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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.

Network12.3.0.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
12.3.0.0
Broadcast address
12.3.15.255
First usable
12.3.0.1
Last usable
12.3.15.254
Usable hosts
4,094 (4,096 less the network and broadcast addresses)
Subnet mask
255.255.240.0
Wildcard mask
0.0.15.255 (Cisco ACLs, OSPF)
Prefix length
/20
Type
Public public
Old class
A (default /8)
As numbers
Hex 0C030000 · Integer 201523200 to 201527295
Reverse DNS zones
0.3.12.in-addr.arpa
1.3.12.in-addr.arpa
2.3.12.in-addr.arpa
3.3.12.in-addr.arpa
4.3.12.in-addr.arpa
5.3.12.in-addr.arpa
6.3.12.in-addr.arpa
7.3.12.in-addr.arpa
8.3.12.in-addr.arpa
9.3.12.in-addr.arpa
10.3.12.in-addr.arpa
11.3.12.in-addr.arpa
12.3.12.in-addr.arpa
13.3.12.in-addr.arpa
14.3.12.in-addr.arpa
15.3.12.in-addr.arpa
/20 is not on a 8-bit boundary, so it takes 16 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001100.00000011.00000000.0000000012.3.0.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network00001100.00000011.00000000.0000000012.3.0.0
Broadcast00001100.00000011.00001111.1111111112.3.15.255
Split into smaller subnets/28
/21 (2)/22 (4)/23 (8)/24 (16)/25 (32)/26 (64)/27 (128)/28 (256)/29 (512)/30 (1,024)/31 (2,048)/32 (4,096)

12.3.0.0/20 makes 256 subnets of /28.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
112.3.0.0/2812.3.0.1 to 12.3.0.1412.3.0.1514
212.3.0.16/2812.3.0.17 to 12.3.0.3012.3.0.3114
312.3.0.32/2812.3.0.33 to 12.3.0.4612.3.0.4714
412.3.0.48/2812.3.0.49 to 12.3.0.6212.3.0.6314
512.3.0.64/2812.3.0.65 to 12.3.0.7812.3.0.7914
612.3.0.80/2812.3.0.81 to 12.3.0.9412.3.0.9514
712.3.0.96/2812.3.0.97 to 12.3.0.11012.3.0.11114
812.3.0.112/2812.3.0.113 to 12.3.0.12612.3.0.12714
912.3.0.128/2812.3.0.129 to 12.3.0.14212.3.0.14314
1012.3.0.144/2812.3.0.145 to 12.3.0.15812.3.0.15914
1112.3.0.160/2812.3.0.161 to 12.3.0.17412.3.0.17514
1212.3.0.176/2812.3.0.177 to 12.3.0.19012.3.0.19114
1312.3.0.192/2812.3.0.193 to 12.3.0.20612.3.0.20714
1412.3.0.208/2812.3.0.209 to 12.3.0.22212.3.0.22314
1512.3.0.224/2812.3.0.225 to 12.3.0.23812.3.0.23914
1612.3.0.240/2812.3.0.241 to 12.3.0.25412.3.0.25514
1712.3.1.0/2812.3.1.1 to 12.3.1.1412.3.1.1514
1812.3.1.16/2812.3.1.17 to 12.3.1.3012.3.1.3114
1912.3.1.32/2812.3.1.33 to 12.3.1.4612.3.1.4714
2012.3.1.48/2812.3.1.49 to 12.3.1.6212.3.1.6314
2112.3.1.64/2812.3.1.65 to 12.3.1.7812.3.1.7914
2212.3.1.80/2812.3.1.81 to 12.3.1.9412.3.1.9514
