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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.

Network10.21.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
10.21.0.0
Broadcast address
10.21.255.255
First usable
10.21.0.1
Last usable
10.21.255.254
Usable hosts
65,534 (65,536 less the network and broadcast addresses)
Subnet mask
255.255.0.0
Wildcard mask
0.0.255.255 (Cisco ACLs, OSPF)
Prefix length
/16
Type
Private (RFC 1918) 10.0.0.0/8
Office and home networks; not routed on the internet
Old class
A (default /8)
As numbers
Hex 0A150000 · Integer 169148416 to 169213951
Reverse DNS zone
21.10.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001010.00010101..00000000.0000000010.21.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network00001010.00010101..00000000.0000000010.21.0.0
Broadcast00001010.00010101..11111111.1111111110.21.255.255
Split into smaller subnets/24
/17 (2)/18 (4)/19 (8)/20 (16)/21 (32)/22 (64)/23 (128)/24 (256)/25 (512)/26 (1,024)/27 (2,048)/28 (4,096)

10.21.0.0/16 makes 256 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
110.21.0.0/2410.21.0.1 to 10.21.0.25410.21.0.255254
210.21.1.0/2410.21.1.1 to 10.21.1.25410.21.1.255254
310.21.2.0/2410.21.2.1 to 10.21.2.25410.21.2.255254
410.21.3.0/2410.21.3.1 to 10.21.3.25410.21.3.255254
510.21.4.0/2410.21.4.1 to 10.21.4.25410.21.4.255254
610.21.5.0/2410.21.5.1 to 10.21.5.25410.21.5.255254
710.21.6.0/2410.21.6.1 to 10.21.6.25410.21.6.255254
810.21.7.0/2410.21.7.1 to 10.21.7.25410.21.7.255254
910.21.8.0/2410.21.8.1 to 10.21.8.25410.21.8.255254
1010.21.9.0/2410.21.9.1 to 10.21.9.25410.21.9.255254
1110.21.10.0/2410.21.10.1 to 10.21.10.25410.21.10.255254
1210.21.11.0/2410.21.11.1 to 10.21.11.25410.21.11.255254
1310.21.12.0/2410.21.12.1 to 10.21.12.25410.21.12.255254
1410.21.13.0/2410.21.13.1 to 10.21.13.25410.21.13.255254
1510.21.14.0/2410.21.14.1 to 10.21.14.25410.21.14.255254
1610.21.15.0/2410.21.15.1 to 10.21.15.25410.21.15.255254
1710.21.16.0/2410.21.16.1 to 10.21.16.25410.21.16.255254
1810.21.17.0/2410.21.17.1 to 10.21.17.25410.21.17.255254
1910.21.18.0/2410.21.18.1 to 10.21.18.25410.21.18.255254
2010.21.19.0/2410.21.19.1 to 10.21.19.25410.21.19.255254
2110.21.20.0/2410.21.20.1 to 10.21.20.25410.21.20.255254
2210.21.21.0/2410.21.21.1 to 10.21.21.25410.21.21.255254
2310.21.22.0/2410.21.22.1 to 10.21.22.25410.21.22.255254
2410.21.23.0/2410.21.23.1 to 10.21.23.25410.21.23.255254
2510.21.24.0/2410.21.24.1 to 10.21.24.25410.21.24.255254
2610.21.25.0/2410.21.25.1 to 10.21.25.25410.21.25.255254
2710.21.26.0/2410.21.26.1 to 10.21.26.25410.21.26.255254
2810.21.27.0/2410.21.27.1 to 10.21.27.25410.21.27.255254
2910.21.28.0/2410.21.28.1 to 10.21.28.25410.21.28.255254
3010.21.29.0/2410.21.29.1 to 10.21.29.25410.21.29.255254
