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.

Network166.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
166.0.0.0
Broadcast address
167.255.255.255
First usable
166.0.0.1
Last usable
167.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
B (default /16)
As numbers
Hex A6000000 · Integer 2785017856 to 2818572287
Reverse DNS zones
166.in-addr.arpa
167.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100110.00000000.00000000.00000000166.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network10100110.00000000.00000000.00000000166.0.0.0
Broadcast10100111.11111111.11111111.11111111167.255.255.255
Split into smaller subnets/16
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

166.0.0.0/7 makes 512 subnets of /16; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1166.0.0.0/16166.0.0.1 to 166.0.255.254166.0.255.25565,534
2166.1.0.0/16166.1.0.1 to 166.1.255.254166.1.255.25565,534
3166.2.0.0/16166.2.0.1 to 166.2.255.254166.2.255.25565,534
4166.3.0.0/16166.3.0.1 to 166.3.255.254166.3.255.25565,534
5166.4.0.0/16166.4.0.1 to 166.4.255.254166.4.255.25565,534
6166.5.0.0/16166.5.0.1 to 166.5.255.254166.5.255.25565,534
7166.6.0.0/16166.6.0.1 to 166.6.255.254166.6.255.25565,534
8166.7.0.0/16166.7.0.1 to 166.7.255.254166.7.255.25565,534
9166.8.0.0/16166.8.0.1 to 166.8.255.254166.8.255.25565,534
10166.9.0.0/16166.9.0.1 to 166.9.255.254166.9.255.25565,534
11166.10.0.0/16166.10.0.1 to 166.10.255.254166.10.255.25565,534
12166.11.0.0/16166.11.0.1 to 166.11.255.254166.11.255.25565,534
13166.12.0.0/16166.12.0.1 to 166.12.255.254166.12.255.25565,534
14166.13.0.0/16166.13.0.1 to 166.13.255.254166.13.255.25565,534
15166.14.0.0/16166.14.0.1 to 166.14.255.254166.14.255.25565,534
16166.15.0.0/16166.15.0.1 to 166.15.255.254166.15.255.25565,534
17166.16.0.0/16166.16.0.1 to 166.16.255.254166.16.255.25565,534
18166.17.0.0/16166.17.0.1 to 166.17.255.254166.17.255.25565,534
19166.18.0.0/16166.18.0.1 to 166.18.255.254166.18.255.25565,534
20166.19.0.0/16166.19.0.1 to 166.19.255.254166.19.255.25565,534
21166.20.0.0/16166.20.0.1 to 166.20.255.254166.20.255.25565,534
22166.21.0.0/16166.21.0.1 to 166.21.255.254166.21.255.25565,534
23166.22.0.0/16166.22.0.1 to 166.22.255.254166.22.255.25565,534
24166.23.0.0/16166.23.0.1 to 166.23.255.254166.23.255.25565,534
25166.24.0.0/16166.24.0.1 to 166.24.255.254166.24.255.25565,534
26166.25.0.0/16166.25.0.1 to 166.25.255.254166.25.255.25565,534
27166.26.0.0/16166.26.0.1 to 166.26.255.254166.26.255.25565,534
28166.27.0.0/16166.27.0.1 to 166.27.255.254166.27.255.25565,534
29166.28.0.0/16166.28.0.1 to 166.28.255.254166.28.255.25565,534
30166.29.0.0/16166.29.0.1 to 166.29.255.254166.29.255.25565,534
31166.30.0.0/16166.30.0.1 to 166.30.255.254166.30.255.25565,534
32166.31.0.0/16166.31.0.1 to 166.31.255.254166.31.255.25565,534
33166.32.0.0/16166.32.0.1 to 166.32.255.254166.32.255.25565,534
34166.33.0.0/16166.33.0.1 to 166.33.255.254166.33.255.25565,534
35166.34.0.0/16166.34.0.1 to 166.34.255.254166.34.255.25565,534