2312.3.1.96/2812.3.1.97 to 12.3.1.11012.3.1.11114
2412.3.1.112/2812.3.1.113 to 12.3.1.12612.3.1.12714
2512.3.1.128/2812.3.1.129 to 12.3.1.14212.3.1.14314
2612.3.1.144/2812.3.1.145 to 12.3.1.15812.3.1.15914
2712.3.1.160/2812.3.1.161 to 12.3.1.17412.3.1.17514
2812.3.1.176/2812.3.1.177 to 12.3.1.19012.3.1.19114
2912.3.1.192/2812.3.1.193 to 12.3.1.20612.3.1.20714
3012.3.1.208/2812.3.1.209 to 12.3.1.22212.3.1.22314
3112.3.1.224/2812.3.1.225 to 12.3.1.23812.3.1.23914
3212.3.1.240/2812.3.1.241 to 12.3.1.25412.3.1.25514
3312.3.2.0/2812.3.2.1 to 12.3.2.1412.3.2.1514
3412.3.2.16/2812.3.2.17 to 12.3.2.3012.3.2.3114
3512.3.2.32/2812.3.2.33 to 12.3.2.4612.3.2.4714
3612.3.2.48/2812.3.2.49 to 12.3.2.6212.3.2.6314
3712.3.2.64/2812.3.2.65 to 12.3.2.7812.3.2.7914
3812.3.2.80/2812.3.2.81 to 12.3.2.9412.3.2.9514
3912.3.2.96/2812.3.2.97 to 12.3.2.11012.3.2.11114
4012.3.2.112/2812.3.2.113 to 12.3.2.12612.3.2.12714
4112.3.2.128/2812.3.2.129 to 12.3.2.14212.3.2.14314
4212.3.2.144/2812.3.2.145 to 12.3.2.15812.3.2.15914
4312.3.2.160/2812.3.2.161 to 12.3.2.17412.3.2.17514
4412.3.2.176/2812.3.2.177 to 12.3.2.19012.3.2.19114
4512.3.2.192/2812.3.2.193 to 12.3.2.20612.3.2.20714
4612.3.2.208/2812.3.2.209 to 12.3.2.22212.3.2.22314
4712.3.2.224/2812.3.2.225 to 12.3.2.23812.3.2.23914
4812.3.2.240/2812.3.2.241 to 12.3.2.25412.3.2.25514
4912.3.3.0/2812.3.3.1 to 12.3.3.1412.3.3.1514
5012.3.3.16/2812.3.3.17 to 12.3.3.3012.3.3.3114
5112.3.3.32/2812.3.3.33 to 12.3.3.4612.3.3.4714
5212.3.3.48/2812.3.3.49 to 12.3.3.6212.3.3.6314
5312.3.3.64/2812.3.3.65 to 12.3.3.7812.3.3.7914
5412.3.3.80/2812.3.3.81 to 12.3.3.9412.3.3.9514
5512.3.3.96/2812.3.3.97 to 12.3.3.11012.3.3.11114
5612.3.3.112/2812.3.3.113 to 12.3.3.12612.3.3.12714
5712.3.3.128/2812.3.3.129 to 12.3.3.14212.3.3.14314
5812.3.3.144/2812.3.3.145 to 12.3.3.15812.3.3.15914
5912.3.3.160/2812.3.3.161 to 12.3.3.17412.3.3.17514
6012.3.3.176/2812.3.3.177 to 12.3.3.19012.3.3.19114
6112.3.3.192/2812.3.3.193 to 12.3.3.20612.3.3.20714
6212.3.3.208/2812.3.3.209 to 12.3.3.22212.3.3.22314
6312.3.3.224/2812.3.3.225 to 12.3.3.23812.3.3.23914
6412.3.3.240/2812.3.3.241 to 12.3.3.25412.3.3.25514
6512.3.4.0/2812.3.4.1 to 12.3.4.1412.3.4.1514
6612.3.4.16/2812.3.4.17 to 12.3.4.3012.3.4.3114
6712.3.4.32/2812.3.4.33 to 12.3.4.4612.3.4.4714
6812.3.4.48/2812.3.4.49 to 12.3.4.6212.3.4.6314
6912.3.4.64/2812.3.4.65 to 12.3.4.7812.3.4.7914
7012.3.4.80/2812.3.4.81 to 12.3.4.9412.3.4.9514
7112.3.4.96/2812.3.4.97 to 12.3.4.11012.3.4.11114
