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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.

Network51.0.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
51.0.0.0
Broadcast address
51.63.255.255
First usable
51.0.0.1
Last usable
51.63.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
A (default /8)
As numbers
Hex 33000000 · Integer 855638016 to 859832319
Reverse DNS zones
0.51.in-addr.arpa
1.51.in-addr.arpa
2.51.in-addr.arpa
3.51.in-addr.arpa
4.51.in-addr.arpa
5.51.in-addr.arpa
6.51.in-addr.arpa
7.51.in-addr.arpa
8.51.in-addr.arpa
9.51.in-addr.arpa
10.51.in-addr.arpa
11.51.in-addr.arpa
12.51.in-addr.arpa
13.51.in-addr.arpa
14.51.in-addr.arpa
15.51.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00110011.00000000.00000000.0000000051.0.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00110011.00000000.00000000.0000000051.0.0.0
Broadcast00110011.00111111.11111111.1111111151.63.255.255
Split into smaller subnets/21
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

51.0.0.0/10 makes 2,048 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
151.0.0.0/2151.0.0.1 to 51.0.7.25451.0.7.2552,046
251.0.8.0/2151.0.8.1 to 51.0.15.25451.0.15.2552,046
351.0.16.0/2151.0.16.1 to 51.0.23.25451.0.23.2552,046
451.0.24.0/2151.0.24.1 to 51.0.31.25451.0.31.2552,046
551.0.32.0/2151.0.32.1 to 51.0.39.25451.0.39.2552,046
651.0.40.0/2151.0.40.1 to 51.0.47.25451.0.47.2552,046
751.0.48.0/2151.0.48.1 to 51.0.55.25451.0.55.2552,046
851.0.56.0/2151.0.56.1 to 51.0.63.25451.0.63.2552,046
951.0.64.0/2151.0.64.1 to 51.0.71.25451.0.71.2552,046
1051.0.72.0/2151.0.72.1 to 51.0.79.25451.0.79.2552,046
1151.0.80.0/2151.0.80.1 to 51.0.87.25451.0.87.2552,046
1251.0.88.0/2151.0.88.1 to 51.0.95.25451.0.95.2552,046
1351.0.96.0/2151.0.96.1 to 51.0.103.25451.0.103.2552,046
1451.0.104.0/2151.0.104.1 to 51.0.111.25451.0.111.2552,046
1551.0.112.0/2151.0.112.1 to 51.0.119.25451.0.119.2552,046
1651.0.120.0/2151.0.120.1 to 51.0.127.25451.0.127.2552,046
1751.0.128.0/2151.0.128.1 to 51.0.135.25451.0.135.2552,046
1851.0.136.0/2151.0.136.1 to 51.0.143.25451.0.143.2552,046
1951.0.144.0/2151.0.144.1 to 51.0.151.25451.0.151.2552,046
2051.0.152.0/2151.0.152.1 to 51.0.159.25451.0.159.2552,046
2151.0.160.0/2151.0.160.1 to 51.0.167.25451.0.167.2552,046
2251.0.168.0/2151.0.168.1 to 51.0.175.25451.0.175.2552,046
2351.0.176.0/2151.0.176.1 to 51.0.183.25451.0.183.2552,046
2451.0.184.0/2151.0.184.1 to 51.0.191.25451.0.191.2552,046
2551.0.192.0/2151.0.192.1 to 51.0.199.25451.0.199.2552,046
2651.0.200.0/2151.0.200.1 to 51.0.207.25451.0.207.2552,046
2751.0.208.0/2151.0.208.1 to 51.0.215.25451.0.215.2552,046
2851.0.216.0/2151.0.216.1 to 51.0.223.25451.0.223.2552,046
