The data storage converter on this page converts between bits, bytes, and every common decimal and binary storage unit β kilobytes, megabytes, gigabytes, terabytes, petabytes, and their binary counterparts kibibytes, mebibytes, gibibytes, and tebibytes β using exact, non-approximated factors. If you've ever bought a "1 TB" hard drive and been confused when your operating system reported only about 931 GB of usable space, this tool exists specifically to clear that up, because the mismatch is not a manufacturing defect β it's two different, both-correct definitions of the same-sounding units colliding.
Arb Digital built this calculator as part of our free everyday tools collection because storage math trips up developers, IT professionals, and everyday computer users alike, and getting it wrong can lead to real confusion when planning backups, cloud storage costs, or file transfers.
What This Data Storage Converter Does
Enter a value, pick the unit you're converting from, and pick the unit you want it in β the tool instantly shows the exact converted amount, plus a reference grid comparing the same value in raw bytes, decimal gigabytes (GB), and binary gibibytes (GiB), along with the percentage gap between the decimal and binary interpretation at that size. This side-by-side view is exactly what makes storage math confusing in the first place: the same number of bytes can honestly be described with two different labels depending on which standard you're using.
The tool routes every conversion through a single base unit β the byte β so a conversion like kibibytes to megabytes goes KiB β bytes β MB using exact multiplication, never chained rounded approximations.
How to Use It
- Enter your value. Type the number you want to convert.
- Choose the "From" unit. Select whether your original figure is in bits, bytes, decimal units (KB/MB/GB/TB/PB), or binary units (KiB/MiB/GiB/TiB).
- Choose the "To" unit. Select the unit you want the result expressed in.
- Read the result. The big number updates instantly, and the grid shows the equivalent in bytes, decimal GB, and binary GiB simultaneously, plus the percentage gap between the two systems at that magnitude.
- Swap when needed. Click "Swap Units" to reverse the from/to selection instantly.
The Formula / How It's Calculated
Every unit converts to bytes using a fixed factor. A bit is 1/8 of a byte (there are 8 bits per byte). Decimal units follow the International System of Units, where each prefix multiplies by exactly 1,000: 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 GB = 1,000,000,000 bytes, 1 TB = 1,000,000,000,000 bytes, and 1 PB = 1,000,000,000,000,000 bytes. Binary units, standardized by the International Electrotechnical Commission (IEC) in 1998 specifically to resolve this ambiguity, multiply by exactly 1,024 (which is 2ΒΉβ°) at each step: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes (1,024Β²), 1 GiB = 1,073,741,824 bytes (1,024Β³), and 1 TiB = 1,099,511,627,776 bytes (1,024β΄). For the authoritative IEC binary prefix standard, see the NIST reference on IEC binary prefixes.
Why 1000 vs. 1024 Even Exists β The Decimal vs. Binary Story
Computers fundamentally work in binary, and memory addressing naturally falls into powers of two β 1,024 (2ΒΉβ°) is a convenient, "round" number in binary even though it looks odd in decimal. For decades, the computing industry informally borrowed the metric prefixes "kilo," "mega," and "giga" (which properly mean exactly 1,000, 1,000,000, and 1,000,000,000 in every other scientific context) and repurposed them to mean 1,024, 1,048,576, and 1,073,741,824 instead, because that matched how memory chips and file systems actually counted. This worked fine as an internal shorthand among engineers, but it created a lasting conflict once storage devices were marketed to the general public.
Hard drive and SSD manufacturers, quite reasonably, use the metric definition: 1 GB literally means 1,000,000,000 bytes, matching every other scientific use of "giga." Operating systems like Windows, however, historically report file and drive sizes using the binary definition while still labeling them "GB" or "TB" instead of the technically correct "GiB" or "TiB." The result: a drive marketed and manufactured as exactly 1,000,000,000,000 bytes (1 TB, decimal) gets divided by 1,024β΄ instead of 1,000β΄ by the operating system's reporting tool, producing a number around 931 β hence "your 1 TB drive shows as 931 GB." Nothing is missing or defective; it's the same physical bytes, described with two different, both technically valid, units.
