.119.1 to 15.0.119.25415.0.119.255254
12115.0.120.0/2415.0.120.1 to 15.0.120.25415.0.120.255254
12215.0.121.0/2415.0.121.1 to 15.0.121.25415.0.121.255254
12315.0.122.0/2415.0.122.1 to 15.0.122.25415.0.122.255254
12415.0.123.0/2415.0.123.1 to 15.0.123.25415.0.123.255254
12515.0.124.0/2415.0.124.1 to 15.0.124.25415.0.124.255254
12615.0.125.0/2415.0.125.1 to 15.0.125.25415.0.125.255254
12715.0.126.0/2415.0.126.1 to 15.0.126.25415.0.126.255254
12815.0.127.0/2415.0.127.1 to 15.0.127.25415.0.127.255254
12915.0.128.0/2415.0.128.1 to 15.0.128.25415.0.128.255254
13015.0.129.0/2415.0.129.1 to 15.0.129.25415.0.129.255254
13115.0.130.0/2415.0.130.1 to 15.0.130.25415.0.130.255254
13215.0.131.0/2415.0.131.1 to 15.0.131.25415.0.131.255254
13315.0.132.0/2415.0.132.1 to 15.0.132.25415.0.132.255254
13415.0.133.0/2415.0.133.1 to 15.0.133.25415.0.133.255254
13515.0.134.0/2415.0.134.1 to 15.0.134.25415.0.134.255254
13615.0.135.0/2415.0.135.1 to 15.0.135.25415.0.135.255254
13715.0.136.0/2415.0.136.1 to 15.0.136.25415.0.136.255254
13815.0.137.0/2415.0.137.1 to 15.0.137.25415.0.137.255254
13915.0.138.0/2415.0.138.1 to 15.0.138.25415.0.138.255254
14015.0.139.0/2415.0.139.1 to 15.0.139.25415.0.139.255254
14115.0.140.0/2415.0.140.1 to 15.0.140.25415.0.140.255254
14215.0.141.0/2415.0.141.1 to 15.0.141.25415.0.141.255254
14315.0.142.0/2415.0.142.1 to 15.0.142.25415.0.142.255254
14415.0.143.0/2415.0.143.1 to 15.0.143.25415.0.143.255254
14515.0.144.0/2415.0.144.1 to 15.0.144.25415.0.144.255254
14615.0.145.0/2415.0.145.1 to 15.0.145.25415.0.145.255254
14715.0.146.0/2415.0.146.1 to 15.0.146.25415.0.146.255254
14815.0.147.0/2415.0.147.1 to 15.0.147.25415.0.147.255254
14915.0.148.0/2415.0.148.1 to 15.0.148.25415.0.148.255254
15015.0.149.0/2415.0.149.1 to 15.0.149.25415.0.149.255254
15115.0.150.0/2415.0.150.1 to 15.0.150.25415.0.150.255254
15215.0.151.0/2415.0.151.1 to 15.0.151.25415.0.151.255254
15315.0.152.0/2415.0.152.1 to 15.0.152.25415.0.152.255254
15415.0.153.0/2415.0.153.1 to 15.0.153.25415.0.153.255254
15515.0.154.0/2415.0.154.1 to 15.0.154.25415.0.154.255254
15615.0.155.0/2415.0.155.1 to 15.0.155.25415.0.155.255254
15715.0.156.0/2415.0.156.1 to 15.0.156.25415.0.156.255254
15815.0.157.0/2415.0.157.1 to 15.0.157.25415.0.157.255254
15915.0.158.0/2415.0.158.1 to 15.0.158.25415.0.158.255254
16015.0.159.0/2415.0.159.1 to 15.0.159.25415.0.159.255254
16115.0.160.0/2415.0.160.1 to 15.0.160.25415.0.160.255254
16215.0.161.0/2415.0.161.1 to 15.0.161.25415.0.161.255254
16315.0.162.0/2415.0.162.1 to 15.0.162.25415.0.162.255254
16415.0.163.0/2415.0.163.1 to 15.0.163.25415.0.163.255254
16515.0.164.0/2415.0.164.1 to 15.0.164.25415.0.164.255254
