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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.

Network3.16.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
3.16.0.0
Broadcast address
3.31.255.255
First usable
3.16.0.1
Last usable
3.31.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
A (default /8)
As numbers
Hex 03100000 · Integer 51380224 to 52428799
Reverse DNS zones
16.3.in-addr.arpa
17.3.in-addr.arpa
18.3.in-addr.arpa
19.3.in-addr.arpa
20.3.in-addr.arpa
21.3.in-addr.arpa
22.3.in-addr.arpa
23.3.in-addr.arpa
24.3.in-addr.arpa
25.3.in-addr.arpa
26.3.in-addr.arpa
27.3.in-addr.arpa
28.3.in-addr.arpa
29.3.in-addr.arpa
30.3.in-addr.arpa
31.3.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00000011.00010000.00000000.000000003.16.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00000011.00010000.00000000.000000003.16.0.0
Broadcast00000011.00011111.11111111.111111113.31.255.255
Split into smaller subnets/21
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

3.16.0.0/12 makes 512 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
13.16.0.0/213.16.0.1 to 3.16.7.2543.16.7.2552,046
23.16.8.0/213.16.8.1 to 3.16.15.2543.16.15.2552,046
33.16.16.0/213.16.16.1 to 3.16.23.2543.16.23.2552,046
43.16.24.0/213.16.24.1 to 3.16.31.2543.16.31.2552,046
53.16.32.0/213.16.32.1 to 3.16.39.2543.16.39.2552,046
63.16.40.0/213.16.40.1 to 3.16.47.2543.16.47.2552,046
73.16.48.0/213.16.48.1 to 3.16.55.2543.16.55.2552,046
83.16.56.0/213.16.56.1 to 3.16.63.2543.16.63.2552,046
93.16.64.0/213.16.64.1 to 3.16.71.2543.16.71.2552,046
103.16.72.0/213.16.72.1 to 3.16.79.2543.16.79.2552,046
113.16.80.0/213.16.80.1 to 3.16.87.2543.16.87.2552,046
123.16.88.0/213.16.88.1 to 3.16.95.2543.16.95.2552,046
133.16.96.0/213.16.96.1 to 3.16.103.2543.16.103.2552,046
143.16.104.0/213.16.104.1 to 3.16.111.2543.16.111.2552,046
153.16.112.0/213.16.112.1 to 3.16.119.2543.16.119.2552,046
163.16.120.0/213.16.120.1 to 3.16.127.2543.16.127.2552,046
173.16.128.0/213.16.128.1 to 3.16.135.2543.16.135.2552,046
183.16.136.0/213.16.136.1 to 3.16.143.2543.16.143.2552,046
193.16.144.0/213.16.144.1 to 3.16.151.2543.16.151.2552,046
203.16.152.0/213.16.152.1 to 3.16.159.2543.16.159.2552,046
213.16.160.0/213.16.160.1 to 3.16.167.2543.16.167.2552,046
223.16.168.0/213.16.168.1 to 3.16.175.2543.16.175.2552,046
233.16.176.0/213.16.176.1 to 3.16.183.2543.16.183.2552,046
243.16.184.0/213.16.184.1 to 3.16.191.2543.16.191.2552,046
253.16.192.0/213.16.192.1 to 3.16.199.2543.16.199.2552,046
263.16.200.0/213.16.200.1 to 3.16.207.2543.16.207.2552,046
273.16.208.0/213.16.208.1 to 3.16.215.2543.16.215.2552,046
283.16.216.0/213.16.216.1 to 3.16.223.2543.16.223.2552,046
