What is a /28 Subnet? 16 IPs, 14 Hosts Explained

What is a /28 Subnet?

Last reviewed: May 2026

A /28 subnet contains 16 total IP addresses and 14 usable host addresses. The "/28" prefix means 28 bits are used for the network portion, leaving 4 bits (2⁴ = 16) for host addressing. The /28 is notable as the smallest subnet allowed in AWS VPC.

Calculate any /28 subnet instantly →

Quick Facts: 192.168.1.0/28 Subnet mask: 255.255.255.240 · Wildcard: 0.0.0.15 · Network: x.x.x.0 (on 16-boundary) · Broadcast: x.x.x.15 · Total IPs: 16 · Usable hosts: 14

Full Breakdown

Property	Value
Prefix length	/28
Subnet mask	255.255.255.240
Wildcard mask	0.0.0.15
Total addresses	16
Usable host addresses	14
Network address	x.x.x.0 (must align to multiples of 16: .0, .16, .32, …)
Broadcast address	x.x.x.15 (last address in the block)
Binary mask	11111111.11111111.11111111.11110000
AWS usable hosts	11 (AWS reserves 5 IPs per subnet)

Property

Value

Prefix length

/28

Subnet mask

255.255.255.240

Wildcard mask

0.0.0.15

Total addresses

Usable host addresses

Network address

x.x.x.0 (must align to multiples of 16: .0, .16, .32, …)

Broadcast address

x.x.x.15 (last address in the block)

Binary mask

11111111.11111111.11111111.11110000

AWS usable hosts

11 (AWS reserves 5 IPs per subnet)

AWS Minimum Subnet Size

/28 is the smallest subnet allowed in an AWS VPC. After AWS reserves 5 IPs (.0 network, .1 VPC router, .2 DNS, .3 future use, .15 broadcast), only 11 IPs are usable for EC2 instances and other resources. Plan accordingly — if you need 12 or more hosts in AWS, use /27 instead.

Common Use Cases for /28 Subnets

Comparison: /28 vs Nearby Prefix Lengths

CIDR	Subnet Mask	Total IPs	Usable Hosts	AWS Usable	Typical Use
/27	255.255.255.224	32	30	27	Azure GatewaySubnet, infrastructure
/28	255.255.255.240	16	14	11	AWS minimum; small managed subnet
/29	255.255.255.248	8	6	3	Very small segment; not AWS-recommended
/30	255.255.255.252	4	2	—	Point-to-point links (not usable in AWS)

CIDR

Subnet Mask

Total IPs

Usable Hosts

AWS Usable

Typical Use

/27

255.255.255.224

Azure GatewaySubnet, infrastructure

/28

255.255.255.240

AWS minimum; small managed subnet

/29

255.255.255.248

Very small segment; not AWS-recommended

/30

255.255.255.252

—

Point-to-point links (not usable in AWS)

How Many /28 Subnets Fit in a /24?

A /24 block contains 2^(28−24) = 16 subnets of /28 size. For example, 192.168.1.0/24 can be subdivided into 192.168.1.0/28, 192.168.1.16/28, 192.168.1.32/28, … 192.168.1.240/28. Each block starts on a multiple of 16.

Frequently Asked Questions

How many usable hosts does a /28 subnet have?

A /28 subnet has 14 usable host addresses out of 16 total IPs. Two addresses are reserved: the network address (x.x.x.0 on a 16-boundary) and the broadcast address (x.x.x.15). In AWS, only 11 IPs are usable because AWS reserves 5 IPs per subnet.

What is the subnet mask for a /28 network?

The subnet mask for a /28 network is 255.255.255.240. In binary, 28 bits are set to 1 followed by 4 bits of 0: 11111111.11111111.11111111.11110000.

How many /28 subnets fit inside a /24 network?

A /24 network can be divided into 16 subnets of /28 size. The difference in prefix length is 28 - 24 = 4 bits, and 2^4 = 16. For example, 192.168.1.0/24 contains 192.168.1.0/28 through 192.168.1.240/28.