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/9
/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 512 subnets of /9; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
10.0.0.0/90.0.0.1 to 0.127.255.2540.127.255.2558,388,606
20.128.0.0/90.128.0.1 to 0.255.255.2540.255.255.2558,388,606
31.0.0.0/91.0.0.1 to 1.127.255.2541.127.255.2558,388,606
41.128.0.0/91.128.0.1 to 1.255.255.2541.255.255.2558,388,606
52.0.0.0/92.0.0.1 to 2.127.255.2542.127.255.2558,388,606
62.128.0.0/92.128.0.1 to 2.255.255.2542.255.255.2558,388,606
73.0.0.0/93.0.0.1 to 3.127.255.2543.127.255.2558,388,606
83.128.0.0/93.128.0.1 to 3.255.255.2543.255.255.2558,388,606
94.0.0.0/94.0.0.1 to 4.127.255.2544.127.255.2558,388,606
104.128.0.0/94.128.0.1 to 4.255.255.2544.255.255.2558,388,606
115.0.0.0/95.0.0.1 to 5.127.255.2545.127.255.2558,388,606
125.128.0.0/95.128.0.1 to 5.255.255.2545.255.255.2558,388,606
136.0.0.0/96.0.0.1 to 6.127.255.2546.127.255.2558,388,606
146.128.0.0/96.128.0.1 to 6.255.255.2546.255.255.2558,388,606
157.0.0.0/97.0.0.1 to 7.127.255.2547.127.255.2558,388,606
167.128.0.0/97.128.0.1 to 7.255.255.2547.255.255.2558,388,606
178.0.0.0/98.0.0.1 to 8.127.255.2548.127.255.2558,388,606
188.128.0.0/98.128.0.1 to 8.255.255.2548.255.255.2558,388,606
199.0.0.0/99.0.0.1 to 9.127.255.2549.127.255.2558,388,606
209.128.0.0/99.128.0.1 to 9.255.255.2549.255.255.2558,388,606
2110.0.0.0/910.0.0.1 to 10.127.255.25410.127.255.2558,388,606
2210.128.0.0/910.128.0.1 to 10.255.255.25410.255.255.2558,388,606
2311.0.0.0/911.0.0.1 to 11.127.255.25411.127.255.2558,388,606
2411.128.0.0/911.128.0.1 to 11.255.255.25411.255.255.2558,388,606
2512.0.0.0/912.0.0.1 to 12.127.255.25412.127.255.2558,388,606
2612.128.0.0/912.128.0.1 to 12.255.255.25412.255.255.2558,388,606
2713.0.0.0/913.0.0.1 to 13.127.255.25413.127.255.2558,388,606
2813.128.0.0/913.128.0.1 to 13.255.255.25413.255.255.2558,388,606
2914.0.0.0/914.0.0.1 to 14.127.255.25414.127.255.2558,388,606
3014.128.0.0/914.128.0.1 to 14.255.255.25414.255.255.2558,388,606
3115.0.0.0/915.0.0.1 to 15.127.255.25415.127.255.2558,388,606
3215.128.0.0/915.128.0.1 to 15.255.255.25415.255.255.2558,388,606
3316.0.0.0/916.0.0.1 to 16.127.255.25416.127.255.2558,388,606
3416.128.0.0/916.128.0.1 to 16.255.255.25416.255.255.2558,388,606
3517.0.0.0/917.0.0.1 to 17.127.255.25417.127.255.2558,388,606
3617.128.0.0/917.128.0.1 to 17.255.255.25417.255.255.2558,388,606
3718.0.0.0/918.0.0.1 to 18.127.255.25418.127.255.2558,388,606
3818.128.0.0/918.128.0.1 to 18.255.255.25418.255.255.2558,388,606
3919.0.0.0/919.0.0.1 to 19.127.255.25419.127.255.2558,388,606
4019.128.0.0/919.128.0.1 to 19.255.255.25419.255.255.2558,388,606
4120.0.0.0/920.0.0.1 to 20.127.255.25420.127.255.2558,388,606
4220.128.0.0/920.128.0.1 to 20.255.255.25420.255.255.2558,388,606
4321.0.0.0/921.0.0.1 to 21.127.255.25421.127.255.2558,388,606