293.16.224.0/213.16.224.1 to 3.16.231.2543.16.231.2552,046
303.16.232.0/213.16.232.1 to 3.16.239.2543.16.239.2552,046
313.16.240.0/213.16.240.1 to 3.16.247.2543.16.247.2552,046
323.16.248.0/213.16.248.1 to 3.16.255.2543.16.255.2552,046
333.17.0.0/213.17.0.1 to 3.17.7.2543.17.7.2552,046
343.17.8.0/213.17.8.1 to 3.17.15.2543.17.15.2552,046
353.17.16.0/213.17.16.1 to 3.17.23.2543.17.23.2552,046
363.17.24.0/213.17.24.1 to 3.17.31.2543.17.31.2552,046
373.17.32.0/213.17.32.1 to 3.17.39.2543.17.39.2552,046
383.17.40.0/213.17.40.1 to 3.17.47.2543.17.47.2552,046
393.17.48.0/213.17.48.1 to 3.17.55.2543.17.55.2552,046
403.17.56.0/213.17.56.1 to 3.17.63.2543.17.63.2552,046
413.17.64.0/213.17.64.1 to 3.17.71.2543.17.71.2552,046
423.17.72.0/213.17.72.1 to 3.17.79.2543.17.79.2552,046
433.17.80.0/213.17.80.1 to 3.17.87.2543.17.87.2552,046
443.17.88.0/213.17.88.1 to 3.17.95.2543.17.95.2552,046
453.17.96.0/213.17.96.1 to 3.17.103.2543.17.103.2552,046
463.17.104.0/213.17.104.1 to 3.17.111.2543.17.111.2552,046
473.17.112.0/213.17.112.1 to 3.17.119.2543.17.119.2552,046
483.17.120.0/213.17.120.1 to 3.17.127.2543.17.127.2552,046
493.17.128.0/213.17.128.1 to 3.17.135.2543.17.135.2552,046
503.17.136.0/213.17.136.1 to 3.17.143.2543.17.143.2552,046
513.17.144.0/213.17.144.1 to 3.17.151.2543.17.151.2552,046
523.17.152.0/213.17.152.1 to 3.17.159.2543.17.159.2552,046
533.17.160.0/213.17.160.1 to 3.17.167.2543.17.167.2552,046
543.17.168.0/213.17.168.1 to 3.17.175.2543.17.175.2552,046
553.17.176.0/213.17.176.1 to 3.17.183.2543.17.183.2552,046
563.17.184.0/213.17.184.1 to 3.17.191.2543.17.191.2552,046
573.17.192.0/213.17.192.1 to 3.17.199.2543.17.199.2552,046
583.17.200.0/213.17.200.1 to 3.17.207.2543.17.207.2552,046
593.17.208.0/213.17.208.1 to 3.17.215.2543.17.215.2552,046
603.17.216.0/213.17.216.1 to 3.17.223.2543.17.223.2552,046
613.17.224.0/213.17.224.1 to 3.17.231.2543.17.231.2552,046
623.17.232.0/213.17.232.1 to 3.17.239.2543.17.239.2552,046
633.17.240.0/213.17.240.1 to 3.17.247.2543.17.247.2552,046
643.17.248.0/213.17.248.1 to 3.17.255.2543.17.255.2552,046
653.18.0.0/213.18.0.1 to 3.18.7.2543.18.7.2552,046
663.18.8.0/213.18.8.1 to 3.18.15.2543.18.15.2552,046
673.18.16.0/213.18.16.1 to 3.18.23.2543.18.23.2552,046
683.18.24.0/213.18.24.1 to 3.18.31.2543.18.31.2552,046
693.18.32.0/213.18.32.1 to 3.18.39.2543.18.39.2552,046
703.18.40.0/213.18.40.1 to 3.18.47.2543.18.47.2552,046
713.18.48.0/213.18.48.1 to 3.18.55.2543.18.55.2552,046
723.18.56.0/213.18.56.1 to 3.18.63.2543.18.63.2552,046
733.18.64.0/213.18.64.1 to 3.18.71.2543.18.71.2552,046
743.18.72.0/213.18.72.1 to 3.18.79.2543.18.79.2552,046
753.18.80.0/213.18.80.1 to 3.18.87.2543.18.87.2552,046