3110.21.30.0/2410.21.30.1 to 10.21.30.25410.21.30.255254
3210.21.31.0/2410.21.31.1 to 10.21.31.25410.21.31.255254
3310.21.32.0/2410.21.32.1 to 10.21.32.25410.21.32.255254
3410.21.33.0/2410.21.33.1 to 10.21.33.25410.21.33.255254
3510.21.34.0/2410.21.34.1 to 10.21.34.25410.21.34.255254
3610.21.35.0/2410.21.35.1 to 10.21.35.25410.21.35.255254
3710.21.36.0/2410.21.36.1 to 10.21.36.25410.21.36.255254
3810.21.37.0/2410.21.37.1 to 10.21.37.25410.21.37.255254
3910.21.38.0/2410.21.38.1 to 10.21.38.25410.21.38.255254
4010.21.39.0/2410.21.39.1 to 10.21.39.25410.21.39.255254
4110.21.40.0/2410.21.40.1 to 10.21.40.25410.21.40.255254
4210.21.41.0/2410.21.41.1 to 10.21.41.25410.21.41.255254
4310.21.42.0/2410.21.42.1 to 10.21.42.25410.21.42.255254
4410.21.43.0/2410.21.43.1 to 10.21.43.25410.21.43.255254
4510.21.44.0/2410.21.44.1 to 10.21.44.25410.21.44.255254
4610.21.45.0/2410.21.45.1 to 10.21.45.25410.21.45.255254
4710.21.46.0/2410.21.46.1 to 10.21.46.25410.21.46.255254
4810.21.47.0/2410.21.47.1 to 10.21.47.25410.21.47.255254
4910.21.48.0/2410.21.48.1 to 10.21.48.25410.21.48.255254
5010.21.49.0/2410.21.49.1 to 10.21.49.25410.21.49.255254
5110.21.50.0/2410.21.50.1 to 10.21.50.25410.21.50.255254
5210.21.51.0/2410.21.51.1 to 10.21.51.25410.21.51.255254
5310.21.52.0/2410.21.52.1 to 10.21.52.25410.21.52.255254
5410.21.53.0/2410.21.53.1 to 10.21.53.25410.21.53.255254
5510.21.54.0/2410.21.54.1 to 10.21.54.25410.21.54.255254
5610.21.55.0/2410.21.55.1 to 10.21.55.25410.21.55.255254
5710.21.56.0/2410.21.56.1 to 10.21.56.25410.21.56.255254
5810.21.57.0/2410.21.57.1 to 10.21.57.25410.21.57.255254
5910.21.58.0/2410.21.58.1 to 10.21.58.25410.21.58.255254
6010.21.59.0/2410.21.59.1 to 10.21.59.25410.21.59.255254
6110.21.60.0/2410.21.60.1 to 10.21.60.25410.21.60.255254
6210.21.61.0/2410.21.61.1 to 10.21.61.25410.21.61.255254
6310.21.62.0/2410.21.62.1 to 10.21.62.25410.21.62.255254
6410.21.63.0/2410.21.63.1 to 10.21.63.25410.21.63.255254
6510.21.64.0/2410.21.64.1 to 10.21.64.25410.21.64.255254
6610.21.65.0/2410.21.65.1 to 10.21.65.25410.21.65.255254
6710.21.66.0/2410.21.66.1 to 10.21.66.25410.21.66.255254
6810.21.67.0/2410.21.67.1 to 10.21.67.25410.21.67.255254
6910.21.68.0/2410.21.68.1 to 10.21.68.25410.21.68.255254
7010.21.69.0/2410.21.69.1 to 10.21.69.25410.21.69.255254
7110.21.70.0/2410.21.70.1 to 10.21.70.25410.21.70.255254
7210.21.71.0/2410.21.71.1 to 10.21.71.25410.21.71.255254
7310.21.72.0/2410.21.72.1 to 10.21.72.25410.21.72.255254
7410.21.73.0/2410.21.73.1 to 10.21.73.25410.21.73.255254
7510.21.74.0/2410.21.74.1 to 10.21.74.25410.21.74.255254
7610.21.75.0/2410.21.75.1 to 10.21.75.25410.21.75.255254
7710.21.76.0/2410.21.76.1 to 10.21.76.25410.21.76.255254
7810.21.77.0/2410.21.77.1 to 10.21.77.25410.21.77.255254
