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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.

Network201.12.0.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
201.12.0.0
Broadcast address
201.12.15.255
First usable
201.12.0.1
Last usable
201.12.15.254
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
C (default /24)
As numbers
Hex C90C0000 · Integer 3373006848 to 3373010943
Reverse DNS zones
0.12.201.in-addr.arpa
1.12.201.in-addr.arpa
2.12.201.in-addr.arpa
3.12.201.in-addr.arpa
4.12.201.in-addr.arpa
5.12.201.in-addr.arpa
6.12.201.in-addr.arpa
7.12.201.in-addr.arpa
8.12.201.in-addr.arpa
9.12.201.in-addr.arpa
10.12.201.in-addr.arpa
11.12.201.in-addr.arpa
12.12.201.in-addr.arpa
13.12.201.in-addr.arpa
14.12.201.in-addr.arpa
15.12.201.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
Address11001001.00001100.00000000.00000000201.12.0.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network11001001.00001100.00000000.00000000201.12.0.0
Broadcast11001001.00001100.00001111.11111111201.12.15.255
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)

201.12.0.0/20 makes 512 subnets of /29; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1201.12.0.0/29201.12.0.1 to 201.12.0.6201.12.0.76
2201.12.0.8/29201.12.0.9 to 201.12.0.14201.12.0.156
3201.12.0.16/29201.12.0.17 to 201.12.0.22201.12.0.236
4201.12.0.24/29201.12.0.25 to 201.12.0.30201.12.0.316
5201.12.0.32/29201.12.0.33 to 201.12.0.38201.12.0.396
6201.12.0.40/29201.12.0.41 to 201.12.0.46201.12.0.476
7201.12.0.48/29201.12.0.49 to 201.12.0.54201.12.0.556
8201.12.0.56/29201.12.0.57 to 201.12.0.62201.12.0.636
9201.12.0.64/29201.12.0.65 to 201.12.0.70201.12.0.716
10201.12.0.72/29201.12.0.73 to 201.12.0.78201.12.0.796
11201.12.0.80/29201.12.0.81 to 201.12.0.86201.12.0.876
12201.12.0.88/29201.12.0.89 to 201.12.0.94201.12.0.956
13201.12.0.96/29201.12.0.97 to 201.12.0.102201.12.0.1036
14201.12.0.104/29201.12.0.105 to 201.12.0.110201.12.0.1116
15201.12.0.112/29201.12.0.113 to 201.12.0.118201.12.0.1196
16201.12.0.120/29201.12.0.121 to 201.12.0.126201.12.0.1276
17201.12.0.128/29201.12.0.129 to 201.12.0.134201.12.0.1356
18201.12.0.136/29201.12.0.137 to 201.12.0.142201.12.0.1436
19201.12.0.144/29201.12.0.145 to 201.12.0.150201.12.0.1516
20201.12.0.152/29201.12.0.153 to 201.12.0.158201.12.0.1596
21201.12.0.160/29201.12.0.161 to 201.12.0.166201.12.0.1676
22201.12.0.168/29201.12.0.169 to 201.12.0.174201.12.0.1756
23201.12.0.176/29201.12.0.177 to 201.12.0.182201.12.0.1836
24201.12.0.184/29201.12.0.185 to 201.12.0.190201.12.0.1916
25201.12.0.192/29201.12.0.193 to 201.12.0.198201.12.0.1996
26201.12.0.200/29201.12.0.201 to 201.12.0.206201.12.0.2076