763.18.88.0/213.18.88.1 to 3.18.95.2543.18.95.2552,046
773.18.96.0/213.18.96.1 to 3.18.103.2543.18.103.2552,046
783.18.104.0/213.18.104.1 to 3.18.111.2543.18.111.2552,046
793.18.112.0/213.18.112.1 to 3.18.119.2543.18.119.2552,046
803.18.120.0/213.18.120.1 to 3.18.127.2543.18.127.2552,046
813.18.128.0/213.18.128.1 to 3.18.135.2543.18.135.2552,046
823.18.136.0/213.18.136.1 to 3.18.143.2543.18.143.2552,046
833.18.144.0/213.18.144.1 to 3.18.151.2543.18.151.2552,046
843.18.152.0/213.18.152.1 to 3.18.159.2543.18.159.2552,046
853.18.160.0/213.18.160.1 to 3.18.167.2543.18.167.2552,046
863.18.168.0/213.18.168.1 to 3.18.175.2543.18.175.2552,046
873.18.176.0/213.18.176.1 to 3.18.183.2543.18.183.2552,046
883.18.184.0/213.18.184.1 to 3.18.191.2543.18.191.2552,046
893.18.192.0/213.18.192.1 to 3.18.199.2543.18.199.2552,046
903.18.200.0/213.18.200.1 to 3.18.207.2543.18.207.2552,046
913.18.208.0/213.18.208.1 to 3.18.215.2543.18.215.2552,046
923.18.216.0/213.18.216.1 to 3.18.223.2543.18.223.2552,046
933.18.224.0/213.18.224.1 to 3.18.231.2543.18.231.2552,046
943.18.232.0/213.18.232.1 to 3.18.239.2543.18.239.2552,046
953.18.240.0/213.18.240.1 to 3.18.247.2543.18.247.2552,046
963.18.248.0/213.18.248.1 to 3.18.255.2543.18.255.2552,046
973.19.0.0/213.19.0.1 to 3.19.7.2543.19.7.2552,046
983.19.8.0/213.19.8.1 to 3.19.15.2543.19.15.2552,046
993.19.16.0/213.19.16.1 to 3.19.23.2543.19.23.2552,046
1003.19.24.0/213.19.24.1 to 3.19.31.2543.19.31.2552,046
1013.19.32.0/213.19.32.1 to 3.19.39.2543.19.39.2552,046
1023.19.40.0/213.19.40.1 to 3.19.47.2543.19.47.2552,046
1033.19.48.0/213.19.48.1 to 3.19.55.2543.19.55.2552,046
1043.19.56.0/213.19.56.1 to 3.19.63.2543.19.63.2552,046
1053.19.64.0/213.19.64.1 to 3.19.71.2543.19.71.2552,046
1063.19.72.0/213.19.72.1 to 3.19.79.2543.19.79.2552,046
1073.19.80.0/213.19.80.1 to 3.19.87.2543.19.87.2552,046
1083.19.88.0/213.19.88.1 to 3.19.95.2543.19.95.2552,046
1093.19.96.0/213.19.96.1 to 3.19.103.2543.19.103.2552,046
1103.19.104.0/213.19.104.1 to 3.19.111.2543.19.111.2552,046
1113.19.112.0/213.19.112.1 to 3.19.119.2543.19.119.2552,046
1123.19.120.0/213.19.120.1 to 3.19.127.2543.19.127.2552,046
1133.19.128.0/213.19.128.1 to 3.19.135.2543.19.135.2552,046
1143.19.136.0/213.19.136.1 to 3.19.143.2543.19.143.2552,046
1153.19.144.0/213.19.144.1 to 3.19.151.2543.19.151.2552,046
1163.19.152.0/213.19.152.1 to 3.19.159.2543.19.159.2552,046
1173.19.160.0/213.19.160.1 to 3.19.167.2543.19.167.2552,046
1183.19.168.0/213.19.168.1 to 3.19.175.2543.19.175.2552,046
1193.19.176.0/213.19.176.1 to 3.19.183.2543.19.183.2552,046
1203.19.184.0/213.19.184.1 to 3.19.191.2543.19.191.2552,046