36166.35.0.0/16166.35.0.1 to 166.35.255.254166.35.255.25565,534
37166.36.0.0/16166.36.0.1 to 166.36.255.254166.36.255.25565,534
38166.37.0.0/16166.37.0.1 to 166.37.255.254166.37.255.25565,534
39166.38.0.0/16166.38.0.1 to 166.38.255.254166.38.255.25565,534
40166.39.0.0/16166.39.0.1 to 166.39.255.254166.39.255.25565,534
41166.40.0.0/16166.40.0.1 to 166.40.255.254166.40.255.25565,534
42166.41.0.0/16166.41.0.1 to 166.41.255.254166.41.255.25565,534
43166.42.0.0/16166.42.0.1 to 166.42.255.254166.42.255.25565,534
44166.43.0.0/16166.43.0.1 to 166.43.255.254166.43.255.25565,534
45166.44.0.0/16166.44.0.1 to 166.44.255.254166.44.255.25565,534
46166.45.0.0/16166.45.0.1 to 166.45.255.254166.45.255.25565,534
47166.46.0.0/16166.46.0.1 to 166.46.255.254166.46.255.25565,534
48166.47.0.0/16166.47.0.1 to 166.47.255.254166.47.255.25565,534
49166.48.0.0/16166.48.0.1 to 166.48.255.254166.48.255.25565,534
50166.49.0.0/16166.49.0.1 to 166.49.255.254166.49.255.25565,534
51166.50.0.0/16166.50.0.1 to 166.50.255.254166.50.255.25565,534
52166.51.0.0/16166.51.0.1 to 166.51.255.254166.51.255.25565,534
53166.52.0.0/16166.52.0.1 to 166.52.255.254166.52.255.25565,534
54166.53.0.0/16166.53.0.1 to 166.53.255.254166.53.255.25565,534
55166.54.0.0/16166.54.0.1 to 166.54.255.254166.54.255.25565,534
56166.55.0.0/16166.55.0.1 to 166.55.255.254166.55.255.25565,534
57166.56.0.0/16166.56.0.1 to 166.56.255.254166.56.255.25565,534
58166.57.0.0/16166.57.0.1 to 166.57.255.254166.57.255.25565,534
59166.58.0.0/16166.58.0.1 to 166.58.255.254166.58.255.25565,534
60166.59.0.0/16166.59.0.1 to 166.59.255.254166.59.255.25565,534
61166.60.0.0/16166.60.0.1 to 166.60.255.254166.60.255.25565,534
62166.61.0.0/16166.61.0.1 to 166.61.255.254166.61.255.25565,534
63166.62.0.0/16166.62.0.1 to 166.62.255.254166.62.255.25565,534
64166.63.0.0/16166.63.0.1 to 166.63.255.254166.63.255.25565,534
65166.64.0.0/16166.64.0.1 to 166.64.255.254166.64.255.25565,534
66166.65.0.0/16166.65.0.1 to 166.65.255.254166.65.255.25565,534
67166.66.0.0/16166.66.0.1 to 166.66.255.254166.66.255.25565,534
68166.67.0.0/16166.67.0.1 to 166.67.255.254166.67.255.25565,534
69166.68.0.0/16166.68.0.1 to 166.68.255.254166.68.255.25565,534
70166.69.0.0/16166.69.0.1 to 166.69.255.254166.69.255.25565,534
71166.70.0.0/16166.70.0.1 to 166.70.255.254166.70.255.25565,534
72166.71.0.0/16166.71.0.1 to 166.71.255.254166.71.255.25565,534
73166.72.0.0/16166.72.0.1 to 166.72.255.254166.72.255.25565,534
74166.73.0.0/16166.73.0.1 to 166.73.255.254166.73.255.25565,534
75166.74.0.0/16166.74.0.1 to 166.74.255.254166.74.255.25565,534
76166.75.0.0/16166.75.0.1 to 166.75.255.254166.75.255.25565,534
77166.76.0.0/16166.76.0.1 to 166.76.255.254166.76.255.25565,534
78166.77.0.0/16166.77.0.1 to 166.77.255.254166.77.255.25565,534
79166.78.0.0/16166.78.0.1 to 166.78.255.254166.78.255.25565,534
80166.79.0.0/16166.79.0.1 to 166.79.255.254166.79.255.25565,534
81166.80.0.0/16166.80.0.1 to 166.80.255.254166.80.255.25565,534
82166.81.0.0/16166.81.0.1 to 166.81.255.254166.81.255.25565,534
