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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.

Network5.0.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
5.0.0.0
Broadcast address
5.15.255.255
First usable
5.0.0.1
Last usable
5.15.255.254
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 05000000 · Integer 83886080 to 84934655
Reverse DNS zones
0.5.in-addr.arpa
1.5.in-addr.arpa
2.5.in-addr.arpa
3.5.in-addr.arpa
4.5.in-addr.arpa
5.5.in-addr.arpa
6.5.in-addr.arpa
7.5.in-addr.arpa
8.5.in-addr.arpa
9.5.in-addr.arpa
10.5.in-addr.arpa
11.5.in-addr.arpa
12.5.in-addr.arpa
13.5.in-addr.arpa
14.5.in-addr.arpa
15.5.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
Address00000101.00000000.00000000.000000005.0.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00000101.00000000.00000000.000000005.0.0.0
Broadcast00000101.00001111.11111111.111111115.15.255.255
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)

5.0.0.0/12 makes 512 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
15.0.0.0/215.0.0.1 to 5.0.7.2545.0.7.2552,046
25.0.8.0/215.0.8.1 to 5.0.15.2545.0.15.2552,046
35.0.16.0/215.0.16.1 to 5.0.23.2545.0.23.2552,046
45.0.24.0/215.0.24.1 to 5.0.31.2545.0.31.2552,046
55.0.32.0/215.0.32.1 to 5.0.39.2545.0.39.2552,046
65.0.40.0/215.0.40.1 to 5.0.47.2545.0.47.2552,046
75.0.48.0/215.0.48.1 to 5.0.55.2545.0.55.2552,046
85.0.56.0/215.0.56.1 to 5.0.63.2545.0.63.2552,046
95.0.64.0/215.0.64.1 to 5.0.71.2545.0.71.2552,046
105.0.72.0/215.0.72.1 to 5.0.79.2545.0.79.2552,046
115.0.80.0/215.0.80.1 to 5.0.87.2545.0.87.2552,046
125.0.88.0/215.0.88.1 to 5.0.95.2545.0.95.2552,046
135.0.96.0/215.0.96.1 to 5.0.103.2545.0.103.2552,046
145.0.104.0/215.0.104.1 to 5.0.111.2545.0.111.2552,046
155.0.112.0/215.0.112.1 to 5.0.119.2545.0.119.2552,046
165.0.120.0/215.0.120.1 to 5.0.127.2545.0.127.2552,046
175.0.128.0/215.0.128.1 to 5.0.135.2545.0.135.2552,046
185.0.136.0/215.0.136.1 to 5.0.143.2545.0.143.2552,046
195.0.144.0/215.0.144.1 to 5.0.151.2545.0.151.2552,046
205.0.152.0/215.0.152.1 to 5.0.159.2545.0.159.2552,046
215.0.160.0/215.0.160.1 to 5.0.167.2545.0.167.2552,046
225.0.168.0/215.0.168.1 to 5.0.175.2545.0.175.2552,046
235.0.176.0/215.0.176.1 to 5.0.183.2545.0.183.2552,046
245.0.184.0/215.0.184.1 to 5.0.191.2545.0.191.2552,046
255.0.192.0/215.0.192.1 to 5.0.199.2545.0.199.2552,046
265.0.200.0/215.0.200.1 to 5.0.207.2545.0.207.2552,046
275.0.208.0/215.0.208.1 to 5.0.215.2545.0.215.2552,046
285.0.216.0/215.0.216.1 to 5.0.223.2545.0.223.2552,046