1213.19.192.0/213.19.192.1 to 3.19.199.2543.19.199.2552,046
1223.19.200.0/213.19.200.1 to 3.19.207.2543.19.207.2552,046
1233.19.208.0/213.19.208.1 to 3.19.215.2543.19.215.2552,046
1243.19.216.0/213.19.216.1 to 3.19.223.2543.19.223.2552,046
1253.19.224.0/213.19.224.1 to 3.19.231.2543.19.231.2552,046
1263.19.232.0/213.19.232.1 to 3.19.239.2543.19.239.2552,046
1273.19.240.0/213.19.240.1 to 3.19.247.2543.19.247.2552,046
1283.19.248.0/213.19.248.1 to 3.19.255.2543.19.255.2552,046
1293.20.0.0/213.20.0.1 to 3.20.7.2543.20.7.2552,046
1303.20.8.0/213.20.8.1 to 3.20.15.2543.20.15.2552,046
1313.20.16.0/213.20.16.1 to 3.20.23.2543.20.23.2552,046
1323.20.24.0/213.20.24.1 to 3.20.31.2543.20.31.2552,046
1333.20.32.0/213.20.32.1 to 3.20.39.2543.20.39.2552,046
1343.20.40.0/213.20.40.1 to 3.20.47.2543.20.47.2552,046
1353.20.48.0/213.20.48.1 to 3.20.55.2543.20.55.2552,046
1363.20.56.0/213.20.56.1 to 3.20.63.2543.20.63.2552,046
1373.20.64.0/213.20.64.1 to 3.20.71.2543.20.71.2552,046
1383.20.72.0/213.20.72.1 to 3.20.79.2543.20.79.2552,046
1393.20.80.0/213.20.80.1 to 3.20.87.2543.20.87.2552,046
1403.20.88.0/213.20.88.1 to 3.20.95.2543.20.95.2552,046
1413.20.96.0/213.20.96.1 to 3.20.103.2543.20.103.2552,046
1423.20.104.0/213.20.104.1 to 3.20.111.2543.20.111.2552,046
1433.20.112.0/213.20.112.1 to 3.20.119.2543.20.119.2552,046
1443.20.120.0/213.20.120.1 to 3.20.127.2543.20.127.2552,046
1453.20.128.0/213.20.128.1 to 3.20.135.2543.20.135.2552,046
1463.20.136.0/213.20.136.1 to 3.20.143.2543.20.143.2552,046
1473.20.144.0/213.20.144.1 to 3.20.151.2543.20.151.2552,046
1483.20.152.0/213.20.152.1 to 3.20.159.2543.20.159.2552,046
1493.20.160.0/213.20.160.1 to 3.20.167.2543.20.167.2552,046
1503.20.168.0/213.20.168.1 to 3.20.175.2543.20.175.2552,046
1513.20.176.0/213.20.176.1 to 3.20.183.2543.20.183.2552,046
1523.20.184.0/213.20.184.1 to 3.20.191.2543.20.191.2552,046
1533.20.192.0/213.20.192.1 to 3.20.199.2543.20.199.2552,046
1543.20.200.0/213.20.200.1 to 3.20.207.2543.20.207.2552,046
1553.20.208.0/213.20.208.1 to 3.20.215.2543.20.215.2552,046
1563.20.216.0/213.20.216.1 to 3.20.223.2543.20.223.2552,046
1573.20.224.0/213.20.224.1 to 3.20.231.2543.20.231.2552,046
1583.20.232.0/213.20.232.1 to 3.20.239.2543.20.239.2552,046
1593.20.240.0/213.20.240.1 to 3.20.247.2543.20.247.2552,046
1603.20.248.0/213.20.248.1 to 3.20.255.2543.20.255.2552,046
1613.21.0.0/213.21.0.1 to 3.21.7.2543.21.7.2552,046
1623.21.8.0/213.21.8.1 to 3.21.15.2543.21.15.2552,046
1633.21.16.0/213.21.16.1 to 3.21.23.2543.21.23.2552,046
1643.21.24.0/213.21.24.1 to 3.21.31.2543.21.31.2552,046
1653.21.32.0/213.21.32.1 to 3.21.39.2543.21.39.2552,046
1663.21.40.0/213.21.40.1 to 3.21.47.2543.21.47.2552,046