27201.12.0.208/29201.12.0.209 to 201.12.0.214201.12.0.2156
28201.12.0.216/29201.12.0.217 to 201.12.0.222201.12.0.2236
29201.12.0.224/29201.12.0.225 to 201.12.0.230201.12.0.2316
30201.12.0.232/29201.12.0.233 to 201.12.0.238201.12.0.2396
31201.12.0.240/29201.12.0.241 to 201.12.0.246201.12.0.2476
32201.12.0.248/29201.12.0.249 to 201.12.0.254201.12.0.2556
33201.12.1.0/29201.12.1.1 to 201.12.1.6201.12.1.76
34201.12.1.8/29201.12.1.9 to 201.12.1.14201.12.1.156
35201.12.1.16/29201.12.1.17 to 201.12.1.22201.12.1.236
36201.12.1.24/29201.12.1.25 to 201.12.1.30201.12.1.316
37201.12.1.32/29201.12.1.33 to 201.12.1.38201.12.1.396
38201.12.1.40/29201.12.1.41 to 201.12.1.46201.12.1.476
39201.12.1.48/29201.12.1.49 to 201.12.1.54201.12.1.556
40201.12.1.56/29201.12.1.57 to 201.12.1.62201.12.1.636
41201.12.1.64/29201.12.1.65 to 201.12.1.70201.12.1.716
42201.12.1.72/29201.12.1.73 to 201.12.1.78201.12.1.796
43201.12.1.80/29201.12.1.81 to 201.12.1.86201.12.1.876
44201.12.1.88/29201.12.1.89 to 201.12.1.94201.12.1.956
45201.12.1.96/29201.12.1.97 to 201.12.1.102201.12.1.1036
46201.12.1.104/29201.12.1.105 to 201.12.1.110201.12.1.1116
47201.12.1.112/29201.12.1.113 to 201.12.1.118201.12.1.1196
48201.12.1.120/29201.12.1.121 to 201.12.1.126201.12.1.1276
49201.12.1.128/29201.12.1.129 to 201.12.1.134201.12.1.1356
50201.12.1.136/29201.12.1.137 to 201.12.1.142201.12.1.1436
51201.12.1.144/29201.12.1.145 to 201.12.1.150201.12.1.1516
52201.12.1.152/29201.12.1.153 to 201.12.1.158201.12.1.1596
53201.12.1.160/29201.12.1.161 to 201.12.1.166201.12.1.1676
54201.12.1.168/29201.12.1.169 to 201.12.1.174201.12.1.1756
55201.12.1.176/29201.12.1.177 to 201.12.1.182201.12.1.1836
56201.12.1.184/29201.12.1.185 to 201.12.1.190201.12.1.1916
57201.12.1.192/29201.12.1.193 to 201.12.1.198201.12.1.1996
58201.12.1.200/29201.12.1.201 to 201.12.1.206201.12.1.2076
59201.12.1.208/29201.12.1.209 to 201.12.1.214201.12.1.2156
60201.12.1.216/29201.12.1.217 to 201.12.1.222201.12.1.2236
61201.12.1.224/29201.12.1.225 to 201.12.1.230201.12.1.2316
62201.12.1.232/29201.12.1.233 to 201.12.1.238201.12.1.2396
63201.12.1.240/29201.12.1.241 to 201.12.1.246201.12.1.2476
64201.12.1.248/29201.12.1.249 to 201.12.1.254201.12.1.2556
65201.12.2.0/29201.12.2.1 to 201.12.2.6201.12.2.76
66201.12.2.8/29201.12.2.9 to 201.12.2.14201.12.2.156
67201.12.2.16/29201.12.2.17 to 201.12.2.22201.12.2.236
68201.12.2.24/29201.12.2.25 to 201.12.2.30201.12.2.316
69201.12.2.32/29201.12.2.33 to 201.12.2.38201.12.2.396
70201.12.2.40/29201.12.2.41 to 201.12.2.46201.12.2.476
71201.12.2.48/29201.12.2.49 to 201.12.2.54201.12.2.556
72201.12.2.56/29201.12.2.57 to 201.12.2.62201.12.2.636
73201.12.2.64/29201.12.2.65 to 201.12.2.70201.12.2.716
