Data Size Converter

Convert digital storage units free online -- bytes, KB, MB, GB, TB. Choose decimal (1000-based, as drives are marketed) or binary (1024-based, as operating systems report).

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How to Use This Tool

Choose decimal or binary modeDecimal for storage marketing, binary for OS file sizes

Enter a value and unitsBytes through terabytes

See the converted resultCalculated using the selected base

The "Missing Storage" Mystery, Explained

Buy a drive marketed as 1TB and your operating system reports roughly 931GB -- not a manufacturing shortfall, but two different, both legitimate, definitions of what a terabyte means. Storage marketing uses decimal (1000-based) units; operating systems typically calculate and display using binary (1024-based) units, and the gap between those two bases widens as the numbers get larger.

Why Both Systems Are "Correct"

Decimal units follow the standard metric prefix convention used throughout science (kilo = 1000). Binary units reflect how computer memory actually addresses in powers of 2 (1024 = 2^10), which is genuinely how computers organize memory at a hardware level. Neither is wrong -- they're answering slightly different questions about the same data.

Choosing the Right Mode for Your Comparison

If you're comparing a drive's marketed capacity to what your OS reports, you need to understand both bases are in play. If you're just converting within one consistent context (like calculating file sizes your OS will display), binary mode matches that context's actual calculation method more accurately.

Frequently Asked Questions

Storage manufacturers market capacity using decimal (1000-based) units, while operating systems typically display capacity using binary (1024-based) calculations -- a 1TB drive marketed as 1,000,000,000,000 bytes shows as roughly 931GB when an OS calculates it using 1024 as the base, which is the actual source of this commonly noticed discrepancy.

Decimal units (kilobyte = 1000 bytes) follow the standard metric prefix convention. Binary units (kibibyte = 1024 bytes) reflect how computers actually address memory in powers of 2. Both are legitimate, standardized definitions -- the discrepancy comes from which one a specific context uses.

Because both are genuinely used in different contexts -- storage marketing and network speeds typically use decimal, while operating system file size displays and memory specifications typically use binary -- and picking the wrong mode for your specific comparison produces a misleading result.

Technically, KiB/MiB/GiB (kibibyte/mebibyte/gibibyte) are the official binary-based unit names, while KB/MB/GB are technically decimal-based -- though in casual usage, KB/MB/GB get used informally for both, which is exactly the ambiguity this calculator's mode toggle resolves.

Internet speeds are conventionally measured in bits per second (Mbps), while file sizes are measured in bytes -- an 8x difference that's a separate, common source of confusion from the decimal/binary issue, worth keeping in mind when comparing a download speed to a file size.