7910.21.78.0/2410.21.78.1 to 10.21.78.25410.21.78.255254
8010.21.79.0/2410.21.79.1 to 10.21.79.25410.21.79.255254
8110.21.80.0/2410.21.80.1 to 10.21.80.25410.21.80.255254
8210.21.81.0/2410.21.81.1 to 10.21.81.25410.21.81.255254
8310.21.82.0/2410.21.82.1 to 10.21.82.25410.21.82.255254
8410.21.83.0/2410.21.83.1 to 10.21.83.25410.21.83.255254
8510.21.84.0/2410.21.84.1 to 10.21.84.25410.21.84.255254
8610.21.85.0/2410.21.85.1 to 10.21.85.25410.21.85.255254
8710.21.86.0/2410.21.86.1 to 10.21.86.25410.21.86.255254
8810.21.87.0/2410.21.87.1 to 10.21.87.25410.21.87.255254
8910.21.88.0/2410.21.88.1 to 10.21.88.25410.21.88.255254
9010.21.89.0/2410.21.89.1 to 10.21.89.25410.21.89.255254
9110.21.90.0/2410.21.90.1 to 10.21.90.25410.21.90.255254
9210.21.91.0/2410.21.91.1 to 10.21.91.25410.21.91.255254
9310.21.92.0/2410.21.92.1 to 10.21.92.25410.21.92.255254
9410.21.93.0/2410.21.93.1 to 10.21.93.25410.21.93.255254
9510.21.94.0/2410.21.94.1 to 10.21.94.25410.21.94.255254
9610.21.95.0/2410.21.95.1 to 10.21.95.25410.21.95.255254
9710.21.96.0/2410.21.96.1 to 10.21.96.25410.21.96.255254
9810.21.97.0/2410.21.97.1 to 10.21.97.25410.21.97.255254
9910.21.98.0/2410.21.98.1 to 10.21.98.25410.21.98.255254
10010.21.99.0/2410.21.99.1 to 10.21.99.25410.21.99.255254
10110.21.100.0/2410.21.100.1 to 10.21.100.25410.21.100.255254
10210.21.101.0/2410.21.101.1 to 10.21.101.25410.21.101.255254
10310.21.102.0/2410.21.102.1 to 10.21.102.25410.21.102.255254
10410.21.103.0/2410.21.103.1 to 10.21.103.25410.21.103.255254
10510.21.104.0/2410.21.104.1 to 10.21.104.25410.21.104.255254
10610.21.105.0/2410.21.105.1 to 10.21.105.25410.21.105.255254
10710.21.106.0/2410.21.106.1 to 10.21.106.25410.21.106.255254
10810.21.107.0/2410.21.107.1 to 10.21.107.25410.21.107.255254
10910.21.108.0/2410.21.108.1 to 10.21.108.25410.21.108.255254
11010.21.109.0/2410.21.109.1 to 10.21.109.25410.21.109.255254
11110.21.110.0/2410.21.110.1 to 10.21.110.25410.21.110.255254
11210.21.111.0/2410.21.111.1 to 10.21.111.25410.21.111.255254
11310.21.112.0/2410.21.112.1 to 10.21.112.25410.21.112.255254
11410.21.113.0/2410.21.113.1 to 10.21.113.25410.21.113.255254
11510.21.114.0/2410.21.114.1 to 10.21.114.25410.21.114.255254
11610.21.115.0/2410.21.115.1 to 10.21.115.25410.21.115.255254
11710.21.116.0/2410.21.116.1 to 10.21.116.25410.21.116.255254
11810.21.117.0/2410.21.117.1 to 10.21.117.25410.21.117.255254
11910.21.118.0/2410.21.118.1 to 10.21.118.25410.21.118.255254
12010.21.119.0/2410.21.119.1 to 10.21.119.25410.21.119.255254
12110.21.120.0/2410.21.120.1 to 10.21.120.25410.21.120.255254
12210.21.121.0/2410.21.121.1 to 10.21.121.25410.21.121.255254
12310.21.122.0/2410.21.122.1 to 10.21.122.25410.21.122.255254
12410.21.123.0/2410.21.123.1 to 10.21.123.25410.21.123.255254