2951.0.224.0/2151.0.224.1 to 51.0.231.25451.0.231.2552,046
3051.0.232.0/2151.0.232.1 to 51.0.239.25451.0.239.2552,046
3151.0.240.0/2151.0.240.1 to 51.0.247.25451.0.247.2552,046
3251.0.248.0/2151.0.248.1 to 51.0.255.25451.0.255.2552,046
3351.1.0.0/2151.1.0.1 to 51.1.7.25451.1.7.2552,046
3451.1.8.0/2151.1.8.1 to 51.1.15.25451.1.15.2552,046
3551.1.16.0/2151.1.16.1 to 51.1.23.25451.1.23.2552,046
3651.1.24.0/2151.1.24.1 to 51.1.31.25451.1.31.2552,046
3751.1.32.0/2151.1.32.1 to 51.1.39.25451.1.39.2552,046
3851.1.40.0/2151.1.40.1 to 51.1.47.25451.1.47.2552,046
3951.1.48.0/2151.1.48.1 to 51.1.55.25451.1.55.2552,046
4051.1.56.0/2151.1.56.1 to 51.1.63.25451.1.63.2552,046
4151.1.64.0/2151.1.64.1 to 51.1.71.25451.1.71.2552,046
4251.1.72.0/2151.1.72.1 to 51.1.79.25451.1.79.2552,046
4351.1.80.0/2151.1.80.1 to 51.1.87.25451.1.87.2552,046
4451.1.88.0/2151.1.88.1 to 51.1.95.25451.1.95.2552,046
4551.1.96.0/2151.1.96.1 to 51.1.103.25451.1.103.2552,046
4651.1.104.0/2151.1.104.1 to 51.1.111.25451.1.111.2552,046
4751.1.112.0/2151.1.112.1 to 51.1.119.25451.1.119.2552,046
4851.1.120.0/2151.1.120.1 to 51.1.127.25451.1.127.2552,046
4951.1.128.0/2151.1.128.1 to 51.1.135.25451.1.135.2552,046
5051.1.136.0/2151.1.136.1 to 51.1.143.25451.1.143.2552,046
5151.1.144.0/2151.1.144.1 to 51.1.151.25451.1.151.2552,046
5251.1.152.0/2151.1.152.1 to 51.1.159.25451.1.159.2552,046
5351.1.160.0/2151.1.160.1 to 51.1.167.25451.1.167.2552,046
5451.1.168.0/2151.1.168.1 to 51.1.175.25451.1.175.2552,046
5551.1.176.0/2151.1.176.1 to 51.1.183.25451.1.183.2552,046
5651.1.184.0/2151.1.184.1 to 51.1.191.25451.1.191.2552,046
5751.1.192.0/2151.1.192.1 to 51.1.199.25451.1.199.2552,046
5851.1.200.0/2151.1.200.1 to 51.1.207.25451.1.207.2552,046
5951.1.208.0/2151.1.208.1 to 51.1.215.25451.1.215.2552,046
6051.1.216.0/2151.1.216.1 to 51.1.223.25451.1.223.2552,046
6151.1.224.0/2151.1.224.1 to 51.1.231.25451.1.231.2552,046
6251.1.232.0/2151.1.232.1 to 51.1.239.25451.1.239.2552,046
6351.1.240.0/2151.1.240.1 to 51.1.247.25451.1.247.2552,046
6451.1.248.0/2151.1.248.1 to 51.1.255.25451.1.255.2552,046
6551.2.0.0/2151.2.0.1 to 51.2.7.25451.2.7.2552,046
6651.2.8.0/2151.2.8.1 to 51.2.15.25451.2.15.2552,046
6751.2.16.0/2151.2.16.1 to 51.2.23.25451.2.23.2552,046
6851.2.24.0/2151.2.24.1 to 51.2.31.25451.2.31.2552,046
6951.2.32.0/2151.2.32.1 to 51.2.39.25451.2.39.2552,046
7051.2.40.0/2151.2.40.1 to 51.2.47.25451.2.47.2552,046
7151.2.48.0/2151.2.48.1 to 51.2.55.25451.2.55.2552,046
7251.2.56.0/2151.2.56.1 to 51.2.63.25451.2.63.2552,046
7351.2.64.0/2151.2.64.1 to 51.2.71.25451.2.71.2552,046
7451.2.72.0/2151.2.72.1 to 51.2.79.25451.2.79.2552,046
