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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.

Network20.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
20.0.0.0
Broadcast address
20.127.255.255
First usable
20.0.0.1
Last usable
20.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 14000000 · Integer 335544320 to 343932927
Reverse DNS zones
0.20.in-addr.arpa
1.20.in-addr.arpa
2.20.in-addr.arpa
3.20.in-addr.arpa
4.20.in-addr.arpa
5.20.in-addr.arpa
6.20.in-addr.arpa
7.20.in-addr.arpa
8.20.in-addr.arpa
9.20.in-addr.arpa
10.20.in-addr.arpa
11.20.in-addr.arpa
12.20.in-addr.arpa
13.20.in-addr.arpa
14.20.in-addr.arpa
15.20.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010100.00000000.00000000.0000000020.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00010100.00000000.00000000.0000000020.0.0.0
Broadcast00010100.01111111.11111111.1111111120.127.255.255
Split into smaller subnets/18
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

20.0.0.0/9 makes 512 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
120.0.0.0/1820.0.0.1 to 20.0.63.25420.0.63.25516,382
220.0.64.0/1820.0.64.1 to 20.0.127.25420.0.127.25516,382
320.0.128.0/1820.0.128.1 to 20.0.191.25420.0.191.25516,382
420.0.192.0/1820.0.192.1 to 20.0.255.25420.0.255.25516,382
520.1.0.0/1820.1.0.1 to 20.1.63.25420.1.63.25516,382
620.1.64.0/1820.1.64.1 to 20.1.127.25420.1.127.25516,382
720.1.128.0/1820.1.128.1 to 20.1.191.25420.1.191.25516,382
820.1.192.0/1820.1.192.1 to 20.1.255.25420.1.255.25516,382
920.2.0.0/1820.2.0.1 to 20.2.63.25420.2.63.25516,382
1020.2.64.0/1820.2.64.1 to 20.2.127.25420.2.127.25516,382
1120.2.128.0/1820.2.128.1 to 20.2.191.25420.2.191.25516,382
1220.2.192.0/1820.2.192.1 to 20.2.255.25420.2.255.25516,382
1320.3.0.0/1820.3.0.1 to 20.3.63.25420.3.63.25516,382
1420.3.64.0/1820.3.64.1 to 20.3.127.25420.3.127.25516,382
1520.3.128.0/1820.3.128.1 to 20.3.191.25420.3.191.25516,382
1620.3.192.0/1820.3.192.1 to 20.3.255.25420.3.255.25516,382
1720.4.0.0/1820.4.0.1 to 20.4.63.25420.4.63.25516,382
1820.4.64.0/1820.4.64.1 to 20.4.127.25420.4.127.25516,382
1920.4.128.0/1820.4.128.1 to 20.4.191.25420.4.191.25516,382
2020.4.192.0/1820.4.192.1 to 20.4.255.25420.4.255.25516,382
2120.5.0.0/1820.5.0.1 to 20.5.63.25420.5.63.25516,382
2220.5.64.0/1820.5.64.1 to 20.5.127.25420.5.127.25516,382
2320.5.128.0/1820.5.128.1 to 20.5.191.25420.5.191.25516,382
2420.5.192.0/1820.5.192.1 to 20.5.255.25420.5.255.25516,382
2520.6.0.0/1820.6.0.1 to 20.6.63.25420.6.63.25516,382
2620.6.64.0/1820.6.64.1 to 20.6.127.25420.6.127.25516,382
2720.6.128.0/1820.6.128.1 to 20.6.191.25420.6.191.25516,382
2820.6.192.0/1820.6.192.1 to 20.6.255.25420.6.255.25516,382
2920.7.0.0/1820.7.0.1 to 20.7.63.25420.7.63.25516,382
3020.7.64.0/1820.7.64.1 to 20.7.127.25420.7.127.25516,382
3120.7.128.0/1820.7.128.1 to 20.7.191.25420.7.191.25516,382
