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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.

Network25.3.0.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
25.3.0.0
Broadcast address
25.3.15.255
First usable
25.3.0.1
Last usable
25.3.15.254
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 19030000 · Integer 419627008 to 419631103
Reverse DNS zones
0.3.25.in-addr.arpa
1.3.25.in-addr.arpa
2.3.25.in-addr.arpa
3.3.25.in-addr.arpa
4.3.25.in-addr.arpa
5.3.25.in-addr.arpa
6.3.25.in-addr.arpa
7.3.25.in-addr.arpa
8.3.25.in-addr.arpa
9.3.25.in-addr.arpa
10.3.25.in-addr.arpa
11.3.25.in-addr.arpa
12.3.25.in-addr.arpa
13.3.25.in-addr.arpa
14.3.25.in-addr.arpa
15.3.25.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
Address00011001.00000011.00000000.0000000025.3.0.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network00011001.00000011.00000000.0000000025.3.0.0
Broadcast00011001.00000011.00001111.1111111125.3.15.255
Split into smaller subnets/29
/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)

25.3.0.0/20 makes 512 subnets of /29; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
125.3.0.0/2925.3.0.1 to 25.3.0.625.3.0.76
225.3.0.8/2925.3.0.9 to 25.3.0.1425.3.0.156
325.3.0.16/2925.3.0.17 to 25.3.0.2225.3.0.236
425.3.0.24/2925.3.0.25 to 25.3.0.3025.3.0.316
525.3.0.32/2925.3.0.33 to 25.3.0.3825.3.0.396
625.3.0.40/2925.3.0.41 to 25.3.0.4625.3.0.476
725.3.0.48/2925.3.0.49 to 25.3.0.5425.3.0.556
825.3.0.56/2925.3.0.57 to 25.3.0.6225.3.0.636
925.3.0.64/2925.3.0.65 to 25.3.0.7025.3.0.716
1025.3.0.72/2925.3.0.73 to 25.3.0.7825.3.0.796
1125.3.0.80/2925.3.0.81 to 25.3.0.8625.3.0.876
1225.3.0.88/2925.3.0.89 to 25.3.0.9425.3.0.956
1325.3.0.96/2925.3.0.97 to 25.3.0.10225.3.0.1036
1425.3.0.104/2925.3.0.105 to 25.3.0.11025.3.0.1116
1525.3.0.112/2925.3.0.113 to 25.3.0.11825.3.0.1196
1625.3.0.120/2925.3.0.121 to 25.3.0.12625.3.0.1276
1725.3.0.128/2925.3.0.129 to 25.3.0.13425.3.0.1356
1825.3.0.136/2925.3.0.137 to 25.3.0.14225.3.0.1436
1925.3.0.144/2925.3.0.145 to 25.3.0.15025.3.0.1516
2025.3.0.152/2925.3.0.153 to 25.3.0.15825.3.0.1596
2125.3.0.160/2925.3.0.161 to 25.3.0.16625.3.0.1676
2225.3.0.168/2925.3.0.169 to 25.3.0.17425.3.0.1756
2325.3.0.176/2925.3.0.177 to 25.3.0.18225.3.0.1836
2425.3.0.184/2925.3.0.185 to 25.3.0.19025.3.0.1916
2525.3.0.192/2925.3.0.193 to 25.3.0.19825.3.0.1996