7551.2.80.0/2151.2.80.1 to 51.2.87.25451.2.87.2552,046
7651.2.88.0/2151.2.88.1 to 51.2.95.25451.2.95.2552,046
7751.2.96.0/2151.2.96.1 to 51.2.103.25451.2.103.2552,046
7851.2.104.0/2151.2.104.1 to 51.2.111.25451.2.111.2552,046
7951.2.112.0/2151.2.112.1 to 51.2.119.25451.2.119.2552,046
8051.2.120.0/2151.2.120.1 to 51.2.127.25451.2.127.2552,046
8151.2.128.0/2151.2.128.1 to 51.2.135.25451.2.135.2552,046
8251.2.136.0/2151.2.136.1 to 51.2.143.25451.2.143.2552,046
8351.2.144.0/2151.2.144.1 to 51.2.151.25451.2.151.2552,046
8451.2.152.0/2151.2.152.1 to 51.2.159.25451.2.159.2552,046
8551.2.160.0/2151.2.160.1 to 51.2.167.25451.2.167.2552,046
8651.2.168.0/2151.2.168.1 to 51.2.175.25451.2.175.2552,046
8751.2.176.0/2151.2.176.1 to 51.2.183.25451.2.183.2552,046
8851.2.184.0/2151.2.184.1 to 51.2.191.25451.2.191.2552,046
8951.2.192.0/2151.2.192.1 to 51.2.199.25451.2.199.2552,046
9051.2.200.0/2151.2.200.1 to 51.2.207.25451.2.207.2552,046
9151.2.208.0/2151.2.208.1 to 51.2.215.25451.2.215.2552,046
9251.2.216.0/2151.2.216.1 to 51.2.223.25451.2.223.2552,046
9351.2.224.0/2151.2.224.1 to 51.2.231.25451.2.231.2552,046
9451.2.232.0/2151.2.232.1 to 51.2.239.25451.2.239.2552,046
9551.2.240.0/2151.2.240.1 to 51.2.247.25451.2.247.2552,046
9651.2.248.0/2151.2.248.1 to 51.2.255.25451.2.255.2552,046
9751.3.0.0/2151.3.0.1 to 51.3.7.25451.3.7.2552,046
9851.3.8.0/2151.3.8.1 to 51.3.15.25451.3.15.2552,046
9951.3.16.0/2151.3.16.1 to 51.3.23.25451.3.23.2552,046
10051.3.24.0/2151.3.24.1 to 51.3.31.25451.3.31.2552,046
10151.3.32.0/2151.3.32.1 to 51.3.39.25451.3.39.2552,046
10251.3.40.0/2151.3.40.1 to 51.3.47.25451.3.47.2552,046
10351.3.48.0/2151.3.48.1 to 51.3.55.25451.3.55.2552,046
10451.3.56.0/2151.3.56.1 to 51.3.63.25451.3.63.2552,046
10551.3.64.0/2151.3.64.1 to 51.3.71.25451.3.71.2552,046
10651.3.72.0/2151.3.72.1 to 51.3.79.25451.3.79.2552,046
10751.3.80.0/2151.3.80.1 to 51.3.87.25451.3.87.2552,046
10851.3.88.0/2151.3.88.1 to 51.3.95.25451.3.95.2552,046
10951.3.96.0/2151.3.96.1 to 51.3.103.25451.3.103.2552,046
11051.3.104.0/2151.3.104.1 to 51.3.111.25451.3.111.2552,046
11151.3.112.0/2151.3.112.1 to 51.3.119.25451.3.119.2552,046
11251.3.120.0/2151.3.120.1 to 51.3.127.25451.3.127.2552,046
11351.3.128.0/2151.3.128.1 to 51.3.135.25451.3.135.2552,046
11451.3.136.0/2151.3.136.1 to 51.3.143.25451.3.143.2552,046
11551.3.144.0/2151.3.144.1 to 51.3.151.25451.3.151.2552,046
11651.3.152.0/2151.3.152.1 to 51.3.159.25451.3.159.2552,046
11751.3.160.0/2151.3.160.1 to 51.3.167.25451.3.167.2552,046
11851.3.168.0/2151.3.168.1 to 51.3.175.25451.3.175.2552,046
11951.3.176.0/2151.3.176.1 to 51.3.183.25451.3.183.2552,046
12051.3.184.0/2151.3.184.1 to 51.3.191.25451.3.191.2552,046