3220.7.192.0/1820.7.192.1 to 20.7.255.25420.7.255.25516,382
3320.8.0.0/1820.8.0.1 to 20.8.63.25420.8.63.25516,382
3420.8.64.0/1820.8.64.1 to 20.8.127.25420.8.127.25516,382
3520.8.128.0/1820.8.128.1 to 20.8.191.25420.8.191.25516,382
3620.8.192.0/1820.8.192.1 to 20.8.255.25420.8.255.25516,382
3720.9.0.0/1820.9.0.1 to 20.9.63.25420.9.63.25516,382
3820.9.64.0/1820.9.64.1 to 20.9.127.25420.9.127.25516,382
3920.9.128.0/1820.9.128.1 to 20.9.191.25420.9.191.25516,382
4020.9.192.0/1820.9.192.1 to 20.9.255.25420.9.255.25516,382
4120.10.0.0/1820.10.0.1 to 20.10.63.25420.10.63.25516,382
4220.10.64.0/1820.10.64.1 to 20.10.127.25420.10.127.25516,382
4320.10.128.0/1820.10.128.1 to 20.10.191.25420.10.191.25516,382
4420.10.192.0/1820.10.192.1 to 20.10.255.25420.10.255.25516,382
4520.11.0.0/1820.11.0.1 to 20.11.63.25420.11.63.25516,382
4620.11.64.0/1820.11.64.1 to 20.11.127.25420.11.127.25516,382
4720.11.128.0/1820.11.128.1 to 20.11.191.25420.11.191.25516,382
4820.11.192.0/1820.11.192.1 to 20.11.255.25420.11.255.25516,382
4920.12.0.0/1820.12.0.1 to 20.12.63.25420.12.63.25516,382
5020.12.64.0/1820.12.64.1 to 20.12.127.25420.12.127.25516,382
5120.12.128.0/1820.12.128.1 to 20.12.191.25420.12.191.25516,382
5220.12.192.0/1820.12.192.1 to 20.12.255.25420.12.255.25516,382
5320.13.0.0/1820.13.0.1 to 20.13.63.25420.13.63.25516,382
5420.13.64.0/1820.13.64.1 to 20.13.127.25420.13.127.25516,382
5520.13.128.0/1820.13.128.1 to 20.13.191.25420.13.191.25516,382
5620.13.192.0/1820.13.192.1 to 20.13.255.25420.13.255.25516,382
5720.14.0.0/1820.14.0.1 to 20.14.63.25420.14.63.25516,382
5820.14.64.0/1820.14.64.1 to 20.14.127.25420.14.127.25516,382
5920.14.128.0/1820.14.128.1 to 20.14.191.25420.14.191.25516,382
6020.14.192.0/1820.14.192.1 to 20.14.255.25420.14.255.25516,382
6120.15.0.0/1820.15.0.1 to 20.15.63.25420.15.63.25516,382
6220.15.64.0/1820.15.64.1 to 20.15.127.25420.15.127.25516,382
6320.15.128.0/1820.15.128.1 to 20.15.191.25420.15.191.25516,382
6420.15.192.0/1820.15.192.1 to 20.15.255.25420.15.255.25516,382
6520.16.0.0/1820.16.0.1 to 20.16.63.25420.16.63.25516,382
6620.16.64.0/1820.16.64.1 to 20.16.127.25420.16.127.25516,382
6720.16.128.0/1820.16.128.1 to 20.16.191.25420.16.191.25516,382
6820.16.192.0/1820.16.192.1 to 20.16.255.25420.16.255.25516,382
6920.17.0.0/1820.17.0.1 to 20.17.63.25420.17.63.25516,382
7020.17.64.0/1820.17.64.1 to 20.17.127.25420.17.127.25516,382
7120.17.128.0/1820.17.128.1 to 20.17.191.25420.17.191.25516,382
7220.17.192.0/1820.17.192.1 to 20.17.255.25420.17.255.25516,382
7320.18.0.0/1820.18.0.1 to 20.18.63.25420.18.63.25516,382
7420.18.64.0/1820.18.64.1 to 20.18.127.25420.18.127.25516,382
7520.18.128.0/1820.18.128.1 to 20.18.191.25420.18.191.25516,382
7620.18.192.0/1820.18.192.1 to 20.18.255.25420.18.255.25516,382
7720.19.0.0/1820.19.0.1 to 20.19.63.25420.19.63.25516,382