74201.12.2.72/29201.12.2.73 to 201.12.2.78201.12.2.796
75201.12.2.80/29201.12.2.81 to 201.12.2.86201.12.2.876
76201.12.2.88/29201.12.2.89 to 201.12.2.94201.12.2.956
77201.12.2.96/29201.12.2.97 to 201.12.2.102201.12.2.1036
78201.12.2.104/29201.12.2.105 to 201.12.2.110201.12.2.1116
79201.12.2.112/29201.12.2.113 to 201.12.2.118201.12.2.1196
80201.12.2.120/29201.12.2.121 to 201.12.2.126201.12.2.1276
81201.12.2.128/29201.12.2.129 to 201.12.2.134201.12.2.1356
82201.12.2.136/29201.12.2.137 to 201.12.2.142201.12.2.1436
83201.12.2.144/29201.12.2.145 to 201.12.2.150201.12.2.1516
84201.12.2.152/29201.12.2.153 to 201.12.2.158201.12.2.1596
85201.12.2.160/29201.12.2.161 to 201.12.2.166201.12.2.1676
86201.12.2.168/29201.12.2.169 to 201.12.2.174201.12.2.1756
87201.12.2.176/29201.12.2.177 to 201.12.2.182201.12.2.1836
88201.12.2.184/29201.12.2.185 to 201.12.2.190201.12.2.1916
89201.12.2.192/29201.12.2.193 to 201.12.2.198201.12.2.1996
90201.12.2.200/29201.12.2.201 to 201.12.2.206201.12.2.2076
91201.12.2.208/29201.12.2.209 to 201.12.2.214201.12.2.2156
92201.12.2.216/29201.12.2.217 to 201.12.2.222201.12.2.2236
93201.12.2.224/29201.12.2.225 to 201.12.2.230201.12.2.2316
94201.12.2.232/29201.12.2.233 to 201.12.2.238201.12.2.2396
95201.12.2.240/29201.12.2.241 to 201.12.2.246201.12.2.2476
96201.12.2.248/29201.12.2.249 to 201.12.2.254201.12.2.2556
97201.12.3.0/29201.12.3.1 to 201.12.3.6201.12.3.76
98201.12.3.8/29201.12.3.9 to 201.12.3.14201.12.3.156
99201.12.3.16/29201.12.3.17 to 201.12.3.22201.12.3.236
100201.12.3.24/29201.12.3.25 to 201.12.3.30201.12.3.316
101201.12.3.32/29201.12.3.33 to 201.12.3.38201.12.3.396
102201.12.3.40/29201.12.3.41 to 201.12.3.46201.12.3.476
103201.12.3.48/29201.12.3.49 to 201.12.3.54201.12.3.556
104201.12.3.56/29201.12.3.57 to 201.12.3.62201.12.3.636
105201.12.3.64/29201.12.3.65 to 201.12.3.70201.12.3.716
106201.12.3.72/29201.12.3.73 to 201.12.3.78201.12.3.796
107201.12.3.80/29201.12.3.81 to 201.12.3.86201.12.3.876
108201.12.3.88/29201.12.3.89 to 201.12.3.94201.12.3.956
109201.12.3.96/29201.12.3.97 to 201.12.3.102201.12.3.1036
110201.12.3.104/29201.12.3.105 to 201.12.3.110201.12.3.1116
111201.12.3.112/29201.12.3.113 to 201.12.3.118201.12.3.1196
112201.12.3.120/29201.12.3.121 to 201.12.3.126201.12.3.1276
113201.12.3.128/29201.12.3.129 to 201.12.3.134201.12.3.1356
114201.12.3.136/29201.12.3.137 to 201.12.3.142201.12.3.1436
115201.12.3.144/29201.12.3.145 to 201.12.3.150201.12.3.1516
116201.12.3.152/29201.12.3.153 to 201.12.3.158201.12.3.1596
117201.12.3.160/29201.12.3.161 to 201.12.3.166201.12.3.1676
118201.12.3.168/29201.12.3.169 to 201.12.3.174201.12.3.1756
119201.12.3.176/29201.12.3.177 to 201.12.3.182201.12.3.1836
120201.12.3.184/29201.12.3.185 to 201.12.3.190201.12.3.1916