12151.3.192.0/2151.3.192.1 to 51.3.199.25451.3.199.2552,046
12251.3.200.0/2151.3.200.1 to 51.3.207.25451.3.207.2552,046
12351.3.208.0/2151.3.208.1 to 51.3.215.25451.3.215.2552,046
12451.3.216.0/2151.3.216.1 to 51.3.223.25451.3.223.2552,046
12551.3.224.0/2151.3.224.1 to 51.3.231.25451.3.231.2552,046
12651.3.232.0/2151.3.232.1 to 51.3.239.25451.3.239.2552,046
12751.3.240.0/2151.3.240.1 to 51.3.247.25451.3.247.2552,046
12851.3.248.0/2151.3.248.1 to 51.3.255.25451.3.255.2552,046
12951.4.0.0/2151.4.0.1 to 51.4.7.25451.4.7.2552,046
13051.4.8.0/2151.4.8.1 to 51.4.15.25451.4.15.2552,046
13151.4.16.0/2151.4.16.1 to 51.4.23.25451.4.23.2552,046
13251.4.24.0/2151.4.24.1 to 51.4.31.25451.4.31.2552,046
13351.4.32.0/2151.4.32.1 to 51.4.39.25451.4.39.2552,046
13451.4.40.0/2151.4.40.1 to 51.4.47.25451.4.47.2552,046
13551.4.48.0/2151.4.48.1 to 51.4.55.25451.4.55.2552,046
13651.4.56.0/2151.4.56.1 to 51.4.63.25451.4.63.2552,046
13751.4.64.0/2151.4.64.1 to 51.4.71.25451.4.71.2552,046
13851.4.72.0/2151.4.72.1 to 51.4.79.25451.4.79.2552,046
13951.4.80.0/2151.4.80.1 to 51.4.87.25451.4.87.2552,046
14051.4.88.0/2151.4.88.1 to 51.4.95.25451.4.95.2552,046
14151.4.96.0/2151.4.96.1 to 51.4.103.25451.4.103.2552,046
14251.4.104.0/2151.4.104.1 to 51.4.111.25451.4.111.2552,046
14351.4.112.0/2151.4.112.1 to 51.4.119.25451.4.119.2552,046
14451.4.120.0/2151.4.120.1 to 51.4.127.25451.4.127.2552,046
14551.4.128.0/2151.4.128.1 to 51.4.135.25451.4.135.2552,046
14651.4.136.0/2151.4.136.1 to 51.4.143.25451.4.143.2552,046
14751.4.144.0/2151.4.144.1 to 51.4.151.25451.4.151.2552,046
14851.4.152.0/2151.4.152.1 to 51.4.159.25451.4.159.2552,046
14951.4.160.0/2151.4.160.1 to 51.4.167.25451.4.167.2552,046
15051.4.168.0/2151.4.168.1 to 51.4.175.25451.4.175.2552,046
15151.4.176.0/2151.4.176.1 to 51.4.183.25451.4.183.2552,046
15251.4.184.0/2151.4.184.1 to 51.4.191.25451.4.191.2552,046
15351.4.192.0/2151.4.192.1 to 51.4.199.25451.4.199.2552,046
15451.4.200.0/2151.4.200.1 to 51.4.207.25451.4.207.2552,046
15551.4.208.0/2151.4.208.1 to 51.4.215.25451.4.215.2552,046
15651.4.216.0/2151.4.216.1 to 51.4.223.25451.4.223.2552,046
15751.4.224.0/2151.4.224.1 to 51.4.231.25451.4.231.2552,046
15851.4.232.0/2151.4.232.1 to 51.4.239.25451.4.239.2552,046
15951.4.240.0/2151.4.240.1 to 51.4.247.25451.4.247.2552,046
16051.4.248.0/2151.4.248.1 to 51.4.255.25451.4.255.2552,046
16151.5.0.0/2151.5.0.1 to 51.5.7.25451.5.7.2552,046
16251.5.8.0/2151.5.8.1 to 51.5.15.25451.5.15.2552,046
16351.5.16.0/2151.5.16.1 to 51.5.23.25451.5.23.2552,046
16451.5.24.0/2151.5.24.1 to 51.5.31.25451.5.31.2552,046
16551.5.32.0/2151.5.32.1 to 51.5.39.25451.5.39.2552,046
16651.5.40.0/2151.5.40.1 to 51.5.47.25451.5.47.2552,046
