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.

Network0.0.0.0/0
Usable hosts4,294,967,294
Subnet mask0.0.0.0
Addresses4,294,967,296
Network address
0.0.0.0
Broadcast address
255.255.255.255
First usable
0.0.0.1
Last usable
255.255.255.254
Usable hosts
4,294,967,294 (4,294,967,296 less the network and broadcast addresses)
Subnet mask
0.0.0.0
Wildcard mask
255.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/0
Type
Public public
Old class
A (default /8)
As numbers
Hex 00000000 · Integer 0 to 4294967295
Reverse DNS zone
in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00000000.00000000.00000000.000000000.0.0.0
Subnet mask00000000.00000000.00000000.000000000.0.0.0
Network00000000.00000000.00000000.000000000.0.0.0
Broadcast11111111.11111111.11111111.11111111255.255.255.255
Split into smaller subnets/8
/1 (2)/2 (4)/3 (8)/4 (16)/5 (32)/6 (64)/7 (128)/8 (256)/9 (512)/10 (1,024)/11 (2,048)/12 (4,096)

0.0.0.0/0 makes 256 subnets of /8.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
10.0.0.0/80.0.0.1 to 0.255.255.2540.255.255.25516,777,214
21.0.0.0/81.0.0.1 to 1.255.255.2541.255.255.25516,777,214
32.0.0.0/82.0.0.1 to 2.255.255.2542.255.255.25516,777,214
43.0.0.0/83.0.0.1 to 3.255.255.2543.255.255.25516,777,214
54.0.0.0/84.0.0.1 to 4.255.255.2544.255.255.25516,777,214
65.0.0.0/85.0.0.1 to 5.255.255.2545.255.255.25516,777,214
76.0.0.0/86.0.0.1 to 6.255.255.2546.255.255.25516,777,214
87.0.0.0/87.0.0.1 to 7.255.255.2547.255.255.25516,777,214
98.0.0.0/88.0.0.1 to 8.255.255.2548.255.255.25516,777,214
109.0.0.0/89.0.0.1 to 9.255.255.2549.255.255.25516,777,214
1110.0.0.0/810.0.0.1 to 10.255.255.25410.255.255.25516,777,214
1211.0.0.0/811.0.0.1 to 11.255.255.25411.255.255.25516,777,214
1312.0.0.0/812.0.0.1 to 12.255.255.25412.255.255.25516,777,214
1413.0.0.0/813.0.0.1 to 13.255.255.25413.255.255.25516,777,214
1514.0.0.0/814.0.0.1 to 14.255.255.25414.255.255.25516,777,214
1615.0.0.0/815.0.0.1 to 15.255.255.25415.255.255.25516,777,214
1716.0.0.0/816.0.0.1 to 16.255.255.25416.255.255.25516,777,214
1817.0.0.0/817.0.0.1 to 17.255.255.25417.255.255.25516,777,214
1918.0.0.0/818.0.0.1 to 18.255.255.25418.255.255.25516,777,214
2019.0.0.0/819.0.0.1 to 19.255.255.25419.255.255.25516,777,214
2120.0.0.0/820.0.0.1 to 20.255.255.25420.255.255.25516,777,214
2221.0.0.0/821.0.0.1 to 21.255.255.25421.255.255.25516,777,214
2322.0.0.0/822.0.0.1 to 22.255.255.25422.255.255.25516,777,214
2423.0.0.0/823.0.0.1 to 23.255.255.25423.255.255.25516,777,214
2524.0.0.0/824.0.0.1 to 24.255.255.25424.255.255.25516,777,214
2625.0.0.0/825.0.0.1 to 25.255.255.25425.255.255.25516,777,214
2726.0.0.0/826.0.0.1 to 26.255.255.25426.255.255.25516,777,214
2827.0.0.0/827.0.0.1 to 27.255.255.25427.255.255.25516,777,214
2928.0.0.0/828.0.0.1 to 28.255.255.25428.255.255.25516,777,214
3029.0.0.0/829.0.0.1 to 29.255.255.25429.255.255.25516,777,214
3130.0.0.0/830.0.0.1 to 30.255.255.25430.255.255.25516,777,214
3231.0.0.0/831.0.0.1 to 31.255.255.25431.255.255.25516,777,214
