Subnet Calculator¶
CIDR Cheat Sheet
| CIDR | Subnet Mask | Usable Hosts | Notes |
|---|---|---|---|
| /32 | 255.255.255.255 | 1 | Single host |
| /31 | 255.255.255.254 | 2 | Point-to-point (RFC 3021) |
| /30 | 255.255.255.252 | 2 | Common for WAN / P2P |
| /29 | 255.255.255.248 | 6 | |
| /28 | 255.255.255.240 | 14 | |
| /27 | 255.255.255.224 | 30 | |
| /26 | 255.255.255.192 | 62 | |
| /25 | 255.255.255.128 | 126 | |
| /24 | 255.255.255.0 | 254 | Common LAN |
| /23 | 255.255.254.0 | 510 | |
| /22 | 255.255.252.0 | 1,022 | |
| /21 | 255.255.248.0 | 2,046 | |
| /20 | 255.255.240.0 | 4,094 | |
| /19 | 255.255.224.0 | 8,190 | |
| /18 | 255.255.192.0 | 16,382 | |
| /17 | 255.255.128.0 | 32,766 | |
| /16 | 255.255.0.0 | 65,534 | Class B sized |
| /12 | 255.240.0.0 | 1,048,574 | RFC 1918 Class B block |
| /10 | 255.192.0.0 | 4,194,302 | CGNAT (RFC 6598) |
| /8 | 255.0.0.0 | 16,777,214 | Class A sized |
Common Private Networks
| 10.0.0.0/8 | Class A Private |
| 172.16.0.0/12 | Class B Private |
| 192.168.0.0/16 | Class C Private |
| 100.64.0.0/10 | CGNAT (ISP Shared) |