2625.3.0.200/2925.3.0.201 to 25.3.0.20625.3.0.2076
2725.3.0.208/2925.3.0.209 to 25.3.0.21425.3.0.2156
2825.3.0.216/2925.3.0.217 to 25.3.0.22225.3.0.2236
2925.3.0.224/2925.3.0.225 to 25.3.0.23025.3.0.2316
3025.3.0.232/2925.3.0.233 to 25.3.0.23825.3.0.2396
3125.3.0.240/2925.3.0.241 to 25.3.0.24625.3.0.2476
3225.3.0.248/2925.3.0.249 to 25.3.0.25425.3.0.2556
3325.3.1.0/2925.3.1.1 to 25.3.1.625.3.1.76
3425.3.1.8/2925.3.1.9 to 25.3.1.1425.3.1.156
3525.3.1.16/2925.3.1.17 to 25.3.1.2225.3.1.236
3625.3.1.24/2925.3.1.25 to 25.3.1.3025.3.1.316
3725.3.1.32/2925.3.1.33 to 25.3.1.3825.3.1.396
3825.3.1.40/2925.3.1.41 to 25.3.1.4625.3.1.476
3925.3.1.48/2925.3.1.49 to 25.3.1.5425.3.1.556
4025.3.1.56/2925.3.1.57 to 25.3.1.6225.3.1.636
4125.3.1.64/2925.3.1.65 to 25.3.1.7025.3.1.716
4225.3.1.72/2925.3.1.73 to 25.3.1.7825.3.1.796
4325.3.1.80/2925.3.1.81 to 25.3.1.8625.3.1.876
4425.3.1.88/2925.3.1.89 to 25.3.1.9425.3.1.956
4525.3.1.96/2925.3.1.97 to 25.3.1.10225.3.1.1036
4625.3.1.104/2925.3.1.105 to 25.3.1.11025.3.1.1116
4725.3.1.112/2925.3.1.113 to 25.3.1.11825.3.1.1196
4825.3.1.120/2925.3.1.121 to 25.3.1.12625.3.1.1276
4925.3.1.128/2925.3.1.129 to 25.3.1.13425.3.1.1356
5025.3.1.136/2925.3.1.137 to 25.3.1.14225.3.1.1436
5125.3.1.144/2925.3.1.145 to 25.3.1.15025.3.1.1516
5225.3.1.152/2925.3.1.153 to 25.3.1.15825.3.1.1596
5325.3.1.160/2925.3.1.161 to 25.3.1.16625.3.1.1676
5425.3.1.168/2925.3.1.169 to 25.3.1.17425.3.1.1756
5525.3.1.176/2925.3.1.177 to 25.3.1.18225.3.1.1836
5625.3.1.184/2925.3.1.185 to 25.3.1.19025.3.1.1916
5725.3.1.192/2925.3.1.193 to 25.3.1.19825.3.1.1996
5825.3.1.200/2925.3.1.201 to 25.3.1.20625.3.1.2076
5925.3.1.208/2925.3.1.209 to 25.3.1.21425.3.1.2156
6025.3.1.216/2925.3.1.217 to 25.3.1.22225.3.1.2236
6125.3.1.224/2925.3.1.225 to 25.3.1.23025.3.1.2316
6225.3.1.232/2925.3.1.233 to 25.3.1.23825.3.1.2396
6325.3.1.240/2925.3.1.241 to 25.3.1.24625.3.1.2476
6425.3.1.248/2925.3.1.249 to 25.3.1.25425.3.1.2556
6525.3.2.0/2925.3.2.1 to 25.3.2.625.3.2.76
6625.3.2.8/2925.3.2.9 to 25.3.2.1425.3.2.156
6725.3.2.16/2925.3.2.17 to 25.3.2.2225.3.2.236
6825.3.2.24/2925.3.2.25 to 25.3.2.3025.3.2.316
6925.3.2.32/2925.3.2.33 to 25.3.2.3825.3.2.396
7025.3.2.40/2925.3.2.41 to 25.3.2.4625.3.2.476
7125.3.2.48/2925.3.2.49 to 25.3.2.5425.3.2.556
7225.3.2.56/2925.3.2.57 to 25.3.2.6225.3.2.636