4421.128.0.0/921.128.0.1 to 21.255.255.25421.255.255.2558,388,606
4522.0.0.0/922.0.0.1 to 22.127.255.25422.127.255.2558,388,606
4622.128.0.0/922.128.0.1 to 22.255.255.25422.255.255.2558,388,606
4723.0.0.0/923.0.0.1 to 23.127.255.25423.127.255.2558,388,606
4823.128.0.0/923.128.0.1 to 23.255.255.25423.255.255.2558,388,606
4924.0.0.0/924.0.0.1 to 24.127.255.25424.127.255.2558,388,606
5024.128.0.0/924.128.0.1 to 24.255.255.25424.255.255.2558,388,606
5125.0.0.0/925.0.0.1 to 25.127.255.25425.127.255.2558,388,606
5225.128.0.0/925.128.0.1 to 25.255.255.25425.255.255.2558,388,606
5326.0.0.0/926.0.0.1 to 26.127.255.25426.127.255.2558,388,606
5426.128.0.0/926.128.0.1 to 26.255.255.25426.255.255.2558,388,606
5527.0.0.0/927.0.0.1 to 27.127.255.25427.127.255.2558,388,606
5627.128.0.0/927.128.0.1 to 27.255.255.25427.255.255.2558,388,606
5728.0.0.0/928.0.0.1 to 28.127.255.25428.127.255.2558,388,606
5828.128.0.0/928.128.0.1 to 28.255.255.25428.255.255.2558,388,606
5929.0.0.0/929.0.0.1 to 29.127.255.25429.127.255.2558,388,606
6029.128.0.0/929.128.0.1 to 29.255.255.25429.255.255.2558,388,606
6130.0.0.0/930.0.0.1 to 30.127.255.25430.127.255.2558,388,606
6230.128.0.0/930.128.0.1 to 30.255.255.25430.255.255.2558,388,606
6331.0.0.0/931.0.0.1 to 31.127.255.25431.127.255.2558,388,606
6431.128.0.0/931.128.0.1 to 31.255.255.25431.255.255.2558,388,606
6532.0.0.0/932.0.0.1 to 32.127.255.25432.127.255.2558,388,606
6632.128.0.0/932.128.0.1 to 32.255.255.25432.255.255.2558,388,606
6733.0.0.0/933.0.0.1 to 33.127.255.25433.127.255.2558,388,606
6833.128.0.0/933.128.0.1 to 33.255.255.25433.255.255.2558,388,606
6934.0.0.0/934.0.0.1 to 34.127.255.25434.127.255.2558,388,606
7034.128.0.0/934.128.0.1 to 34.255.255.25434.255.255.2558,388,606
7135.0.0.0/935.0.0.1 to 35.127.255.25435.127.255.2558,388,606
7235.128.0.0/935.128.0.1 to 35.255.255.25435.255.255.2558,388,606
7336.0.0.0/936.0.0.1 to 36.127.255.25436.127.255.2558,388,606
7436.128.0.0/936.128.0.1 to 36.255.255.25436.255.255.2558,388,606
7537.0.0.0/937.0.0.1 to 37.127.255.25437.127.255.2558,388,606
7637.128.0.0/937.128.0.1 to 37.255.255.25437.255.255.2558,388,606
7738.0.0.0/938.0.0.1 to 38.127.255.25438.127.255.2558,388,606
7838.128.0.0/938.128.0.1 to 38.255.255.25438.255.255.2558,388,606
7939.0.0.0/939.0.0.1 to 39.127.255.25439.127.255.2558,388,606
8039.128.0.0/939.128.0.1 to 39.255.255.25439.255.255.2558,388,606
8140.0.0.0/940.0.0.1 to 40.127.255.25440.127.255.2558,388,606
8240.128.0.0/940.128.0.1 to 40.255.255.25440.255.255.2558,388,606
8341.0.0.0/941.0.0.1 to 41.127.255.25441.127.255.2558,388,606
8441.128.0.0/941.128.0.1 to 41.255.255.25441.255.255.2558,388,606
8542.0.0.0/942.0.0.1 to 42.127.255.25442.127.255.2558,388,606
8642.128.0.0/942.128.0.1 to 42.255.255.25442.255.255.2558,388,606
8743.0.0.0/943.0.0.1 to 43.127.255.25443.127.255.2558,388,606