16751.5.48.0/2151.5.48.1 to 51.5.55.25451.5.55.2552,046
16851.5.56.0/2151.5.56.1 to 51.5.63.25451.5.63.2552,046
16951.5.64.0/2151.5.64.1 to 51.5.71.25451.5.71.2552,046
17051.5.72.0/2151.5.72.1 to 51.5.79.25451.5.79.2552,046
17151.5.80.0/2151.5.80.1 to 51.5.87.25451.5.87.2552,046
17251.5.88.0/2151.5.88.1 to 51.5.95.25451.5.95.2552,046
17351.5.96.0/2151.5.96.1 to 51.5.103.25451.5.103.2552,046
17451.5.104.0/2151.5.104.1 to 51.5.111.25451.5.111.2552,046
17551.5.112.0/2151.5.112.1 to 51.5.119.25451.5.119.2552,046
17651.5.120.0/2151.5.120.1 to 51.5.127.25451.5.127.2552,046
17751.5.128.0/2151.5.128.1 to 51.5.135.25451.5.135.2552,046
17851.5.136.0/2151.5.136.1 to 51.5.143.25451.5.143.2552,046
17951.5.144.0/2151.5.144.1 to 51.5.151.25451.5.151.2552,046
18051.5.152.0/2151.5.152.1 to 51.5.159.25451.5.159.2552,046
18151.5.160.0/2151.5.160.1 to 51.5.167.25451.5.167.2552,046
18251.5.168.0/2151.5.168.1 to 51.5.175.25451.5.175.2552,046
18351.5.176.0/2151.5.176.1 to 51.5.183.25451.5.183.2552,046
18451.5.184.0/2151.5.184.1 to 51.5.191.25451.5.191.2552,046
18551.5.192.0/2151.5.192.1 to 51.5.199.25451.5.199.2552,046
18651.5.200.0/2151.5.200.1 to 51.5.207.25451.5.207.2552,046
18751.5.208.0/2151.5.208.1 to 51.5.215.25451.5.215.2552,046
18851.5.216.0/2151.5.216.1 to 51.5.223.25451.5.223.2552,046
18951.5.224.0/2151.5.224.1 to 51.5.231.25451.5.231.2552,046
19051.5.232.0/2151.5.232.1 to 51.5.239.25451.5.239.2552,046
19151.5.240.0/2151.5.240.1 to 51.5.247.25451.5.247.2552,046
19251.5.248.0/2151.5.248.1 to 51.5.255.25451.5.255.2552,046
19351.6.0.0/2151.6.0.1 to 51.6.7.25451.6.7.2552,046
19451.6.8.0/2151.6.8.1 to 51.6.15.25451.6.15.2552,046
19551.6.16.0/2151.6.16.1 to 51.6.23.25451.6.23.2552,046
19651.6.24.0/2151.6.24.1 to 51.6.31.25451.6.31.2552,046
19751.6.32.0/2151.6.32.1 to 51.6.39.25451.6.39.2552,046
19851.6.40.0/2151.6.40.1 to 51.6.47.25451.6.47.2552,046
19951.6.48.0/2151.6.48.1 to 51.6.55.25451.6.55.2552,046
20051.6.56.0/2151.6.56.1 to 51.6.63.25451.6.63.2552,046
20151.6.64.0/2151.6.64.1 to 51.6.71.25451.6.71.2552,046
20251.6.72.0/2151.6.72.1 to 51.6.79.25451.6.79.2552,046
20351.6.80.0/2151.6.80.1 to 51.6.87.25451.6.87.2552,046
20451.6.88.0/2151.6.88.1 to 51.6.95.25451.6.95.2552,046
20551.6.96.0/2151.6.96.1 to 51.6.103.25451.6.103.2552,046
20651.6.104.0/2151.6.104.1 to 51.6.111.25451.6.111.2552,046
20751.6.112.0/2151.6.112.1 to 51.6.119.25451.6.119.2552,046
20851.6.120.0/2151.6.120.1 to 51.6.127.25451.6.127.2552,046
20951.6.128.0/2151.6.128.1 to 51.6.135.25451.6.135.2552,046
21051.6.136.0/2151.6.136.1 to 51.6.143.25451.6.143.2552,046
21151.6.144.0/2151.6.144.1 to 51.6.151.25451.6.151.2552,046
21251.6.152.0/2151.6.152.1 to 51.6.159.25451.6.159.2552,046
