What is the size of a 3.5 inch hard drive in CM?

Hard drives come in a variety of physical sizes, but the most common size for desktop computers is 3.5 inches. This refers to the width of the drive bay that the hard drive slides into. But what does 3.5 inches correspond to in centimeters? Let’s take a closer look at converting inches to centimeters and find out the size of a standard 3.5 inch hard drive in CM.

Converting Inches to Centimeters

To convert inches to centimeters, we need to know the conversion ratio between the two units. Here are the key details:

  • 1 inch = 2.54 centimeters
  • This ratio is exact by definition of the international inch.
  • So to convert, we simply multiply the inch value by 2.54.

This conversion ratio allows us to easily convert between inches and centimeters. Now let’s apply it to find the size of a 3.5 inch hard drive in centimeters.

Calculating the Size of a 3.5 inch Hard Drive in CM

Using the conversion ratio above, we can calculate the size in centimeters as follows:

  • 1 inch = 2.54 cm
  • 3.5 inches * 2.54 cm/inch = 3.5 * 2.54 cm
  • = 8.89 cm

So a standard 3.5 inch hard drive has a width of approximately 8.89 cm. Let’s round this to 9 cm for simpler notation.

Summary of Calculation

To summarize the key details:

  • Standard size of a desktop hard drive: 3.5 inches
  • Conversion ratio: 1 inch = 2.54 cm
  • Calculation: 3.5 inches * 2.54 cm/inch = 8.89 cm ≈ 9 cm

So a 3.5 inch hard drive has a width of about 9 cm. This approximate size in centimeters is useful to know when measuring drive bays and planning hard drive installations.

Visualizing the Size

To provide a visual for the size of a 3.5 inch hard drive in cm, here is a simple comparison image:

3.5 inch hard drive size comparison

As you can see, the width of a typical 3.5 inch hard drive is about 9 cm. This corresponds to the calculation we did above to convert the imperial inches measurement to centimeters.

Common Uses of 3.5 Inch Hard Drives

Some additional context around the common uses of 3.5 inch hard drives:

  • Typically used as the main drive in desktop PCs
  • Offer large storage capacities from hundreds of GB to tens of TB
  • Designed to be installed in desktop PC drive bays
  • Require more power and larger interface cables than smaller laptop drives

So in summary, 3.5 inch hard drives are designed for desktop use and their width of approximately 9 cm allows them to slot into standard desktop drive bays.

Converting Other Common Hard Drive Sizes

We can also use the inch to cm conversion ratio to look at some other common hard drive form factors and their size in cm:

Hard Drive Size Size in CM
2.5 inch (laptop drive) 2.5 * 2.54 = 6.35 cm
1.8 inch (micro drive) 1.8 * 2.54 = 4.57 cm
1 inch (early HDDs) 1 * 2.54 = 2.54 cm

This gives a sense of how the physical size of hard drives translates to measurements in centimeters. The 3.5 inch form factor remains the most popular for desktop PCs.


In summary, a standard 3.5 inch hard drive, as used in most desktop PCs, has a width of approximately 9 cm when converted from inches to centimeters. This measurement in cm allows us to understand the true physical dimensions of these common storage drives beyond just the imperial inch units. Knowing the size in centimeters makes it easier to measure component spacing and compatibility when installing 3.5 inch hard drives into desktop computer cases.