16615.0.165.0/2415.0.165.1 to 15.0.165.25415.0.165.255254
16715.0.166.0/2415.0.166.1 to 15.0.166.25415.0.166.255254
16815.0.167.0/2415.0.167.1 to 15.0.167.25415.0.167.255254
16915.0.168.0/2415.0.168.1 to 15.0.168.25415.0.168.255254
17015.0.169.0/2415.0.169.1 to 15.0.169.25415.0.169.255254
17115.0.170.0/2415.0.170.1 to 15.0.170.25415.0.170.255254
17215.0.171.0/2415.0.171.1 to 15.0.171.25415.0.171.255254
17315.0.172.0/2415.0.172.1 to 15.0.172.25415.0.172.255254
17415.0.173.0/2415.0.173.1 to 15.0.173.25415.0.173.255254
17515.0.174.0/2415.0.174.1 to 15.0.174.25415.0.174.255254
17615.0.175.0/2415.0.175.1 to 15.0.175.25415.0.175.255254
17715.0.176.0/2415.0.176.1 to 15.0.176.25415.0.176.255254
17815.0.177.0/2415.0.177.1 to 15.0.177.25415.0.177.255254
17915.0.178.0/2415.0.178.1 to 15.0.178.25415.0.178.255254
18015.0.179.0/2415.0.179.1 to 15.0.179.25415.0.179.255254
18115.0.180.0/2415.0.180.1 to 15.0.180.25415.0.180.255254
18215.0.181.0/2415.0.181.1 to 15.0.181.25415.0.181.255254
18315.0.182.0/2415.0.182.1 to 15.0.182.25415.0.182.255254
18415.0.183.0/2415.0.183.1 to 15.0.183.25415.0.183.255254
18515.0.184.0/2415.0.184.1 to 15.0.184.25415.0.184.255254
18615.0.185.0/2415.0.185.1 to 15.0.185.25415.0.185.255254
18715.0.186.0/2415.0.186.1 to 15.0.186.25415.0.186.255254
18815.0.187.0/2415.0.187.1 to 15.0.187.25415.0.187.255254
18915.0.188.0/2415.0.188.1 to 15.0.188.25415.0.188.255254
19015.0.189.0/2415.0.189.1 to 15.0.189.25415.0.189.255254
19115.0.190.0/2415.0.190.1 to 15.0.190.25415.0.190.255254
19215.0.191.0/2415.0.191.1 to 15.0.191.25415.0.191.255254
19315.0.192.0/2415.0.192.1 to 15.0.192.25415.0.192.255254
19415.0.193.0/2415.0.193.1 to 15.0.193.25415.0.193.255254
19515.0.194.0/2415.0.194.1 to 15.0.194.25415.0.194.255254
19615.0.195.0/2415.0.195.1 to 15.0.195.25415.0.195.255254
19715.0.196.0/2415.0.196.1 to 15.0.196.25415.0.196.255254
19815.0.197.0/2415.0.197.1 to 15.0.197.25415.0.197.255254
19915.0.198.0/2415.0.198.1 to 15.0.198.25415.0.198.255254
20015.0.199.0/2415.0.199.1 to 15.0.199.25415.0.199.255254
20115.0.200.0/2415.0.200.1 to 15.0.200.25415.0.200.255254
20215.0.201.0/2415.0.201.1 to 15.0.201.25415.0.201.255254
20315.0.202.0/2415.0.202.1 to 15.0.202.25415.0.202.255254
20415.0.203.0/2415.0.203.1 to 15.0.203.25415.0.203.255254
20515.0.204.0/2415.0.204.1 to 15.0.204.25415.0.204.255254
20615.0.205.0/2415.0.205.1 to 15.0.205.25415.0.205.255254
20715.0.206.0/2415.0.206.1 to 15.0.206.25415.0.206.255254
20815.0.207.0/2415.0.207.1 to 15.0.207.25415.0.207.255254
20915.0.208.0/2415.0.208.1 to 15.0.208.25415.0.208.255254
21015.0.209.0/2415.0.209.1 to 15.0.209.25415.0.209.255254
21115.0.210.0/2415.0.210.1 to 15.0.210.25415.0.210.255254