7325.3.2.64/2925.3.2.65 to 25.3.2.7025.3.2.716
7425.3.2.72/2925.3.2.73 to 25.3.2.7825.3.2.796
7525.3.2.80/2925.3.2.81 to 25.3.2.8625.3.2.876
7625.3.2.88/2925.3.2.89 to 25.3.2.9425.3.2.956
7725.3.2.96/2925.3.2.97 to 25.3.2.10225.3.2.1036
7825.3.2.104/2925.3.2.105 to 25.3.2.11025.3.2.1116
7925.3.2.112/2925.3.2.113 to 25.3.2.11825.3.2.1196
8025.3.2.120/2925.3.2.121 to 25.3.2.12625.3.2.1276
8125.3.2.128/2925.3.2.129 to 25.3.2.13425.3.2.1356
8225.3.2.136/2925.3.2.137 to 25.3.2.14225.3.2.1436
8325.3.2.144/2925.3.2.145 to 25.3.2.15025.3.2.1516
8425.3.2.152/2925.3.2.153 to 25.3.2.15825.3.2.1596
8525.3.2.160/2925.3.2.161 to 25.3.2.16625.3.2.1676
8625.3.2.168/2925.3.2.169 to 25.3.2.17425.3.2.1756
8725.3.2.176/2925.3.2.177 to 25.3.2.18225.3.2.1836
8825.3.2.184/2925.3.2.185 to 25.3.2.19025.3.2.1916
8925.3.2.192/2925.3.2.193 to 25.3.2.19825.3.2.1996
9025.3.2.200/2925.3.2.201 to 25.3.2.20625.3.2.2076
9125.3.2.208/2925.3.2.209 to 25.3.2.21425.3.2.2156
9225.3.2.216/2925.3.2.217 to 25.3.2.22225.3.2.2236
9325.3.2.224/2925.3.2.225 to 25.3.2.23025.3.2.2316
9425.3.2.232/2925.3.2.233 to 25.3.2.23825.3.2.2396
9525.3.2.240/2925.3.2.241 to 25.3.2.24625.3.2.2476
9625.3.2.248/2925.3.2.249 to 25.3.2.25425.3.2.2556
9725.3.3.0/2925.3.3.1 to 25.3.3.625.3.3.76
9825.3.3.8/2925.3.3.9 to 25.3.3.1425.3.3.156
9925.3.3.16/2925.3.3.17 to 25.3.3.2225.3.3.236
10025.3.3.24/2925.3.3.25 to 25.3.3.3025.3.3.316
10125.3.3.32/2925.3.3.33 to 25.3.3.3825.3.3.396
10225.3.3.40/2925.3.3.41 to 25.3.3.4625.3.3.476
10325.3.3.48/2925.3.3.49 to 25.3.3.5425.3.3.556
10425.3.3.56/2925.3.3.57 to 25.3.3.6225.3.3.636
10525.3.3.64/2925.3.3.65 to 25.3.3.7025.3.3.716
10625.3.3.72/2925.3.3.73 to 25.3.3.7825.3.3.796
10725.3.3.80/2925.3.3.81 to 25.3.3.8625.3.3.876
10825.3.3.88/2925.3.3.89 to 25.3.3.9425.3.3.956
10925.3.3.96/2925.3.3.97 to 25.3.3.10225.3.3.1036
11025.3.3.104/2925.3.3.105 to 25.3.3.11025.3.3.1116
11125.3.3.112/2925.3.3.113 to 25.3.3.11825.3.3.1196
11225.3.3.120/2925.3.3.121 to 25.3.3.12625.3.3.1276
11325.3.3.128/2925.3.3.129 to 25.3.3.13425.3.3.1356
11425.3.3.136/2925.3.3.137 to 25.3.3.14225.3.3.1436
11525.3.3.144/2925.3.3.145 to 25.3.3.15025.3.3.1516
11625.3.3.152/2925.3.3.153 to 25.3.3.15825.3.3.1596
11725.3.3.160/2925.3.3.161 to 25.3.3.16625.3.3.1676
11825.3.3.168/2925.3.3.169 to 25.3.3.17425.3.3.1756
11925.3.3.176/2925.3.3.177 to 25.3.3.18225.3.3.1836