21351.6.160.0/2151.6.160.1 to 51.6.167.25451.6.167.2552,046
21451.6.168.0/2151.6.168.1 to 51.6.175.25451.6.175.2552,046
21551.6.176.0/2151.6.176.1 to 51.6.183.25451.6.183.2552,046
21651.6.184.0/2151.6.184.1 to 51.6.191.25451.6.191.2552,046
21751.6.192.0/2151.6.192.1 to 51.6.199.25451.6.199.2552,046
21851.6.200.0/2151.6.200.1 to 51.6.207.25451.6.207.2552,046
21951.6.208.0/2151.6.208.1 to 51.6.215.25451.6.215.2552,046
22051.6.216.0/2151.6.216.1 to 51.6.223.25451.6.223.2552,046
22151.6.224.0/2151.6.224.1 to 51.6.231.25451.6.231.2552,046
22251.6.232.0/2151.6.232.1 to 51.6.239.25451.6.239.2552,046
22351.6.240.0/2151.6.240.1 to 51.6.247.25451.6.247.2552,046
22451.6.248.0/2151.6.248.1 to 51.6.255.25451.6.255.2552,046
22551.7.0.0/2151.7.0.1 to 51.7.7.25451.7.7.2552,046
22651.7.8.0/2151.7.8.1 to 51.7.15.25451.7.15.2552,046
22751.7.16.0/2151.7.16.1 to 51.7.23.25451.7.23.2552,046
22851.7.24.0/2151.7.24.1 to 51.7.31.25451.7.31.2552,046
22951.7.32.0/2151.7.32.1 to 51.7.39.25451.7.39.2552,046
23051.7.40.0/2151.7.40.1 to 51.7.47.25451.7.47.2552,046
23151.7.48.0/2151.7.48.1 to 51.7.55.25451.7.55.2552,046
23251.7.56.0/2151.7.56.1 to 51.7.63.25451.7.63.2552,046
23351.7.64.0/2151.7.64.1 to 51.7.71.25451.7.71.2552,046
23451.7.72.0/2151.7.72.1 to 51.7.79.25451.7.79.2552,046
23551.7.80.0/2151.7.80.1 to 51.7.87.25451.7.87.2552,046
23651.7.88.0/2151.7.88.1 to 51.7.95.25451.7.95.2552,046
23751.7.96.0/2151.7.96.1 to 51.7.103.25451.7.103.2552,046
23851.7.104.0/2151.7.104.1 to 51.7.111.25451.7.111.2552,046
23951.7.112.0/2151.7.112.1 to 51.7.119.25451.7.119.2552,046
24051.7.120.0/2151.7.120.1 to 51.7.127.25451.7.127.2552,046
24151.7.128.0/2151.7.128.1 to 51.7.135.25451.7.135.2552,046
24251.7.136.0/2151.7.136.1 to 51.7.143.25451.7.143.2552,046
24351.7.144.0/2151.7.144.1 to 51.7.151.25451.7.151.2552,046
24451.7.152.0/2151.7.152.1 to 51.7.159.25451.7.159.2552,046
24551.7.160.0/2151.7.160.1 to 51.7.167.25451.7.167.2552,046
24651.7.168.0/2151.7.168.1 to 51.7.175.25451.7.175.2552,046
24751.7.176.0/2151.7.176.1 to 51.7.183.25451.7.183.2552,046
24851.7.184.0/2151.7.184.1 to 51.7.191.25451.7.191.2552,046
24951.7.192.0/2151.7.192.1 to 51.7.199.25451.7.199.2552,046
25051.7.200.0/2151.7.200.1 to 51.7.207.25451.7.207.2552,046
25151.7.208.0/2151.7.208.1 to 51.7.215.25451.7.215.2552,046
25251.7.216.0/2151.7.216.1 to 51.7.223.25451.7.223.2552,046
25351.7.224.0/2151.7.224.1 to 51.7.231.25451.7.231.2552,046
25451.7.232.0/2151.7.232.1 to 51.7.239.25451.7.239.2552,046
25551.7.240.0/2151.7.240.1 to 51.7.247.25451.7.247.2552,046
25651.7.248.0/2151.7.248.1 to 51.7.255.25451.7.255.2552,046

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.