295.0.224.0/215.0.224.1 to 5.0.231.2545.0.231.2552,046
305.0.232.0/215.0.232.1 to 5.0.239.2545.0.239.2552,046
315.0.240.0/215.0.240.1 to 5.0.247.2545.0.247.2552,046
325.0.248.0/215.0.248.1 to 5.0.255.2545.0.255.2552,046
335.1.0.0/215.1.0.1 to 5.1.7.2545.1.7.2552,046
345.1.8.0/215.1.8.1 to 5.1.15.2545.1.15.2552,046
355.1.16.0/215.1.16.1 to 5.1.23.2545.1.23.2552,046
365.1.24.0/215.1.24.1 to 5.1.31.2545.1.31.2552,046
375.1.32.0/215.1.32.1 to 5.1.39.2545.1.39.2552,046
385.1.40.0/215.1.40.1 to 5.1.47.2545.1.47.2552,046
395.1.48.0/215.1.48.1 to 5.1.55.2545.1.55.2552,046
405.1.56.0/215.1.56.1 to 5.1.63.2545.1.63.2552,046
415.1.64.0/215.1.64.1 to 5.1.71.2545.1.71.2552,046
425.1.72.0/215.1.72.1 to 5.1.79.2545.1.79.2552,046
435.1.80.0/215.1.80.1 to 5.1.87.2545.1.87.2552,046
445.1.88.0/215.1.88.1 to 5.1.95.2545.1.95.2552,046
455.1.96.0/215.1.96.1 to 5.1.103.2545.1.103.2552,046
465.1.104.0/215.1.104.1 to 5.1.111.2545.1.111.2552,046
475.1.112.0/215.1.112.1 to 5.1.119.2545.1.119.2552,046
485.1.120.0/215.1.120.1 to 5.1.127.2545.1.127.2552,046
495.1.128.0/215.1.128.1 to 5.1.135.2545.1.135.2552,046
505.1.136.0/215.1.136.1 to 5.1.143.2545.1.143.2552,046
515.1.144.0/215.1.144.1 to 5.1.151.2545.1.151.2552,046
525.1.152.0/215.1.152.1 to 5.1.159.2545.1.159.2552,046
535.1.160.0/215.1.160.1 to 5.1.167.2545.1.167.2552,046
545.1.168.0/215.1.168.1 to 5.1.175.2545.1.175.2552,046
555.1.176.0/215.1.176.1 to 5.1.183.2545.1.183.2552,046
565.1.184.0/215.1.184.1 to 5.1.191.2545.1.191.2552,046
575.1.192.0/215.1.192.1 to 5.1.199.2545.1.199.2552,046
585.1.200.0/215.1.200.1 to 5.1.207.2545.1.207.2552,046
595.1.208.0/215.1.208.1 to 5.1.215.2545.1.215.2552,046
605.1.216.0/215.1.216.1 to 5.1.223.2545.1.223.2552,046
615.1.224.0/215.1.224.1 to 5.1.231.2545.1.231.2552,046
625.1.232.0/215.1.232.1 to 5.1.239.2545.1.239.2552,046
635.1.240.0/215.1.240.1 to 5.1.247.2545.1.247.2552,046
645.1.248.0/215.1.248.1 to 5.1.255.2545.1.255.2552,046
655.2.0.0/215.2.0.1 to 5.2.7.2545.2.7.2552,046
665.2.8.0/215.2.8.1 to 5.2.15.2545.2.15.2552,046
675.2.16.0/215.2.16.1 to 5.2.23.2545.2.23.2552,046
685.2.24.0/215.2.24.1 to 5.2.31.2545.2.31.2552,046
695.2.32.0/215.2.32.1 to 5.2.39.2545.2.39.2552,046
705.2.40.0/215.2.40.1 to 5.2.47.2545.2.47.2552,046
715.2.48.0/215.2.48.1 to 5.2.55.2545.2.55.2552,046
725.2.56.0/215.2.56.1 to 5.2.63.2545.2.63.2552,046
735.2.64.0/215.2.64.1 to 5.2.71.2545.2.71.2552,046
745.2.72.0/215.2.72.1 to 5.2.79.2545.2.79.2552,046
755.2.80.0/215.2.80.1 to 5.2.87.2545.2.87.2552,046