12510.21.124.0/2410.21.124.1 to 10.21.124.25410.21.124.255254
12610.21.125.0/2410.21.125.1 to 10.21.125.25410.21.125.255254
12710.21.126.0/2410.21.126.1 to 10.21.126.25410.21.126.255254
12810.21.127.0/2410.21.127.1 to 10.21.127.25410.21.127.255254
12910.21.128.0/2410.21.128.1 to 10.21.128.25410.21.128.255254
13010.21.129.0/2410.21.129.1 to 10.21.129.25410.21.129.255254
13110.21.130.0/2410.21.130.1 to 10.21.130.25410.21.130.255254
13210.21.131.0/2410.21.131.1 to 10.21.131.25410.21.131.255254
13310.21.132.0/2410.21.132.1 to 10.21.132.25410.21.132.255254
13410.21.133.0/2410.21.133.1 to 10.21.133.25410.21.133.255254
13510.21.134.0/2410.21.134.1 to 10.21.134.25410.21.134.255254
13610.21.135.0/2410.21.135.1 to 10.21.135.25410.21.135.255254
13710.21.136.0/2410.21.136.1 to 10.21.136.25410.21.136.255254
13810.21.137.0/2410.21.137.1 to 10.21.137.25410.21.137.255254
13910.21.138.0/2410.21.138.1 to 10.21.138.25410.21.138.255254
14010.21.139.0/2410.21.139.1 to 10.21.139.25410.21.139.255254
14110.21.140.0/2410.21.140.1 to 10.21.140.25410.21.140.255254
14210.21.141.0/2410.21.141.1 to 10.21.141.25410.21.141.255254
14310.21.142.0/2410.21.142.1 to 10.21.142.25410.21.142.255254
14410.21.143.0/2410.21.143.1 to 10.21.143.25410.21.143.255254
14510.21.144.0/2410.21.144.1 to 10.21.144.25410.21.144.255254
14610.21.145.0/2410.21.145.1 to 10.21.145.25410.21.145.255254
14710.21.146.0/2410.21.146.1 to 10.21.146.25410.21.146.255254
14810.21.147.0/2410.21.147.1 to 10.21.147.25410.21.147.255254
14910.21.148.0/2410.21.148.1 to 10.21.148.25410.21.148.255254
15010.21.149.0/2410.21.149.1 to 10.21.149.25410.21.149.255254
15110.21.150.0/2410.21.150.1 to 10.21.150.25410.21.150.255254
15210.21.151.0/2410.21.151.1 to 10.21.151.25410.21.151.255254
15310.21.152.0/2410.21.152.1 to 10.21.152.25410.21.152.255254
15410.21.153.0/2410.21.153.1 to 10.21.153.25410.21.153.255254
15510.21.154.0/2410.21.154.1 to 10.21.154.25410.21.154.255254
15610.21.155.0/2410.21.155.1 to 10.21.155.25410.21.155.255254
15710.21.156.0/2410.21.156.1 to 10.21.156.25410.21.156.255254
15810.21.157.0/2410.21.157.1 to 10.21.157.25410.21.157.255254
15910.21.158.0/2410.21.158.1 to 10.21.158.25410.21.158.255254
16010.21.159.0/2410.21.159.1 to 10.21.159.25410.21.159.255254
16110.21.160.0/2410.21.160.1 to 10.21.160.25410.21.160.255254
16210.21.161.0/2410.21.161.1 to 10.21.161.25410.21.161.255254
16310.21.162.0/2410.21.162.1 to 10.21.162.25410.21.162.255254
16410.21.163.0/2410.21.163.1 to 10.21.163.25410.21.163.255254
16510.21.164.0/2410.21.164.1 to 10.21.164.25410.21.164.255254
16610.21.165.0/2410.21.165.1 to 10.21.165.25410.21.165.255254
16710.21.166.0/2410.21.166.1 to 10.21.166.25410.21.166.255254
16810.21.167.0/2410.21.167.1 to 10.21.167.25410.21.167.255254