83166.82.0.0/16166.82.0.1 to 166.82.255.254166.82.255.25565,534
84166.83.0.0/16166.83.0.1 to 166.83.255.254166.83.255.25565,534
85166.84.0.0/16166.84.0.1 to 166.84.255.254166.84.255.25565,534
86166.85.0.0/16166.85.0.1 to 166.85.255.254166.85.255.25565,534
87166.86.0.0/16166.86.0.1 to 166.86.255.254166.86.255.25565,534
88166.87.0.0/16166.87.0.1 to 166.87.255.254166.87.255.25565,534
89166.88.0.0/16166.88.0.1 to 166.88.255.254166.88.255.25565,534
90166.89.0.0/16166.89.0.1 to 166.89.255.254166.89.255.25565,534
91166.90.0.0/16166.90.0.1 to 166.90.255.254166.90.255.25565,534
92166.91.0.0/16166.91.0.1 to 166.91.255.254166.91.255.25565,534
93166.92.0.0/16166.92.0.1 to 166.92.255.254166.92.255.25565,534
94166.93.0.0/16166.93.0.1 to 166.93.255.254166.93.255.25565,534
95166.94.0.0/16166.94.0.1 to 166.94.255.254166.94.255.25565,534
96166.95.0.0/16166.95.0.1 to 166.95.255.254166.95.255.25565,534
97166.96.0.0/16166.96.0.1 to 166.96.255.254166.96.255.25565,534
98166.97.0.0/16166.97.0.1 to 166.97.255.254166.97.255.25565,534
99166.98.0.0/16166.98.0.1 to 166.98.255.254166.98.255.25565,534
100166.99.0.0/16166.99.0.1 to 166.99.255.254166.99.255.25565,534
101166.100.0.0/16166.100.0.1 to 166.100.255.254166.100.255.25565,534
102166.101.0.0/16166.101.0.1 to 166.101.255.254166.101.255.25565,534
103166.102.0.0/16166.102.0.1 to 166.102.255.254166.102.255.25565,534
104166.103.0.0/16166.103.0.1 to 166.103.255.254166.103.255.25565,534
105166.104.0.0/16166.104.0.1 to 166.104.255.254166.104.255.25565,534
106166.105.0.0/16166.105.0.1 to 166.105.255.254166.105.255.25565,534
107166.106.0.0/16166.106.0.1 to 166.106.255.254166.106.255.25565,534
108166.107.0.0/16166.107.0.1 to 166.107.255.254166.107.255.25565,534
109166.108.0.0/16166.108.0.1 to 166.108.255.254166.108.255.25565,534
110166.109.0.0/16166.109.0.1 to 166.109.255.254166.109.255.25565,534
111166.110.0.0/16166.110.0.1 to 166.110.255.254166.110.255.25565,534
112166.111.0.0/16166.111.0.1 to 166.111.255.254166.111.255.25565,534
113166.112.0.0/16166.112.0.1 to 166.112.255.254166.112.255.25565,534
114166.113.0.0/16166.113.0.1 to 166.113.255.254166.113.255.25565,534
115166.114.0.0/16166.114.0.1 to 166.114.255.254166.114.255.25565,534
116166.115.0.0/16166.115.0.1 to 166.115.255.254166.115.255.25565,534
117166.116.0.0/16166.116.0.1 to 166.116.255.254166.116.255.25565,534
118166.117.0.0/16166.117.0.1 to 166.117.255.254166.117.255.25565,534
119166.118.0.0/16166.118.0.1 to 166.118.255.254166.118.255.25565,534
120166.119.0.0/16166.119.0.1 to 166.119.255.254166.119.255.25565,534
121166.120.0.0/16166.120.0.1 to 166.120.255.254166.120.255.25565,534
122166.121.0.0/16166.121.0.1 to 166.121.255.254166.121.255.25565,534
123166.122.0.0/16166.122.0.1 to 166.122.255.254166.122.255.25565,534
124166.123.0.0/16166.123.0.1 to 166.123.255.254166.123.255.25565,534
125166.124.0.0/16166.124.0.1 to 166.124.255.254166.124.255.25565,534
126166.125.0.0/16166.125.0.1 to 166.125.255.254166.125.255.25565,534
127166.126.0.0/16166.126.0.1 to 166.126.255.254166.126.255.25565,534
