CIDR Subnet Cheatsheet
IPv4 prefix lengths with subnet masks, wildcard masks, and host counts.
| Prefix | Subnet mask | Wildcard mask | Addresses | Class |
|---|---|---|---|---|
| /32 | 255.255.255.255 | 0.0.0.0 | 1 | /24+ (LAN) |
| /31 | 255.255.255.254 | 0.0.0.1 | 2 | /24+ (LAN) |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 (2 usable) | /24+ (LAN) |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 (6 usable) | /24+ (LAN) |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 (14 usable) | /24+ (LAN) |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 (30 usable) | /24+ (LAN) |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 (62 usable) | /24+ (LAN) |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 (126 usable) | /24+ (LAN) |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 (254 usable) | /24+ (LAN) |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 (510 usable) | Class B-ish |
| /22 | 255.255.252.0 | 0.0.3.255 | 1.02K (1.02K usable) | Class B-ish |
| /21 | 255.255.248.0 | 0.0.7.255 | 2.05K (2.05K usable) | Class B-ish |
| /20 | 255.255.240.0 | 0.0.15.255 | 4.1K (4.09K usable) | Class B-ish |
| /19 | 255.255.224.0 | 0.0.31.255 | 8.19K (8.19K usable) | Class B-ish |
| /18 | 255.255.192.0 | 0.0.63.255 | 16.38K (16.38K usable) | Class B-ish |
| /17 | 255.255.128.0 | 0.0.127.255 | 32.77K (32.77K usable) | Class B-ish |
| /16 | 255.255.0.0 | 0.0.255.255 | 65.54K (65.53K usable) | Class B-ish |
| /15 | 255.254.0.0 | 0.1.255.255 | 131.07K (131.07K usable) | Class A-ish |
| /14 | 255.252.0.0 | 0.3.255.255 | 262.14K (262.14K usable) | Class A-ish |
| /13 | 255.248.0.0 | 0.7.255.255 | 524.29K (524.29K usable) | Class A-ish |
| /12 | 255.240.0.0 | 0.15.255.255 | 1.05M (1.05M usable) | Class A-ish |
| /11 | 255.224.0.0 | 0.31.255.255 | 2.1M (2.1M usable) | Class A-ish |
| /10 | 255.192.0.0 | 0.63.255.255 | 4.19M (4.19M usable) | Class A-ish |
| /9 | 255.128.0.0 | 0.127.255.255 | 8.39M (8.39M usable) | Class A-ish |
| /8 | 255.0.0.0 | 0.255.255.255 | 16.78M (16.78M usable) | Class A-ish |
| /7 | 254.0.0.0 | 1.255.255.255 | 33.55M (33.55M usable) | Internet routing |
| /6 | 252.0.0.0 | 3.255.255.255 | 67.11M (67.11M usable) | Internet routing |
| /5 | 248.0.0.0 | 7.255.255.255 | 134.22M (134.22M usable) | Internet routing |
| /4 | 240.0.0.0 | 15.255.255.255 | 268.44M (268.44M usable) | Internet routing |
| /3 | 224.0.0.0 | 31.255.255.255 | 536.87M (536.87M usable) | Internet routing |
| /2 | 192.0.0.0 | 63.255.255.255 | 1.07B (1.07B usable) | Internet routing |
| /1 | 128.0.0.0 | 127.255.255.255 | 2.15B (2.15B usable) | Internet routing |
| /0 | 0.0.0.0 | 0.0.0.0 | 4.29B (4.29B usable) | Internet routing |