7820.19.64.0/1820.19.64.1 to 20.19.127.25420.19.127.25516,382
7920.19.128.0/1820.19.128.1 to 20.19.191.25420.19.191.25516,382
8020.19.192.0/1820.19.192.1 to 20.19.255.25420.19.255.25516,382
8120.20.0.0/1820.20.0.1 to 20.20.63.25420.20.63.25516,382
8220.20.64.0/1820.20.64.1 to 20.20.127.25420.20.127.25516,382
8320.20.128.0/1820.20.128.1 to 20.20.191.25420.20.191.25516,382
8420.20.192.0/1820.20.192.1 to 20.20.255.25420.20.255.25516,382
8520.21.0.0/1820.21.0.1 to 20.21.63.25420.21.63.25516,382
8620.21.64.0/1820.21.64.1 to 20.21.127.25420.21.127.25516,382
8720.21.128.0/1820.21.128.1 to 20.21.191.25420.21.191.25516,382
8820.21.192.0/1820.21.192.1 to 20.21.255.25420.21.255.25516,382
8920.22.0.0/1820.22.0.1 to 20.22.63.25420.22.63.25516,382
9020.22.64.0/1820.22.64.1 to 20.22.127.25420.22.127.25516,382
9120.22.128.0/1820.22.128.1 to 20.22.191.25420.22.191.25516,382
9220.22.192.0/1820.22.192.1 to 20.22.255.25420.22.255.25516,382
9320.23.0.0/1820.23.0.1 to 20.23.63.25420.23.63.25516,382
9420.23.64.0/1820.23.64.1 to 20.23.127.25420.23.127.25516,382
9520.23.128.0/1820.23.128.1 to 20.23.191.25420.23.191.25516,382
9620.23.192.0/1820.23.192.1 to 20.23.255.25420.23.255.25516,382
9720.24.0.0/1820.24.0.1 to 20.24.63.25420.24.63.25516,382
9820.24.64.0/1820.24.64.1 to 20.24.127.25420.24.127.25516,382
9920.24.128.0/1820.24.128.1 to 20.24.191.25420.24.191.25516,382
10020.24.192.0/1820.24.192.1 to 20.24.255.25420.24.255.25516,382
10120.25.0.0/1820.25.0.1 to 20.25.63.25420.25.63.25516,382
10220.25.64.0/1820.25.64.1 to 20.25.127.25420.25.127.25516,382
10320.25.128.0/1820.25.128.1 to 20.25.191.25420.25.191.25516,382
10420.25.192.0/1820.25.192.1 to 20.25.255.25420.25.255.25516,382
10520.26.0.0/1820.26.0.1 to 20.26.63.25420.26.63.25516,382
10620.26.64.0/1820.26.64.1 to 20.26.127.25420.26.127.25516,382
10720.26.128.0/1820.26.128.1 to 20.26.191.25420.26.191.25516,382
10820.26.192.0/1820.26.192.1 to 20.26.255.25420.26.255.25516,382
10920.27.0.0/1820.27.0.1 to 20.27.63.25420.27.63.25516,382
11020.27.64.0/1820.27.64.1 to 20.27.127.25420.27.127.25516,382
11120.27.128.0/1820.27.128.1 to 20.27.191.25420.27.191.25516,382
11220.27.192.0/1820.27.192.1 to 20.27.255.25420.27.255.25516,382
11320.28.0.0/1820.28.0.1 to 20.28.63.25420.28.63.25516,382
11420.28.64.0/1820.28.64.1 to 20.28.127.25420.28.127.25516,382
11520.28.128.0/1820.28.128.1 to 20.28.191.25420.28.191.25516,382
11620.28.192.0/1820.28.192.1 to 20.28.255.25420.28.255.25516,382
11720.29.0.0/1820.29.0.1 to 20.29.63.25420.29.63.25516,382
11820.29.64.0/1820.29.64.1 to 20.29.127.25420.29.127.25516,382
11920.29.128.0/1820.29.128.1 to 20.29.191.25420.29.191.25516,382
12020.29.192.0/1820.29.192.1 to 20.29.255.25420.29.255.25516,382
12120.30.0.0/1820.30.0.1 to 20.30.63.25420.30.63.25516,382
12220.30.64.0/1820.30.64.1 to 20.30.127.25420.30.127.25516,382