128166.127.0.0/16166.127.0.1 to 166.127.255.254166.127.255.25565,534
129166.128.0.0/16166.128.0.1 to 166.128.255.254166.128.255.25565,534
130166.129.0.0/16166.129.0.1 to 166.129.255.254166.129.255.25565,534
131166.130.0.0/16166.130.0.1 to 166.130.255.254166.130.255.25565,534
132166.131.0.0/16166.131.0.1 to 166.131.255.254166.131.255.25565,534
133166.132.0.0/16166.132.0.1 to 166.132.255.254166.132.255.25565,534
134166.133.0.0/16166.133.0.1 to 166.133.255.254166.133.255.25565,534
135166.134.0.0/16166.134.0.1 to 166.134.255.254166.134.255.25565,534
136166.135.0.0/16166.135.0.1 to 166.135.255.254166.135.255.25565,534
137166.136.0.0/16166.136.0.1 to 166.136.255.254166.136.255.25565,534
138166.137.0.0/16166.137.0.1 to 166.137.255.254166.137.255.25565,534
139166.138.0.0/16166.138.0.1 to 166.138.255.254166.138.255.25565,534
140166.139.0.0/16166.139.0.1 to 166.139.255.254166.139.255.25565,534
141166.140.0.0/16166.140.0.1 to 166.140.255.254166.140.255.25565,534
142166.141.0.0/16166.141.0.1 to 166.141.255.254166.141.255.25565,534
143166.142.0.0/16166.142.0.1 to 166.142.255.254166.142.255.25565,534
144166.143.0.0/16166.143.0.1 to 166.143.255.254166.143.255.25565,534
145166.144.0.0/16166.144.0.1 to 166.144.255.254166.144.255.25565,534
146166.145.0.0/16166.145.0.1 to 166.145.255.254166.145.255.25565,534
147166.146.0.0/16166.146.0.1 to 166.146.255.254166.146.255.25565,534
148166.147.0.0/16166.147.0.1 to 166.147.255.254166.147.255.25565,534
149166.148.0.0/16166.148.0.1 to 166.148.255.254166.148.255.25565,534
150166.149.0.0/16166.149.0.1 to 166.149.255.254166.149.255.25565,534
151166.150.0.0/16166.150.0.1 to 166.150.255.254166.150.255.25565,534
152166.151.0.0/16166.151.0.1 to 166.151.255.254166.151.255.25565,534
153166.152.0.0/16166.152.0.1 to 166.152.255.254166.152.255.25565,534
154166.153.0.0/16166.153.0.1 to 166.153.255.254166.153.255.25565,534
155166.154.0.0/16166.154.0.1 to 166.154.255.254166.154.255.25565,534
156166.155.0.0/16166.155.0.1 to 166.155.255.254166.155.255.25565,534
157166.156.0.0/16166.156.0.1 to 166.156.255.254166.156.255.25565,534
158166.157.0.0/16166.157.0.1 to 166.157.255.254166.157.255.25565,534
159166.158.0.0/16166.158.0.1 to 166.158.255.254166.158.255.25565,534
160166.159.0.0/16166.159.0.1 to 166.159.255.254166.159.255.25565,534
161166.160.0.0/16166.160.0.1 to 166.160.255.254166.160.255.25565,534
162166.161.0.0/16166.161.0.1 to 166.161.255.254166.161.255.25565,534
163166.162.0.0/16166.162.0.1 to 166.162.255.254166.162.255.25565,534
164166.163.0.0/16166.163.0.1 to 166.163.255.254166.163.255.25565,534
165166.164.0.0/16166.164.0.1 to 166.164.255.254166.164.255.25565,534
166166.165.0.0/16166.165.0.1 to 166.165.255.254166.165.255.25565,534
167166.166.0.0/16166.166.0.1 to 166.166.255.254166.166.255.25565,534
168166.167.0.0/16166.167.0.1 to 166.167.255.254166.167.255.25565,534
169166.168.0.0/16166.168.0.1 to 166.168.255.254166.168.255.25565,534
170166.169.0.0/16166.169.0.1 to 166.169.255.254166.169.255.25565,534