3332.0.0.0/832.0.0.1 to 32.255.255.25432.255.255.25516,777,214
3433.0.0.0/833.0.0.1 to 33.255.255.25433.255.255.25516,777,214
3534.0.0.0/834.0.0.1 to 34.255.255.25434.255.255.25516,777,214
3635.0.0.0/835.0.0.1 to 35.255.255.25435.255.255.25516,777,214
3736.0.0.0/836.0.0.1 to 36.255.255.25436.255.255.25516,777,214
3837.0.0.0/837.0.0.1 to 37.255.255.25437.255.255.25516,777,214
3938.0.0.0/838.0.0.1 to 38.255.255.25438.255.255.25516,777,214
4039.0.0.0/839.0.0.1 to 39.255.255.25439.255.255.25516,777,214
4140.0.0.0/840.0.0.1 to 40.255.255.25440.255.255.25516,777,214
4241.0.0.0/841.0.0.1 to 41.255.255.25441.255.255.25516,777,214
4342.0.0.0/842.0.0.1 to 42.255.255.25442.255.255.25516,777,214
4443.0.0.0/843.0.0.1 to 43.255.255.25443.255.255.25516,777,214
4544.0.0.0/844.0.0.1 to 44.255.255.25444.255.255.25516,777,214
4645.0.0.0/845.0.0.1 to 45.255.255.25445.255.255.25516,777,214
4746.0.0.0/846.0.0.1 to 46.255.255.25446.255.255.25516,777,214
4847.0.0.0/847.0.0.1 to 47.255.255.25447.255.255.25516,777,214
4948.0.0.0/848.0.0.1 to 48.255.255.25448.255.255.25516,777,214
5049.0.0.0/849.0.0.1 to 49.255.255.25449.255.255.25516,777,214
5150.0.0.0/850.0.0.1 to 50.255.255.25450.255.255.25516,777,214
5251.0.0.0/851.0.0.1 to 51.255.255.25451.255.255.25516,777,214
5352.0.0.0/852.0.0.1 to 52.255.255.25452.255.255.25516,777,214
5453.0.0.0/853.0.0.1 to 53.255.255.25453.255.255.25516,777,214
5554.0.0.0/854.0.0.1 to 54.255.255.25454.255.255.25516,777,214
5655.0.0.0/855.0.0.1 to 55.255.255.25455.255.255.25516,777,214
5756.0.0.0/856.0.0.1 to 56.255.255.25456.255.255.25516,777,214
5857.0.0.0/857.0.0.1 to 57.255.255.25457.255.255.25516,777,214
5958.0.0.0/858.0.0.1 to 58.255.255.25458.255.255.25516,777,214
6059.0.0.0/859.0.0.1 to 59.255.255.25459.255.255.25516,777,214
6160.0.0.0/860.0.0.1 to 60.255.255.25460.255.255.25516,777,214
6261.0.0.0/861.0.0.1 to 61.255.255.25461.255.255.25516,777,214
6362.0.0.0/862.0.0.1 to 62.255.255.25462.255.255.25516,777,214
6463.0.0.0/863.0.0.1 to 63.255.255.25463.255.255.25516,777,214
6564.0.0.0/864.0.0.1 to 64.255.255.25464.255.255.25516,777,214
6665.0.0.0/865.0.0.1 to 65.255.255.25465.255.255.25516,777,214
6766.0.0.0/866.0.0.1 to 66.255.255.25466.255.255.25516,777,214
6867.0.0.0/867.0.0.1 to 67.255.255.25467.255.255.25516,777,214
6968.0.0.0/868.0.0.1 to 68.255.255.25468.255.255.25516,777,214
7069.0.0.0/869.0.0.1 to 69.255.255.25469.255.255.25516,777,214
7170.0.0.0/870.0.0.1 to 70.255.255.25470.255.255.25516,777,214
7271.0.0.0/871.0.0.1 to 71.255.255.25471.255.255.25516,777,214
7372.0.0.0/872.0.0.1 to 72.255.255.25472.255.255.25516,777,214
7473.0.0.0/873.0.0.1 to 73.255.255.25473.255.255.25516,777,214
7574.0.0.0/874.0.0.1 to 74.255.255.25474.255.255.25516,777,214
7675.0.0.0/875.0.0.1 to 75.255.255.25475.255.255.25516,777,214
7776.0.0.0/876.0.0.1 to 76.255.255.25476.255.255.25516,777,214
7877.0.0.0/877.0.0.1 to 77.255.255.25477.255.255.25516,777,214
7978.0.0.0/878.0.0.1 to 78.255.255.25478.255.255.25516,777,214
8079.0.0.0/879.0.0.1 to 79.255.255.25479.255.255.25516,777,214