12025.3.3.184/2925.3.3.185 to 25.3.3.19025.3.3.1916
12125.3.3.192/2925.3.3.193 to 25.3.3.19825.3.3.1996
12225.3.3.200/2925.3.3.201 to 25.3.3.20625.3.3.2076
12325.3.3.208/2925.3.3.209 to 25.3.3.21425.3.3.2156
12425.3.3.216/2925.3.3.217 to 25.3.3.22225.3.3.2236
12525.3.3.224/2925.3.3.225 to 25.3.3.23025.3.3.2316
12625.3.3.232/2925.3.3.233 to 25.3.3.23825.3.3.2396
12725.3.3.240/2925.3.3.241 to 25.3.3.24625.3.3.2476
12825.3.3.248/2925.3.3.249 to 25.3.3.25425.3.3.2556
12925.3.4.0/2925.3.4.1 to 25.3.4.625.3.4.76
13025.3.4.8/2925.3.4.9 to 25.3.4.1425.3.4.156
13125.3.4.16/2925.3.4.17 to 25.3.4.2225.3.4.236
13225.3.4.24/2925.3.4.25 to 25.3.4.3025.3.4.316
13325.3.4.32/2925.3.4.33 to 25.3.4.3825.3.4.396
13425.3.4.40/2925.3.4.41 to 25.3.4.4625.3.4.476
13525.3.4.48/2925.3.4.49 to 25.3.4.5425.3.4.556
13625.3.4.56/2925.3.4.57 to 25.3.4.6225.3.4.636
13725.3.4.64/2925.3.4.65 to 25.3.4.7025.3.4.716
13825.3.4.72/2925.3.4.73 to 25.3.4.7825.3.4.796
13925.3.4.80/2925.3.4.81 to 25.3.4.8625.3.4.876
14025.3.4.88/2925.3.4.89 to 25.3.4.9425.3.4.956
14125.3.4.96/2925.3.4.97 to 25.3.4.10225.3.4.1036
14225.3.4.104/2925.3.4.105 to 25.3.4.11025.3.4.1116
14325.3.4.112/2925.3.4.113 to 25.3.4.11825.3.4.1196
14425.3.4.120/2925.3.4.121 to 25.3.4.12625.3.4.1276
14525.3.4.128/2925.3.4.129 to 25.3.4.13425.3.4.1356
14625.3.4.136/2925.3.4.137 to 25.3.4.14225.3.4.1436
14725.3.4.144/2925.3.4.145 to 25.3.4.15025.3.4.1516
14825.3.4.152/2925.3.4.153 to 25.3.4.15825.3.4.1596
14925.3.4.160/2925.3.4.161 to 25.3.4.16625.3.4.1676
15025.3.4.168/2925.3.4.169 to 25.3.4.17425.3.4.1756
15125.3.4.176/2925.3.4.177 to 25.3.4.18225.3.4.1836
15225.3.4.184/2925.3.4.185 to 25.3.4.19025.3.4.1916
15325.3.4.192/2925.3.4.193 to 25.3.4.19825.3.4.1996
15425.3.4.200/2925.3.4.201 to 25.3.4.20625.3.4.2076
15525.3.4.208/2925.3.4.209 to 25.3.4.21425.3.4.2156
15625.3.4.216/2925.3.4.217 to 25.3.4.22225.3.4.2236
15725.3.4.224/2925.3.4.225 to 25.3.4.23025.3.4.2316
15825.3.4.232/2925.3.4.233 to 25.3.4.23825.3.4.2396
15925.3.4.240/2925.3.4.241 to 25.3.4.24625.3.4.2476
16025.3.4.248/2925.3.4.249 to 25.3.4.25425.3.4.2556
16125.3.5.0/2925.3.5.1 to 25.3.5.625.3.5.76
16225.3.5.8/2925.3.5.9 to 25.3.5.1425.3.5.156
16325.3.5.16/2925.3.5.17 to 25.3.5.2225.3.5.236
16425.3.5.24/2925.3.5.25 to 25.3.5.3025.3.5.316
16525.3.5.32/2925.3.5.33 to 25.3.5.3825.3.5.396