171166.170.0.0/16166.170.0.1 to 166.170.255.254166.170.255.25565,534
172166.171.0.0/16166.171.0.1 to 166.171.255.254166.171.255.25565,534
173166.172.0.0/16166.172.0.1 to 166.172.255.254166.172.255.25565,534
174166.173.0.0/16166.173.0.1 to 166.173.255.254166.173.255.25565,534
175166.174.0.0/16166.174.0.1 to 166.174.255.254166.174.255.25565,534
176166.175.0.0/16166.175.0.1 to 166.175.255.254166.175.255.25565,534
177166.176.0.0/16166.176.0.1 to 166.176.255.254166.176.255.25565,534
178166.177.0.0/16166.177.0.1 to 166.177.255.254166.177.255.25565,534
179166.178.0.0/16166.178.0.1 to 166.178.255.254166.178.255.25565,534
180166.179.0.0/16166.179.0.1 to 166.179.255.254166.179.255.25565,534
181166.180.0.0/16166.180.0.1 to 166.180.255.254166.180.255.25565,534
182166.181.0.0/16166.181.0.1 to 166.181.255.254166.181.255.25565,534
183166.182.0.0/16166.182.0.1 to 166.182.255.254166.182.255.25565,534
184166.183.0.0/16166.183.0.1 to 166.183.255.254166.183.255.25565,534
185166.184.0.0/16166.184.0.1 to 166.184.255.254166.184.255.25565,534
186166.185.0.0/16166.185.0.1 to 166.185.255.254166.185.255.25565,534
187166.186.0.0/16166.186.0.1 to 166.186.255.254166.186.255.25565,534
188166.187.0.0/16166.187.0.1 to 166.187.255.254166.187.255.25565,534
189166.188.0.0/16166.188.0.1 to 166.188.255.254166.188.255.25565,534
190166.189.0.0/16166.189.0.1 to 166.189.255.254166.189.255.25565,534
191166.190.0.0/16166.190.0.1 to 166.190.255.254166.190.255.25565,534
192166.191.0.0/16166.191.0.1 to 166.191.255.254166.191.255.25565,534
193166.192.0.0/16166.192.0.1 to 166.192.255.254166.192.255.25565,534
194166.193.0.0/16166.193.0.1 to 166.193.255.254166.193.255.25565,534
195166.194.0.0/16166.194.0.1 to 166.194.255.254166.194.255.25565,534
196166.195.0.0/16166.195.0.1 to 166.195.255.254166.195.255.25565,534
197166.196.0.0/16166.196.0.1 to 166.196.255.254166.196.255.25565,534
198166.197.0.0/16166.197.0.1 to 166.197.255.254166.197.255.25565,534
199166.198.0.0/16166.198.0.1 to 166.198.255.254166.198.255.25565,534
200166.199.0.0/16166.199.0.1 to 166.199.255.254166.199.255.25565,534
201166.200.0.0/16166.200.0.1 to 166.200.255.254166.200.255.25565,534
202166.201.0.0/16166.201.0.1 to 166.201.255.254166.201.255.25565,534
203166.202.0.0/16166.202.0.1 to 166.202.255.254166.202.255.25565,534
204166.203.0.0/16166.203.0.1 to 166.203.255.254166.203.255.25565,534
205166.204.0.0/16166.204.0.1 to 166.204.255.254166.204.255.25565,534
206166.205.0.0/16166.205.0.1 to 166.205.255.254166.205.255.25565,534
207166.206.0.0/16166.206.0.1 to 166.206.255.254166.206.255.25565,534
208166.207.0.0/16166.207.0.1 to 166.207.255.254166.207.255.25565,534
209166.208.0.0/16166.208.0.1 to 166.208.255.254166.208.255.25565,534
210166.209.0.0/16166.209.0.1 to 166.209.255.254166.209.255.25565,534
211166.210.0.0/16166.210.0.1 to 166.210.255.254166.210.255.25565,534
212166.211.0.0/16166.211.0.1 to 166.211.255.254166.211.255.25565,534
213166.212.0.0/16166.212.0.1 to 166.212.255.254166.212.255.25565,534