8843.128.0.0/943.128.0.1 to 43.255.255.25443.255.255.2558,388,606
8944.0.0.0/944.0.0.1 to 44.127.255.25444.127.255.2558,388,606
9044.128.0.0/944.128.0.1 to 44.255.255.25444.255.255.2558,388,606
9145.0.0.0/945.0.0.1 to 45.127.255.25445.127.255.2558,388,606
9245.128.0.0/945.128.0.1 to 45.255.255.25445.255.255.2558,388,606
9346.0.0.0/946.0.0.1 to 46.127.255.25446.127.255.2558,388,606
9446.128.0.0/946.128.0.1 to 46.255.255.25446.255.255.2558,388,606
9547.0.0.0/947.0.0.1 to 47.127.255.25447.127.255.2558,388,606
9647.128.0.0/947.128.0.1 to 47.255.255.25447.255.255.2558,388,606
9748.0.0.0/948.0.0.1 to 48.127.255.25448.127.255.2558,388,606
9848.128.0.0/948.128.0.1 to 48.255.255.25448.255.255.2558,388,606
9949.0.0.0/949.0.0.1 to 49.127.255.25449.127.255.2558,388,606
10049.128.0.0/949.128.0.1 to 49.255.255.25449.255.255.2558,388,606
10150.0.0.0/950.0.0.1 to 50.127.255.25450.127.255.2558,388,606
10250.128.0.0/950.128.0.1 to 50.255.255.25450.255.255.2558,388,606
10351.0.0.0/951.0.0.1 to 51.127.255.25451.127.255.2558,388,606
10451.128.0.0/951.128.0.1 to 51.255.255.25451.255.255.2558,388,606
10552.0.0.0/952.0.0.1 to 52.127.255.25452.127.255.2558,388,606
10652.128.0.0/952.128.0.1 to 52.255.255.25452.255.255.2558,388,606
10753.0.0.0/953.0.0.1 to 53.127.255.25453.127.255.2558,388,606
10853.128.0.0/953.128.0.1 to 53.255.255.25453.255.255.2558,388,606
10954.0.0.0/954.0.0.1 to 54.127.255.25454.127.255.2558,388,606
11054.128.0.0/954.128.0.1 to 54.255.255.25454.255.255.2558,388,606
11155.0.0.0/955.0.0.1 to 55.127.255.25455.127.255.2558,388,606
11255.128.0.0/955.128.0.1 to 55.255.255.25455.255.255.2558,388,606
11356.0.0.0/956.0.0.1 to 56.127.255.25456.127.255.2558,388,606
11456.128.0.0/956.128.0.1 to 56.255.255.25456.255.255.2558,388,606
11557.0.0.0/957.0.0.1 to 57.127.255.25457.127.255.2558,388,606
11657.128.0.0/957.128.0.1 to 57.255.255.25457.255.255.2558,388,606
11758.0.0.0/958.0.0.1 to 58.127.255.25458.127.255.2558,388,606
11858.128.0.0/958.128.0.1 to 58.255.255.25458.255.255.2558,388,606
11959.0.0.0/959.0.0.1 to 59.127.255.25459.127.255.2558,388,606
12059.128.0.0/959.128.0.1 to 59.255.255.25459.255.255.2558,388,606
12160.0.0.0/960.0.0.1 to 60.127.255.25460.127.255.2558,388,606
12260.128.0.0/960.128.0.1 to 60.255.255.25460.255.255.2558,388,606
12361.0.0.0/961.0.0.1 to 61.127.255.25461.127.255.2558,388,606
12461.128.0.0/961.128.0.1 to 61.255.255.25461.255.255.2558,388,606
12562.0.0.0/962.0.0.1 to 62.127.255.25462.127.255.2558,388,606
12662.128.0.0/962.128.0.1 to 62.255.255.25462.255.255.2558,388,606
12763.0.0.0/963.0.0.1 to 63.127.255.25463.127.255.2558,388,606
12863.128.0.0/963.128.0.1 to 63.255.255.25463.255.255.2558,388,606
12964.0.0.0/964.0.0.1 to 64.127.255.25464.127.255.2558,388,606
13064.128.0.0/964.128.0.1 to 64.255.255.25464.255.255.2558,388,606
