Glossary of Terms - Hard Drive Capacity

Hard drive is a kind of data storage device which is used to store and retrieve different kinds of digital data by using one or more rigid rapidly rotating disks coated with magnetic material. In this post, there is some basic information about hard drive capacity which can help you make full use of hard drive in your daily life and work.

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Some Basic Information about Hard Drive Capacity

1. The Unit of Hard Drive Capacity

MB (megabytes) was mainly used when the hard disk was produced at the beginning in 1956. As time goes by, MB is too small to meet the demand for calculating the hard drive capacity. Now, the main units of the hard drive are GB (gigabytes) and TB (terabytes). Usually, manufacturers use these SI-based units to indicate the total capacity of hard drive. For example, a hard drive can be 100 GB, 1 TB, 12 TB, or even bigger.

External hard disk is also widely used all over the world which is typically connected to your computer via USB. When you are using external hard drive, you may encounter "external hard drive not recognized" issue. This issue may be caused by different reasons, and you need to use different methods to deal with it. Here, we recommend you to read this post to learn some available solutions: Solved - External Hard Drive Not Recognized.

2. Capacity Calculation Method

In general, the hard drive capacity which is reported by an operating system is smaller than the amount stated by manufacturers. Why? There are some possible reasons: the operating system occupying some space, some space for data redundancy or file system structure. The difference between true SI-based units and binary prefixes can also cause capacity difference.

For example, the total capacity of hard disks is given by manufacturers in SI-based units such as gigabytes (1 GB = 109 bytes) and terabytes (1 TB = 1012 bytes). But Windows operating system uses the binary convention when reporting storage capacity such as gigabytes (1 GB = 230 bytes) and terabytes (1 TB = 240 bytes).

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In addition, hard disk needs to be partitioned and formatted before using. More disk capacity will be taken up for they are installed in different operating systems and the action of file copy will happen when Windows operating system is installed. So the actual capacity in operating system doesn't match the nominal capacity. And it is normal when the difference is between 5% - 10%. Here, you can use a piece of professional partition software to manage your new hard drive. MiniTool Partition Wizard is a good choice.

So, when the hard drive capacity shown in your Windows computer is smaller than the capacity advertised by manufacturers, you should consider these reasons.