214166.213.0.0/16166.213.0.1 to 166.213.255.254166.213.255.25565,534
215166.214.0.0/16166.214.0.1 to 166.214.255.254166.214.255.25565,534
216166.215.0.0/16166.215.0.1 to 166.215.255.254166.215.255.25565,534
217166.216.0.0/16166.216.0.1 to 166.216.255.254166.216.255.25565,534
218166.217.0.0/16166.217.0.1 to 166.217.255.254166.217.255.25565,534
219166.218.0.0/16166.218.0.1 to 166.218.255.254166.218.255.25565,534
220166.219.0.0/16166.219.0.1 to 166.219.255.254166.219.255.25565,534
221166.220.0.0/16166.220.0.1 to 166.220.255.254166.220.255.25565,534
222166.221.0.0/16166.221.0.1 to 166.221.255.254166.221.255.25565,534
223166.222.0.0/16166.222.0.1 to 166.222.255.254166.222.255.25565,534
224166.223.0.0/16166.223.0.1 to 166.223.255.254166.223.255.25565,534
225166.224.0.0/16166.224.0.1 to 166.224.255.254166.224.255.25565,534
226166.225.0.0/16166.225.0.1 to 166.225.255.254166.225.255.25565,534
227166.226.0.0/16166.226.0.1 to 166.226.255.254166.226.255.25565,534
228166.227.0.0/16166.227.0.1 to 166.227.255.254166.227.255.25565,534
229166.228.0.0/16166.228.0.1 to 166.228.255.254166.228.255.25565,534
230166.229.0.0/16166.229.0.1 to 166.229.255.254166.229.255.25565,534
231166.230.0.0/16166.230.0.1 to 166.230.255.254166.230.255.25565,534
232166.231.0.0/16166.231.0.1 to 166.231.255.254166.231.255.25565,534
233166.232.0.0/16166.232.0.1 to 166.232.255.254166.232.255.25565,534
234166.233.0.0/16166.233.0.1 to 166.233.255.254166.233.255.25565,534
235166.234.0.0/16166.234.0.1 to 166.234.255.254166.234.255.25565,534
236166.235.0.0/16166.235.0.1 to 166.235.255.254166.235.255.25565,534
237166.236.0.0/16166.236.0.1 to 166.236.255.254166.236.255.25565,534
238166.237.0.0/16166.237.0.1 to 166.237.255.254166.237.255.25565,534
239166.238.0.0/16166.238.0.1 to 166.238.255.254166.238.255.25565,534
240166.239.0.0/16166.239.0.1 to 166.239.255.254166.239.255.25565,534
241166.240.0.0/16166.240.0.1 to 166.240.255.254166.240.255.25565,534
242166.241.0.0/16166.241.0.1 to 166.241.255.254166.241.255.25565,534
243166.242.0.0/16166.242.0.1 to 166.242.255.254166.242.255.25565,534
244166.243.0.0/16166.243.0.1 to 166.243.255.254166.243.255.25565,534
245166.244.0.0/16166.244.0.1 to 166.244.255.254166.244.255.25565,534
246166.245.0.0/16166.245.0.1 to 166.245.255.254166.245.255.25565,534
247166.246.0.0/16166.246.0.1 to 166.246.255.254166.246.255.25565,534
248166.247.0.0/16166.247.0.1 to 166.247.255.254166.247.255.25565,534
249166.248.0.0/16166.248.0.1 to 166.248.255.254166.248.255.25565,534
250166.249.0.0/16166.249.0.1 to 166.249.255.254166.249.255.25565,534
251166.250.0.0/16166.250.0.1 to 166.250.255.254166.250.255.25565,534
252166.251.0.0/16166.251.0.1 to 166.251.255.254166.251.255.25565,534
253166.252.0.0/16166.252.0.1 to 166.252.255.254166.252.255.25565,534
254166.253.0.0/16166.253.0.1 to 166.253.255.254166.253.255.25565,534
255166.254.0.0/16166.254.0.1 to 166.254.255.254166.254.255.25565,534
256166.255.0.0/16166.255.0.1 to 166.255.255.254166.255.255.25565,534

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.