> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/hacking-tools/calculators/subnetting-calculator.md).

# Subnetting Calculator

Subnetting calculator for CIDR, subnet masks, wildcard masks, host counts, block sizes, private ranges, and quick subnet calculation examples.

Search a CIDR prefix such as `/24`, `/27`, or `/30` to get the subnet mask, wildcard mask, number of addresses, usable host range size, and block size.

## CIDR Finder

<table data-view="cards" data-full-width="true" data-search="true"><thead><tr><th>CIDR</th><th>Subnet Mask</th><th>Wildcard</th><th>Total IPs</th><th>Usable Hosts</th><th>Block Size</th><th>Common Use</th></tr></thead><tbody><tr><td><code>/0</code></td><td>0.0.0.0</td><td>255.255.255.255</td><td>4,294,967,296</td><td>4,294,967,294</td><td>256 in 1st octet</td><td>Default route</td></tr><tr><td><code>/8</code></td><td>255.0.0.0</td><td>0.255.255.255</td><td>16,777,216</td><td>16,777,214</td><td>1 in 1st octet</td><td>Very large network</td></tr><tr><td><code>/9</code></td><td>255.128.0.0</td><td>0.127.255.255</td><td>8,388,608</td><td>8,388,606</td><td>128 in 2nd octet</td><td>Large split</td></tr><tr><td><code>/10</code></td><td>255.192.0.0</td><td>0.63.255.255</td><td>4,194,304</td><td>4,194,302</td><td>64 in 2nd octet</td><td>Large split</td></tr><tr><td><code>/11</code></td><td>255.224.0.0</td><td>0.31.255.255</td><td>2,097,152</td><td>2,097,150</td><td>32 in 2nd octet</td><td>Large split</td></tr><tr><td><code>/12</code></td><td>255.240.0.0</td><td>0.15.255.255</td><td>1,048,576</td><td>1,048,574</td><td>16 in 2nd octet</td><td>RFC1918 172.16.0.0/12</td></tr><tr><td><code>/13</code></td><td>255.248.0.0</td><td>0.7.255.255</td><td>524,288</td><td>524,286</td><td>8 in 2nd octet</td><td>Large enterprise</td></tr><tr><td><code>/14</code></td><td>255.252.0.0</td><td>0.3.255.255</td><td>262,144</td><td>262,142</td><td>4 in 2nd octet</td><td>Large enterprise</td></tr><tr><td><code>/15</code></td><td>255.254.0.0</td><td>0.1.255.255</td><td>131,072</td><td>131,070</td><td>2 in 2nd octet</td><td>Large enterprise</td></tr><tr><td><code>/16</code></td><td>255.255.0.0</td><td>0.0.255.255</td><td>65,536</td><td>65,534</td><td>1 in 2nd octet</td><td>Large LAN</td></tr><tr><td><code>/17</code></td><td>255.255.128.0</td><td>0.0.127.255</td><td>32,768</td><td>32,766</td><td>128 in 3rd octet</td><td>Large VLAN block</td></tr><tr><td><code>/18</code></td><td>255.255.192.0</td><td>0.0.63.255</td><td>16,384</td><td>16,382</td><td>64 in 3rd octet</td><td>Large VLAN block</td></tr><tr><td><code>/19</code></td><td>255.255.224.0</td><td>0.0.31.255</td><td>8,192</td><td>8,190</td><td>32 in 3rd octet</td><td>Large VLAN block</td></tr><tr><td><code>/20</code></td><td>255.255.240.0</td><td>0.0.15.255</td><td>4,096</td><td>4,094</td><td>16 in 3rd octet</td><td>Medium network</td></tr><tr><td><code>/21</code></td><td>255.255.248.0</td><td>0.0.7.255</td><td>2,048</td><td>2,046</td><td>8 in 3rd octet</td><td>Medium network</td></tr><tr><td><code>/22</code></td><td>255.255.252.0</td><td>0.0.3.255</td><td>1,024</td><td>1,022</td><td>4 in 3rd octet</td><td>Medium network</td></tr><tr><td><code>/23</code></td><td>255.255.254.0</td><td>0.0.1.255</td><td>512</td><td>510</td><td>2 in 3rd octet</td><td>Two /24 networks</td></tr><tr><td><code>/24</code></td><td>255.255.255.0</td><td>0.0.0.255</td><td>256</td><td>254</td><td>1 in 3rd octet</td><td>Common LAN</td></tr><tr><td><code>/25</code></td><td>255.255.255.128</td><td>0.0.0.127</td><td>128</td><td>126</td><td>128 in 4th octet</td><td>Half /24</td></tr><tr><td><code>/26</code></td><td>255.255.255.192</td><td>0.0.0.63</td><td>64</td><td>62</td><td>64 in 4th octet</td><td>Small VLAN</td></tr><tr><td><code>/27</code></td><td>255.255.255.224</td><td>0.0.0.31</td><td>32</td><td>30</td><td>32 in 4th octet</td><td>Small subnet</td></tr><tr><td><code>/28</code></td><td>255.255.255.240</td><td>0.0.0.15</td><td>16</td><td>14</td><td>16 in 4th octet</td><td>Tiny subnet</td></tr><tr><td><code>/29</code></td><td>255.255.255.248</td><td>0.0.0.7</td><td>8</td><td>6</td><td>8 in 4th octet</td><td>Small routed segment</td></tr><tr><td><code>/30</code></td><td>255.255.255.252</td><td>0.0.0.3</td><td>4</td><td>2</td><td>4 in 4th octet</td><td>Point-to-point</td></tr><tr><td><code>/31</code></td><td>255.255.255.254</td><td>0.0.0.1</td><td>2</td><td>2 for point-to-point</td><td>2 in 4th octet</td><td>Point-to-point link</td></tr><tr><td><code>/32</code></td><td>255.255.255.255</td><td>0.0.0.0</td><td>1</td><td>1 host route</td><td>1 IP</td><td>Single host</td></tr></tbody></table>