12320.30.128.0/1820.30.128.1 to 20.30.191.25420.30.191.25516,382
12420.30.192.0/1820.30.192.1 to 20.30.255.25420.30.255.25516,382
12520.31.0.0/1820.31.0.1 to 20.31.63.25420.31.63.25516,382
12620.31.64.0/1820.31.64.1 to 20.31.127.25420.31.127.25516,382
12720.31.128.0/1820.31.128.1 to 20.31.191.25420.31.191.25516,382
12820.31.192.0/1820.31.192.1 to 20.31.255.25420.31.255.25516,382
12920.32.0.0/1820.32.0.1 to 20.32.63.25420.32.63.25516,382
13020.32.64.0/1820.32.64.1 to 20.32.127.25420.32.127.25516,382
13120.32.128.0/1820.32.128.1 to 20.32.191.25420.32.191.25516,382
13220.32.192.0/1820.32.192.1 to 20.32.255.25420.32.255.25516,382
13320.33.0.0/1820.33.0.1 to 20.33.63.25420.33.63.25516,382
13420.33.64.0/1820.33.64.1 to 20.33.127.25420.33.127.25516,382
13520.33.128.0/1820.33.128.1 to 20.33.191.25420.33.191.25516,382
13620.33.192.0/1820.33.192.1 to 20.33.255.25420.33.255.25516,382
13720.34.0.0/1820.34.0.1 to 20.34.63.25420.34.63.25516,382
13820.34.64.0/1820.34.64.1 to 20.34.127.25420.34.127.25516,382
13920.34.128.0/1820.34.128.1 to 20.34.191.25420.34.191.25516,382
14020.34.192.0/1820.34.192.1 to 20.34.255.25420.34.255.25516,382
14120.35.0.0/1820.35.0.1 to 20.35.63.25420.35.63.25516,382
14220.35.64.0/1820.35.64.1 to 20.35.127.25420.35.127.25516,382
14320.35.128.0/1820.35.128.1 to 20.35.191.25420.35.191.25516,382
14420.35.192.0/1820.35.192.1 to 20.35.255.25420.35.255.25516,382
14520.36.0.0/1820.36.0.1 to 20.36.63.25420.36.63.25516,382
14620.36.64.0/1820.36.64.1 to 20.36.127.25420.36.127.25516,382
14720.36.128.0/1820.36.128.1 to 20.36.191.25420.36.191.25516,382
14820.36.192.0/1820.36.192.1 to 20.36.255.25420.36.255.25516,382
14920.37.0.0/1820.37.0.1 to 20.37.63.25420.37.63.25516,382
15020.37.64.0/1820.37.64.1 to 20.37.127.25420.37.127.25516,382
15120.37.128.0/1820.37.128.1 to 20.37.191.25420.37.191.25516,382
15220.37.192.0/1820.37.192.1 to 20.37.255.25420.37.255.25516,382
15320.38.0.0/1820.38.0.1 to 20.38.63.25420.38.63.25516,382
15420.38.64.0/1820.38.64.1 to 20.38.127.25420.38.127.25516,382
15520.38.128.0/1820.38.128.1 to 20.38.191.25420.38.191.25516,382
15620.38.192.0/1820.38.192.1 to 20.38.255.25420.38.255.25516,382
15720.39.0.0/1820.39.0.1 to 20.39.63.25420.39.63.25516,382
15820.39.64.0/1820.39.64.1 to 20.39.127.25420.39.127.25516,382
15920.39.128.0/1820.39.128.1 to 20.39.191.25420.39.191.25516,382
16020.39.192.0/1820.39.192.1 to 20.39.255.25420.39.255.25516,382
16120.40.0.0/1820.40.0.1 to 20.40.63.25420.40.63.25516,382
16220.40.64.0/1820.40.64.1 to 20.40.127.25420.40.127.25516,382
16320.40.128.0/1820.40.128.1 to 20.40.191.25420.40.191.25516,382
16420.40.192.0/1820.40.192.1 to 20.40.255.25420.40.255.25516,382
16520.41.0.0/1820.41.0.1 to 20.41.63.25420.41.63.25516,382
16620.41.64.0/1820.41.64.1 to 20.41.127.25420.41.127.25516,382
16720.41.128.0/1820.41.128.1 to 20.41.191.25420.41.191.25516,382