1673.21.48.0/213.21.48.1 to 3.21.55.2543.21.55.2552,046
1683.21.56.0/213.21.56.1 to 3.21.63.2543.21.63.2552,046
1693.21.64.0/213.21.64.1 to 3.21.71.2543.21.71.2552,046
1703.21.72.0/213.21.72.1 to 3.21.79.2543.21.79.2552,046
1713.21.80.0/213.21.80.1 to 3.21.87.2543.21.87.2552,046
1723.21.88.0/213.21.88.1 to 3.21.95.2543.21.95.2552,046
1733.21.96.0/213.21.96.1 to 3.21.103.2543.21.103.2552,046
1743.21.104.0/213.21.104.1 to 3.21.111.2543.21.111.2552,046
1753.21.112.0/213.21.112.1 to 3.21.119.2543.21.119.2552,046
1763.21.120.0/213.21.120.1 to 3.21.127.2543.21.127.2552,046
1773.21.128.0/213.21.128.1 to 3.21.135.2543.21.135.2552,046
1783.21.136.0/213.21.136.1 to 3.21.143.2543.21.143.2552,046
1793.21.144.0/213.21.144.1 to 3.21.151.2543.21.151.2552,046
1803.21.152.0/213.21.152.1 to 3.21.159.2543.21.159.2552,046
1813.21.160.0/213.21.160.1 to 3.21.167.2543.21.167.2552,046
1823.21.168.0/213.21.168.1 to 3.21.175.2543.21.175.2552,046
1833.21.176.0/213.21.176.1 to 3.21.183.2543.21.183.2552,046
1843.21.184.0/213.21.184.1 to 3.21.191.2543.21.191.2552,046
1853.21.192.0/213.21.192.1 to 3.21.199.2543.21.199.2552,046
1863.21.200.0/213.21.200.1 to 3.21.207.2543.21.207.2552,046
1873.21.208.0/213.21.208.1 to 3.21.215.2543.21.215.2552,046
1883.21.216.0/213.21.216.1 to 3.21.223.2543.21.223.2552,046
1893.21.224.0/213.21.224.1 to 3.21.231.2543.21.231.2552,046
1903.21.232.0/213.21.232.1 to 3.21.239.2543.21.239.2552,046
1913.21.240.0/213.21.240.1 to 3.21.247.2543.21.247.2552,046
1923.21.248.0/213.21.248.1 to 3.21.255.2543.21.255.2552,046
1933.22.0.0/213.22.0.1 to 3.22.7.2543.22.7.2552,046
1943.22.8.0/213.22.8.1 to 3.22.15.2543.22.15.2552,046
1953.22.16.0/213.22.16.1 to 3.22.23.2543.22.23.2552,046
1963.22.24.0/213.22.24.1 to 3.22.31.2543.22.31.2552,046
1973.22.32.0/213.22.32.1 to 3.22.39.2543.22.39.2552,046
1983.22.40.0/213.22.40.1 to 3.22.47.2543.22.47.2552,046
1993.22.48.0/213.22.48.1 to 3.22.55.2543.22.55.2552,046
2003.22.56.0/213.22.56.1 to 3.22.63.2543.22.63.2552,046
2013.22.64.0/213.22.64.1 to 3.22.71.2543.22.71.2552,046
2023.22.72.0/213.22.72.1 to 3.22.79.2543.22.79.2552,046
2033.22.80.0/213.22.80.1 to 3.22.87.2543.22.87.2552,046
2043.22.88.0/213.22.88.1 to 3.22.95.2543.22.95.2552,046
2053.22.96.0/213.22.96.1 to 3.22.103.2543.22.103.2552,046
2063.22.104.0/213.22.104.1 to 3.22.111.2543.22.111.2552,046
2073.22.112.0/213.22.112.1 to 3.22.119.2543.22.119.2552,046
2083.22.120.0/213.22.120.1 to 3.22.127.2543.22.127.2552,046
2093.22.128.0/213.22.128.1 to 3.22.135.2543.22.135.2552,046
2103.22.136.0/213.22.136.1 to 3.22.143.2543.22.143.2552,046
2113.22.144.0/213.22.144.1 to 3.22.151.2543.22.151.2552,046
2123.22.152.0/213.22.152.1 to 3.22.159.2543.22.159.2552,046