121201.12.3.192/29201.12.3.193 to 201.12.3.198201.12.3.1996
122201.12.3.200/29201.12.3.201 to 201.12.3.206201.12.3.2076
123201.12.3.208/29201.12.3.209 to 201.12.3.214201.12.3.2156
124201.12.3.216/29201.12.3.217 to 201.12.3.222201.12.3.2236
125201.12.3.224/29201.12.3.225 to 201.12.3.230201.12.3.2316
126201.12.3.232/29201.12.3.233 to 201.12.3.238201.12.3.2396
127201.12.3.240/29201.12.3.241 to 201.12.3.246201.12.3.2476
128201.12.3.248/29201.12.3.249 to 201.12.3.254201.12.3.2556
129201.12.4.0/29201.12.4.1 to 201.12.4.6201.12.4.76
130201.12.4.8/29201.12.4.9 to 201.12.4.14201.12.4.156
131201.12.4.16/29201.12.4.17 to 201.12.4.22201.12.4.236
132201.12.4.24/29201.12.4.25 to 201.12.4.30201.12.4.316
133201.12.4.32/29201.12.4.33 to 201.12.4.38201.12.4.396
134201.12.4.40/29201.12.4.41 to 201.12.4.46201.12.4.476
135201.12.4.48/29201.12.4.49 to 201.12.4.54201.12.4.556
136201.12.4.56/29201.12.4.57 to 201.12.4.62201.12.4.636
137201.12.4.64/29201.12.4.65 to 201.12.4.70201.12.4.716
138201.12.4.72/29201.12.4.73 to 201.12.4.78201.12.4.796
139201.12.4.80/29201.12.4.81 to 201.12.4.86201.12.4.876
140201.12.4.88/29201.12.4.89 to 201.12.4.94201.12.4.956
141201.12.4.96/29201.12.4.97 to 201.12.4.102201.12.4.1036
142201.12.4.104/29201.12.4.105 to 201.12.4.110201.12.4.1116
143201.12.4.112/29201.12.4.113 to 201.12.4.118201.12.4.1196
144201.12.4.120/29201.12.4.121 to 201.12.4.126201.12.4.1276
145201.12.4.128/29201.12.4.129 to 201.12.4.134201.12.4.1356
146201.12.4.136/29201.12.4.137 to 201.12.4.142201.12.4.1436
147201.12.4.144/29201.12.4.145 to 201.12.4.150201.12.4.1516
148201.12.4.152/29201.12.4.153 to 201.12.4.158201.12.4.1596
149201.12.4.160/29201.12.4.161 to 201.12.4.166201.12.4.1676
150201.12.4.168/29201.12.4.169 to 201.12.4.174201.12.4.1756
151201.12.4.176/29201.12.4.177 to 201.12.4.182201.12.4.1836
152201.12.4.184/29201.12.4.185 to 201.12.4.190201.12.4.1916
153201.12.4.192/29201.12.4.193 to 201.12.4.198201.12.4.1996
154201.12.4.200/29201.12.4.201 to 201.12.4.206201.12.4.2076
155201.12.4.208/29201.12.4.209 to 201.12.4.214201.12.4.2156
156201.12.4.216/29201.12.4.217 to 201.12.4.222201.12.4.2236
157201.12.4.224/29201.12.4.225 to 201.12.4.230201.12.4.2316
158201.12.4.232/29201.12.4.233 to 201.12.4.238201.12.4.2396
159201.12.4.240/29201.12.4.241 to 201.12.4.246201.12.4.2476
160201.12.4.248/29201.12.4.249 to 201.12.4.254201.12.4.2556
161201.12.5.0/29201.12.5.1 to 201.12.5.6201.12.5.76
162201.12.5.8/29201.12.5.9 to 201.12.5.14201.12.5.156
163201.12.5.16/29201.12.5.17 to 201.12.5.22201.12.5.236
164201.12.5.24/29201.12.5.25 to 201.12.5.30201.12.5.316
165201.12.5.32/29201.12.5.33 to 201.12.5.38201.12.5.396