21215.0.211.0/2415.0.211.1 to 15.0.211.25415.0.211.255254
21315.0.212.0/2415.0.212.1 to 15.0.212.25415.0.212.255254
21415.0.213.0/2415.0.213.1 to 15.0.213.25415.0.213.255254
21515.0.214.0/2415.0.214.1 to 15.0.214.25415.0.214.255254
21615.0.215.0/2415.0.215.1 to 15.0.215.25415.0.215.255254
21715.0.216.0/2415.0.216.1 to 15.0.216.25415.0.216.255254
21815.0.217.0/2415.0.217.1 to 15.0.217.25415.0.217.255254
21915.0.218.0/2415.0.218.1 to 15.0.218.25415.0.218.255254
22015.0.219.0/2415.0.219.1 to 15.0.219.25415.0.219.255254
22115.0.220.0/2415.0.220.1 to 15.0.220.25415.0.220.255254
22215.0.221.0/2415.0.221.1 to 15.0.221.25415.0.221.255254
22315.0.222.0/2415.0.222.1 to 15.0.222.25415.0.222.255254
22415.0.223.0/2415.0.223.1 to 15.0.223.25415.0.223.255254
22515.0.224.0/2415.0.224.1 to 15.0.224.25415.0.224.255254
22615.0.225.0/2415.0.225.1 to 15.0.225.25415.0.225.255254
22715.0.226.0/2415.0.226.1 to 15.0.226.25415.0.226.255254
22815.0.227.0/2415.0.227.1 to 15.0.227.25415.0.227.255254
22915.0.228.0/2415.0.228.1 to 15.0.228.25415.0.228.255254
23015.0.229.0/2415.0.229.1 to 15.0.229.25415.0.229.255254
23115.0.230.0/2415.0.230.1 to 15.0.230.25415.0.230.255254
23215.0.231.0/2415.0.231.1 to 15.0.231.25415.0.231.255254
23315.0.232.0/2415.0.232.1 to 15.0.232.25415.0.232.255254
23415.0.233.0/2415.0.233.1 to 15.0.233.25415.0.233.255254
23515.0.234.0/2415.0.234.1 to 15.0.234.25415.0.234.255254
23615.0.235.0/2415.0.235.1 to 15.0.235.25415.0.235.255254
23715.0.236.0/2415.0.236.1 to 15.0.236.25415.0.236.255254
23815.0.237.0/2415.0.237.1 to 15.0.237.25415.0.237.255254
23915.0.238.0/2415.0.238.1 to 15.0.238.25415.0.238.255254
24015.0.239.0/2415.0.239.1 to 15.0.239.25415.0.239.255254
24115.0.240.0/2415.0.240.1 to 15.0.240.25415.0.240.255254
24215.0.241.0/2415.0.241.1 to 15.0.241.25415.0.241.255254
24315.0.242.0/2415.0.242.1 to 15.0.242.25415.0.242.255254
24415.0.243.0/2415.0.243.1 to 15.0.243.25415.0.243.255254
24515.0.244.0/2415.0.244.1 to 15.0.244.25415.0.244.255254
24615.0.245.0/2415.0.245.1 to 15.0.245.25415.0.245.255254
24715.0.246.0/2415.0.246.1 to 15.0.246.25415.0.246.255254
24815.0.247.0/2415.0.247.1 to 15.0.247.25415.0.247.255254
24915.0.248.0/2415.0.248.1 to 15.0.248.25415.0.248.255254
25015.0.249.0/2415.0.249.1 to 15.0.249.25415.0.249.255254
25115.0.250.0/2415.0.250.1 to 15.0.250.25415.0.250.255254
25215.0.251.0/2415.0.251.1 to 15.0.251.25415.0.251.255254
25315.0.252.0/2415.0.252.1 to 15.0.252.25415.0.252.255254
25415.0.253.0/2415.0.253.1 to 15.0.253.25415.0.253.255254
25515.0.254.0/2415.0.254.1 to 15.0.254.25415.0.254.255254
25615.0.255.0/2415.0.255.1 to 15.0.255.25415.0.255.255254

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.