## Manual Calculation

| Step              | Formula                                               |
| ----------------- | ----------------------------------------------------- |
| Total IPs         | `2^(32 - CIDR)`                                       |
| Usable hosts      | `total - 2`, except `/31` and `/32` special cases     |
| Block size        | `256 - interesting mask octet`                        |
| Network address   | Round the interesting octet down to the nearest block |
| Broadcast address | Next network minus 1                                  |
| First host        | Network address plus 1                                |
| Last host         | Broadcast address minus 1                             |

## Worked Examples

<table data-view="cards" data-full-width="true" data-search="true"><thead><tr><th>IP/CIDR</th><th>Network</th><th>First Host</th><th>Last Host</th><th>Broadcast</th><th>Notes</th></tr></thead><tbody><tr><td><code>192.168.1.37/27</code></td><td>192.168.1.32</td><td>192.168.1.33</td><td>192.168.1.62</td><td>192.168.1.63</td><td>/27 blocks increment by 32.</td></tr><tr><td><code>10.10.10.10/30</code></td><td>10.10.10.8</td><td>10.10.10.9</td><td>10.10.10.10</td><td>10.10.10.11</td><td>/30 blocks increment by 4.</td></tr><tr><td><code>172.16.44.201/26</code></td><td>172.16.44.192</td><td>172.16.44.193</td><td>172.16.44.254</td><td>172.16.44.255</td><td>/26 blocks increment by 64.</td></tr><tr><td><code>192.168.56.90/28</code></td><td>192.168.56.80</td><td>192.168.56.81</td><td>192.168.56.94</td><td>192.168.56.95</td><td>/28 blocks increment by 16.</td></tr></tbody></table>

## Useful Ranges

| Range                         | CIDR             | Use             |
| ----------------------------- | ---------------- | --------------- |
| 10.0.0.0 - 10.255.255.255     | `10.0.0.0/8`     | Private network |
| 172.16.0.0 - 172.31.255.255   | `172.16.0.0/12`  | Private network |
| 192.168.0.0 - 192.168.255.255 | `192.168.0.0/16` | Private network |
| 127.0.0.0 - 127.255.255.255   | `127.0.0.0/8`    | Loopback        |
| 169.254.0.0 - 169.254.255.255 | `169.254.0.0/16` | Link-local      |
| 224.0.0.0 - 239.255.255.255   | `224.0.0.0/4`    | Multicast       |


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