7212.3.4.112/2812.3.4.113 to 12.3.4.12612.3.4.12714
7312.3.4.128/2812.3.4.129 to 12.3.4.14212.3.4.14314
7412.3.4.144/2812.3.4.145 to 12.3.4.15812.3.4.15914
7512.3.4.160/2812.3.4.161 to 12.3.4.17412.3.4.17514
7612.3.4.176/2812.3.4.177 to 12.3.4.19012.3.4.19114
7712.3.4.192/2812.3.4.193 to 12.3.4.20612.3.4.20714
7812.3.4.208/2812.3.4.209 to 12.3.4.22212.3.4.22314
7912.3.4.224/2812.3.4.225 to 12.3.4.23812.3.4.23914
8012.3.4.240/2812.3.4.241 to 12.3.4.25412.3.4.25514
8112.3.5.0/2812.3.5.1 to 12.3.5.1412.3.5.1514
8212.3.5.16/2812.3.5.17 to 12.3.5.3012.3.5.3114
8312.3.5.32/2812.3.5.33 to 12.3.5.4612.3.5.4714
8412.3.5.48/2812.3.5.49 to 12.3.5.6212.3.5.6314
8512.3.5.64/2812.3.5.65 to 12.3.5.7812.3.5.7914
8612.3.5.80/2812.3.5.81 to 12.3.5.9412.3.5.9514
8712.3.5.96/2812.3.5.97 to 12.3.5.11012.3.5.11114
8812.3.5.112/2812.3.5.113 to 12.3.5.12612.3.5.12714
8912.3.5.128/2812.3.5.129 to 12.3.5.14212.3.5.14314
9012.3.5.144/2812.3.5.145 to 12.3.5.15812.3.5.15914
9112.3.5.160/2812.3.5.161 to 12.3.5.17412.3.5.17514
9212.3.5.176/2812.3.5.177 to 12.3.5.19012.3.5.19114
9312.3.5.192/2812.3.5.193 to 12.3.5.20612.3.5.20714
9412.3.5.208/2812.3.5.209 to 12.3.5.22212.3.5.22314
9512.3.5.224/2812.3.5.225 to 12.3.5.23812.3.5.23914
9612.3.5.240/2812.3.5.241 to 12.3.5.25412.3.5.25514
9712.3.6.0/2812.3.6.1 to 12.3.6.1412.3.6.1514
9812.3.6.16/2812.3.6.17 to 12.3.6.3012.3.6.3114
9912.3.6.32/2812.3.6.33 to 12.3.6.4612.3.6.4714
10012.3.6.48/2812.3.6.49 to 12.3.6.6212.3.6.6314
10112.3.6.64/2812.3.6.65 to 12.3.6.7812.3.6.7914
10212.3.6.80/2812.3.6.81 to 12.3.6.9412.3.6.9514
10312.3.6.96/2812.3.6.97 to 12.3.6.11012.3.6.11114
10412.3.6.112/2812.3.6.113 to 12.3.6.12612.3.6.12714
10512.3.6.128/2812.3.6.129 to 12.3.6.14212.3.6.14314
10612.3.6.144/2812.3.6.145 to 12.3.6.15812.3.6.15914
10712.3.6.160/2812.3.6.161 to 12.3.6.17412.3.6.17514
10812.3.6.176/2812.3.6.177 to 12.3.6.19012.3.6.19114
10912.3.6.192/2812.3.6.193 to 12.3.6.20612.3.6.20714
11012.3.6.208/2812.3.6.209 to 12.3.6.22212.3.6.22314
11112.3.6.224/2812.3.6.225 to 12.3.6.23812.3.6.23914
11212.3.6.240/2812.3.6.241 to 12.3.6.25412.3.6.25514
11312.3.7.0/2812.3.7.1 to 12.3.7.1412.3.7.1514
11412.3.7.16/2812.3.7.17 to 12.3.7.3012.3.7.3114
11512.3.7.32/2812.3.7.33 to 12.3.7.4612.3.7.4714
11612.3.7.48/2812.3.7.49 to 12.3.7.6212.3.7.6314
11712.3.7.64/2812.3.7.65 to 12.3.7.7812.3.7.7914
11812.3.7.80/2812.3.7.81 to 12.3.7.9412.3.7.9514
11912.3.7.96/2812.3.7.97 to 12.3.7.11012.3.7.11114
12012.3.7.112/2812.3.7.113 to 12.3.7.12612.3.7.12714
