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.

Network255.64.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
255.64.0.0
Broadcast address
255.127.255.255
First usable
255.64.0.1
Last usable
255.127.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FF400000 · Integer 4282384384 to 4286578687
Reverse DNS zones
64.255.in-addr.arpa
65.255.in-addr.arpa
66.255.in-addr.arpa
67.255.in-addr.arpa
68.255.in-addr.arpa
69.255.in-addr.arpa
70.255.in-addr.arpa
71.255.in-addr.arpa
72.255.in-addr.arpa
73.255.in-addr.arpa
74.255.in-addr.arpa
75.255.in-addr.arpa
76.255.in-addr.arpa
77.255.in-addr.arpa
78.255.in-addr.arpa
79.255.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111111.01000000.00000000.00000000255.64.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network11111111.01000000.00000000.00000000255.64.0.0
Broadcast11111111.01111111.11111111.11111111255.127.255.255
Split into smaller subnets/19
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

255.64.0.0/10 makes 512 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1255.64.0.0/19255.64.0.1 to 255.64.31.254255.64.31.2558,190
2255.64.32.0/19255.64.32.1 to 255.64.63.254255.64.63.2558,190
3255.64.64.0/19255.64.64.1 to 255.64.95.254255.64.95.2558,190
4255.64.96.0/19255.64.96.1 to 255.64.127.254255.64.127.2558,190
5255.64.128.0/19255.64.128.1 to 255.64.159.254255.64.159.2558,190
6255.64.160.0/19255.64.160.1 to 255.64.191.254255.64.191.2558,190
7255.64.192.0/19255.64.192.1 to 255.64.223.254255.64.223.2558,190
8255.64.224.0/19255.64.224.1 to 255.64.255.254255.64.255.2558,190
9255.65.0.0/19255.65.0.1 to 255.65.31.254255.65.31.2558,190
10255.65.32.0/19255.65.32.1 to 255.65.63.254255.65.63.2558,190
11255.65.64.0/19255.65.64.1 to 255.65.95.254255.65.95.2558,190
12255.65.96.0/19255.65.96.1 to 255.65.127.254255.65.127.2558,190
13255.65.128.0/19255.65.128.1 to 255.65.159.254255.65.159.2558,190
14255.65.160.0/19255.65.160.1 to 255.65.191.254255.65.191.2558,190
15255.65.192.0/19255.65.192.1 to 255.65.223.254255.65.223.2558,190
16255.65.224.0/19255.65.224.1 to 255.65.255.254255.65.255.2558,190
17255.66.0.0/19255.66.0.1 to 255.66.31.254255.66.31.2558,190
18255.66.32.0/19255.66.32.1 to 255.66.63.254255.66.63.2558,190
19255.66.64.0/19255.66.64.1 to 255.66.95.254255.66.95.2558,190
20255.66.96.0/19255.66.96.1 to 255.66.127.254255.66.127.2558,190
21255.66.128.0/19255.66.128.1 to 255.66.159.254255.66.159.2558,190
22255.66.160.0/19255.66.160.1 to 255.66.191.254255.66.191.2558,190
23255.66.192.0/19255.66.192.1 to 255.66.223.254255.66.223.2558,190
24255.66.224.0/19255.66.224.1 to 255.66.255.254255.66.255.2558,190
25255.67.0.0/19255.67.0.1 to 255.67.31.254255.67.31.2558,190
26255.67.32.0/19255.67.32.1 to 255.67.63.254255.67.63.2558,190
27255.67.64.0/19255.67.64.1 to 255.67.95.254255.67.95.2558,190
28255.67.96.0/19255.67.96.1 to 255.67.127.254255.67.127.2558,190
29255.67.128.0/19255.67.128.1 to 255.67.159.254255.67.159.2558,190
30255.67.160.0/19255.67.160.1 to 255.67.191.254255.67.191.2558,190
