What is a /16 Subnet? 65,536 Addresses Explained

What is a /16 Subnet?

Last reviewed: May 2026

A /16 subnet uses 16 bits for the network portion of an IPv4 address, leaving 16 bits for host addressing. This produces 65,536 total IP addresses and 65,534 usable hosts — making it the standard building block for large enterprise networks, cloud VPCs, and campus infrastructure.

Calculate any /16 subnet instantly →

Quick Facts: 10.0.0.0/16 Subnet mask: 255.255.0.0 · Wildcard: 0.0.255.255 · Network: 10.0.0.0 · Broadcast: 10.0.255.255 · Usable range: 10.0.0.1 – 10.0.255.254 · Usable hosts: 65,534

Full Breakdown

Property	Value
Prefix length	/16
Subnet mask	255.255.0.0
Wildcard mask	0.0.255.255
Total addresses	65,536
Usable host addresses	65,534
Network address	x.x.0.0
Broadcast address	x.x.255.255
Binary mask	11111111.11111111.00000000.00000000

Property

Value

Prefix length

/16

Subnet mask

255.255.0.0

Wildcard mask

0.0.255.255

Total addresses

65,536

Usable host addresses

65,534

Network address

x.x.0.0

Broadcast address

x.x.255.255

Binary mask

11111111.11111111.00000000.00000000

Common Use Cases for /16 Subnets

AWS VPCs — /16 is the recommended maximum CIDR for a VPC, giving you the most flexibility to carve out subnets later

Azure VNets — hub VNets and spoke VNets for enterprise landing zones typically start at /16

GCP VPC networks — custom mode VPCs commonly use /16 per region

Corporate campus networks — large offices allocate a /16 per campus and subnet it by building or floor

RFC 1918 private address space — the 172.16.0.0/12 block contains 16 consecutive /16 networks (172.16.x.x through 172.31.x.x)

Subnet Size	Number of Subnets in a /16	Hosts per Subnet
/17	2	32,766
/18	4	16,382
/20	16	4,094
/22	64	1,022
/24	256	254
/26	1,024	62
/28	4,096	14

Subnet Size

Number of Subnets in a /16

Hosts per Subnet

/17

32,766

/18

16,382

/20

4,094

/22

1,022

/24

256

254

/26

1,024

/28

4,096

Comparison: /16 vs Nearby Prefix Lengths

CIDR	Subnet Mask	Total IPs	Usable Hosts	Typical Use
/8	255.0.0.0	16,777,216	16,777,214	ISP / Class A legacy
/12	255.240.0.0	1,048,576	1,048,574	172.16.0.0/12 RFC 1918 block
/14	255.252.0.0	262,144	262,142	Large enterprise aggregation
/16	255.255.0.0	65,536	65,534	VPC root CIDR, campus network
/18	255.255.192.0	16,384	16,382	Regional subnet block
/20	255.255.240.0	4,096	4,094	Large availability zone subnet
/24	255.255.255.0	256	254	Standard workload subnet

CIDR

Subnet Mask

Total IPs

Usable Hosts

Typical Use

255.0.0.0

16,777,216

16,777,214

ISP / Class A legacy

/12

255.240.0.0

1,048,576

1,048,574

172.16.0.0/12 RFC 1918 block

/14

255.252.0.0

262,144

262,142

Large enterprise aggregation

/16

255.255.0.0

65,536

65,534

VPC root CIDR, campus network

/18

255.255.192.0

16,384

16,382

Regional subnet block

/20

255.255.240.0

4,096

4,094

Large availability zone subnet

/24

255.255.255.0

256

254

Standard workload subnet

Split a /16 into subnets with SubnetSolver →

Frequently Asked Questions

How many usable hosts does a /16 subnet have?

A /16 subnet has 65,534 usable host addresses. The total address count is 65,536 (2^16), minus 2 reserved addresses: the network address and the broadcast address.

Why is /16 the recommended VPC CIDR in AWS?

AWS recommends /16 as the VPC CIDR because it provides the maximum flexibility for subnet design. With 65,536 addresses you can create hundreds of subnets of varying sizes for different availability zones, tiers, and services, without running out of IP space.

What RFC 1918 ranges contain /16 blocks?

All three RFC 1918 private ranges support /16 blocks: 10.0.0.0/8 (contains 256 /16 blocks from 10.0.0.0/16 to 10.255.0.0/16), 172.16.0.0/12 (contains 16 /16 blocks from 172.16.0.0/16 to 172.31.0.0/16), and 192.168.0.0/16 (is exactly one /16 block).