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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.

Network12.240.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
12.240.0.0
Broadcast address
12.255.255.255
First usable
12.240.0.1
Last usable
12.255.255.254
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 0CF00000 · Integer 217055232 to 218103807
Reverse DNS zones
240.12.in-addr.arpa
241.12.in-addr.arpa
242.12.in-addr.arpa
243.12.in-addr.arpa
244.12.in-addr.arpa
245.12.in-addr.arpa
246.12.in-addr.arpa
247.12.in-addr.arpa
248.12.in-addr.arpa
249.12.in-addr.arpa
250.12.in-addr.arpa
251.12.in-addr.arpa
252.12.in-addr.arpa
253.12.in-addr.arpa
254.12.in-addr.arpa
255.12.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
Address00001100.11110000.00000000.0000000012.240.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00001100.11110000.00000000.0000000012.240.0.0
Broadcast00001100.11111111.11111111.1111111112.255.255.255
Split into smaller subnets/20
/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)

12.240.0.0/12 makes 256 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
112.240.0.0/2012.240.0.1 to 12.240.15.25412.240.15.2554,094
212.240.16.0/2012.240.16.1 to 12.240.31.25412.240.31.2554,094
312.240.32.0/2012.240.32.1 to 12.240.47.25412.240.47.2554,094
412.240.48.0/2012.240.48.1 to 12.240.63.25412.240.63.2554,094
512.240.64.0/2012.240.64.1 to 12.240.79.25412.240.79.2554,094
612.240.80.0/2012.240.80.1 to 12.240.95.25412.240.95.2554,094
712.240.96.0/2012.240.96.1 to 12.240.111.25412.240.111.2554,094
812.240.112.0/2012.240.112.1 to 12.240.127.25412.240.127.2554,094
912.240.128.0/2012.240.128.1 to 12.240.143.25412.240.143.2554,094
1012.240.144.0/2012.240.144.1 to 12.240.159.25412.240.159.2554,094
1112.240.160.0/2012.240.160.1 to 12.240.175.25412.240.175.2554,094
1212.240.176.0/2012.240.176.1 to 12.240.191.25412.240.191.2554,094
1312.240.192.0/2012.240.192.1 to 12.240.207.25412.240.207.2554,094
1412.240.208.0/2012.240.208.1 to 12.240.223.25412.240.223.2554,094
1512.240.224.0/2012.240.224.1 to 12.240.239.25412.240.239.2554,094
1612.240.240.0/2012.240.240.1 to 12.240.255.25412.240.255.2554,094
1712.241.0.0/2012.241.0.1 to 12.241.15.25412.241.15.2554,094
1812.241.16.0/2012.241.16.1 to 12.241.31.25412.241.31.2554,094
1912.241.32.0/2012.241.32.1 to 12.241.47.25412.241.47.2554,094
2012.241.48.0/2012.241.48.1 to 12.241.63.25412.241.63.2554,094
2112.241.64.0/2012.241.64.1 to 12.241.79.25412.241.79.2554,094
2212.241.80.0/2012.241.80.1 to 12.241.95.25412.241.95.2554,094
2312.241.96.0/2012.241.96.1 to 12.241.111.25412.241.111.2554,094
2412.241.112.0/2012.241.112.1 to 12.241.127.25412.241.127.2554,094
2512.241.128.0/2012.241.128.1 to 12.241.143.25412.241.143.2554,094
2612.241.144.0/2012.241.144.1 to 12.241.159.25412.241.159.2554,094
2712.241.160.0/2012.241.160.1 to 12.241.175.25412.241.175.2554,094
2812.241.176.0/2012.241.176.1 to 12.241.191.25412.241.191.2554,094
2912.241.192.0/2012.241.192.1 to 12.241.207.25412.241.207.2554,094
