/20 Subnet Mask (255.255.240.0)
| Prefix | /20 |
|---|---|
| Subnet mask | 255.255.240.0 |
| Wildcard mask | 0.0.15.255 |
| Binary mask | 11111111.11111111.11110000.00000000 |
| Total addresses | 4,096 |
| Usable hosts | 4,094 |
| Host bits | 12 |
| Subnets of /20 in a /16 | 16 |
e.g. 10.0.0.5/22 or 10.0.0.5 255.255.252.0
| Network address | 172.16.0.0 | |
|---|---|---|
| Broadcast address | 172.16.15.255 | |
| First usable host | 172.16.0.1 | |
| Last usable host | 172.16.15.254 | |
| Total addresses | 4,096 | |
| Usable hosts | 4,094 | |
| Subnet mask | 255.255.240.0 | |
| Wildcard mask | 0.0.15.255 | |
| CIDR notation | 172.16.0.0/20 | |
| IP class | Class B (legacy) | |
| Address type | Private (RFC 1918) | |
| IP address (binary) | 10101100.00010000.00000000.00000000 | |
| Subnet mask (binary) | 11111111.11111111.11110000.00000000 |
■ network bits ■ host bits
| Requested hosts | CIDR | First host | Last host | Broadcast | Usable hosts |
|---|
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What is a /20 subnet?
A /20 subnet uses the first 20 bits of an IPv4 address for the network and leaves 12 bits for hosts. Its subnet mask is 255.255.240.0, and it contains 2¹² = 4,096 addresses, of which 4,094 can be assigned to devices. Typical use: Default size of AWS default-VPC subnets (4,096 addresses). Use the subnet calculator above to check any /20 network.
/20 subnet example
For 172.16.0.0/20: network address 172.16.0.0, usable hosts 172.16.0.1 – 172.16.15.254, broadcast address 172.16.15.255, wildcard mask 0.0.15.255.
/20 networks in 172.16.0.0/16
A /16 holds 16 /20 networks:
- 172.16.0.0/20
- 172.16.16.0/20
- 172.16.32.0/20
- 172.16.48.0/20
- 172.16.64.0/20
- 172.16.80.0/20
- 172.16.96.0/20
- 172.16.112.0/20
- 172.16.128.0/20
- 172.16.144.0/20
- 172.16.160.0/20
- 172.16.176.0/20
- 172.16.192.0/20
- 172.16.208.0/20
- 172.16.224.0/20
- 172.16.240.0/20
Frequently asked questions
How many usable IPs are in a /20?
4,094. The block has 4,096 addresses; the first is the network address and the last is the broadcast address.
What is the subnet mask for /20?
255.255.240.0, or 11111111.11111111.11110000.00000000 in binary.
How many /20 subnets are in a /16?
16 (2⁴), because a /20 uses 4 more network bits than a /16.
What is the difference between /20 and /19?
A /19 (255.255.224.0) is twice as large: 8,192 addresses and 8,190 usable hosts, spanning two consecutive /20 blocks such as 172.16.0.0–172.16.31.255.