765.2.88.0/215.2.88.1 to 5.2.95.2545.2.95.2552,046
775.2.96.0/215.2.96.1 to 5.2.103.2545.2.103.2552,046
785.2.104.0/215.2.104.1 to 5.2.111.2545.2.111.2552,046
795.2.112.0/215.2.112.1 to 5.2.119.2545.2.119.2552,046
805.2.120.0/215.2.120.1 to 5.2.127.2545.2.127.2552,046
815.2.128.0/215.2.128.1 to 5.2.135.2545.2.135.2552,046
825.2.136.0/215.2.136.1 to 5.2.143.2545.2.143.2552,046
835.2.144.0/215.2.144.1 to 5.2.151.2545.2.151.2552,046
845.2.152.0/215.2.152.1 to 5.2.159.2545.2.159.2552,046
855.2.160.0/215.2.160.1 to 5.2.167.2545.2.167.2552,046
865.2.168.0/215.2.168.1 to 5.2.175.2545.2.175.2552,046
875.2.176.0/215.2.176.1 to 5.2.183.2545.2.183.2552,046
885.2.184.0/215.2.184.1 to 5.2.191.2545.2.191.2552,046
895.2.192.0/215.2.192.1 to 5.2.199.2545.2.199.2552,046
905.2.200.0/215.2.200.1 to 5.2.207.2545.2.207.2552,046
915.2.208.0/215.2.208.1 to 5.2.215.2545.2.215.2552,046
925.2.216.0/215.2.216.1 to 5.2.223.2545.2.223.2552,046
935.2.224.0/215.2.224.1 to 5.2.231.2545.2.231.2552,046
945.2.232.0/215.2.232.1 to 5.2.239.2545.2.239.2552,046
955.2.240.0/215.2.240.1 to 5.2.247.2545.2.247.2552,046
965.2.248.0/215.2.248.1 to 5.2.255.2545.2.255.2552,046
975.3.0.0/215.3.0.1 to 5.3.7.2545.3.7.2552,046
985.3.8.0/215.3.8.1 to 5.3.15.2545.3.15.2552,046
995.3.16.0/215.3.16.1 to 5.3.23.2545.3.23.2552,046
1005.3.24.0/215.3.24.1 to 5.3.31.2545.3.31.2552,046
1015.3.32.0/215.3.32.1 to 5.3.39.2545.3.39.2552,046
1025.3.40.0/215.3.40.1 to 5.3.47.2545.3.47.2552,046
1035.3.48.0/215.3.48.1 to 5.3.55.2545.3.55.2552,046
1045.3.56.0/215.3.56.1 to 5.3.63.2545.3.63.2552,046
1055.3.64.0/215.3.64.1 to 5.3.71.2545.3.71.2552,046
1065.3.72.0/215.3.72.1 to 5.3.79.2545.3.79.2552,046
1075.3.80.0/215.3.80.1 to 5.3.87.2545.3.87.2552,046
1085.3.88.0/215.3.88.1 to 5.3.95.2545.3.95.2552,046
1095.3.96.0/215.3.96.1 to 5.3.103.2545.3.103.2552,046
1105.3.104.0/215.3.104.1 to 5.3.111.2545.3.111.2552,046
1115.3.112.0/215.3.112.1 to 5.3.119.2545.3.119.2552,046
1125.3.120.0/215.3.120.1 to 5.3.127.2545.3.127.2552,046
1135.3.128.0/215.3.128.1 to 5.3.135.2545.3.135.2552,046
1145.3.136.0/215.3.136.1 to 5.3.143.2545.3.143.2552,046
1155.3.144.0/215.3.144.1 to 5.3.151.2545.3.151.2552,046
1165.3.152.0/215.3.152.1 to 5.3.159.2545.3.159.2552,046
1175.3.160.0/215.3.160.1 to 5.3.167.2545.3.167.2552,046
1185.3.168.0/215.3.168.1 to 5.3.175.2545.3.175.2552,046
1195.3.176.0/215.3.176.1 to 5.3.183.2545.3.183.2552,046
1205.3.184.0/215.3.184.1 to 5.3.191.2545.3.191.2552,046