2133.22.160.0/213.22.160.1 to 3.22.167.2543.22.167.2552,046
2143.22.168.0/213.22.168.1 to 3.22.175.2543.22.175.2552,046
2153.22.176.0/213.22.176.1 to 3.22.183.2543.22.183.2552,046
2163.22.184.0/213.22.184.1 to 3.22.191.2543.22.191.2552,046
2173.22.192.0/213.22.192.1 to 3.22.199.2543.22.199.2552,046
2183.22.200.0/213.22.200.1 to 3.22.207.2543.22.207.2552,046
2193.22.208.0/213.22.208.1 to 3.22.215.2543.22.215.2552,046
2203.22.216.0/213.22.216.1 to 3.22.223.2543.22.223.2552,046
2213.22.224.0/213.22.224.1 to 3.22.231.2543.22.231.2552,046
2223.22.232.0/213.22.232.1 to 3.22.239.2543.22.239.2552,046
2233.22.240.0/213.22.240.1 to 3.22.247.2543.22.247.2552,046
2243.22.248.0/213.22.248.1 to 3.22.255.2543.22.255.2552,046
2253.23.0.0/213.23.0.1 to 3.23.7.2543.23.7.2552,046
2263.23.8.0/213.23.8.1 to 3.23.15.2543.23.15.2552,046
2273.23.16.0/213.23.16.1 to 3.23.23.2543.23.23.2552,046
2283.23.24.0/213.23.24.1 to 3.23.31.2543.23.31.2552,046
2293.23.32.0/213.23.32.1 to 3.23.39.2543.23.39.2552,046
2303.23.40.0/213.23.40.1 to 3.23.47.2543.23.47.2552,046
2313.23.48.0/213.23.48.1 to 3.23.55.2543.23.55.2552,046
2323.23.56.0/213.23.56.1 to 3.23.63.2543.23.63.2552,046
2333.23.64.0/213.23.64.1 to 3.23.71.2543.23.71.2552,046
2343.23.72.0/213.23.72.1 to 3.23.79.2543.23.79.2552,046
2353.23.80.0/213.23.80.1 to 3.23.87.2543.23.87.2552,046
2363.23.88.0/213.23.88.1 to 3.23.95.2543.23.95.2552,046
2373.23.96.0/213.23.96.1 to 3.23.103.2543.23.103.2552,046
2383.23.104.0/213.23.104.1 to 3.23.111.2543.23.111.2552,046
2393.23.112.0/213.23.112.1 to 3.23.119.2543.23.119.2552,046
2403.23.120.0/213.23.120.1 to 3.23.127.2543.23.127.2552,046
2413.23.128.0/213.23.128.1 to 3.23.135.2543.23.135.2552,046
2423.23.136.0/213.23.136.1 to 3.23.143.2543.23.143.2552,046
2433.23.144.0/213.23.144.1 to 3.23.151.2543.23.151.2552,046
2443.23.152.0/213.23.152.1 to 3.23.159.2543.23.159.2552,046
2453.23.160.0/213.23.160.1 to 3.23.167.2543.23.167.2552,046
2463.23.168.0/213.23.168.1 to 3.23.175.2543.23.175.2552,046
2473.23.176.0/213.23.176.1 to 3.23.183.2543.23.183.2552,046
2483.23.184.0/213.23.184.1 to 3.23.191.2543.23.191.2552,046
2493.23.192.0/213.23.192.1 to 3.23.199.2543.23.199.2552,046
2503.23.200.0/213.23.200.1 to 3.23.207.2543.23.207.2552,046
2513.23.208.0/213.23.208.1 to 3.23.215.2543.23.215.2552,046
2523.23.216.0/213.23.216.1 to 3.23.223.2543.23.223.2552,046
2533.23.224.0/213.23.224.1 to 3.23.231.2543.23.231.2552,046
2543.23.232.0/213.23.232.1 to 3.23.239.2543.23.239.2552,046
2553.23.240.0/213.23.240.1 to 3.23.247.2543.23.247.2552,046
2563.23.248.0/213.23.248.1 to 3.23.255.2543.23.255.2552,046

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.