3012.241.208.0/2012.241.208.1 to 12.241.223.25412.241.223.2554,094
3112.241.224.0/2012.241.224.1 to 12.241.239.25412.241.239.2554,094
3212.241.240.0/2012.241.240.1 to 12.241.255.25412.241.255.2554,094
3312.242.0.0/2012.242.0.1 to 12.242.15.25412.242.15.2554,094
3412.242.16.0/2012.242.16.1 to 12.242.31.25412.242.31.2554,094
3512.242.32.0/2012.242.32.1 to 12.242.47.25412.242.47.2554,094
3612.242.48.0/2012.242.48.1 to 12.242.63.25412.242.63.2554,094
3712.242.64.0/2012.242.64.1 to 12.242.79.25412.242.79.2554,094
3812.242.80.0/2012.242.80.1 to 12.242.95.25412.242.95.2554,094
3912.242.96.0/2012.242.96.1 to 12.242.111.25412.242.111.2554,094
4012.242.112.0/2012.242.112.1 to 12.242.127.25412.242.127.2554,094
4112.242.128.0/2012.242.128.1 to 12.242.143.25412.242.143.2554,094
4212.242.144.0/2012.242.144.1 to 12.242.159.25412.242.159.2554,094
4312.242.160.0/2012.242.160.1 to 12.242.175.25412.242.175.2554,094
4412.242.176.0/2012.242.176.1 to 12.242.191.25412.242.191.2554,094
4512.242.192.0/2012.242.192.1 to 12.242.207.25412.242.207.2554,094
4612.242.208.0/2012.242.208.1 to 12.242.223.25412.242.223.2554,094
4712.242.224.0/2012.242.224.1 to 12.242.239.25412.242.239.2554,094
4812.242.240.0/2012.242.240.1 to 12.242.255.25412.242.255.2554,094
4912.243.0.0/2012.243.0.1 to 12.243.15.25412.243.15.2554,094
5012.243.16.0/2012.243.16.1 to 12.243.31.25412.243.31.2554,094
5112.243.32.0/2012.243.32.1 to 12.243.47.25412.243.47.2554,094
5212.243.48.0/2012.243.48.1 to 12.243.63.25412.243.63.2554,094
5312.243.64.0/2012.243.64.1 to 12.243.79.25412.243.79.2554,094
5412.243.80.0/2012.243.80.1 to 12.243.95.25412.243.95.2554,094
5512.243.96.0/2012.243.96.1 to 12.243.111.25412.243.111.2554,094
5612.243.112.0/2012.243.112.1 to 12.243.127.25412.243.127.2554,094
5712.243.128.0/2012.243.128.1 to 12.243.143.25412.243.143.2554,094
5812.243.144.0/2012.243.144.1 to 12.243.159.25412.243.159.2554,094
5912.243.160.0/2012.243.160.1 to 12.243.175.25412.243.175.2554,094
6012.243.176.0/2012.243.176.1 to 12.243.191.25412.243.191.2554,094
6112.243.192.0/2012.243.192.1 to 12.243.207.25412.243.207.2554,094
6212.243.208.0/2012.243.208.1 to 12.243.223.25412.243.223.2554,094
6312.243.224.0/2012.243.224.1 to 12.243.239.25412.243.239.2554,094
6412.243.240.0/2012.243.240.1 to 12.243.255.25412.243.255.2554,094
6512.244.0.0/2012.244.0.1 to 12.244.15.25412.244.15.2554,094
6612.244.16.0/2012.244.16.1 to 12.244.31.25412.244.31.2554,094
6712.244.32.0/2012.244.32.1 to 12.244.47.25412.244.47.2554,094
6812.244.48.0/2012.244.48.1 to 12.244.63.25412.244.63.2554,094
6912.244.64.0/2012.244.64.1 to 12.244.79.25412.244.79.2554,094
7012.244.80.0/2012.244.80.1 to 12.244.95.25412.244.95.2554,094
7112.244.96.0/2012.244.96.1 to 12.244.111.25412.244.111.2554,094
7212.244.112.0/2012.244.112.1 to 12.244.127.25412.244.127.2554,094
7312.244.128.0/2012.244.128.1 to 12.244.143.25412.244.143.2554,094
7412.244.144.0/2012.244.144.1 to 12.244.159.25412.244.159.2554,094
7512.244.160.0/2012.244.160.1 to 12.244.175.25412.244.175.2554,094