8180.0.0.0/880.0.0.1 to 80.255.255.25480.255.255.25516,777,214
8281.0.0.0/881.0.0.1 to 81.255.255.25481.255.255.25516,777,214
8382.0.0.0/882.0.0.1 to 82.255.255.25482.255.255.25516,777,214
8483.0.0.0/883.0.0.1 to 83.255.255.25483.255.255.25516,777,214
8584.0.0.0/884.0.0.1 to 84.255.255.25484.255.255.25516,777,214
8685.0.0.0/885.0.0.1 to 85.255.255.25485.255.255.25516,777,214
8786.0.0.0/886.0.0.1 to 86.255.255.25486.255.255.25516,777,214
8887.0.0.0/887.0.0.1 to 87.255.255.25487.255.255.25516,777,214
8988.0.0.0/888.0.0.1 to 88.255.255.25488.255.255.25516,777,214
9089.0.0.0/889.0.0.1 to 89.255.255.25489.255.255.25516,777,214
9190.0.0.0/890.0.0.1 to 90.255.255.25490.255.255.25516,777,214
9291.0.0.0/891.0.0.1 to 91.255.255.25491.255.255.25516,777,214
9392.0.0.0/892.0.0.1 to 92.255.255.25492.255.255.25516,777,214
9493.0.0.0/893.0.0.1 to 93.255.255.25493.255.255.25516,777,214
9594.0.0.0/894.0.0.1 to 94.255.255.25494.255.255.25516,777,214
9695.0.0.0/895.0.0.1 to 95.255.255.25495.255.255.25516,777,214
9796.0.0.0/896.0.0.1 to 96.255.255.25496.255.255.25516,777,214
9897.0.0.0/897.0.0.1 to 97.255.255.25497.255.255.25516,777,214
9998.0.0.0/898.0.0.1 to 98.255.255.25498.255.255.25516,777,214
10099.0.0.0/899.0.0.1 to 99.255.255.25499.255.255.25516,777,214
101100.0.0.0/8100.0.0.1 to 100.255.255.254100.255.255.25516,777,214
102101.0.0.0/8101.0.0.1 to 101.255.255.254101.255.255.25516,777,214
103102.0.0.0/8102.0.0.1 to 102.255.255.254102.255.255.25516,777,214
104103.0.0.0/8103.0.0.1 to 103.255.255.254103.255.255.25516,777,214
105104.0.0.0/8104.0.0.1 to 104.255.255.254104.255.255.25516,777,214
106105.0.0.0/8105.0.0.1 to 105.255.255.254105.255.255.25516,777,214
107106.0.0.0/8106.0.0.1 to 106.255.255.254106.255.255.25516,777,214
108107.0.0.0/8107.0.0.1 to 107.255.255.254107.255.255.25516,777,214
109108.0.0.0/8108.0.0.1 to 108.255.255.254108.255.255.25516,777,214
110109.0.0.0/8109.0.0.1 to 109.255.255.254109.255.255.25516,777,214
111110.0.0.0/8110.0.0.1 to 110.255.255.254110.255.255.25516,777,214
112111.0.0.0/8111.0.0.1 to 111.255.255.254111.255.255.25516,777,214
113112.0.0.0/8112.0.0.1 to 112.255.255.254112.255.255.25516,777,214
114113.0.0.0/8113.0.0.1 to 113.255.255.254113.255.255.25516,777,214
115114.0.0.0/8114.0.0.1 to 114.255.255.254114.255.255.25516,777,214
116115.0.0.0/8115.0.0.1 to 115.255.255.254115.255.255.25516,777,214
117116.0.0.0/8116.0.0.1 to 116.255.255.254116.255.255.25516,777,214
118117.0.0.0/8117.0.0.1 to 117.255.255.254117.255.255.25516,777,214
119118.0.0.0/8118.0.0.1 to 118.255.255.254118.255.255.25516,777,214
120119.0.0.0/8119.0.0.1 to 119.255.255.254119.255.255.25516,777,214
121120.0.0.0/8120.0.0.1 to 120.255.255.254120.255.255.25516,777,214
122121.0.0.0/8121.0.0.1 to 121.255.255.254121.255.255.25516,777,214
123122.0.0.0/8122.0.0.1 to 122.255.255.254122.255.255.25516,777,214
124123.0.0.0/8123.0.0.1 to 123.255.255.254123.255.255.25516,777,214
125124.0.0.0/8124.0.0.1 to 124.255.255.254124.255.255.25516,777,214