16625.3.5.40/2925.3.5.41 to 25.3.5.4625.3.5.476
16725.3.5.48/2925.3.5.49 to 25.3.5.5425.3.5.556
16825.3.5.56/2925.3.5.57 to 25.3.5.6225.3.5.636
16925.3.5.64/2925.3.5.65 to 25.3.5.7025.3.5.716
17025.3.5.72/2925.3.5.73 to 25.3.5.7825.3.5.796
17125.3.5.80/2925.3.5.81 to 25.3.5.8625.3.5.876
17225.3.5.88/2925.3.5.89 to 25.3.5.9425.3.5.956
17325.3.5.96/2925.3.5.97 to 25.3.5.10225.3.5.1036
17425.3.5.104/2925.3.5.105 to 25.3.5.11025.3.5.1116
17525.3.5.112/2925.3.5.113 to 25.3.5.11825.3.5.1196
17625.3.5.120/2925.3.5.121 to 25.3.5.12625.3.5.1276
17725.3.5.128/2925.3.5.129 to 25.3.5.13425.3.5.1356
17825.3.5.136/2925.3.5.137 to 25.3.5.14225.3.5.1436
17925.3.5.144/2925.3.5.145 to 25.3.5.15025.3.5.1516
18025.3.5.152/2925.3.5.153 to 25.3.5.15825.3.5.1596
18125.3.5.160/2925.3.5.161 to 25.3.5.16625.3.5.1676
18225.3.5.168/2925.3.5.169 to 25.3.5.17425.3.5.1756
18325.3.5.176/2925.3.5.177 to 25.3.5.18225.3.5.1836
18425.3.5.184/2925.3.5.185 to 25.3.5.19025.3.5.1916
18525.3.5.192/2925.3.5.193 to 25.3.5.19825.3.5.1996
18625.3.5.200/2925.3.5.201 to 25.3.5.20625.3.5.2076
18725.3.5.208/2925.3.5.209 to 25.3.5.21425.3.5.2156
18825.3.5.216/2925.3.5.217 to 25.3.5.22225.3.5.2236
18925.3.5.224/2925.3.5.225 to 25.3.5.23025.3.5.2316
19025.3.5.232/2925.3.5.233 to 25.3.5.23825.3.5.2396
19125.3.5.240/2925.3.5.241 to 25.3.5.24625.3.5.2476
19225.3.5.248/2925.3.5.249 to 25.3.5.25425.3.5.2556
19325.3.6.0/2925.3.6.1 to 25.3.6.625.3.6.76
19425.3.6.8/2925.3.6.9 to 25.3.6.1425.3.6.156
19525.3.6.16/2925.3.6.17 to 25.3.6.2225.3.6.236
19625.3.6.24/2925.3.6.25 to 25.3.6.3025.3.6.316
19725.3.6.32/2925.3.6.33 to 25.3.6.3825.3.6.396
19825.3.6.40/2925.3.6.41 to 25.3.6.4625.3.6.476
19925.3.6.48/2925.3.6.49 to 25.3.6.5425.3.6.556
20025.3.6.56/2925.3.6.57 to 25.3.6.6225.3.6.636
20125.3.6.64/2925.3.6.65 to 25.3.6.7025.3.6.716
20225.3.6.72/2925.3.6.73 to 25.3.6.7825.3.6.796
20325.3.6.80/2925.3.6.81 to 25.3.6.8625.3.6.876
20425.3.6.88/2925.3.6.89 to 25.3.6.9425.3.6.956
20525.3.6.96/2925.3.6.97 to 25.3.6.10225.3.6.1036
20625.3.6.104/2925.3.6.105 to 25.3.6.11025.3.6.1116
20725.3.6.112/2925.3.6.113 to 25.3.6.11825.3.6.1196
20825.3.6.120/2925.3.6.121 to 25.3.6.12625.3.6.1276
20925.3.6.128/2925.3.6.129 to 25.3.6.13425.3.6.1356
21025.3.6.136/2925.3.6.137 to 25.3.6.14225.3.6.1436
21125.3.6.144/2925.3.6.145 to 25.3.6.15025.3.6.1516
