Conversions

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Data Size Converter.

Convert between bits, bytes, KB, MB, GB, TB and PB — and between the decimal (1,000) and binary (1,024) standards that make your new drive look smaller than advertised.

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Which standard?

1 KB = 1,000 bytes. This is the SI standard used by hard drive and SSD manufacturers, and by most network and storage marketing.

How to Use

KB = 1,000 bytes (SI decimal, what drive manufacturers print on the box). KiB = 1,024 bytes (IEC binary, what your operating system actually reports). The gap compounds at every step, which is why a 1 TB drive shows up as about 931 GB in Windows.

8 bits = 1 byte. Network speeds are quoted in bits per second (Mbps) while file sizes are in bytes (MB), so a 100 Mbps line downloads at roughly 12.5 MB/s at best.

RAM is always measured in binary units, and file sizes in most operating systems are too, even when the label says MB or GB.

FAQs

Is 1 GB 1000 MB or 1024 MB?

Both answers are used, which is the whole confusion. Under the SI decimal standard, 1 GB = 1,000 MB — this is what hard drive, SSD and USB manufacturers print on the box. Under the binary standard, 1 GiB = 1,024 MiB, and that is what your operating system reports. Use the decimal/binary toggle on this page to switch between them.

Why does my 1 TB hard drive only show 931 GB?

The manufacturer sold you 1 TB = 1,000,000,000,000 bytes (decimal). Windows then divides by 1,024 three times and labels the result 'GB' even though it is really GiB: 1,000,000,000,000 / 1024³ ≈ 931. No storage is missing — the two sides are just using different definitions of the same word.

What is the difference between KB and KiB?

KB (kilobyte) is 1,000 bytes under the SI standard. KiB (kibibyte) is 1,024 bytes under the IEC standard introduced in 1998 specifically to remove this ambiguity. The gap is 2.4% at the kilobyte level but compounds to about 10% by the terabyte level.

How many MB is a GB for file sizes on my computer?

On Windows and most Linux file managers, treat 1 GB as 1,024 MB, because those systems report binary sizes under decimal labels. macOS has used true decimal units (1 GB = 1,000 MB) since OS X 10.6, so a file's reported size differs slightly between the two platforms.

Why is my 100 Mbps internet only downloading at 12 MB/s?

Network speeds are quoted in bits per second, file transfers in bytes per second, and there are 8 bits in a byte. 100 Mbps ÷ 8 = 12.5 MB/s, which is the theoretical maximum before protocol overhead. Switch the 'from' unit to bits on this page to convert between the two.

Cite this calculator

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

Cite as: Mathify. (2026). Data Size Converter. https://mathify.one/en/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