7612.244.176.0/2012.244.176.1 to 12.244.191.25412.244.191.2554,094
7712.244.192.0/2012.244.192.1 to 12.244.207.25412.244.207.2554,094
7812.244.208.0/2012.244.208.1 to 12.244.223.25412.244.223.2554,094
7912.244.224.0/2012.244.224.1 to 12.244.239.25412.244.239.2554,094
8012.244.240.0/2012.244.240.1 to 12.244.255.25412.244.255.2554,094
8112.245.0.0/2012.245.0.1 to 12.245.15.25412.245.15.2554,094
8212.245.16.0/2012.245.16.1 to 12.245.31.25412.245.31.2554,094
8312.245.32.0/2012.245.32.1 to 12.245.47.25412.245.47.2554,094
8412.245.48.0/2012.245.48.1 to 12.245.63.25412.245.63.2554,094
8512.245.64.0/2012.245.64.1 to 12.245.79.25412.245.79.2554,094
8612.245.80.0/2012.245.80.1 to 12.245.95.25412.245.95.2554,094
8712.245.96.0/2012.245.96.1 to 12.245.111.25412.245.111.2554,094
8812.245.112.0/2012.245.112.1 to 12.245.127.25412.245.127.2554,094
8912.245.128.0/2012.245.128.1 to 12.245.143.25412.245.143.2554,094
9012.245.144.0/2012.245.144.1 to 12.245.159.25412.245.159.2554,094
9112.245.160.0/2012.245.160.1 to 12.245.175.25412.245.175.2554,094
9212.245.176.0/2012.245.176.1 to 12.245.191.25412.245.191.2554,094
9312.245.192.0/2012.245.192.1 to 12.245.207.25412.245.207.2554,094
9412.245.208.0/2012.245.208.1 to 12.245.223.25412.245.223.2554,094
9512.245.224.0/2012.245.224.1 to 12.245.239.25412.245.239.2554,094
9612.245.240.0/2012.245.240.1 to 12.245.255.25412.245.255.2554,094
9712.246.0.0/2012.246.0.1 to 12.246.15.25412.246.15.2554,094
9812.246.16.0/2012.246.16.1 to 12.246.31.25412.246.31.2554,094
9912.246.32.0/2012.246.32.1 to 12.246.47.25412.246.47.2554,094
10012.246.48.0/2012.246.48.1 to 12.246.63.25412.246.63.2554,094
10112.246.64.0/2012.246.64.1 to 12.246.79.25412.246.79.2554,094
10212.246.80.0/2012.246.80.1 to 12.246.95.25412.246.95.2554,094
10312.246.96.0/2012.246.96.1 to 12.246.111.25412.246.111.2554,094
10412.246.112.0/2012.246.112.1 to 12.246.127.25412.246.127.2554,094
10512.246.128.0/2012.246.128.1 to 12.246.143.25412.246.143.2554,094
10612.246.144.0/2012.246.144.1 to 12.246.159.25412.246.159.2554,094
10712.246.160.0/2012.246.160.1 to 12.246.175.25412.246.175.2554,094
10812.246.176.0/2012.246.176.1 to 12.246.191.25412.246.191.2554,094
10912.246.192.0/2012.246.192.1 to 12.246.207.25412.246.207.2554,094
11012.246.208.0/2012.246.208.1 to 12.246.223.25412.246.223.2554,094
11112.246.224.0/2012.246.224.1 to 12.246.239.25412.246.239.2554,094
11212.246.240.0/2012.246.240.1 to 12.246.255.25412.246.255.2554,094
11312.247.0.0/2012.247.0.1 to 12.247.15.25412.247.15.2554,094
11412.247.16.0/2012.247.16.1 to 12.247.31.25412.247.31.2554,094
11512.247.32.0/2012.247.32.1 to 12.247.47.25412.247.47.2554,094
11612.247.48.0/2012.247.48.1 to 12.247.63.25412.247.63.2554,094
11712.247.64.0/2012.247.64.1 to 12.247.79.25412.247.79.2554,094
11812.247.80.0/2012.247.80.1 to 12.247.95.25412.247.95.2554,094
11912.247.96.0/2012.247.96.1 to 12.247.111.25412.247.111.2554,094
12012.247.112.0/2012.247.112.1 to 12.247.127.25412.247.127.2554,094
12112.247.128.0/2012.247.128.1 to 12.247.143.25412.247.143.2554,094
