Learn about 2.5 inch, 3.5 inch, 1.8 inch hard drive sizes ...

Since the invention of the drives, it has been used with various standardized form factors in computer systems. So we will learn about different types of hard drive sizes in this article.

Since the invention of the drives, it has been used with various standardized form factors in computer systems. So we will learn about different types of hard drive sizes in this article.

Hard drive size

Below is the table size of HDD before and after:

Standard hard drive size (inch)


Size (each size is measured in mm)

Largest hard drive capacity

Maximum number of disks (platter)

Imagination of each word disk (GB)




Hard drive 3.5

Currently being used



19; 25.4 or 26.1

14TB (October 2017)



Hard drive 2.5

Currently being used



5, 7, 9.5 12.5, 15 or 19




Hard drive 1.8

No longer used



5 or 8

320GB (2009)



Hard drive 8

No longer used




Do not know the maximum capacity.
Minimum of 64.5 MB

No number of disks from max.
Minimum of 6

Do not know the maximum capacity.
Minimum of 0.01075

5.25 (FH) hard drive

No longer used




47GB (1998)



5.25 Hard Drive (HH)

No longer used




19.3GB (1998)



Hard drive 1.3

No longer used




40GB (2007)



Hard drive 1 (CFII / ZIF / IDE-Flex)

No longer used




20GB (2006)



0.85 hard drive

No longer used




8GB (2004)



IBM's first hard drive, IBM 350, uses a stack of 50 24-inch disks and is about the same size as two large refrigerators. In 1962, IBM introduced a model 1311 hard drive, using 6 disks from 14 inches (nominal size) in a removable pack and nearly the size of a washing machine. This is considered the magnetic disk size and the standard hard drive size for many years, used by many other manufacturers. IBM 2314 uses magnetic disks of the same size in an eleven-high pack and introduces the layout of the 'hard drive in the drawer' even though 'drawer' is not a complete hard drive.

The following hard drives are designed to fit perfectly into a chassis that can be mounted on a 19-inch rack. Digital's RK05 and RL01 are a testament to how soon a single 14-inch magnetic disc is used in a removable pack, the whole medium hard drive in a 10.5-inch (6 rack) rack space. In the mid-1980s, the similarly sized Fujitsu Eagle used (randomly) a 10.5-inch disk to become a popular product.

This large disk is not used in processor-based systems. With the proliferation of floppy drive integrated computers (FDD), HDD hard drives can be compatible with FDD mounting frames. Therefore, the size of the HDD is initially made up of 8-inch, 5.25-inch and 3.5-inch floppy drives. Because there is no smaller floppy drive, the size of the HDD is created according to the product or industry standard.

Learn about 2.5 inch, 3.5 inch, 1.8 inch hard drive sizes ... Picture 1

8 inch hard drive

An 8-inch hard drive has dimensions of 9.5 inches × 4.624 inches × 14.25 inches (241.3 mm × 117.5 mm × 362 mm). In 1979, Shugart Associates was the first company to introduce the SA1000 hard drive size compatible with the 8 inch floppy drive size.

5.25 inch hard drive

The 5.25-inch hard drive measures 5.75 inches × 3.25 inches × 8 inches (146.1 mm × 82.55 mm × 203 mm). This is a smaller size, first used by Seagate in an HDD in 1980, the same size as the floppy disk drive 5 1⁄4 inch (130mm) full-height, 3.25 inches tall. It is twice as high as the 'haft height' ie 1.63 inches (41.4mm). Most desktop drive models for 120 mm optical discs (DVD, CD) use a 5¼ haft height diameter, but are no longer used for HDD hard drives. This size is manufactured according to the standard EIA-741 and SFF-8501 for hard drives with other SFF-85xx standards related to 5.25 inch devices (optical drives, etc.). HDD hard drive Quantum Bigfoot is the last hard drive to use this size in the late 1990s.

3.5 inch hard drive

3.5-inch hard drive with 4 inch × 1 inch × 5.75 inch (101.6 mm × 25.4 mm × 146 mm) size = 376.77344 cm³. This smaller hard drive is similar in size to the 1983 Rodime HDD, which is the same size as the "haft height", which means 1.63 inches in height. 1 inch height of this size becomes popular and is used in most desktop computers, this size is standardized on EIA / ECA-740 standard diameter and mounting holes along with the standard. SFF-8301.

