Subnet Mask Table
Quick reference table for all CIDR notations, subnet masks, wildcard masks, and host counts.
Embed this tool| CIDR | Subnet Mask | Wildcard | Usable Hosts |
|---|---|---|---|
| /0 | 0.0.0.0 | 255.255.255.255 | 4,294,967,294 |
| /1 | 128.0.0.0 | 127.255.255.255 | 2,147,483,646 |
| /2 | 192.0.0.0 | 63.255.255.255 | 1,073,741,822 |
| /3 | 224.0.0.0 | 31.255.255.255 | 536,870,910 |
| /4 | 240.0.0.0 | 15.255.255.255 | 268,435,454 |
| /5 | 248.0.0.0 | 7.255.255.255 | 134,217,726 |
| /6 | 252.0.0.0 | 3.255.255.255 | 67,108,862 |
| /7 | 254.0.0.0 | 1.255.255.255 | 33,554,430 |
| /8 | 255.0.0.0 | 0.255.255.255 | 16,777,214 |
| /9 | 255.128.0.0 | 0.127.255.255 | 8,388,606 |
| /10 | 255.192.0.0 | 0.63.255.255 | 4,194,302 |
| /11 | 255.224.0.0 | 0.31.255.255 | 2,097,150 |
| /12 | 255.240.0.0 | 0.15.255.255 | 1,048,574 |
| /13 | 255.248.0.0 | 0.7.255.255 | 524,286 |
| /14 | 255.252.0.0 | 0.3.255.255 | 262,142 |
| /15 | 255.254.0.0 | 0.1.255.255 | 131,070 |
| /16 | 255.255.0.0 | 0.0.255.255 | 65,534 |
| /17 | 255.255.128.0 | 0.0.127.255 | 32,766 |
| /18 | 255.255.192.0 | 0.0.63.255 | 16,382 |
| /19 | 255.255.224.0 | 0.0.31.255 | 8,190 |
| /20 | 255.255.240.0 | 0.0.15.255 | 4,094 |
| /21 | 255.255.248.0 | 0.0.7.255 | 2,046 |
| /22 | 255.255.252.0 | 0.0.3.255 | 1,022 |
| /23 | 255.255.254.0 | 0.0.1.255 | 510 |
| /24 | 255.255.255.0 | 0.0.0.255 | 254 |
| /25 | 255.255.255.128 | 0.0.0.127 | 126 |
| /26 | 255.255.255.192 | 0.0.0.63 | 62 |
| /27 | 255.255.255.224 | 0.0.0.31 | 30 |
| /28 | 255.255.255.240 | 0.0.0.15 | 14 |
| /29 | 255.255.255.248 | 0.0.0.7 | 6 |
| /30 | 255.255.255.252 | 0.0.0.3 | 2 |
| /31 | 255.255.255.254 | 0.0.0.1 | 0 |
| /32 | 255.255.255.255 | 0.0.0.0 | 0 |
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Common Subnet Sizes
Network engineers memorize common CIDR values. /24 is the standard for small networks (254 hosts), /16 for medium organizations (65,534 hosts), and /30 for router-to-router links (2 hosts).
Frequently Asked Questions
CIDR (Classless Inter-Domain Routing) uses a slash followed by a number to indicate how many bits are used for the network portion of an IP address. For example, /24 means the first 24 bits are the network address.