A /20 subnet mask is 255.255.240.0, with 4,096 addresses and 4,094 usable hosts.
| CIDR prefix | /20 |
|---|---|
| Subnet mask | 255.255.240.0 |
| Subnet mask (binary) | 11111111.11111111.11110000.00000000 |
| Wildcard mask | 0.0.15.255 |
| Network bits / host bits | 20 / 12 |
| Total addresses | 4,096 |
| Usable hosts | 4,094 |
| /20 subnets in a /8 | 4,096 |
| /20 subnets in a /16 | 16 |
The mask ends 4 bits into octet 3, so blocks step in increments of 16 in that octet.
| Network | First usable host | Last usable host | Broadcast |
|---|---|---|---|
| 192.168.0.0/20 | 192.168.0.1 | 192.168.15.254 | 192.168.15.255 |
| 192.168.16.0/20 | 192.168.16.1 | 192.168.31.254 | 192.168.31.255 |
| 192.168.32.0/20 | 192.168.32.1 | 192.168.47.254 | 192.168.47.255 |
| 192.168.48.0/20 | 192.168.48.1 | 192.168.63.254 | 192.168.63.255 |
| 192.168.64.0/20 | 192.168.64.1 | 192.168.79.254 | 192.168.79.255 |
| 192.168.80.0/20 | 192.168.80.1 | 192.168.95.254 | 192.168.95.255 |
| 192.168.96.0/20 | 192.168.96.1 | 192.168.111.254 | 192.168.111.255 |
| 192.168.112.0/20 | 192.168.112.1 | 192.168.127.254 | 192.168.127.255 |
A /20 subnet mask is 255.255.240.0. In binary that is 11111111.11111111.11110000.00000000: 20 network bits followed by 12 host bits. The wildcard mask is 0.0.15.255.
A /20 holds 4,096 addresses in total. Subtracting the network and broadcast addresses leaves 4,094 usable hosts.
A /16 divides into 16 subnets of size /20, because each extra mask bit doubles the number of subnets.
Calculate this over HTTP: curl https://networkcalc.com/api/ip/192.168.1.0/20.
See the Subnet Calculator API.