12212.247.144.0/2012.247.144.1 to 12.247.159.25412.247.159.2554,094
12312.247.160.0/2012.247.160.1 to 12.247.175.25412.247.175.2554,094
12412.247.176.0/2012.247.176.1 to 12.247.191.25412.247.191.2554,094
12512.247.192.0/2012.247.192.1 to 12.247.207.25412.247.207.2554,094
12612.247.208.0/2012.247.208.1 to 12.247.223.25412.247.223.2554,094
12712.247.224.0/2012.247.224.1 to 12.247.239.25412.247.239.2554,094
12812.247.240.0/2012.247.240.1 to 12.247.255.25412.247.255.2554,094
12912.248.0.0/2012.248.0.1 to 12.248.15.25412.248.15.2554,094
13012.248.16.0/2012.248.16.1 to 12.248.31.25412.248.31.2554,094
13112.248.32.0/2012.248.32.1 to 12.248.47.25412.248.47.2554,094
13212.248.48.0/2012.248.48.1 to 12.248.63.25412.248.63.2554,094
13312.248.64.0/2012.248.64.1 to 12.248.79.25412.248.79.2554,094
13412.248.80.0/2012.248.80.1 to 12.248.95.25412.248.95.2554,094
13512.248.96.0/2012.248.96.1 to 12.248.111.25412.248.111.2554,094
13612.248.112.0/2012.248.112.1 to 12.248.127.25412.248.127.2554,094
13712.248.128.0/2012.248.128.1 to 12.248.143.25412.248.143.2554,094
13812.248.144.0/2012.248.144.1 to 12.248.159.25412.248.159.2554,094
13912.248.160.0/2012.248.160.1 to 12.248.175.25412.248.175.2554,094
14012.248.176.0/2012.248.176.1 to 12.248.191.25412.248.191.2554,094
14112.248.192.0/2012.248.192.1 to 12.248.207.25412.248.207.2554,094
14212.248.208.0/2012.248.208.1 to 12.248.223.25412.248.223.2554,094
14312.248.224.0/2012.248.224.1 to 12.248.239.25412.248.239.2554,094
14412.248.240.0/2012.248.240.1 to 12.248.255.25412.248.255.2554,094
14512.249.0.0/2012.249.0.1 to 12.249.15.25412.249.15.2554,094
14612.249.16.0/2012.249.16.1 to 12.249.31.25412.249.31.2554,094
14712.249.32.0/2012.249.32.1 to 12.249.47.25412.249.47.2554,094
14812.249.48.0/2012.249.48.1 to 12.249.63.25412.249.63.2554,094
14912.249.64.0/2012.249.64.1 to 12.249.79.25412.249.79.2554,094
15012.249.80.0/2012.249.80.1 to 12.249.95.25412.249.95.2554,094
15112.249.96.0/2012.249.96.1 to 12.249.111.25412.249.111.2554,094
15212.249.112.0/2012.249.112.1 to 12.249.127.25412.249.127.2554,094
15312.249.128.0/2012.249.128.1 to 12.249.143.25412.249.143.2554,094
15412.249.144.0/2012.249.144.1 to 12.249.159.25412.249.159.2554,094
15512.249.160.0/2012.249.160.1 to 12.249.175.25412.249.175.2554,094
15612.249.176.0/2012.249.176.1 to 12.249.191.25412.249.191.2554,094
15712.249.192.0/2012.249.192.1 to 12.249.207.25412.249.207.2554,094
15812.249.208.0/2012.249.208.1 to 12.249.223.25412.249.223.2554,094
15912.249.224.0/2012.249.224.1 to 12.249.239.25412.249.239.2554,094
16012.249.240.0/2012.249.240.1 to 12.249.255.25412.249.255.2554,094
16112.250.0.0/2012.250.0.1 to 12.250.15.25412.250.15.2554,094
16212.250.16.0/2012.250.16.1 to 12.250.31.25412.250.31.2554,094
16312.250.32.0/2012.250.32.1 to 12.250.47.25412.250.47.2554,094
16412.250.48.0/2012.250.48.1 to 12.250.63.25412.250.63.2554,094
16512.250.64.0/2012.250.64.1 to 12.250.79.25412.250.79.2554,094
16612.250.80.0/2012.250.80.1 to 12.250.95.25412.250.95.2554,094