31255.67.192.0/19255.67.192.1 to 255.67.223.254255.67.223.2558,190
32255.67.224.0/19255.67.224.1 to 255.67.255.254255.67.255.2558,190
33255.68.0.0/19255.68.0.1 to 255.68.31.254255.68.31.2558,190
34255.68.32.0/19255.68.32.1 to 255.68.63.254255.68.63.2558,190
35255.68.64.0/19255.68.64.1 to 255.68.95.254255.68.95.2558,190
36255.68.96.0/19255.68.96.1 to 255.68.127.254255.68.127.2558,190
37255.68.128.0/19255.68.128.1 to 255.68.159.254255.68.159.2558,190
38255.68.160.0/19255.68.160.1 to 255.68.191.254255.68.191.2558,190
39255.68.192.0/19255.68.192.1 to 255.68.223.254255.68.223.2558,190
40255.68.224.0/19255.68.224.1 to 255.68.255.254255.68.255.2558,190
41255.69.0.0/19255.69.0.1 to 255.69.31.254255.69.31.2558,190
42255.69.32.0/19255.69.32.1 to 255.69.63.254255.69.63.2558,190
43255.69.64.0/19255.69.64.1 to 255.69.95.254255.69.95.2558,190
44255.69.96.0/19255.69.96.1 to 255.69.127.254255.69.127.2558,190
45255.69.128.0/19255.69.128.1 to 255.69.159.254255.69.159.2558,190
46255.69.160.0/19255.69.160.1 to 255.69.191.254255.69.191.2558,190
47255.69.192.0/19255.69.192.1 to 255.69.223.254255.69.223.2558,190
48255.69.224.0/19255.69.224.1 to 255.69.255.254255.69.255.2558,190
49255.70.0.0/19255.70.0.1 to 255.70.31.254255.70.31.2558,190
50255.70.32.0/19255.70.32.1 to 255.70.63.254255.70.63.2558,190
51255.70.64.0/19255.70.64.1 to 255.70.95.254255.70.95.2558,190
52255.70.96.0/19255.70.96.1 to 255.70.127.254255.70.127.2558,190
53255.70.128.0/19255.70.128.1 to 255.70.159.254255.70.159.2558,190
54255.70.160.0/19255.70.160.1 to 255.70.191.254255.70.191.2558,190
55255.70.192.0/19255.70.192.1 to 255.70.223.254255.70.223.2558,190
56255.70.224.0/19255.70.224.1 to 255.70.255.254255.70.255.2558,190
57255.71.0.0/19255.71.0.1 to 255.71.31.254255.71.31.2558,190
58255.71.32.0/19255.71.32.1 to 255.71.63.254255.71.63.2558,190
59255.71.64.0/19255.71.64.1 to 255.71.95.254255.71.95.2558,190
60255.71.96.0/19255.71.96.1 to 255.71.127.254255.71.127.2558,190
61255.71.128.0/19255.71.128.1 to 255.71.159.254255.71.159.2558,190
62255.71.160.0/19255.71.160.1 to 255.71.191.254255.71.191.2558,190
63255.71.192.0/19255.71.192.1 to 255.71.223.254255.71.223.2558,190
64255.71.224.0/19255.71.224.1 to 255.71.255.254255.71.255.2558,190
65255.72.0.0/19255.72.0.1 to 255.72.31.254255.72.31.2558,190
66255.72.32.0/19255.72.32.1 to 255.72.63.254255.72.63.2558,190
67255.72.64.0/19255.72.64.1 to 255.72.95.254255.72.95.2558,190
68255.72.96.0/19255.72.96.1 to 255.72.127.254255.72.127.2558,190
69255.72.128.0/19255.72.128.1 to 255.72.159.254255.72.159.2558,190
70255.72.160.0/19255.72.160.1 to 255.72.191.254255.72.191.2558,190
71255.72.192.0/19255.72.192.1 to 255.72.223.254255.72.223.2558,190
72255.72.224.0/19255.72.224.1 to 255.72.255.254255.72.255.2558,190
73255.73.0.0/19255.73.0.1 to 255.73.31.254255.73.31.2558,190
74255.73.32.0/19255.73.32.1 to 255.73.63.254255.73.63.2558,190
75255.73.64.0/19255.73.64.1 to 255.73.95.254255.73.95.2558,190
76255.73.96.0/19255.73.96.1 to 255.73.127.254255.73.127.2558,190