16910.21.168.0/2410.21.168.1 to 10.21.168.25410.21.168.255254
17010.21.169.0/2410.21.169.1 to 10.21.169.25410.21.169.255254
17110.21.170.0/2410.21.170.1 to 10.21.170.25410.21.170.255254
17210.21.171.0/2410.21.171.1 to 10.21.171.25410.21.171.255254
17310.21.172.0/2410.21.172.1 to 10.21.172.25410.21.172.255254
17410.21.173.0/2410.21.173.1 to 10.21.173.25410.21.173.255254
17510.21.174.0/2410.21.174.1 to 10.21.174.25410.21.174.255254
17610.21.175.0/2410.21.175.1 to 10.21.175.25410.21.175.255254
17710.21.176.0/2410.21.176.1 to 10.21.176.25410.21.176.255254
17810.21.177.0/2410.21.177.1 to 10.21.177.25410.21.177.255254
17910.21.178.0/2410.21.178.1 to 10.21.178.25410.21.178.255254
18010.21.179.0/2410.21.179.1 to 10.21.179.25410.21.179.255254
18110.21.180.0/2410.21.180.1 to 10.21.180.25410.21.180.255254
18210.21.181.0/2410.21.181.1 to 10.21.181.25410.21.181.255254
18310.21.182.0/2410.21.182.1 to 10.21.182.25410.21.182.255254
18410.21.183.0/2410.21.183.1 to 10.21.183.25410.21.183.255254
18510.21.184.0/2410.21.184.1 to 10.21.184.25410.21.184.255254
18610.21.185.0/2410.21.185.1 to 10.21.185.25410.21.185.255254
18710.21.186.0/2410.21.186.1 to 10.21.186.25410.21.186.255254
18810.21.187.0/2410.21.187.1 to 10.21.187.25410.21.187.255254
18910.21.188.0/2410.21.188.1 to 10.21.188.25410.21.188.255254
19010.21.189.0/2410.21.189.1 to 10.21.189.25410.21.189.255254
19110.21.190.0/2410.21.190.1 to 10.21.190.25410.21.190.255254
19210.21.191.0/2410.21.191.1 to 10.21.191.25410.21.191.255254
19310.21.192.0/2410.21.192.1 to 10.21.192.25410.21.192.255254
19410.21.193.0/2410.21.193.1 to 10.21.193.25410.21.193.255254
19510.21.194.0/2410.21.194.1 to 10.21.194.25410.21.194.255254
19610.21.195.0/2410.21.195.1 to 10.21.195.25410.21.195.255254
19710.21.196.0/2410.21.196.1 to 10.21.196.25410.21.196.255254
19810.21.197.0/2410.21.197.1 to 10.21.197.25410.21.197.255254
19910.21.198.0/2410.21.198.1 to 10.21.198.25410.21.198.255254
20010.21.199.0/2410.21.199.1 to 10.21.199.25410.21.199.255254
20110.21.200.0/2410.21.200.1 to 10.21.200.25410.21.200.255254
20210.21.201.0/2410.21.201.1 to 10.21.201.25410.21.201.255254
20310.21.202.0/2410.21.202.1 to 10.21.202.25410.21.202.255254
20410.21.203.0/2410.21.203.1 to 10.21.203.25410.21.203.255254
20510.21.204.0/2410.21.204.1 to 10.21.204.25410.21.204.255254
20610.21.205.0/2410.21.205.1 to 10.21.205.25410.21.205.255254
20710.21.206.0/2410.21.206.1 to 10.21.206.25410.21.206.255254
20810.21.207.0/2410.21.207.1 to 10.21.207.25410.21.207.255254
20910.21.208.0/2410.21.208.1 to 10.21.208.25410.21.208.255254
21010.21.209.0/2410.21.209.1 to 10.21.209.25410.21.209.255254
21110.21.210.0/2410.21.210.1 to 10.21.210.25410.21.210.255254
21210.21.211.0/2410.21.211.1 to 10.21.211.25410.21.211.255254
21310.21.212.0/2410.21.212.1 to 10.21.212.25410.21.212.255254
