Why does my new hard drive show less capacity than advertised?

Manufacturers use decimal (1,000) units, so 1 TB = 1,000,000,000,000 bytes. Operating systems often use binary (1,024) units, so 1 TB = 1,099,511,627,776 bytes. This difference makes the drive appear smaller in your OS.

What is the difference between decimal and binary units?

Decimal units (KB, MB, GB) are based on powers of 1,000, while binary units (KiB, MiB, GiB) are based on powers of 1,024. For example, 1 MB = 1,000,000 bytes, but 1 MiB = 1,048,576 bytes.

How do I convert between bits and bytes?

1 byte = 8 bits. To convert bits to bytes, divide by 8. To convert bytes to bits, multiply by 8. This calculator handles both directions for all units.

Conversion

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Convertisseur de Taille de Données.

Convertissez entre bits, octets, Ko, Mo, Go, To et Po — et entre les normes décimale (1 000) et binaire (1 024) qui font paraître votre nouveau disque plus petit qu'annoncé.

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Cite this calculator

Canonical URL: https://mathify.one/fr/conversion/data-size

Cite as: Mathify. (n.d.). Convertisseur de Taille de Données. https://mathify.one/fr/conversion/data-size

Use Cases

Check actual storage capacity

Compare advertised drive size (decimal) with the capacity shown by your OS (binary) to understand the difference.

Example: A 500 GB drive (decimal) shows as about 465 GiB in Windows.

Estimate file transfer sizes

Convert file sizes between units to estimate download times or storage needs, especially when dealing with large media files.

Example: Convert 2.5 GB to MB to see if it fits on a 4.7 GB DVD.

Frequently Asked Questions

Why does my new hard drive show less capacity than advertised?: Manufacturers use decimal (1,000) units, so 1 TB = 1,000,000,000,000 bytes. Operating systems often use binary (1,024) units, so 1 TB = 1,099,511,627,776 bytes. This difference makes the drive appear smaller in your OS.
What is the difference between decimal and binary units?: Decimal units (KB, MB, GB) are based on powers of 1,000, while binary units (KiB, MiB, GiB) are based on powers of 1,024. For example, 1 MB = 1,000,000 bytes, but 1 MiB = 1,048,576 bytes.
How do I convert between bits and bytes?: 1 byte = 8 bits. To convert bits to bytes, divide by 8. To convert bytes to bits, multiply by 8. This calculator handles both directions for all units.

Tips & Common Mistakes

Tips

Always check whether your device uses decimal or binary units to avoid confusion.
When comparing storage, use the same standard (decimal or binary) for accurate results.
Remember that 1 byte = 8 bits, so a 100 Mbps connection transfers about 12.5 MB per second.
Use binary units (KiB, MiB) when working with RAM or file systems that use 1024-based calculations.

Common Mistakes to Avoid

Assuming 1 KB = 1,024 bytes when the calculator uses decimal (1,000) by default.
Confusing bits and bytes, leading to off-by-8 errors in conversions.
Mixing decimal and binary units in the same calculation without converting.

Last updated: August 13, 2026