1215.3.192.0/215.3.192.1 to 5.3.199.2545.3.199.2552,046
1225.3.200.0/215.3.200.1 to 5.3.207.2545.3.207.2552,046
1235.3.208.0/215.3.208.1 to 5.3.215.2545.3.215.2552,046
1245.3.216.0/215.3.216.1 to 5.3.223.2545.3.223.2552,046
1255.3.224.0/215.3.224.1 to 5.3.231.2545.3.231.2552,046
1265.3.232.0/215.3.232.1 to 5.3.239.2545.3.239.2552,046
1275.3.240.0/215.3.240.1 to 5.3.247.2545.3.247.2552,046
1285.3.248.0/215.3.248.1 to 5.3.255.2545.3.255.2552,046
1295.4.0.0/215.4.0.1 to 5.4.7.2545.4.7.2552,046
1305.4.8.0/215.4.8.1 to 5.4.15.2545.4.15.2552,046
1315.4.16.0/215.4.16.1 to 5.4.23.2545.4.23.2552,046
1325.4.24.0/215.4.24.1 to 5.4.31.2545.4.31.2552,046
1335.4.32.0/215.4.32.1 to 5.4.39.2545.4.39.2552,046
1345.4.40.0/215.4.40.1 to 5.4.47.2545.4.47.2552,046
1355.4.48.0/215.4.48.1 to 5.4.55.2545.4.55.2552,046
1365.4.56.0/215.4.56.1 to 5.4.63.2545.4.63.2552,046
1375.4.64.0/215.4.64.1 to 5.4.71.2545.4.71.2552,046
1385.4.72.0/215.4.72.1 to 5.4.79.2545.4.79.2552,046
1395.4.80.0/215.4.80.1 to 5.4.87.2545.4.87.2552,046
1405.4.88.0/215.4.88.1 to 5.4.95.2545.4.95.2552,046
1415.4.96.0/215.4.96.1 to 5.4.103.2545.4.103.2552,046
1425.4.104.0/215.4.104.1 to 5.4.111.2545.4.111.2552,046
1435.4.112.0/215.4.112.1 to 5.4.119.2545.4.119.2552,046
1445.4.120.0/215.4.120.1 to 5.4.127.2545.4.127.2552,046
1455.4.128.0/215.4.128.1 to 5.4.135.2545.4.135.2552,046
1465.4.136.0/215.4.136.1 to 5.4.143.2545.4.143.2552,046
1475.4.144.0/215.4.144.1 to 5.4.151.2545.4.151.2552,046
1485.4.152.0/215.4.152.1 to 5.4.159.2545.4.159.2552,046
1495.4.160.0/215.4.160.1 to 5.4.167.2545.4.167.2552,046
1505.4.168.0/215.4.168.1 to 5.4.175.2545.4.175.2552,046
1515.4.176.0/215.4.176.1 to 5.4.183.2545.4.183.2552,046
1525.4.184.0/215.4.184.1 to 5.4.191.2545.4.191.2552,046
1535.4.192.0/215.4.192.1 to 5.4.199.2545.4.199.2552,046
1545.4.200.0/215.4.200.1 to 5.4.207.2545.4.207.2552,046
1555.4.208.0/215.4.208.1 to 5.4.215.2545.4.215.2552,046
1565.4.216.0/215.4.216.1 to 5.4.223.2545.4.223.2552,046
1575.4.224.0/215.4.224.1 to 5.4.231.2545.4.231.2552,046
1585.4.232.0/215.4.232.1 to 5.4.239.2545.4.239.2552,046
1595.4.240.0/215.4.240.1 to 5.4.247.2545.4.247.2552,046
1605.4.248.0/215.4.248.1 to 5.4.255.2545.4.255.2552,046
1615.5.0.0/215.5.0.1 to 5.5.7.2545.5.7.2552,046
1625.5.8.0/215.5.8.1 to 5.5.15.2545.5.15.2552,046
1635.5.16.0/215.5.16.1 to 5.5.23.2545.5.23.2552,046
1645.5.24.0/215.5.24.1 to 5.5.31.2545.5.31.2552,046
1655.5.32.0/215.5.32.1 to 5.5.39.2545.5.39.2552,046
1665.5.40.0/215.5.40.1 to 5.5.47.2545.5.47.2552,046