21410.21.213.0/2410.21.213.1 to 10.21.213.25410.21.213.255254
21510.21.214.0/2410.21.214.1 to 10.21.214.25410.21.214.255254
21610.21.215.0/2410.21.215.1 to 10.21.215.25410.21.215.255254
21710.21.216.0/2410.21.216.1 to 10.21.216.25410.21.216.255254
21810.21.217.0/2410.21.217.1 to 10.21.217.25410.21.217.255254
21910.21.218.0/2410.21.218.1 to 10.21.218.25410.21.218.255254
22010.21.219.0/2410.21.219.1 to 10.21.219.25410.21.219.255254
22110.21.220.0/2410.21.220.1 to 10.21.220.25410.21.220.255254
22210.21.221.0/2410.21.221.1 to 10.21.221.25410.21.221.255254
22310.21.222.0/2410.21.222.1 to 10.21.222.25410.21.222.255254
22410.21.223.0/2410.21.223.1 to 10.21.223.25410.21.223.255254
22510.21.224.0/2410.21.224.1 to 10.21.224.25410.21.224.255254
22610.21.225.0/2410.21.225.1 to 10.21.225.25410.21.225.255254
22710.21.226.0/2410.21.226.1 to 10.21.226.25410.21.226.255254
22810.21.227.0/2410.21.227.1 to 10.21.227.25410.21.227.255254
22910.21.228.0/2410.21.228.1 to 10.21.228.25410.21.228.255254
23010.21.229.0/2410.21.229.1 to 10.21.229.25410.21.229.255254
23110.21.230.0/2410.21.230.1 to 10.21.230.25410.21.230.255254
23210.21.231.0/2410.21.231.1 to 10.21.231.25410.21.231.255254
23310.21.232.0/2410.21.232.1 to 10.21.232.25410.21.232.255254
23410.21.233.0/2410.21.233.1 to 10.21.233.25410.21.233.255254
23510.21.234.0/2410.21.234.1 to 10.21.234.25410.21.234.255254
23610.21.235.0/2410.21.235.1 to 10.21.235.25410.21.235.255254
23710.21.236.0/2410.21.236.1 to 10.21.236.25410.21.236.255254
23810.21.237.0/2410.21.237.1 to 10.21.237.25410.21.237.255254
23910.21.238.0/2410.21.238.1 to 10.21.238.25410.21.238.255254
24010.21.239.0/2410.21.239.1 to 10.21.239.25410.21.239.255254
24110.21.240.0/2410.21.240.1 to 10.21.240.25410.21.240.255254
24210.21.241.0/2410.21.241.1 to 10.21.241.25410.21.241.255254
24310.21.242.0/2410.21.242.1 to 10.21.242.25410.21.242.255254
24410.21.243.0/2410.21.243.1 to 10.21.243.25410.21.243.255254
24510.21.244.0/2410.21.244.1 to 10.21.244.25410.21.244.255254
24610.21.245.0/2410.21.245.1 to 10.21.245.25410.21.245.255254
24710.21.246.0/2410.21.246.1 to 10.21.246.25410.21.246.255254
24810.21.247.0/2410.21.247.1 to 10.21.247.25410.21.247.255254
24910.21.248.0/2410.21.248.1 to 10.21.248.25410.21.248.255254
25010.21.249.0/2410.21.249.1 to 10.21.249.25410.21.249.255254
25110.21.250.0/2410.21.250.1 to 10.21.250.25410.21.250.255254
25210.21.251.0/2410.21.251.1 to 10.21.251.25410.21.251.255254
25310.21.252.0/2410.21.252.1 to 10.21.252.25410.21.252.255254
25410.21.253.0/2410.21.253.1 to 10.21.253.25410.21.253.255254
25510.21.254.0/2410.21.254.1 to 10.21.254.25410.21.254.255254
25610.21.255.0/2410.21.255.1 to 10.21.255.25410.21.255.255254

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.