2.5 inch hard drive

Learn about 2.5 inch, 3.5 inch, 1.8 inch hard drive sizes ... Picture 2

The 2.5-inch hard drive measures 2.75 inches × 0.25 - 0.75 inches × 3.945 inches (69.85 mm x 7–19 mm x 100 mm) = 48.895– 132.715 cm³. This smaller hard drive size was introduced by PrairieTek in 1988 and has no corresponding floppy drive. 2.5 inch hard drive size is standardized according to EIA / ECA-720 standard with SFF-8201 standard. When used with specific connectors, you will need more detailed specifications such as SFF-8212 for 50-pin connector (laptop ATA), SFF-8223 for SATA or SAS and SFF-8222 connectors for heads. SCA-2 connector.

This size is widely used for HDD hard drives in mobile devices (laptops, music players, etc.) and for SSD hard drives, replacing some enterprise-class 3.5 hard drives in 2008. Also It is also used in PlayStation 3 and Xbox 360 games.

The 9.5-mm hard drive has become an unofficial standard for all hard drives except for the largest notebook hard drives (usually with two disks from inside). 12.5 mm high hard drive, usually with three magnetic discs, is used for maximum capacity, but will not be suitable for most laptops. The enterprise type hard drive can have a maximum height of 15 mm. Seagate released a 7 mm hard drive aimed at affordable laptops and high-end netbooks in December 2009. Western Digital released a 5 mm height hard drive for Ultrabooks on April 23, 2013.

1.8 inch hard drive

The 1.8 inch hard drive has a size of 54 mm × 8 mm × 78.5 mm [c] = 33,912 cm³. This hard drive size was originally introduced by Integral Peripherals in 1993, developed with the ATA-7 LIF standard. For a while, it was used extensively in digital music players and subnotebooks, but its popularity decreased when this size was rare and accounted for only a small portion of the entire market.

1 inch hard drive

A 1-inch hard drive measures 42.8 mm x 5 mm x 36.4 mm. This size was introduced in 1999 so IBM's Microdrive fits snugly with CF Type II slot. Samsung also calls a 1.3-inch hard drive a 1-inch drive in their product documentation.

0.85 inch hard drive

0.85 inch hard drive with dimensions of 24 mm x 5 mm x 32 mm. Toshiba announced the size of this hard drive in January 2004 for use in mobile phones and similar applications, including an SD / MMC compatible HDD hard drive optimized for on-device video storage. 4G handset. Toshiba produces 4GB version (MK4001MTD) and 8GB (MK8003MTD), keeps Guinness record for the smallest HDD.

As of 2012, 2.5-inch and 3.5-inch hard drives are the most popular sizes. By 2009, all manufacturers had stopped developing new products for 1.3-inch, 1-inch and 0.85-inch sizes due to reduced flash memory prices, no moving parts.

Compare 2.5-inch and 3.5-inch hard drives

In general, 3.5-inch hard drives are manufactured for desktop computers while 2.5-inch hard drives are for laptops. A 3.5-inch hard drive can't fit a laptop, making a 2.5-inch hard drive your only upgrade option in this case. However, desktop computers have more internal space, you can use either of these hard drives.

Advantages of a 3.5-inch hard drive

Speed, power, price and convenience are the main reasons for users to choose a 3.5-inch hard drive compared to a 2.5-inch hard drive. The largest capacity of this hard drive can hold 2000GB of data and new computer users can also easily install. For most modern hard drives, just twist a few screws and connect two cables, the computer will handle the rest. The fastest 3.5-inch hard drive can read data at speeds of more than 131 MB per second. The price of this 3.5-inch hard drive is low, a 2000GB hard drive costs $ 200.

Advantages of 2.5 inch hard drive

The main reason for installing a 2.5-inch hard drive on a desktop is the extremely low noise level. A quietest 2.5-inch hard drive can produce 19 to 21 decibels at a distance of 1 meter while an average 3.5-inch hard drive produces 21 to 23 decibels. Especially when the computer is in a small space, 2 to 3 decibels make a difference. For most desktops, users still prefer to use a 3.5-inch hard drive. A 2.5-inch hard drive can't compete with a 3.5-inch hard drive in terms of speed or price, it has a maximum read speed of 101MB / sec and costs $ 150 for a 750GB hard drive.

The 2.5-inch hard drive cannot be installed directly on the desktop, the computer case does not have a drive bay to store it. However, this problem can be solved by adapters such as Upgradeware HD25-S, which costs only about 10 USD. HD25-S allows you to install a 2.5 inch hard drive into the desktop expansion card slot.

See more:

  1. 25 interesting things about hard drives you may not know
  2. 6 ways to check hard drive effectively for periodic health check of hard drive
  3. Notes when buying a computer hard drive