77255.73.128.0/19255.73.128.1 to 255.73.159.254255.73.159.2558,190
78255.73.160.0/19255.73.160.1 to 255.73.191.254255.73.191.2558,190
79255.73.192.0/19255.73.192.1 to 255.73.223.254255.73.223.2558,190
80255.73.224.0/19255.73.224.1 to 255.73.255.254255.73.255.2558,190
81255.74.0.0/19255.74.0.1 to 255.74.31.254255.74.31.2558,190
82255.74.32.0/19255.74.32.1 to 255.74.63.254255.74.63.2558,190
83255.74.64.0/19255.74.64.1 to 255.74.95.254255.74.95.2558,190
84255.74.96.0/19255.74.96.1 to 255.74.127.254255.74.127.2558,190
85255.74.128.0/19255.74.128.1 to 255.74.159.254255.74.159.2558,190
86255.74.160.0/19255.74.160.1 to 255.74.191.254255.74.191.2558,190
87255.74.192.0/19255.74.192.1 to 255.74.223.254255.74.223.2558,190
88255.74.224.0/19255.74.224.1 to 255.74.255.254255.74.255.2558,190
89255.75.0.0/19255.75.0.1 to 255.75.31.254255.75.31.2558,190
90255.75.32.0/19255.75.32.1 to 255.75.63.254255.75.63.2558,190
91255.75.64.0/19255.75.64.1 to 255.75.95.254255.75.95.2558,190
92255.75.96.0/19255.75.96.1 to 255.75.127.254255.75.127.2558,190
93255.75.128.0/19255.75.128.1 to 255.75.159.254255.75.159.2558,190
94255.75.160.0/19255.75.160.1 to 255.75.191.254255.75.191.2558,190
95255.75.192.0/19255.75.192.1 to 255.75.223.254255.75.223.2558,190
96255.75.224.0/19255.75.224.1 to 255.75.255.254255.75.255.2558,190
97255.76.0.0/19255.76.0.1 to 255.76.31.254255.76.31.2558,190
98255.76.32.0/19255.76.32.1 to 255.76.63.254255.76.63.2558,190
99255.76.64.0/19255.76.64.1 to 255.76.95.254255.76.95.2558,190
100255.76.96.0/19255.76.96.1 to 255.76.127.254255.76.127.2558,190
101255.76.128.0/19255.76.128.1 to 255.76.159.254255.76.159.2558,190
102255.76.160.0/19255.76.160.1 to 255.76.191.254255.76.191.2558,190
103255.76.192.0/19255.76.192.1 to 255.76.223.254255.76.223.2558,190
104255.76.224.0/19255.76.224.1 to 255.76.255.254255.76.255.2558,190
105255.77.0.0/19255.77.0.1 to 255.77.31.254255.77.31.2558,190
106255.77.32.0/19255.77.32.1 to 255.77.63.254255.77.63.2558,190
107255.77.64.0/19255.77.64.1 to 255.77.95.254255.77.95.2558,190
108255.77.96.0/19255.77.96.1 to 255.77.127.254255.77.127.2558,190
109255.77.128.0/19255.77.128.1 to 255.77.159.254255.77.159.2558,190
110255.77.160.0/19255.77.160.1 to 255.77.191.254255.77.191.2558,190
111255.77.192.0/19255.77.192.1 to 255.77.223.254255.77.223.2558,190
112255.77.224.0/19255.77.224.1 to 255.77.255.254255.77.255.2558,190
113255.78.0.0/19255.78.0.1 to 255.78.31.254255.78.31.2558,190
114255.78.32.0/19255.78.32.1 to 255.78.63.254255.78.63.2558,190
115255.78.64.0/19255.78.64.1 to 255.78.95.254255.78.95.2558,190
116255.78.96.0/19255.78.96.1 to 255.78.127.254255.78.127.2558,190
117255.78.128.0/19255.78.128.1 to 255.78.159.254255.78.159.2558,190
118255.78.160.0/19255.78.160.1 to 255.78.191.254255.78.191.2558,190
119255.78.192.0/19255.78.192.1 to 255.78.223.254255.78.223.2558,190
120255.78.224.0/19255.78.224.1 to 255.78.255.254255.78.255.2558,190
121255.79.0.0/19255.79.0.1 to 255.79.31.254255.79.31.2558,190