126125.0.0.0/8125.0.0.1 to 125.255.255.254125.255.255.25516,777,214
127126.0.0.0/8126.0.0.1 to 126.255.255.254126.255.255.25516,777,214
128127.0.0.0/8127.0.0.1 to 127.255.255.254127.255.255.25516,777,214
129128.0.0.0/8128.0.0.1 to 128.255.255.254128.255.255.25516,777,214
130129.0.0.0/8129.0.0.1 to 129.255.255.254129.255.255.25516,777,214
131130.0.0.0/8130.0.0.1 to 130.255.255.254130.255.255.25516,777,214
132131.0.0.0/8131.0.0.1 to 131.255.255.254131.255.255.25516,777,214
133132.0.0.0/8132.0.0.1 to 132.255.255.254132.255.255.25516,777,214
134133.0.0.0/8133.0.0.1 to 133.255.255.254133.255.255.25516,777,214
135134.0.0.0/8134.0.0.1 to 134.255.255.254134.255.255.25516,777,214
136135.0.0.0/8135.0.0.1 to 135.255.255.254135.255.255.25516,777,214
137136.0.0.0/8136.0.0.1 to 136.255.255.254136.255.255.25516,777,214
138137.0.0.0/8137.0.0.1 to 137.255.255.254137.255.255.25516,777,214
139138.0.0.0/8138.0.0.1 to 138.255.255.254138.255.255.25516,777,214
140139.0.0.0/8139.0.0.1 to 139.255.255.254139.255.255.25516,777,214
141140.0.0.0/8140.0.0.1 to 140.255.255.254140.255.255.25516,777,214
142141.0.0.0/8141.0.0.1 to 141.255.255.254141.255.255.25516,777,214
143142.0.0.0/8142.0.0.1 to 142.255.255.254142.255.255.25516,777,214
144143.0.0.0/8143.0.0.1 to 143.255.255.254143.255.255.25516,777,214
145144.0.0.0/8144.0.0.1 to 144.255.255.254144.255.255.25516,777,214
146145.0.0.0/8145.0.0.1 to 145.255.255.254145.255.255.25516,777,214
147146.0.0.0/8146.0.0.1 to 146.255.255.254146.255.255.25516,777,214
148147.0.0.0/8147.0.0.1 to 147.255.255.254147.255.255.25516,777,214
149148.0.0.0/8148.0.0.1 to 148.255.255.254148.255.255.25516,777,214
150149.0.0.0/8149.0.0.1 to 149.255.255.254149.255.255.25516,777,214
151150.0.0.0/8150.0.0.1 to 150.255.255.254150.255.255.25516,777,214
152151.0.0.0/8151.0.0.1 to 151.255.255.254151.255.255.25516,777,214
153152.0.0.0/8152.0.0.1 to 152.255.255.254152.255.255.25516,777,214
154153.0.0.0/8153.0.0.1 to 153.255.255.254153.255.255.25516,777,214
155154.0.0.0/8154.0.0.1 to 154.255.255.254154.255.255.25516,777,214
156155.0.0.0/8155.0.0.1 to 155.255.255.254155.255.255.25516,777,214
157156.0.0.0/8156.0.0.1 to 156.255.255.254156.255.255.25516,777,214
158157.0.0.0/8157.0.0.1 to 157.255.255.254157.255.255.25516,777,214
159158.0.0.0/8158.0.0.1 to 158.255.255.254158.255.255.25516,777,214
160159.0.0.0/8159.0.0.1 to 159.255.255.254159.255.255.25516,777,214
161160.0.0.0/8160.0.0.1 to 160.255.255.254160.255.255.25516,777,214
162161.0.0.0/8161.0.0.1 to 161.255.255.254161.255.255.25516,777,214
163162.0.0.0/8162.0.0.1 to 162.255.255.254162.255.255.25516,777,214
164163.0.0.0/8163.0.0.1 to 163.255.255.254163.255.255.25516,777,214
165164.0.0.0/8164.0.0.1 to 164.255.255.254164.255.255.25516,777,214
166165.0.0.0/8165.0.0.1 to 165.255.255.254165.255.255.25516,777,214
167166.0.0.0/8166.0.0.1 to 166.255.255.254166.255.255.25516,777,214
168167.0.0.0/8167.0.0.1 to 167.255.255.254167.255.255.25516,777,214
169168.0.0.0/8168.0.0.1 to 168.255.255.254168.255.255.25516,777,214