12112.3.7.128/2812.3.7.129 to 12.3.7.14212.3.7.14314
12212.3.7.144/2812.3.7.145 to 12.3.7.15812.3.7.15914
12312.3.7.160/2812.3.7.161 to 12.3.7.17412.3.7.17514
12412.3.7.176/2812.3.7.177 to 12.3.7.19012.3.7.19114
12512.3.7.192/2812.3.7.193 to 12.3.7.20612.3.7.20714
12612.3.7.208/2812.3.7.209 to 12.3.7.22212.3.7.22314
12712.3.7.224/2812.3.7.225 to 12.3.7.23812.3.7.23914
12812.3.7.240/2812.3.7.241 to 12.3.7.25412.3.7.25514
12912.3.8.0/2812.3.8.1 to 12.3.8.1412.3.8.1514
13012.3.8.16/2812.3.8.17 to 12.3.8.3012.3.8.3114
13112.3.8.32/2812.3.8.33 to 12.3.8.4612.3.8.4714
13212.3.8.48/2812.3.8.49 to 12.3.8.6212.3.8.6314
13312.3.8.64/2812.3.8.65 to 12.3.8.7812.3.8.7914
13412.3.8.80/2812.3.8.81 to 12.3.8.9412.3.8.9514
13512.3.8.96/2812.3.8.97 to 12.3.8.11012.3.8.11114
13612.3.8.112/2812.3.8.113 to 12.3.8.12612.3.8.12714
13712.3.8.128/2812.3.8.129 to 12.3.8.14212.3.8.14314
13812.3.8.144/2812.3.8.145 to 12.3.8.15812.3.8.15914
13912.3.8.160/2812.3.8.161 to 12.3.8.17412.3.8.17514
14012.3.8.176/2812.3.8.177 to 12.3.8.19012.3.8.19114
14112.3.8.192/2812.3.8.193 to 12.3.8.20612.3.8.20714
14212.3.8.208/2812.3.8.209 to 12.3.8.22212.3.8.22314
14312.3.8.224/2812.3.8.225 to 12.3.8.23812.3.8.23914
14412.3.8.240/2812.3.8.241 to 12.3.8.25412.3.8.25514
14512.3.9.0/2812.3.9.1 to 12.3.9.1412.3.9.1514
14612.3.9.16/2812.3.9.17 to 12.3.9.3012.3.9.3114
14712.3.9.32/2812.3.9.33 to 12.3.9.4612.3.9.4714
14812.3.9.48/2812.3.9.49 to 12.3.9.6212.3.9.6314
14912.3.9.64/2812.3.9.65 to 12.3.9.7812.3.9.7914
15012.3.9.80/2812.3.9.81 to 12.3.9.9412.3.9.9514
15112.3.9.96/2812.3.9.97 to 12.3.9.11012.3.9.11114
15212.3.9.112/2812.3.9.113 to 12.3.9.12612.3.9.12714
15312.3.9.128/2812.3.9.129 to 12.3.9.14212.3.9.14314
15412.3.9.144/2812.3.9.145 to 12.3.9.15812.3.9.15914
15512.3.9.160/2812.3.9.161 to 12.3.9.17412.3.9.17514
15612.3.9.176/2812.3.9.177 to 12.3.9.19012.3.9.19114
15712.3.9.192/2812.3.9.193 to 12.3.9.20612.3.9.20714
15812.3.9.208/2812.3.9.209 to 12.3.9.22212.3.9.22314
15912.3.9.224/2812.3.9.225 to 12.3.9.23812.3.9.23914
16012.3.9.240/2812.3.9.241 to 12.3.9.25412.3.9.25514
16112.3.10.0/2812.3.10.1 to 12.3.10.1412.3.10.1514
16212.3.10.16/2812.3.10.17 to 12.3.10.3012.3.10.3114
16312.3.10.32/2812.3.10.33 to 12.3.10.4612.3.10.4714
16412.3.10.48/2812.3.10.49 to 12.3.10.6212.3.10.6314
16512.3.10.64/2812.3.10.65 to 12.3.10.7812.3.10.7914
16612.3.10.80/2812.3.10.81 to 12.3.10.9412.3.10.9514
16712.3.10.96/2812.3.10.97 to 12.3.10.11012.3.10.11114
16812.3.10.112/2812.3.10.113 to 12.3.10.12612.3.10.12714