122255.79.32.0/19255.79.32.1 to 255.79.63.254255.79.63.2558,190
123255.79.64.0/19255.79.64.1 to 255.79.95.254255.79.95.2558,190
124255.79.96.0/19255.79.96.1 to 255.79.127.254255.79.127.2558,190
125255.79.128.0/19255.79.128.1 to 255.79.159.254255.79.159.2558,190
126255.79.160.0/19255.79.160.1 to 255.79.191.254255.79.191.2558,190
127255.79.192.0/19255.79.192.1 to 255.79.223.254255.79.223.2558,190
128255.79.224.0/19255.79.224.1 to 255.79.255.254255.79.255.2558,190
129255.80.0.0/19255.80.0.1 to 255.80.31.254255.80.31.2558,190
130255.80.32.0/19255.80.32.1 to 255.80.63.254255.80.63.2558,190
131255.80.64.0/19255.80.64.1 to 255.80.95.254255.80.95.2558,190
132255.80.96.0/19255.80.96.1 to 255.80.127.254255.80.127.2558,190
133255.80.128.0/19255.80.128.1 to 255.80.159.254255.80.159.2558,190
134255.80.160.0/19255.80.160.1 to 255.80.191.254255.80.191.2558,190
135255.80.192.0/19255.80.192.1 to 255.80.223.254255.80.223.2558,190
136255.80.224.0/19255.80.224.1 to 255.80.255.254255.80.255.2558,190
137255.81.0.0/19255.81.0.1 to 255.81.31.254255.81.31.2558,190
138255.81.32.0/19255.81.32.1 to 255.81.63.254255.81.63.2558,190
139255.81.64.0/19255.81.64.1 to 255.81.95.254255.81.95.2558,190
140255.81.96.0/19255.81.96.1 to 255.81.127.254255.81.127.2558,190
141255.81.128.0/19255.81.128.1 to 255.81.159.254255.81.159.2558,190
142255.81.160.0/19255.81.160.1 to 255.81.191.254255.81.191.2558,190
143255.81.192.0/19255.81.192.1 to 255.81.223.254255.81.223.2558,190
144255.81.224.0/19255.81.224.1 to 255.81.255.254255.81.255.2558,190
145255.82.0.0/19255.82.0.1 to 255.82.31.254255.82.31.2558,190
146255.82.32.0/19255.82.32.1 to 255.82.63.254255.82.63.2558,190
147255.82.64.0/19255.82.64.1 to 255.82.95.254255.82.95.2558,190
148255.82.96.0/19255.82.96.1 to 255.82.127.254255.82.127.2558,190
149255.82.128.0/19255.82.128.1 to 255.82.159.254255.82.159.2558,190
150255.82.160.0/19255.82.160.1 to 255.82.191.254255.82.191.2558,190
151255.82.192.0/19255.82.192.1 to 255.82.223.254255.82.223.2558,190
152255.82.224.0/19255.82.224.1 to 255.82.255.254255.82.255.2558,190
153255.83.0.0/19255.83.0.1 to 255.83.31.254255.83.31.2558,190
154255.83.32.0/19255.83.32.1 to 255.83.63.254255.83.63.2558,190
155255.83.64.0/19255.83.64.1 to 255.83.95.254255.83.95.2558,190
156255.83.96.0/19255.83.96.1 to 255.83.127.254255.83.127.2558,190
157255.83.128.0/19255.83.128.1 to 255.83.159.254255.83.159.2558,190
158255.83.160.0/19255.83.160.1 to 255.83.191.254255.83.191.2558,190
159255.83.192.0/19255.83.192.1 to 255.83.223.254255.83.223.2558,190
160255.83.224.0/19255.83.224.1 to 255.83.255.254255.83.255.2558,190
161255.84.0.0/19255.84.0.1 to 255.84.31.254255.84.31.2558,190
162255.84.32.0/19255.84.32.1 to 255.84.63.254255.84.63.2558,190
163255.84.64.0/19255.84.64.1 to 255.84.95.254255.84.95.2558,190
164255.84.96.0/19255.84.96.1 to 255.84.127.254255.84.127.2558,190
165255.84.128.0/19255.84.128.1 to 255.84.159.254255.84.159.2558,190
166255.84.160.0/19255.84.160.1 to 255.84.191.254255.84.191.2558,190