21225.3.6.152/2925.3.6.153 to 25.3.6.15825.3.6.1596
21325.3.6.160/2925.3.6.161 to 25.3.6.16625.3.6.1676
21425.3.6.168/2925.3.6.169 to 25.3.6.17425.3.6.1756
21525.3.6.176/2925.3.6.177 to 25.3.6.18225.3.6.1836
21625.3.6.184/2925.3.6.185 to 25.3.6.19025.3.6.1916
21725.3.6.192/2925.3.6.193 to 25.3.6.19825.3.6.1996
21825.3.6.200/2925.3.6.201 to 25.3.6.20625.3.6.2076
21925.3.6.208/2925.3.6.209 to 25.3.6.21425.3.6.2156
22025.3.6.216/2925.3.6.217 to 25.3.6.22225.3.6.2236
22125.3.6.224/2925.3.6.225 to 25.3.6.23025.3.6.2316
22225.3.6.232/2925.3.6.233 to 25.3.6.23825.3.6.2396
22325.3.6.240/2925.3.6.241 to 25.3.6.24625.3.6.2476
22425.3.6.248/2925.3.6.249 to 25.3.6.25425.3.6.2556
22525.3.7.0/2925.3.7.1 to 25.3.7.625.3.7.76
22625.3.7.8/2925.3.7.9 to 25.3.7.1425.3.7.156
22725.3.7.16/2925.3.7.17 to 25.3.7.2225.3.7.236
22825.3.7.24/2925.3.7.25 to 25.3.7.3025.3.7.316
22925.3.7.32/2925.3.7.33 to 25.3.7.3825.3.7.396
23025.3.7.40/2925.3.7.41 to 25.3.7.4625.3.7.476
23125.3.7.48/2925.3.7.49 to 25.3.7.5425.3.7.556
23225.3.7.56/2925.3.7.57 to 25.3.7.6225.3.7.636
23325.3.7.64/2925.3.7.65 to 25.3.7.7025.3.7.716
23425.3.7.72/2925.3.7.73 to 25.3.7.7825.3.7.796
23525.3.7.80/2925.3.7.81 to 25.3.7.8625.3.7.876
23625.3.7.88/2925.3.7.89 to 25.3.7.9425.3.7.956
23725.3.7.96/2925.3.7.97 to 25.3.7.10225.3.7.1036
23825.3.7.104/2925.3.7.105 to 25.3.7.11025.3.7.1116
23925.3.7.112/2925.3.7.113 to 25.3.7.11825.3.7.1196
24025.3.7.120/2925.3.7.121 to 25.3.7.12625.3.7.1276
24125.3.7.128/2925.3.7.129 to 25.3.7.13425.3.7.1356
24225.3.7.136/2925.3.7.137 to 25.3.7.14225.3.7.1436
24325.3.7.144/2925.3.7.145 to 25.3.7.15025.3.7.1516
24425.3.7.152/2925.3.7.153 to 25.3.7.15825.3.7.1596
24525.3.7.160/2925.3.7.161 to 25.3.7.16625.3.7.1676
24625.3.7.168/2925.3.7.169 to 25.3.7.17425.3.7.1756
24725.3.7.176/2925.3.7.177 to 25.3.7.18225.3.7.1836
24825.3.7.184/2925.3.7.185 to 25.3.7.19025.3.7.1916
24925.3.7.192/2925.3.7.193 to 25.3.7.19825.3.7.1996
25025.3.7.200/2925.3.7.201 to 25.3.7.20625.3.7.2076
25125.3.7.208/2925.3.7.209 to 25.3.7.21425.3.7.2156
25225.3.7.216/2925.3.7.217 to 25.3.7.22225.3.7.2236
25325.3.7.224/2925.3.7.225 to 25.3.7.23025.3.7.2316
25425.3.7.232/2925.3.7.233 to 25.3.7.23825.3.7.2396
25525.3.7.240/2925.3.7.241 to 25.3.7.24625.3.7.2476
25625.3.7.248/2925.3.7.249 to 25.3.7.25425.3.7.2556

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.