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Data Size Converter

Data size conversions are confusing because of two competing standards: SI (1 KB = 1,000 bytes, used by hard drive manufacturers) and IEC (1 KiB = 1,024 bytes, used by operating systems). This discrepancy is why a "1 TB" hard drive shows as ~931 GB in Windows. Our converter handles both systems and explains the difference clearly.

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About the Data Storage Size Converter

Data size conversions are confusing because of two competing standards: SI (1 KB = 1,000 bytes, used by hard drive manufacturers) and IEC (1 KiB = 1,024 bytes, used by operating systems). This discrepancy is why a "1 TB" hard drive shows as ~931 GB in Windows. Our converter handles both systems and explains the difference clearly.

How to use it

  1. Enter a value and select the unit (bit, byte, KB, MB, GB, TB, KiB, MiB, GiB, TiB).
  2. See conversions across all units in both SI and IEC standards.
  3. Toggle between SI (powers of 10) and IEC (powers of 2) display.
  4. Use the "hard drive vs OS display" comparison to understand the real vs advertised capacity gap.

Formula & methodology

SI: 1 KB = 10³ bytes = 1,000 bytes. 1 MB = 10⁶ bytes. 1 GB = 10⁹ bytes. 1 TB = 10¹² bytes. IEC: 1 KiB = 2¹⁰ bytes = 1,024 bytes. 1 MiB = 2²⁰ bytes. 1 GiB = 2³⁰ bytes. 1 TiB = 2⁴⁰ bytes. Bit/byte: 8 bits = 1 byte. Network speeds in bits/s; storage in bytes.

Common use cases

  • Understanding why a "1 TB" drive shows as 931 GB in Windows
  • Calculating required storage for a video at a given bitrate and duration
  • Comparing internet speeds (Mbps) to file download time (MB file ÷ MB/s = seconds)
  • AWS/cloud cost estimation: pricing in GB vs GiB
  • Embedded development: RAM and flash sizing in KiB/MiB

Frequently asked questions

Hard drive manufacturers use the SI (decimal) definition because it makes their drives sound larger. A 1,000,000,000,000-byte drive is marketed as "1 TB." Operating systems use binary (IEC) definitions: 1 TiB = 2⁴⁰ bytes = 1,099,511,627,776 bytes. The gap: 1 "TB" drive = only 0.909 TiB in OS terms.
Historical convention: early serial communication was measured in bits per second (baud rate). File sizes evolved from byte-addressable memory. The distinction matters practically: a 100 Mbps (megabits/second) connection downloads at ~12.5 MB/second. Always check whether a speed figure is Mb (megabits) or MB (megabytes).

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