167255.84.192.0/19255.84.192.1 to 255.84.223.254255.84.223.2558,190
168255.84.224.0/19255.84.224.1 to 255.84.255.254255.84.255.2558,190
169255.85.0.0/19255.85.0.1 to 255.85.31.254255.85.31.2558,190
170255.85.32.0/19255.85.32.1 to 255.85.63.254255.85.63.2558,190
171255.85.64.0/19255.85.64.1 to 255.85.95.254255.85.95.2558,190
172255.85.96.0/19255.85.96.1 to 255.85.127.254255.85.127.2558,190
173255.85.128.0/19255.85.128.1 to 255.85.159.254255.85.159.2558,190
174255.85.160.0/19255.85.160.1 to 255.85.191.254255.85.191.2558,190
175255.85.192.0/19255.85.192.1 to 255.85.223.254255.85.223.2558,190
176255.85.224.0/19255.85.224.1 to 255.85.255.254255.85.255.2558,190
177255.86.0.0/19255.86.0.1 to 255.86.31.254255.86.31.2558,190
178255.86.32.0/19255.86.32.1 to 255.86.63.254255.86.63.2558,190
179255.86.64.0/19255.86.64.1 to 255.86.95.254255.86.95.2558,190
180255.86.96.0/19255.86.96.1 to 255.86.127.254255.86.127.2558,190
181255.86.128.0/19255.86.128.1 to 255.86.159.254255.86.159.2558,190
182255.86.160.0/19255.86.160.1 to 255.86.191.254255.86.191.2558,190
183255.86.192.0/19255.86.192.1 to 255.86.223.254255.86.223.2558,190
184255.86.224.0/19255.86.224.1 to 255.86.255.254255.86.255.2558,190
185255.87.0.0/19255.87.0.1 to 255.87.31.254255.87.31.2558,190
186255.87.32.0/19255.87.32.1 to 255.87.63.254255.87.63.2558,190
187255.87.64.0/19255.87.64.1 to 255.87.95.254255.87.95.2558,190
188255.87.96.0/19255.87.96.1 to 255.87.127.254255.87.127.2558,190
189255.87.128.0/19255.87.128.1 to 255.87.159.254255.87.159.2558,190
190255.87.160.0/19255.87.160.1 to 255.87.191.254255.87.191.2558,190
191255.87.192.0/19255.87.192.1 to 255.87.223.254255.87.223.2558,190
192255.87.224.0/19255.87.224.1 to 255.87.255.254255.87.255.2558,190
193255.88.0.0/19255.88.0.1 to 255.88.31.254255.88.31.2558,190
194255.88.32.0/19255.88.32.1 to 255.88.63.254255.88.63.2558,190
195255.88.64.0/19255.88.64.1 to 255.88.95.254255.88.95.2558,190
196255.88.96.0/19255.88.96.1 to 255.88.127.254255.88.127.2558,190
197255.88.128.0/19255.88.128.1 to 255.88.159.254255.88.159.2558,190
198255.88.160.0/19255.88.160.1 to 255.88.191.254255.88.191.2558,190
199255.88.192.0/19255.88.192.1 to 255.88.223.254255.88.223.2558,190
200255.88.224.0/19255.88.224.1 to 255.88.255.254255.88.255.2558,190
201255.89.0.0/19255.89.0.1 to 255.89.31.254255.89.31.2558,190
202255.89.32.0/19255.89.32.1 to 255.89.63.254255.89.63.2558,190
203255.89.64.0/19255.89.64.1 to 255.89.95.254255.89.95.2558,190
204255.89.96.0/19255.89.96.1 to 255.89.127.254255.89.127.2558,190
205255.89.128.0/19255.89.128.1 to 255.89.159.254255.89.159.2558,190
206255.89.160.0/19255.89.160.1 to 255.89.191.254255.89.191.2558,190
207255.89.192.0/19255.89.192.1 to 255.89.223.254255.89.223.2558,190
208255.89.224.0/19255.89.224.1 to 255.89.255.254255.89.255.2558,190
209255.90.0.0/19255.90.0.1 to 255.90.31.254255.90.31.2558,190
210255.90.32.0/19255.90.32.1 to 255.90.63.254255.90.63.2558,190
211255.90.64.0/19255.90.64.1 to 255.90.95.254255.90.95.2558,190
212255.90.96.0/19255.90.96.1 to 255.90.127.254255.90.127.2558,190