1675.5.48.0/215.5.48.1 to 5.5.55.2545.5.55.2552,046
1685.5.56.0/215.5.56.1 to 5.5.63.2545.5.63.2552,046
1695.5.64.0/215.5.64.1 to 5.5.71.2545.5.71.2552,046
1705.5.72.0/215.5.72.1 to 5.5.79.2545.5.79.2552,046
1715.5.80.0/215.5.80.1 to 5.5.87.2545.5.87.2552,046
1725.5.88.0/215.5.88.1 to 5.5.95.2545.5.95.2552,046
1735.5.96.0/215.5.96.1 to 5.5.103.2545.5.103.2552,046
1745.5.104.0/215.5.104.1 to 5.5.111.2545.5.111.2552,046
1755.5.112.0/215.5.112.1 to 5.5.119.2545.5.119.2552,046
1765.5.120.0/215.5.120.1 to 5.5.127.2545.5.127.2552,046
1775.5.128.0/215.5.128.1 to 5.5.135.2545.5.135.2552,046
1785.5.136.0/215.5.136.1 to 5.5.143.2545.5.143.2552,046
1795.5.144.0/215.5.144.1 to 5.5.151.2545.5.151.2552,046
1805.5.152.0/215.5.152.1 to 5.5.159.2545.5.159.2552,046
1815.5.160.0/215.5.160.1 to 5.5.167.2545.5.167.2552,046
1825.5.168.0/215.5.168.1 to 5.5.175.2545.5.175.2552,046
1835.5.176.0/215.5.176.1 to 5.5.183.2545.5.183.2552,046
1845.5.184.0/215.5.184.1 to 5.5.191.2545.5.191.2552,046
1855.5.192.0/215.5.192.1 to 5.5.199.2545.5.199.2552,046
1865.5.200.0/215.5.200.1 to 5.5.207.2545.5.207.2552,046
1875.5.208.0/215.5.208.1 to 5.5.215.2545.5.215.2552,046
1885.5.216.0/215.5.216.1 to 5.5.223.2545.5.223.2552,046
1895.5.224.0/215.5.224.1 to 5.5.231.2545.5.231.2552,046
1905.5.232.0/215.5.232.1 to 5.5.239.2545.5.239.2552,046
1915.5.240.0/215.5.240.1 to 5.5.247.2545.5.247.2552,046
1925.5.248.0/215.5.248.1 to 5.5.255.2545.5.255.2552,046
1935.6.0.0/215.6.0.1 to 5.6.7.2545.6.7.2552,046
1945.6.8.0/215.6.8.1 to 5.6.15.2545.6.15.2552,046
1955.6.16.0/215.6.16.1 to 5.6.23.2545.6.23.2552,046
1965.6.24.0/215.6.24.1 to 5.6.31.2545.6.31.2552,046
1975.6.32.0/215.6.32.1 to 5.6.39.2545.6.39.2552,046
1985.6.40.0/215.6.40.1 to 5.6.47.2545.6.47.2552,046
1995.6.48.0/215.6.48.1 to 5.6.55.2545.6.55.2552,046
2005.6.56.0/215.6.56.1 to 5.6.63.2545.6.63.2552,046
2015.6.64.0/215.6.64.1 to 5.6.71.2545.6.71.2552,046
2025.6.72.0/215.6.72.1 to 5.6.79.2545.6.79.2552,046
2035.6.80.0/215.6.80.1 to 5.6.87.2545.6.87.2552,046
2045.6.88.0/215.6.88.1 to 5.6.95.2545.6.95.2552,046
2055.6.96.0/215.6.96.1 to 5.6.103.2545.6.103.2552,046
2065.6.104.0/215.6.104.1 to 5.6.111.2545.6.111.2552,046
2075.6.112.0/215.6.112.1 to 5.6.119.2545.6.119.2552,046
2085.6.120.0/215.6.120.1 to 5.6.127.2545.6.127.2552,046
2095.6.128.0/215.6.128.1 to 5.6.135.2545.6.135.2552,046
2105.6.136.0/215.6.136.1 to 5.6.143.2545.6.143.2552,046
2115.6.144.0/215.6.144.1 to 5.6.151.2545.6.151.2552,046
2125.6.152.0/215.6.152.1 to 5.6.159.2545.6.159.2552,046