166201.12.5.40/29201.12.5.41 to 201.12.5.46201.12.5.476
167201.12.5.48/29201.12.5.49 to 201.12.5.54201.12.5.556
168201.12.5.56/29201.12.5.57 to 201.12.5.62201.12.5.636
169201.12.5.64/29201.12.5.65 to 201.12.5.70201.12.5.716
170201.12.5.72/29201.12.5.73 to 201.12.5.78201.12.5.796
171201.12.5.80/29201.12.5.81 to 201.12.5.86201.12.5.876
172201.12.5.88/29201.12.5.89 to 201.12.5.94201.12.5.956
173201.12.5.96/29201.12.5.97 to 201.12.5.102201.12.5.1036
174201.12.5.104/29201.12.5.105 to 201.12.5.110201.12.5.1116
175201.12.5.112/29201.12.5.113 to 201.12.5.118201.12.5.1196
176201.12.5.120/29201.12.5.121 to 201.12.5.126201.12.5.1276
177201.12.5.128/29201.12.5.129 to 201.12.5.134201.12.5.1356
178201.12.5.136/29201.12.5.137 to 201.12.5.142201.12.5.1436
179201.12.5.144/29201.12.5.145 to 201.12.5.150201.12.5.1516
180201.12.5.152/29201.12.5.153 to 201.12.5.158201.12.5.1596
181201.12.5.160/29201.12.5.161 to 201.12.5.166201.12.5.1676
182201.12.5.168/29201.12.5.169 to 201.12.5.174201.12.5.1756
183201.12.5.176/29201.12.5.177 to 201.12.5.182201.12.5.1836
184201.12.5.184/29201.12.5.185 to 201.12.5.190201.12.5.1916
185201.12.5.192/29201.12.5.193 to 201.12.5.198201.12.5.1996
186201.12.5.200/29201.12.5.201 to 201.12.5.206201.12.5.2076
187201.12.5.208/29201.12.5.209 to 201.12.5.214201.12.5.2156
188201.12.5.216/29201.12.5.217 to 201.12.5.222201.12.5.2236
189201.12.5.224/29201.12.5.225 to 201.12.5.230201.12.5.2316
190201.12.5.232/29201.12.5.233 to 201.12.5.238201.12.5.2396
191201.12.5.240/29201.12.5.241 to 201.12.5.246201.12.5.2476
192201.12.5.248/29201.12.5.249 to 201.12.5.254201.12.5.2556
193201.12.6.0/29201.12.6.1 to 201.12.6.6201.12.6.76
194201.12.6.8/29201.12.6.9 to 201.12.6.14201.12.6.156
195201.12.6.16/29201.12.6.17 to 201.12.6.22201.12.6.236
196201.12.6.24/29201.12.6.25 to 201.12.6.30201.12.6.316
197201.12.6.32/29201.12.6.33 to 201.12.6.38201.12.6.396
198201.12.6.40/29201.12.6.41 to 201.12.6.46201.12.6.476
199201.12.6.48/29201.12.6.49 to 201.12.6.54201.12.6.556
200201.12.6.56/29201.12.6.57 to 201.12.6.62201.12.6.636
201201.12.6.64/29201.12.6.65 to 201.12.6.70201.12.6.716
202201.12.6.72/29201.12.6.73 to 201.12.6.78201.12.6.796
203201.12.6.80/29201.12.6.81 to 201.12.6.86201.12.6.876
204201.12.6.88/29201.12.6.89 to 201.12.6.94201.12.6.956
205201.12.6.96/29201.12.6.97 to 201.12.6.102201.12.6.1036
206201.12.6.104/29201.12.6.105 to 201.12.6.110201.12.6.1116
207201.12.6.112/29201.12.6.113 to 201.12.6.118201.12.6.1196
208201.12.6.120/29201.12.6.121 to 201.12.6.126201.12.6.1276
209201.12.6.128/29201.12.6.129 to 201.12.6.134201.12.6.1356
210201.12.6.136/29201.12.6.137 to 201.12.6.142201.12.6.1436
211201.12.6.144/29201.12.6.145 to 201.12.6.150201.12.6.1516