170169.0.0.0/8169.0.0.1 to 169.255.255.254169.255.255.25516,777,214
171170.0.0.0/8170.0.0.1 to 170.255.255.254170.255.255.25516,777,214
172171.0.0.0/8171.0.0.1 to 171.255.255.254171.255.255.25516,777,214
173172.0.0.0/8172.0.0.1 to 172.255.255.254172.255.255.25516,777,214
174173.0.0.0/8173.0.0.1 to 173.255.255.254173.255.255.25516,777,214
175174.0.0.0/8174.0.0.1 to 174.255.255.254174.255.255.25516,777,214
176175.0.0.0/8175.0.0.1 to 175.255.255.254175.255.255.25516,777,214
177176.0.0.0/8176.0.0.1 to 176.255.255.254176.255.255.25516,777,214
178177.0.0.0/8177.0.0.1 to 177.255.255.254177.255.255.25516,777,214
179178.0.0.0/8178.0.0.1 to 178.255.255.254178.255.255.25516,777,214
180179.0.0.0/8179.0.0.1 to 179.255.255.254179.255.255.25516,777,214
181180.0.0.0/8180.0.0.1 to 180.255.255.254180.255.255.25516,777,214
182181.0.0.0/8181.0.0.1 to 181.255.255.254181.255.255.25516,777,214
183182.0.0.0/8182.0.0.1 to 182.255.255.254182.255.255.25516,777,214
184183.0.0.0/8183.0.0.1 to 183.255.255.254183.255.255.25516,777,214
185184.0.0.0/8184.0.0.1 to 184.255.255.254184.255.255.25516,777,214
186185.0.0.0/8185.0.0.1 to 185.255.255.254185.255.255.25516,777,214
187186.0.0.0/8186.0.0.1 to 186.255.255.254186.255.255.25516,777,214
188187.0.0.0/8187.0.0.1 to 187.255.255.254187.255.255.25516,777,214
189188.0.0.0/8188.0.0.1 to 188.255.255.254188.255.255.25516,777,214
190189.0.0.0/8189.0.0.1 to 189.255.255.254189.255.255.25516,777,214
191190.0.0.0/8190.0.0.1 to 190.255.255.254190.255.255.25516,777,214
192191.0.0.0/8191.0.0.1 to 191.255.255.254191.255.255.25516,777,214
193192.0.0.0/8192.0.0.1 to 192.255.255.254192.255.255.25516,777,214
194193.0.0.0/8193.0.0.1 to 193.255.255.254193.255.255.25516,777,214
195194.0.0.0/8194.0.0.1 to 194.255.255.254194.255.255.25516,777,214
196195.0.0.0/8195.0.0.1 to 195.255.255.254195.255.255.25516,777,214
197196.0.0.0/8196.0.0.1 to 196.255.255.254196.255.255.25516,777,214
198197.0.0.0/8197.0.0.1 to 197.255.255.254197.255.255.25516,777,214
199198.0.0.0/8198.0.0.1 to 198.255.255.254198.255.255.25516,777,214
200199.0.0.0/8199.0.0.1 to 199.255.255.254199.255.255.25516,777,214
201200.0.0.0/8200.0.0.1 to 200.255.255.254200.255.255.25516,777,214
202201.0.0.0/8201.0.0.1 to 201.255.255.254201.255.255.25516,777,214
203202.0.0.0/8202.0.0.1 to 202.255.255.254202.255.255.25516,777,214
204203.0.0.0/8203.0.0.1 to 203.255.255.254203.255.255.25516,777,214
205204.0.0.0/8204.0.0.1 to 204.255.255.254204.255.255.25516,777,214
206205.0.0.0/8205.0.0.1 to 205.255.255.254205.255.255.25516,777,214
207206.0.0.0/8206.0.0.1 to 206.255.255.254206.255.255.25516,777,214
208207.0.0.0/8207.0.0.1 to 207.255.255.254207.255.255.25516,777,214
209208.0.0.0/8208.0.0.1 to 208.255.255.254208.255.255.25516,777,214
210209.0.0.0/8209.0.0.1 to 209.255.255.254209.255.255.25516,777,214
211210.0.0.0/8210.0.0.1 to 210.255.255.254210.255.255.25516,777,214
212211.0.0.0/8211.0.0.1 to 211.255.255.254211.255.255.25516,777,214
213212.0.0.0/8212.0.0.1 to 212.255.255.254212.255.255.25516,777,214