13165.0.0.0/965.0.0.1 to 65.127.255.25465.127.255.2558,388,606
13265.128.0.0/965.128.0.1 to 65.255.255.25465.255.255.2558,388,606
13366.0.0.0/966.0.0.1 to 66.127.255.25466.127.255.2558,388,606
13466.128.0.0/966.128.0.1 to 66.255.255.25466.255.255.2558,388,606
13567.0.0.0/967.0.0.1 to 67.127.255.25467.127.255.2558,388,606
13667.128.0.0/967.128.0.1 to 67.255.255.25467.255.255.2558,388,606
13768.0.0.0/968.0.0.1 to 68.127.255.25468.127.255.2558,388,606
13868.128.0.0/968.128.0.1 to 68.255.255.25468.255.255.2558,388,606
13969.0.0.0/969.0.0.1 to 69.127.255.25469.127.255.2558,388,606
14069.128.0.0/969.128.0.1 to 69.255.255.25469.255.255.2558,388,606
14170.0.0.0/970.0.0.1 to 70.127.255.25470.127.255.2558,388,606
14270.128.0.0/970.128.0.1 to 70.255.255.25470.255.255.2558,388,606
14371.0.0.0/971.0.0.1 to 71.127.255.25471.127.255.2558,388,606
14471.128.0.0/971.128.0.1 to 71.255.255.25471.255.255.2558,388,606
14572.0.0.0/972.0.0.1 to 72.127.255.25472.127.255.2558,388,606
14672.128.0.0/972.128.0.1 to 72.255.255.25472.255.255.2558,388,606
14773.0.0.0/973.0.0.1 to 73.127.255.25473.127.255.2558,388,606
14873.128.0.0/973.128.0.1 to 73.255.255.25473.255.255.2558,388,606
14974.0.0.0/974.0.0.1 to 74.127.255.25474.127.255.2558,388,606
15074.128.0.0/974.128.0.1 to 74.255.255.25474.255.255.2558,388,606
15175.0.0.0/975.0.0.1 to 75.127.255.25475.127.255.2558,388,606
15275.128.0.0/975.128.0.1 to 75.255.255.25475.255.255.2558,388,606
15376.0.0.0/976.0.0.1 to 76.127.255.25476.127.255.2558,388,606
15476.128.0.0/976.128.0.1 to 76.255.255.25476.255.255.2558,388,606
15577.0.0.0/977.0.0.1 to 77.127.255.25477.127.255.2558,388,606
15677.128.0.0/977.128.0.1 to 77.255.255.25477.255.255.2558,388,606
15778.0.0.0/978.0.0.1 to 78.127.255.25478.127.255.2558,388,606
15878.128.0.0/978.128.0.1 to 78.255.255.25478.255.255.2558,388,606
15979.0.0.0/979.0.0.1 to 79.127.255.25479.127.255.2558,388,606
16079.128.0.0/979.128.0.1 to 79.255.255.25479.255.255.2558,388,606
16180.0.0.0/980.0.0.1 to 80.127.255.25480.127.255.2558,388,606
16280.128.0.0/980.128.0.1 to 80.255.255.25480.255.255.2558,388,606
16381.0.0.0/981.0.0.1 to 81.127.255.25481.127.255.2558,388,606
16481.128.0.0/981.128.0.1 to 81.255.255.25481.255.255.2558,388,606
16582.0.0.0/982.0.0.1 to 82.127.255.25482.127.255.2558,388,606
16682.128.0.0/982.128.0.1 to 82.255.255.25482.255.255.2558,388,606
16783.0.0.0/983.0.0.1 to 83.127.255.25483.127.255.2558,388,606
16883.128.0.0/983.128.0.1 to 83.255.255.25483.255.255.2558,388,606
16984.0.0.0/984.0.0.1 to 84.127.255.25484.127.255.2558,388,606
17084.128.0.0/984.128.0.1 to 84.255.255.25484.255.255.2558,388,606
17185.0.0.0/985.0.0.1 to 85.127.255.25485.127.255.2558,388,606
17285.128.0.0/985.128.0.1 to 85.255.255.25485.255.255.2558,388,606
17386.0.0.0/986.0.0.1 to 86.127.255.25486.127.255.2558,388,606
17486.128.0.0/986.128.0.1 to 86.255.255.25486.255.255.2558,388,606