212201.12.6.152/29201.12.6.153 to 201.12.6.158201.12.6.1596
213201.12.6.160/29201.12.6.161 to 201.12.6.166201.12.6.1676
214201.12.6.168/29201.12.6.169 to 201.12.6.174201.12.6.1756
215201.12.6.176/29201.12.6.177 to 201.12.6.182201.12.6.1836
216201.12.6.184/29201.12.6.185 to 201.12.6.190201.12.6.1916
217201.12.6.192/29201.12.6.193 to 201.12.6.198201.12.6.1996
218201.12.6.200/29201.12.6.201 to 201.12.6.206201.12.6.2076
219201.12.6.208/29201.12.6.209 to 201.12.6.214201.12.6.2156
220201.12.6.216/29201.12.6.217 to 201.12.6.222201.12.6.2236
221201.12.6.224/29201.12.6.225 to 201.12.6.230201.12.6.2316
222201.12.6.232/29201.12.6.233 to 201.12.6.238201.12.6.2396
223201.12.6.240/29201.12.6.241 to 201.12.6.246201.12.6.2476
224201.12.6.248/29201.12.6.249 to 201.12.6.254201.12.6.2556
225201.12.7.0/29201.12.7.1 to 201.12.7.6201.12.7.76
226201.12.7.8/29201.12.7.9 to 201.12.7.14201.12.7.156
227201.12.7.16/29201.12.7.17 to 201.12.7.22201.12.7.236
228201.12.7.24/29201.12.7.25 to 201.12.7.30201.12.7.316
229201.12.7.32/29201.12.7.33 to 201.12.7.38201.12.7.396
230201.12.7.40/29201.12.7.41 to 201.12.7.46201.12.7.476
231201.12.7.48/29201.12.7.49 to 201.12.7.54201.12.7.556
232201.12.7.56/29201.12.7.57 to 201.12.7.62201.12.7.636
233201.12.7.64/29201.12.7.65 to 201.12.7.70201.12.7.716
234201.12.7.72/29201.12.7.73 to 201.12.7.78201.12.7.796
235201.12.7.80/29201.12.7.81 to 201.12.7.86201.12.7.876
236201.12.7.88/29201.12.7.89 to 201.12.7.94201.12.7.956
237201.12.7.96/29201.12.7.97 to 201.12.7.102201.12.7.1036
238201.12.7.104/29201.12.7.105 to 201.12.7.110201.12.7.1116
239201.12.7.112/29201.12.7.113 to 201.12.7.118201.12.7.1196
240201.12.7.120/29201.12.7.121 to 201.12.7.126201.12.7.1276
241201.12.7.128/29201.12.7.129 to 201.12.7.134201.12.7.1356
242201.12.7.136/29201.12.7.137 to 201.12.7.142201.12.7.1436
243201.12.7.144/29201.12.7.145 to 201.12.7.150201.12.7.1516
244201.12.7.152/29201.12.7.153 to 201.12.7.158201.12.7.1596
245201.12.7.160/29201.12.7.161 to 201.12.7.166201.12.7.1676
246201.12.7.168/29201.12.7.169 to 201.12.7.174201.12.7.1756
247201.12.7.176/29201.12.7.177 to 201.12.7.182201.12.7.1836
248201.12.7.184/29201.12.7.185 to 201.12.7.190201.12.7.1916
249201.12.7.192/29201.12.7.193 to 201.12.7.198201.12.7.1996
250201.12.7.200/29201.12.7.201 to 201.12.7.206201.12.7.2076
251201.12.7.208/29201.12.7.209 to 201.12.7.214201.12.7.2156
252201.12.7.216/29201.12.7.217 to 201.12.7.222201.12.7.2236
253201.12.7.224/29201.12.7.225 to 201.12.7.230201.12.7.2316
254201.12.7.232/29201.12.7.233 to 201.12.7.238201.12.7.2396
255201.12.7.240/29201.12.7.241 to 201.12.7.246201.12.7.2476
256201.12.7.248/29201.12.7.249 to 201.12.7.254201.12.7.2556

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.