213255.90.128.0/19255.90.128.1 to 255.90.159.254255.90.159.2558,190
214255.90.160.0/19255.90.160.1 to 255.90.191.254255.90.191.2558,190
215255.90.192.0/19255.90.192.1 to 255.90.223.254255.90.223.2558,190
216255.90.224.0/19255.90.224.1 to 255.90.255.254255.90.255.2558,190
217255.91.0.0/19255.91.0.1 to 255.91.31.254255.91.31.2558,190
218255.91.32.0/19255.91.32.1 to 255.91.63.254255.91.63.2558,190
219255.91.64.0/19255.91.64.1 to 255.91.95.254255.91.95.2558,190
220255.91.96.0/19255.91.96.1 to 255.91.127.254255.91.127.2558,190
221255.91.128.0/19255.91.128.1 to 255.91.159.254255.91.159.2558,190
222255.91.160.0/19255.91.160.1 to 255.91.191.254255.91.191.2558,190
223255.91.192.0/19255.91.192.1 to 255.91.223.254255.91.223.2558,190
224255.91.224.0/19255.91.224.1 to 255.91.255.254255.91.255.2558,190
225255.92.0.0/19255.92.0.1 to 255.92.31.254255.92.31.2558,190
226255.92.32.0/19255.92.32.1 to 255.92.63.254255.92.63.2558,190
227255.92.64.0/19255.92.64.1 to 255.92.95.254255.92.95.2558,190
228255.92.96.0/19255.92.96.1 to 255.92.127.254255.92.127.2558,190
229255.92.128.0/19255.92.128.1 to 255.92.159.254255.92.159.2558,190
230255.92.160.0/19255.92.160.1 to 255.92.191.254255.92.191.2558,190
231255.92.192.0/19255.92.192.1 to 255.92.223.254255.92.223.2558,190
232255.92.224.0/19255.92.224.1 to 255.92.255.254255.92.255.2558,190
233255.93.0.0/19255.93.0.1 to 255.93.31.254255.93.31.2558,190
234255.93.32.0/19255.93.32.1 to 255.93.63.254255.93.63.2558,190
235255.93.64.0/19255.93.64.1 to 255.93.95.254255.93.95.2558,190
236255.93.96.0/19255.93.96.1 to 255.93.127.254255.93.127.2558,190
237255.93.128.0/19255.93.128.1 to 255.93.159.254255.93.159.2558,190
238255.93.160.0/19255.93.160.1 to 255.93.191.254255.93.191.2558,190
239255.93.192.0/19255.93.192.1 to 255.93.223.254255.93.223.2558,190
240255.93.224.0/19255.93.224.1 to 255.93.255.254255.93.255.2558,190
241255.94.0.0/19255.94.0.1 to 255.94.31.254255.94.31.2558,190
242255.94.32.0/19255.94.32.1 to 255.94.63.254255.94.63.2558,190
243255.94.64.0/19255.94.64.1 to 255.94.95.254255.94.95.2558,190
244255.94.96.0/19255.94.96.1 to 255.94.127.254255.94.127.2558,190
245255.94.128.0/19255.94.128.1 to 255.94.159.254255.94.159.2558,190
246255.94.160.0/19255.94.160.1 to 255.94.191.254255.94.191.2558,190
247255.94.192.0/19255.94.192.1 to 255.94.223.254255.94.223.2558,190
248255.94.224.0/19255.94.224.1 to 255.94.255.254255.94.255.2558,190
249255.95.0.0/19255.95.0.1 to 255.95.31.254255.95.31.2558,190
250255.95.32.0/19255.95.32.1 to 255.95.63.254255.95.63.2558,190
251255.95.64.0/19255.95.64.1 to 255.95.95.254255.95.95.2558,190
252255.95.96.0/19255.95.96.1 to 255.95.127.254255.95.127.2558,190
253255.95.128.0/19255.95.128.1 to 255.95.159.254255.95.159.2558,190
254255.95.160.0/19255.95.160.1 to 255.95.191.254255.95.191.2558,190
255255.95.192.0/19255.95.192.1 to 255.95.223.254255.95.223.2558,190
256255.95.224.0/19255.95.224.1 to 255.95.255.254255.95.255.2558,190

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.