16820.41.192.0/1820.41.192.1 to 20.41.255.25420.41.255.25516,382
16920.42.0.0/1820.42.0.1 to 20.42.63.25420.42.63.25516,382
17020.42.64.0/1820.42.64.1 to 20.42.127.25420.42.127.25516,382
17120.42.128.0/1820.42.128.1 to 20.42.191.25420.42.191.25516,382
17220.42.192.0/1820.42.192.1 to 20.42.255.25420.42.255.25516,382
17320.43.0.0/1820.43.0.1 to 20.43.63.25420.43.63.25516,382
17420.43.64.0/1820.43.64.1 to 20.43.127.25420.43.127.25516,382
17520.43.128.0/1820.43.128.1 to 20.43.191.25420.43.191.25516,382
17620.43.192.0/1820.43.192.1 to 20.43.255.25420.43.255.25516,382
17720.44.0.0/1820.44.0.1 to 20.44.63.25420.44.63.25516,382
17820.44.64.0/1820.44.64.1 to 20.44.127.25420.44.127.25516,382
17920.44.128.0/1820.44.128.1 to 20.44.191.25420.44.191.25516,382
18020.44.192.0/1820.44.192.1 to 20.44.255.25420.44.255.25516,382
18120.45.0.0/1820.45.0.1 to 20.45.63.25420.45.63.25516,382
18220.45.64.0/1820.45.64.1 to 20.45.127.25420.45.127.25516,382
18320.45.128.0/1820.45.128.1 to 20.45.191.25420.45.191.25516,382
18420.45.192.0/1820.45.192.1 to 20.45.255.25420.45.255.25516,382
18520.46.0.0/1820.46.0.1 to 20.46.63.25420.46.63.25516,382
18620.46.64.0/1820.46.64.1 to 20.46.127.25420.46.127.25516,382
18720.46.128.0/1820.46.128.1 to 20.46.191.25420.46.191.25516,382
18820.46.192.0/1820.46.192.1 to 20.46.255.25420.46.255.25516,382
18920.47.0.0/1820.47.0.1 to 20.47.63.25420.47.63.25516,382
19020.47.64.0/1820.47.64.1 to 20.47.127.25420.47.127.25516,382
19120.47.128.0/1820.47.128.1 to 20.47.191.25420.47.191.25516,382
19220.47.192.0/1820.47.192.1 to 20.47.255.25420.47.255.25516,382
19320.48.0.0/1820.48.0.1 to 20.48.63.25420.48.63.25516,382
19420.48.64.0/1820.48.64.1 to 20.48.127.25420.48.127.25516,382
19520.48.128.0/1820.48.128.1 to 20.48.191.25420.48.191.25516,382
19620.48.192.0/1820.48.192.1 to 20.48.255.25420.48.255.25516,382
19720.49.0.0/1820.49.0.1 to 20.49.63.25420.49.63.25516,382
19820.49.64.0/1820.49.64.1 to 20.49.127.25420.49.127.25516,382
19920.49.128.0/1820.49.128.1 to 20.49.191.25420.49.191.25516,382
20020.49.192.0/1820.49.192.1 to 20.49.255.25420.49.255.25516,382
20120.50.0.0/1820.50.0.1 to 20.50.63.25420.50.63.25516,382
20220.50.64.0/1820.50.64.1 to 20.50.127.25420.50.127.25516,382
20320.50.128.0/1820.50.128.1 to 20.50.191.25420.50.191.25516,382
20420.50.192.0/1820.50.192.1 to 20.50.255.25420.50.255.25516,382
20520.51.0.0/1820.51.0.1 to 20.51.63.25420.51.63.25516,382
20620.51.64.0/1820.51.64.1 to 20.51.127.25420.51.127.25516,382
20720.51.128.0/1820.51.128.1 to 20.51.191.25420.51.191.25516,382
20820.51.192.0/1820.51.192.1 to 20.51.255.25420.51.255.25516,382
20920.52.0.0/1820.52.0.1 to 20.52.63.25420.52.63.25516,382
21020.52.64.0/1820.52.64.1 to 20.52.127.25420.52.127.25516,382
21120.52.128.0/1820.52.128.1 to 20.52.191.25420.52.191.25516,382
21220.52.192.0/1820.52.192.1 to 20.52.255.25420.52.255.25516,382
