Why Hard Drive Capacity is Less Than Advertised

Learn why your 1TB hard drive shows only 931GB or 953GB due to differences in binary and decimal measurement.
Why Hard Drive Capacity is Less Than Advertised

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Recently, customers in the DIY market have been consulting us about why hard drive capacities shown are not the same as the nominal ones, with actual capacities being slightly less. They wonder why their self-purchased 1TB hard drive only shows 931GB or 953GB.

To address this issue, let me provide some related information.

The discrepancy in hard drive capacity is often attributed to the difference in calculation methods between hard drive manufacturers and Windows operating systems.

Manufacturers typically use decimal notation to represent storage capacity, while operating systems use binary calculations.

Manufacturers: 1TB = 1000 bytes * 1000 kilobytes * 1000 megabytes * 1000 gigabytes, in decimal GB;

Operating systems: 1TB = 1024 bytes * 1024 kilobytes * 1024 megabytes * 1024 gigabytes, in binary GiB;

So, the operating system displays the capacity as:

However, some hard drive manufacturers may use calculations based on 1000GB, or they might use 1024GB. Therefore, the operating system displays the capacity as:

Hence, when consumers purchase a 1TB hard drive and find that it’s not exactly 1024GB or 1000GB, but actually only 931GB or 953GB, the main reason is the difference in calculation between hard drive manufacturers and operating systems.

This calculation method can also be applied to other capacity hard drives, such as 500GB, 512GB, 2TB, etc., to determine the actual displayed capacity by the system:

500GB * 0.93132 ≈ 465.66GB;

512GB * 0.93132 ≈ 476.83GB;

1000GB * 0.93132 ≈ 931.32GB;

2000GB * 0.93132 ≈ 1862.64GB;

Certainly, not only solid-state drives and mechanical hard drives but also TF memory cards, USB drives, external hard drives, etc., require such calculations to determine the actual displayed capacity by the system. Hopefully, this knowledge helps to clear up any confusion.

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DiskMFR Field Sales Manager - Leo

It’s Leo Zhi. He was born on August 1987. Major in Electronic Engineering & Business English, He is an Enthusiastic professional, a responsible person, and computer hardware & software literate. Proficient in NAND flash products for more than 10 years, critical thinking skills, outstanding leadership, excellent Teamwork, and interpersonal skills.  Understanding customer technical queries and issues, providing initial analysis and solutions. If you have any queries, Please feel free to let me know, Thanks

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