How thick is a 3.5 hard drive?

Hard disk drives (HDDs) come in a variety of sizes, but two of the most common are 3.5-inch and 2.5-inch drives. As the names suggest, the size designation refers to the width of the drive enclosure in inches. But how thick are 3.5-inch hard drives actually?

What is a 3.5-inch hard drive?

A 3.5-inch hard drive is a HDD designed to fit into a drive bay that is 3.5 inches wide. Formally known as Advanced Technology Attachment (ATA) drives, these drives provide an interface for the motherboard of a computer to communicate with HDD storage devices. Most desktop computers are equipped with 3.5-inch drive bays to house 3.5-inch ATA hard drives.

Compared to 2.5-inch notebook hard drives, 3.5-inch desktop drives have higher storage capacities and faster speeds. They require an external power source to operate, unlike smaller 2.5-inch drives that are designed to draw power over their data cable. While 2.5-inch drives max out at 5TB, 3.5-inch drives are available with capacities up to 16TB for consumer models and 18TB for enterprise models.

Typical dimensions

The typical dimensions of a 3.5-inch hard drive are:

  • 3.5 inches wide (about 88.9 mm)
  • 5.75 inches deep (about 146.05 mm)
  • 1 inch tall (25.4 mm)

However, the height can vary slightly between models, typically ranging from 0.94 inches to 1.028 inches tall (24 mm to 26.1 mm).

Drive thickness by interface type

3.5-inch drives are available with different interfaces that connect them to the computer. The interface impacts the overall drive thickness slightly.

SATA drives

Serial ATA or SATA is the most common interface for modern internal hard drives. For 3.5-inch SATA drives, the typical thickness is:

  • 1 inch (25.4 mm) for desktop HDDs
  • 0.787 inches (20 mm) for enterprise “low profile” models

SAS drives

Serial Attached SCSI or SAS interfaces are found on enterprise and server-grade drives. For 3.5-inch SAS drives, the common thicknesses are:

  • 1 inch (25.4 mm) for desktop models
  • 0.984 inches (25 mm) for standard enterprise models
  • 0.787 inches (20 mm) for low profile enterprise models

SCSI drives

Older parallel SCSI interface drives, if still in use, are typically 1.023 inches (26 mm) thick for desktop models and 0.787 inches (20 mm) thick for low profile server models.

Thickness by drive type

In addition to the interface, the intended use of the hard drive also impacts its height.

Desktop HDDs

Desktop hard disk drives (HDDs) designed for use in towers, all-in-one PCs, and external enclosures are usually 1 inch (25.4 mm) thick.

Enterprise drives

Enterprise and NAS drives designed for data centers and home servers often come in “low profile” models that are 0.787 inches (20 mm) thick to fit space-constrained drive bays.

SSD heights

Solid state drives (SSDs) that fit 3.5-inch drive bays are typically 0.787 inches (20 mm) thick if low profile and 1 inch (25.4 mm) if desktop height.

Thickness of common 3.5-inch hard drive models

Here are some examples of the height for popular 3.5-inch hard drive models from major manufacturers:

Model Type Interface Height
WD Blue Desktop HDD SATA 1 inch (25.4 mm)
Seagate Barracuda Desktop HDD SATA 1 inch (25.4 mm)
Toshiba N300 NAS Hard Drive SATA 1 inch (25.4 mm)
WD Red Pro NAS Hard Drive SATA 1 inch (25.4 mm)
WD Gold Datacenter HDD SATA 1 inch (25.4 mm)
Seagate IronWolf Pro NAS HDD SATA 1 inch (25.4 mm)
WD VelociRaptor Enterprise HDD SATA 1 inch (25.4 mm)
Seagate Enterprise Capacity Enterprise HDD SAS 1 inch (25.4 mm)
Seagate Enterprise Performance Enterprise HDD SAS 1 inch (25.4 mm)
Toshiba MG08 Datacenter HDD SAS 0.984 inches (25 mm)
WD Ultrastar DC HC530 Datacenter HDD SAS 0.787 inches (20 mm)


In summary, most 3.5-inch hard drives designed for desktop use are 1 inch (25.4 mm) thick. Enterprise and datacenter models may be slightly thinner at 0.787 inches (20 mm) for a low profile design to fit space-constrained drive bays in servers. But essentially, the most common thickness for a 3.5-inch hard drive is right around 1 inch thick.