21320.53.0.0/1820.53.0.1 to 20.53.63.25420.53.63.25516,382
21420.53.64.0/1820.53.64.1 to 20.53.127.25420.53.127.25516,382
21520.53.128.0/1820.53.128.1 to 20.53.191.25420.53.191.25516,382
21620.53.192.0/1820.53.192.1 to 20.53.255.25420.53.255.25516,382
21720.54.0.0/1820.54.0.1 to 20.54.63.25420.54.63.25516,382
21820.54.64.0/1820.54.64.1 to 20.54.127.25420.54.127.25516,382
21920.54.128.0/1820.54.128.1 to 20.54.191.25420.54.191.25516,382
22020.54.192.0/1820.54.192.1 to 20.54.255.25420.54.255.25516,382
22120.55.0.0/1820.55.0.1 to 20.55.63.25420.55.63.25516,382
22220.55.64.0/1820.55.64.1 to 20.55.127.25420.55.127.25516,382
22320.55.128.0/1820.55.128.1 to 20.55.191.25420.55.191.25516,382
22420.55.192.0/1820.55.192.1 to 20.55.255.25420.55.255.25516,382
22520.56.0.0/1820.56.0.1 to 20.56.63.25420.56.63.25516,382
22620.56.64.0/1820.56.64.1 to 20.56.127.25420.56.127.25516,382
22720.56.128.0/1820.56.128.1 to 20.56.191.25420.56.191.25516,382
22820.56.192.0/1820.56.192.1 to 20.56.255.25420.56.255.25516,382
22920.57.0.0/1820.57.0.1 to 20.57.63.25420.57.63.25516,382
23020.57.64.0/1820.57.64.1 to 20.57.127.25420.57.127.25516,382
23120.57.128.0/1820.57.128.1 to 20.57.191.25420.57.191.25516,382
23220.57.192.0/1820.57.192.1 to 20.57.255.25420.57.255.25516,382
23320.58.0.0/1820.58.0.1 to 20.58.63.25420.58.63.25516,382
23420.58.64.0/1820.58.64.1 to 20.58.127.25420.58.127.25516,382
23520.58.128.0/1820.58.128.1 to 20.58.191.25420.58.191.25516,382
23620.58.192.0/1820.58.192.1 to 20.58.255.25420.58.255.25516,382
23720.59.0.0/1820.59.0.1 to 20.59.63.25420.59.63.25516,382
23820.59.64.0/1820.59.64.1 to 20.59.127.25420.59.127.25516,382
23920.59.128.0/1820.59.128.1 to 20.59.191.25420.59.191.25516,382
24020.59.192.0/1820.59.192.1 to 20.59.255.25420.59.255.25516,382
24120.60.0.0/1820.60.0.1 to 20.60.63.25420.60.63.25516,382
24220.60.64.0/1820.60.64.1 to 20.60.127.25420.60.127.25516,382
24320.60.128.0/1820.60.128.1 to 20.60.191.25420.60.191.25516,382
24420.60.192.0/1820.60.192.1 to 20.60.255.25420.60.255.25516,382
24520.61.0.0/1820.61.0.1 to 20.61.63.25420.61.63.25516,382
24620.61.64.0/1820.61.64.1 to 20.61.127.25420.61.127.25516,382
24720.61.128.0/1820.61.128.1 to 20.61.191.25420.61.191.25516,382
24820.61.192.0/1820.61.192.1 to 20.61.255.25420.61.255.25516,382
24920.62.0.0/1820.62.0.1 to 20.62.63.25420.62.63.25516,382
25020.62.64.0/1820.62.64.1 to 20.62.127.25420.62.127.25516,382
25120.62.128.0/1820.62.128.1 to 20.62.191.25420.62.191.25516,382
25220.62.192.0/1820.62.192.1 to 20.62.255.25420.62.255.25516,382
25320.63.0.0/1820.63.0.1 to 20.63.63.25420.63.63.25516,382
25420.63.64.0/1820.63.64.1 to 20.63.127.25420.63.127.25516,382
25520.63.128.0/1820.63.128.1 to 20.63.191.25420.63.191.25516,382
25620.63.192.0/1820.63.192.1 to 20.63.255.25420.63.255.25516,382

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.