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) |
Conclusion
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.