2135.6.160.0/215.6.160.1 to 5.6.167.2545.6.167.2552,046
2145.6.168.0/215.6.168.1 to 5.6.175.2545.6.175.2552,046
2155.6.176.0/215.6.176.1 to 5.6.183.2545.6.183.2552,046
2165.6.184.0/215.6.184.1 to 5.6.191.2545.6.191.2552,046
2175.6.192.0/215.6.192.1 to 5.6.199.2545.6.199.2552,046
2185.6.200.0/215.6.200.1 to 5.6.207.2545.6.207.2552,046
2195.6.208.0/215.6.208.1 to 5.6.215.2545.6.215.2552,046
2205.6.216.0/215.6.216.1 to 5.6.223.2545.6.223.2552,046
2215.6.224.0/215.6.224.1 to 5.6.231.2545.6.231.2552,046
2225.6.232.0/215.6.232.1 to 5.6.239.2545.6.239.2552,046
2235.6.240.0/215.6.240.1 to 5.6.247.2545.6.247.2552,046
2245.6.248.0/215.6.248.1 to 5.6.255.2545.6.255.2552,046
2255.7.0.0/215.7.0.1 to 5.7.7.2545.7.7.2552,046
2265.7.8.0/215.7.8.1 to 5.7.15.2545.7.15.2552,046
2275.7.16.0/215.7.16.1 to 5.7.23.2545.7.23.2552,046
2285.7.24.0/215.7.24.1 to 5.7.31.2545.7.31.2552,046
2295.7.32.0/215.7.32.1 to 5.7.39.2545.7.39.2552,046
2305.7.40.0/215.7.40.1 to 5.7.47.2545.7.47.2552,046
2315.7.48.0/215.7.48.1 to 5.7.55.2545.7.55.2552,046
2325.7.56.0/215.7.56.1 to 5.7.63.2545.7.63.2552,046
2335.7.64.0/215.7.64.1 to 5.7.71.2545.7.71.2552,046
2345.7.72.0/215.7.72.1 to 5.7.79.2545.7.79.2552,046
2355.7.80.0/215.7.80.1 to 5.7.87.2545.7.87.2552,046
2365.7.88.0/215.7.88.1 to 5.7.95.2545.7.95.2552,046
2375.7.96.0/215.7.96.1 to 5.7.103.2545.7.103.2552,046
2385.7.104.0/215.7.104.1 to 5.7.111.2545.7.111.2552,046
2395.7.112.0/215.7.112.1 to 5.7.119.2545.7.119.2552,046
2405.7.120.0/215.7.120.1 to 5.7.127.2545.7.127.2552,046
2415.7.128.0/215.7.128.1 to 5.7.135.2545.7.135.2552,046
2425.7.136.0/215.7.136.1 to 5.7.143.2545.7.143.2552,046
2435.7.144.0/215.7.144.1 to 5.7.151.2545.7.151.2552,046
2445.7.152.0/215.7.152.1 to 5.7.159.2545.7.159.2552,046
2455.7.160.0/215.7.160.1 to 5.7.167.2545.7.167.2552,046
2465.7.168.0/215.7.168.1 to 5.7.175.2545.7.175.2552,046
2475.7.176.0/215.7.176.1 to 5.7.183.2545.7.183.2552,046
2485.7.184.0/215.7.184.1 to 5.7.191.2545.7.191.2552,046
2495.7.192.0/215.7.192.1 to 5.7.199.2545.7.199.2552,046
2505.7.200.0/215.7.200.1 to 5.7.207.2545.7.207.2552,046
2515.7.208.0/215.7.208.1 to 5.7.215.2545.7.215.2552,046
2525.7.216.0/215.7.216.1 to 5.7.223.2545.7.223.2552,046
2535.7.224.0/215.7.224.1 to 5.7.231.2545.7.231.2552,046
2545.7.232.0/215.7.232.1 to 5.7.239.2545.7.239.2552,046
2555.7.240.0/215.7.240.1 to 5.7.247.2545.7.247.2552,046
2565.7.248.0/215.7.248.1 to 5.7.255.2545.7.255.2552,046

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.