16712.250.96.0/2012.250.96.1 to 12.250.111.25412.250.111.2554,094
16812.250.112.0/2012.250.112.1 to 12.250.127.25412.250.127.2554,094
16912.250.128.0/2012.250.128.1 to 12.250.143.25412.250.143.2554,094
17012.250.144.0/2012.250.144.1 to 12.250.159.25412.250.159.2554,094
17112.250.160.0/2012.250.160.1 to 12.250.175.25412.250.175.2554,094
17212.250.176.0/2012.250.176.1 to 12.250.191.25412.250.191.2554,094
17312.250.192.0/2012.250.192.1 to 12.250.207.25412.250.207.2554,094
17412.250.208.0/2012.250.208.1 to 12.250.223.25412.250.223.2554,094
17512.250.224.0/2012.250.224.1 to 12.250.239.25412.250.239.2554,094
17612.250.240.0/2012.250.240.1 to 12.250.255.25412.250.255.2554,094
17712.251.0.0/2012.251.0.1 to 12.251.15.25412.251.15.2554,094
17812.251.16.0/2012.251.16.1 to 12.251.31.25412.251.31.2554,094
17912.251.32.0/2012.251.32.1 to 12.251.47.25412.251.47.2554,094
18012.251.48.0/2012.251.48.1 to 12.251.63.25412.251.63.2554,094
18112.251.64.0/2012.251.64.1 to 12.251.79.25412.251.79.2554,094
18212.251.80.0/2012.251.80.1 to 12.251.95.25412.251.95.2554,094
18312.251.96.0/2012.251.96.1 to 12.251.111.25412.251.111.2554,094
18412.251.112.0/2012.251.112.1 to 12.251.127.25412.251.127.2554,094
18512.251.128.0/2012.251.128.1 to 12.251.143.25412.251.143.2554,094
18612.251.144.0/2012.251.144.1 to 12.251.159.25412.251.159.2554,094
18712.251.160.0/2012.251.160.1 to 12.251.175.25412.251.175.2554,094
18812.251.176.0/2012.251.176.1 to 12.251.191.25412.251.191.2554,094
18912.251.192.0/2012.251.192.1 to 12.251.207.25412.251.207.2554,094
19012.251.208.0/2012.251.208.1 to 12.251.223.25412.251.223.2554,094
19112.251.224.0/2012.251.224.1 to 12.251.239.25412.251.239.2554,094
19212.251.240.0/2012.251.240.1 to 12.251.255.25412.251.255.2554,094
19312.252.0.0/2012.252.0.1 to 12.252.15.25412.252.15.2554,094
19412.252.16.0/2012.252.16.1 to 12.252.31.25412.252.31.2554,094
19512.252.32.0/2012.252.32.1 to 12.252.47.25412.252.47.2554,094
19612.252.48.0/2012.252.48.1 to 12.252.63.25412.252.63.2554,094
19712.252.64.0/2012.252.64.1 to 12.252.79.25412.252.79.2554,094
19812.252.80.0/2012.252.80.1 to 12.252.95.25412.252.95.2554,094
19912.252.96.0/2012.252.96.1 to 12.252.111.25412.252.111.2554,094
20012.252.112.0/2012.252.112.1 to 12.252.127.25412.252.127.2554,094
20112.252.128.0/2012.252.128.1 to 12.252.143.25412.252.143.2554,094
20212.252.144.0/2012.252.144.1 to 12.252.159.25412.252.159.2554,094
20312.252.160.0/2012.252.160.1 to 12.252.175.25412.252.175.2554,094
20412.252.176.0/2012.252.176.1 to 12.252.191.25412.252.191.2554,094
20512.252.192.0/2012.252.192.1 to 12.252.207.25412.252.207.2554,094
20612.252.208.0/2012.252.208.1 to 12.252.223.25412.252.223.2554,094
20712.252.224.0/2012.252.224.1 to 12.252.239.25412.252.239.2554,094
20812.252.240.0/2012.252.240.1 to 12.252.255.25412.252.255.2554,094
20912.253.0.0/2012.253.0.1 to 12.253.15.25412.253.15.2554,094
21012.253.16.0/2012.253.16.1 to 12.253.31.25412.253.31.2554,094
21112.253.32.0/2012.253.32.1 to 12.253.47.25412.253.47.2554,094
21212.253.48.0/2012.253.48.1 to 12.253.63.25412.253.63.2554,094