17587.0.0.0/987.0.0.1 to 87.127.255.25487.127.255.2558,388,606
17687.128.0.0/987.128.0.1 to 87.255.255.25487.255.255.2558,388,606
17788.0.0.0/988.0.0.1 to 88.127.255.25488.127.255.2558,388,606
17888.128.0.0/988.128.0.1 to 88.255.255.25488.255.255.2558,388,606
17989.0.0.0/989.0.0.1 to 89.127.255.25489.127.255.2558,388,606
18089.128.0.0/989.128.0.1 to 89.255.255.25489.255.255.2558,388,606
18190.0.0.0/990.0.0.1 to 90.127.255.25490.127.255.2558,388,606
18290.128.0.0/990.128.0.1 to 90.255.255.25490.255.255.2558,388,606
18391.0.0.0/991.0.0.1 to 91.127.255.25491.127.255.2558,388,606
18491.128.0.0/991.128.0.1 to 91.255.255.25491.255.255.2558,388,606
18592.0.0.0/992.0.0.1 to 92.127.255.25492.127.255.2558,388,606
18692.128.0.0/992.128.0.1 to 92.255.255.25492.255.255.2558,388,606
18793.0.0.0/993.0.0.1 to 93.127.255.25493.127.255.2558,388,606
18893.128.0.0/993.128.0.1 to 93.255.255.25493.255.255.2558,388,606
18994.0.0.0/994.0.0.1 to 94.127.255.25494.127.255.2558,388,606
19094.128.0.0/994.128.0.1 to 94.255.255.25494.255.255.2558,388,606
19195.0.0.0/995.0.0.1 to 95.127.255.25495.127.255.2558,388,606
19295.128.0.0/995.128.0.1 to 95.255.255.25495.255.255.2558,388,606
19396.0.0.0/996.0.0.1 to 96.127.255.25496.127.255.2558,388,606
19496.128.0.0/996.128.0.1 to 96.255.255.25496.255.255.2558,388,606
19597.0.0.0/997.0.0.1 to 97.127.255.25497.127.255.2558,388,606
19697.128.0.0/997.128.0.1 to 97.255.255.25497.255.255.2558,388,606
19798.0.0.0/998.0.0.1 to 98.127.255.25498.127.255.2558,388,606
19898.128.0.0/998.128.0.1 to 98.255.255.25498.255.255.2558,388,606
19999.0.0.0/999.0.0.1 to 99.127.255.25499.127.255.2558,388,606
20099.128.0.0/999.128.0.1 to 99.255.255.25499.255.255.2558,388,606
201100.0.0.0/9100.0.0.1 to 100.127.255.254100.127.255.2558,388,606
202100.128.0.0/9100.128.0.1 to 100.255.255.254100.255.255.2558,388,606
203101.0.0.0/9101.0.0.1 to 101.127.255.254101.127.255.2558,388,606
204101.128.0.0/9101.128.0.1 to 101.255.255.254101.255.255.2558,388,606
205102.0.0.0/9102.0.0.1 to 102.127.255.254102.127.255.2558,388,606
206102.128.0.0/9102.128.0.1 to 102.255.255.254102.255.255.2558,388,606
207103.0.0.0/9103.0.0.1 to 103.127.255.254103.127.255.2558,388,606
208103.128.0.0/9103.128.0.1 to 103.255.255.254103.255.255.2558,388,606
209104.0.0.0/9104.0.0.1 to 104.127.255.254104.127.255.2558,388,606
210104.128.0.0/9104.128.0.1 to 104.255.255.254104.255.255.2558,388,606
211105.0.0.0/9105.0.0.1 to 105.127.255.254105.127.255.2558,388,606
212105.128.0.0/9105.128.0.1 to 105.255.255.254105.255.255.2558,388,606
213106.0.0.0/9106.0.0.1 to 106.127.255.254106.127.255.2558,388,606
214106.128.0.0/9106.128.0.1 to 106.255.255.254106.255.255.2558,388,606
215107.0.0.0/9107.0.0.1 to 107.127.255.254107.127.255.2558,388,606
216107.128.0.0/9107.128.0.1 to 107.255.255.254107.255.255.2558,388,606