16912.3.10.128/2812.3.10.129 to 12.3.10.14212.3.10.14314
17012.3.10.144/2812.3.10.145 to 12.3.10.15812.3.10.15914
17112.3.10.160/2812.3.10.161 to 12.3.10.17412.3.10.17514
17212.3.10.176/2812.3.10.177 to 12.3.10.19012.3.10.19114
17312.3.10.192/2812.3.10.193 to 12.3.10.20612.3.10.20714
17412.3.10.208/2812.3.10.209 to 12.3.10.22212.3.10.22314
17512.3.10.224/2812.3.10.225 to 12.3.10.23812.3.10.23914
17612.3.10.240/2812.3.10.241 to 12.3.10.25412.3.10.25514
17712.3.11.0/2812.3.11.1 to 12.3.11.1412.3.11.1514
17812.3.11.16/2812.3.11.17 to 12.3.11.3012.3.11.3114
17912.3.11.32/2812.3.11.33 to 12.3.11.4612.3.11.4714
18012.3.11.48/2812.3.11.49 to 12.3.11.6212.3.11.6314
18112.3.11.64/2812.3.11.65 to 12.3.11.7812.3.11.7914
18212.3.11.80/2812.3.11.81 to 12.3.11.9412.3.11.9514
18312.3.11.96/2812.3.11.97 to 12.3.11.11012.3.11.11114
18412.3.11.112/2812.3.11.113 to 12.3.11.12612.3.11.12714
18512.3.11.128/2812.3.11.129 to 12.3.11.14212.3.11.14314
18612.3.11.144/2812.3.11.145 to 12.3.11.15812.3.11.15914
18712.3.11.160/2812.3.11.161 to 12.3.11.17412.3.11.17514
18812.3.11.176/2812.3.11.177 to 12.3.11.19012.3.11.19114
18912.3.11.192/2812.3.11.193 to 12.3.11.20612.3.11.20714
19012.3.11.208/2812.3.11.209 to 12.3.11.22212.3.11.22314
19112.3.11.224/2812.3.11.225 to 12.3.11.23812.3.11.23914
19212.3.11.240/2812.3.11.241 to 12.3.11.25412.3.11.25514
19312.3.12.0/2812.3.12.1 to 12.3.12.1412.3.12.1514
19412.3.12.16/2812.3.12.17 to 12.3.12.3012.3.12.3114
19512.3.12.32/2812.3.12.33 to 12.3.12.4612.3.12.4714
19612.3.12.48/2812.3.12.49 to 12.3.12.6212.3.12.6314
19712.3.12.64/2812.3.12.65 to 12.3.12.7812.3.12.7914
19812.3.12.80/2812.3.12.81 to 12.3.12.9412.3.12.9514
19912.3.12.96/2812.3.12.97 to 12.3.12.11012.3.12.11114
20012.3.12.112/2812.3.12.113 to 12.3.12.12612.3.12.12714
20112.3.12.128/2812.3.12.129 to 12.3.12.14212.3.12.14314
20212.3.12.144/2812.3.12.145 to 12.3.12.15812.3.12.15914
20312.3.12.160/2812.3.12.161 to 12.3.12.17412.3.12.17514
20412.3.12.176/2812.3.12.177 to 12.3.12.19012.3.12.19114
20512.3.12.192/2812.3.12.193 to 12.3.12.20612.3.12.20714
20612.3.12.208/2812.3.12.209 to 12.3.12.22212.3.12.22314
20712.3.12.224/2812.3.12.225 to 12.3.12.23812.3.12.23914
20812.3.12.240/2812.3.12.241 to 12.3.12.25412.3.12.25514
20912.3.13.0/2812.3.13.1 to 12.3.13.1412.3.13.1514
21012.3.13.16/2812.3.13.17 to 12.3.13.3012.3.13.3114
21112.3.13.32/2812.3.13.33 to 12.3.13.4612.3.13.4714
21212.3.13.48/2812.3.13.49 to 12.3.13.6212.3.13.6314