21312.253.64.0/2012.253.64.1 to 12.253.79.25412.253.79.2554,094
21412.253.80.0/2012.253.80.1 to 12.253.95.25412.253.95.2554,094
21512.253.96.0/2012.253.96.1 to 12.253.111.25412.253.111.2554,094
21612.253.112.0/2012.253.112.1 to 12.253.127.25412.253.127.2554,094
21712.253.128.0/2012.253.128.1 to 12.253.143.25412.253.143.2554,094
21812.253.144.0/2012.253.144.1 to 12.253.159.25412.253.159.2554,094
21912.253.160.0/2012.253.160.1 to 12.253.175.25412.253.175.2554,094
22012.253.176.0/2012.253.176.1 to 12.253.191.25412.253.191.2554,094
22112.253.192.0/2012.253.192.1 to 12.253.207.25412.253.207.2554,094
22212.253.208.0/2012.253.208.1 to 12.253.223.25412.253.223.2554,094
22312.253.224.0/2012.253.224.1 to 12.253.239.25412.253.239.2554,094
22412.253.240.0/2012.253.240.1 to 12.253.255.25412.253.255.2554,094
22512.254.0.0/2012.254.0.1 to 12.254.15.25412.254.15.2554,094
22612.254.16.0/2012.254.16.1 to 12.254.31.25412.254.31.2554,094
22712.254.32.0/2012.254.32.1 to 12.254.47.25412.254.47.2554,094
22812.254.48.0/2012.254.48.1 to 12.254.63.25412.254.63.2554,094
22912.254.64.0/2012.254.64.1 to 12.254.79.25412.254.79.2554,094
23012.254.80.0/2012.254.80.1 to 12.254.95.25412.254.95.2554,094
23112.254.96.0/2012.254.96.1 to 12.254.111.25412.254.111.2554,094
23212.254.112.0/2012.254.112.1 to 12.254.127.25412.254.127.2554,094
23312.254.128.0/2012.254.128.1 to 12.254.143.25412.254.143.2554,094
23412.254.144.0/2012.254.144.1 to 12.254.159.25412.254.159.2554,094
23512.254.160.0/2012.254.160.1 to 12.254.175.25412.254.175.2554,094
23612.254.176.0/2012.254.176.1 to 12.254.191.25412.254.191.2554,094
23712.254.192.0/2012.254.192.1 to 12.254.207.25412.254.207.2554,094
23812.254.208.0/2012.254.208.1 to 12.254.223.25412.254.223.2554,094
23912.254.224.0/2012.254.224.1 to 12.254.239.25412.254.239.2554,094
24012.254.240.0/2012.254.240.1 to 12.254.255.25412.254.255.2554,094
24112.255.0.0/2012.255.0.1 to 12.255.15.25412.255.15.2554,094
24212.255.16.0/2012.255.16.1 to 12.255.31.25412.255.31.2554,094
24312.255.32.0/2012.255.32.1 to 12.255.47.25412.255.47.2554,094
24412.255.48.0/2012.255.48.1 to 12.255.63.25412.255.63.2554,094
24512.255.64.0/2012.255.64.1 to 12.255.79.25412.255.79.2554,094
24612.255.80.0/2012.255.80.1 to 12.255.95.25412.255.95.2554,094
24712.255.96.0/2012.255.96.1 to 12.255.111.25412.255.111.2554,094
24812.255.112.0/2012.255.112.1 to 12.255.127.25412.255.127.2554,094
24912.255.128.0/2012.255.128.1 to 12.255.143.25412.255.143.2554,094
25012.255.144.0/2012.255.144.1 to 12.255.159.25412.255.159.2554,094
25112.255.160.0/2012.255.160.1 to 12.255.175.25412.255.175.2554,094
25212.255.176.0/2012.255.176.1 to 12.255.191.25412.255.191.2554,094
25312.255.192.0/2012.255.192.1 to 12.255.207.25412.255.207.2554,094
25412.255.208.0/2012.255.208.1 to 12.255.223.25412.255.223.2554,094
25512.255.224.0/2012.255.224.1 to 12.255.239.25412.255.239.2554,094
25612.255.240.0/2012.255.240.1 to 12.255.255.25412.255.255.2554,094

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.