217108.0.0.0/9108.0.0.1 to 108.127.255.254108.127.255.2558,388,606
218108.128.0.0/9108.128.0.1 to 108.255.255.254108.255.255.2558,388,606
219109.0.0.0/9109.0.0.1 to 109.127.255.254109.127.255.2558,388,606
220109.128.0.0/9109.128.0.1 to 109.255.255.254109.255.255.2558,388,606
221110.0.0.0/9110.0.0.1 to 110.127.255.254110.127.255.2558,388,606
222110.128.0.0/9110.128.0.1 to 110.255.255.254110.255.255.2558,388,606
223111.0.0.0/9111.0.0.1 to 111.127.255.254111.127.255.2558,388,606
224111.128.0.0/9111.128.0.1 to 111.255.255.254111.255.255.2558,388,606
225112.0.0.0/9112.0.0.1 to 112.127.255.254112.127.255.2558,388,606
226112.128.0.0/9112.128.0.1 to 112.255.255.254112.255.255.2558,388,606
227113.0.0.0/9113.0.0.1 to 113.127.255.254113.127.255.2558,388,606
228113.128.0.0/9113.128.0.1 to 113.255.255.254113.255.255.2558,388,606
229114.0.0.0/9114.0.0.1 to 114.127.255.254114.127.255.2558,388,606
230114.128.0.0/9114.128.0.1 to 114.255.255.254114.255.255.2558,388,606
231115.0.0.0/9115.0.0.1 to 115.127.255.254115.127.255.2558,388,606
232115.128.0.0/9115.128.0.1 to 115.255.255.254115.255.255.2558,388,606
233116.0.0.0/9116.0.0.1 to 116.127.255.254116.127.255.2558,388,606
234116.128.0.0/9116.128.0.1 to 116.255.255.254116.255.255.2558,388,606
235117.0.0.0/9117.0.0.1 to 117.127.255.254117.127.255.2558,388,606
236117.128.0.0/9117.128.0.1 to 117.255.255.254117.255.255.2558,388,606
237118.0.0.0/9118.0.0.1 to 118.127.255.254118.127.255.2558,388,606
238118.128.0.0/9118.128.0.1 to 118.255.255.254118.255.255.2558,388,606
239119.0.0.0/9119.0.0.1 to 119.127.255.254119.127.255.2558,388,606
240119.128.0.0/9119.128.0.1 to 119.255.255.254119.255.255.2558,388,606
241120.0.0.0/9120.0.0.1 to 120.127.255.254120.127.255.2558,388,606
242120.128.0.0/9120.128.0.1 to 120.255.255.254120.255.255.2558,388,606
243121.0.0.0/9121.0.0.1 to 121.127.255.254121.127.255.2558,388,606
244121.128.0.0/9121.128.0.1 to 121.255.255.254121.255.255.2558,388,606
245122.0.0.0/9122.0.0.1 to 122.127.255.254122.127.255.2558,388,606
246122.128.0.0/9122.128.0.1 to 122.255.255.254122.255.255.2558,388,606
247123.0.0.0/9123.0.0.1 to 123.127.255.254123.127.255.2558,388,606
248123.128.0.0/9123.128.0.1 to 123.255.255.254123.255.255.2558,388,606
249124.0.0.0/9124.0.0.1 to 124.127.255.254124.127.255.2558,388,606
250124.128.0.0/9124.128.0.1 to 124.255.255.254124.255.255.2558,388,606
251125.0.0.0/9125.0.0.1 to 125.127.255.254125.127.255.2558,388,606
252125.128.0.0/9125.128.0.1 to 125.255.255.254125.255.255.2558,388,606
253126.0.0.0/9126.0.0.1 to 126.127.255.254126.127.255.2558,388,606
254126.128.0.0/9126.128.0.1 to 126.255.255.254126.255.255.2558,388,606
255127.0.0.0/9127.0.0.1 to 127.127.255.254127.127.255.2558,388,606
256127.128.0.0/9127.128.0.1 to 127.255.255.254127.255.255.2558,388,606

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.