CIDR prefix
/20
255.255.240.0
4,094 usable hosts · 4,096 addresses
The mask for /20 is 255.255.240.0 — 4,096 addresses, 4,094 usable hosts. Campus and larger office networks; /22–/23 are common for offices with a few hundred devices.
Mask
255.255.240.0
Wildcard
0.0.15.255
Addresses
4,096
Hosts
4,094
Worked example: 192.168.0.0/20
Network address192.168.0.0/20
Broadcast address192.168.15.255
First host192.168.0.1
Last host192.168.15.254
FAQ — /20
What is the subnet mask for /20?
The subnet mask for /20 is 255.255.240.0 (wildcard: 0.0.15.255). The first 20 bits are the network part, the remaining 12 are the host part.
How many hosts fit in a /20?
A /20 block holds 4,096 addresses, of which 4,094 are usable hosts (the network and broadcast addresses are excluded).
How many /20 subnets fit in a /16?
A /16 network divides into 16 /20 subnets.
What is a /20 used for?
Campus and larger office networks; /22–/23 are common for offices with a few hundred devices.