214213.0.0.0/8213.0.0.1 to 213.255.255.254213.255.255.25516,777,214
215214.0.0.0/8214.0.0.1 to 214.255.255.254214.255.255.25516,777,214
216215.0.0.0/8215.0.0.1 to 215.255.255.254215.255.255.25516,777,214
217216.0.0.0/8216.0.0.1 to 216.255.255.254216.255.255.25516,777,214
218217.0.0.0/8217.0.0.1 to 217.255.255.254217.255.255.25516,777,214
219218.0.0.0/8218.0.0.1 to 218.255.255.254218.255.255.25516,777,214
220219.0.0.0/8219.0.0.1 to 219.255.255.254219.255.255.25516,777,214
221220.0.0.0/8220.0.0.1 to 220.255.255.254220.255.255.25516,777,214
222221.0.0.0/8221.0.0.1 to 221.255.255.254221.255.255.25516,777,214
223222.0.0.0/8222.0.0.1 to 222.255.255.254222.255.255.25516,777,214
224223.0.0.0/8223.0.0.1 to 223.255.255.254223.255.255.25516,777,214
225224.0.0.0/8224.0.0.1 to 224.255.255.254224.255.255.25516,777,214
226225.0.0.0/8225.0.0.1 to 225.255.255.254225.255.255.25516,777,214
227226.0.0.0/8226.0.0.1 to 226.255.255.254226.255.255.25516,777,214
228227.0.0.0/8227.0.0.1 to 227.255.255.254227.255.255.25516,777,214
229228.0.0.0/8228.0.0.1 to 228.255.255.254228.255.255.25516,777,214
230229.0.0.0/8229.0.0.1 to 229.255.255.254229.255.255.25516,777,214
231230.0.0.0/8230.0.0.1 to 230.255.255.254230.255.255.25516,777,214
232231.0.0.0/8231.0.0.1 to 231.255.255.254231.255.255.25516,777,214
233232.0.0.0/8232.0.0.1 to 232.255.255.254232.255.255.25516,777,214
234233.0.0.0/8233.0.0.1 to 233.255.255.254233.255.255.25516,777,214
235234.0.0.0/8234.0.0.1 to 234.255.255.254234.255.255.25516,777,214
236235.0.0.0/8235.0.0.1 to 235.255.255.254235.255.255.25516,777,214
237236.0.0.0/8236.0.0.1 to 236.255.255.254236.255.255.25516,777,214
238237.0.0.0/8237.0.0.1 to 237.255.255.254237.255.255.25516,777,214
239238.0.0.0/8238.0.0.1 to 238.255.255.254238.255.255.25516,777,214
240239.0.0.0/8239.0.0.1 to 239.255.255.254239.255.255.25516,777,214
241240.0.0.0/8240.0.0.1 to 240.255.255.254240.255.255.25516,777,214
242241.0.0.0/8241.0.0.1 to 241.255.255.254241.255.255.25516,777,214
243242.0.0.0/8242.0.0.1 to 242.255.255.254242.255.255.25516,777,214
244243.0.0.0/8243.0.0.1 to 243.255.255.254243.255.255.25516,777,214
245244.0.0.0/8244.0.0.1 to 244.255.255.254244.255.255.25516,777,214
246245.0.0.0/8245.0.0.1 to 245.255.255.254245.255.255.25516,777,214
247246.0.0.0/8246.0.0.1 to 246.255.255.254246.255.255.25516,777,214
248247.0.0.0/8247.0.0.1 to 247.255.255.254247.255.255.25516,777,214
249248.0.0.0/8248.0.0.1 to 248.255.255.254248.255.255.25516,777,214
250249.0.0.0/8249.0.0.1 to 249.255.255.254249.255.255.25516,777,214
251250.0.0.0/8250.0.0.1 to 250.255.255.254250.255.255.25516,777,214
252251.0.0.0/8251.0.0.1 to 251.255.255.254251.255.255.25516,777,214
253252.0.0.0/8252.0.0.1 to 252.255.255.254252.255.255.25516,777,214
254253.0.0.0/8253.0.0.1 to 253.255.255.254253.255.255.25516,777,214
255254.0.0.0/8254.0.0.1 to 254.255.255.254254.255.255.25516,777,214
256255.0.0.0/8255.0.0.1 to 255.255.255.254255.255.255.25516,777,214

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.