21312.3.13.64/2812.3.13.65 to 12.3.13.7812.3.13.7914
21412.3.13.80/2812.3.13.81 to 12.3.13.9412.3.13.9514
21512.3.13.96/2812.3.13.97 to 12.3.13.11012.3.13.11114
21612.3.13.112/2812.3.13.113 to 12.3.13.12612.3.13.12714
21712.3.13.128/2812.3.13.129 to 12.3.13.14212.3.13.14314
21812.3.13.144/2812.3.13.145 to 12.3.13.15812.3.13.15914
21912.3.13.160/2812.3.13.161 to 12.3.13.17412.3.13.17514
22012.3.13.176/2812.3.13.177 to 12.3.13.19012.3.13.19114
22112.3.13.192/2812.3.13.193 to 12.3.13.20612.3.13.20714
22212.3.13.208/2812.3.13.209 to 12.3.13.22212.3.13.22314
22312.3.13.224/2812.3.13.225 to 12.3.13.23812.3.13.23914
22412.3.13.240/2812.3.13.241 to 12.3.13.25412.3.13.25514
22512.3.14.0/2812.3.14.1 to 12.3.14.1412.3.14.1514
22612.3.14.16/2812.3.14.17 to 12.3.14.3012.3.14.3114
22712.3.14.32/2812.3.14.33 to 12.3.14.4612.3.14.4714
22812.3.14.48/2812.3.14.49 to 12.3.14.6212.3.14.6314
22912.3.14.64/2812.3.14.65 to 12.3.14.7812.3.14.7914
23012.3.14.80/2812.3.14.81 to 12.3.14.9412.3.14.9514
23112.3.14.96/2812.3.14.97 to 12.3.14.11012.3.14.11114
23212.3.14.112/2812.3.14.113 to 12.3.14.12612.3.14.12714
23312.3.14.128/2812.3.14.129 to 12.3.14.14212.3.14.14314
23412.3.14.144/2812.3.14.145 to 12.3.14.15812.3.14.15914
23512.3.14.160/2812.3.14.161 to 12.3.14.17412.3.14.17514
23612.3.14.176/2812.3.14.177 to 12.3.14.19012.3.14.19114
23712.3.14.192/2812.3.14.193 to 12.3.14.20612.3.14.20714
23812.3.14.208/2812.3.14.209 to 12.3.14.22212.3.14.22314
23912.3.14.224/2812.3.14.225 to 12.3.14.23812.3.14.23914
24012.3.14.240/2812.3.14.241 to 12.3.14.25412.3.14.25514
24112.3.15.0/2812.3.15.1 to 12.3.15.1412.3.15.1514
24212.3.15.16/2812.3.15.17 to 12.3.15.3012.3.15.3114
24312.3.15.32/2812.3.15.33 to 12.3.15.4612.3.15.4714
24412.3.15.48/2812.3.15.49 to 12.3.15.6212.3.15.6314
24512.3.15.64/2812.3.15.65 to 12.3.15.7812.3.15.7914
24612.3.15.80/2812.3.15.81 to 12.3.15.9412.3.15.9514
24712.3.15.96/2812.3.15.97 to 12.3.15.11012.3.15.11114
24812.3.15.112/2812.3.15.113 to 12.3.15.12612.3.15.12714
24912.3.15.128/2812.3.15.129 to 12.3.15.14212.3.15.14314
25012.3.15.144/2812.3.15.145 to 12.3.15.15812.3.15.15914
25112.3.15.160/2812.3.15.161 to 12.3.15.17412.3.15.17514
25212.3.15.176/2812.3.15.177 to 12.3.15.19012.3.15.19114
25312.3.15.192/2812.3.15.193 to 12.3.15.20612.3.15.20714
25412.3.15.208/2812.3.15.209 to 12.3.15.22212.3.15.22314
25512.3.15.224/2812.3.15.225 to 12.3.15.23812.3.15.23914
25612.3.15.240/2812.3.15.241 to 12.3.15.25412.3.15.25514

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.