The IEC introduced kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), and tebibyte (TiB) in 1998 precisely to give binary quantities their own unambiguous names, so that "GB" could be reserved for the clean decimal meaning and "GiB" for the binary one. Adoption has been slow and inconsistent β macOS and modern Linux distributions have shifted toward decimal-based reporting for drive capacities in recent years, while Windows' File Explorer still reports binary values labeled as decimal units, which is exactly why this discrepancy still confuses people today.
Real-World Impact: Cloud Storage, Downloads, and Internet Plans
This 1000-vs-1024 gap compounds as numbers get larger, which is why the confusion is worse for terabytes than for kilobytes. At the kilobyte level the difference is only 2.4%, but by the terabyte level it grows to a full 10% β meaning a "2 TB" drive (2,000,000,000,000 bytes) reports as roughly 1.818 TiB in a binary-reporting operating system. This matters when budgeting cloud storage plans (most cloud providers, including AWS and Google Cloud, bill and display storage in true decimal or true binary units β check which one your invoice uses), planning backups where "how many GB do I actually have left" needs a precise answer, and understanding why download managers, video game install sizes, and photo library apps sometimes report noticeably different totals for what should be the same folder of files.
Photographers and videographers dealing with large RAW image and 4K video libraries run into this constantly when planning how many files fit on a memory card or external drive β a "128 GB" card is manufactured as 128,000,000,000 bytes, but photo management software might report available space in GiB, making the card appear to hold noticeably fewer files than the marketed capacity implied. Similarly, RAM (memory) has always been measured in true binary units without the decimal-vs-binary confusion that affects storage drives, because memory chips are physically organized in binary address spaces β this is part of why "8 GB of RAM" and "8 GB of hard drive space" behave consistently within their own category but can seem inconsistent when compared side by side.
How Developers and IT Professionals Use This Converter
Software developers frequently need to convert between units when setting memory limits, estimating database growth, or sizing server infrastructure. A common task is converting a memory limit specified in MiB (as many programming languages and container platforms like Docker or Kubernetes use for memory allocation) into a decimal MB figure for a client-facing capacity report, or vice versa. Network engineers regularly convert between bits and bytes when translating a bandwidth cap in Mbps into an expected file transfer time in MB or GB β a task that trips up beginners because the "8" factor between bits and bytes is easy to forget under time pressure. IT administrators provisioning cloud storage buckets or calculating backup retention costs need precise conversions to avoid under- or over-provisioning, since even a small percentage error at the petabyte scale of enterprise storage can translate into a meaningful cost difference on a monthly invoice.
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Talk to Arb Digital All Free ToolsCommon Mistakes to Avoid
- Assuming "GB" always means the same thing. Context matters β hard drive marketing uses decimal GB (1,000Β³ bytes), while many operating systems label binary GiB values as "GB."
- Mixing bits and bytes. Internet speeds are usually advertised in megabits per second (Mbps), while file sizes are shown in megabytes (MB) β 1 byte is 8 bits, so a "100 Mbps" connection downloads at roughly 12.5 MB/s at best, not 100 MB/s.
- Expecting a drive's "listed" and "reported" capacity to match exactly. A 1 TB drive showing 931 GB in Windows is not missing storage β it's the same bytes measured with a different unit system.
- Rounding too early in multi-step conversions. Always convert through a single base unit (bytes) rather than chaining KB β MB β GB with rounded intermediate values.
- Forgetting that some file systems and OS overhead genuinely do reduce usable space. Beyond the 1000-vs-1024 labeling gap, formatting, the file system's own metadata, and reserved system space also reduce the actual free space you see, separate from the unit-definition issue.
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Frequently Asked Questions
A "1 TB" drive is manufactured to hold exactly 1,000,000,000,000 bytes (decimal terabyte). Windows reports storage using binary units (1 TiB = 1,099,511,627,776 bytes) but labels them "TB," so dividing 1,000,000,000,000 by 1,024β΄ gives approximately 931 β hence 931 GB shown instead of 1,000.
A gigabyte (GB) is exactly 1,000,000,000 bytes under the decimal (SI) standard. A gibibyte (GiB) is exactly 1,073,741,824 bytes under the binary (IEC) standard. A gibibyte is about 7.4% larger than a gigabyte.
One gibibyte (GiB) equals exactly 1,073,741,824 bytes, calculated as 1,024 cubed (1,024 Γ 1,024 Γ 1,024).
There are exactly 8 bits in one byte. This is a fixed, universal definition used across all computing systems.
Internet and telecommunications speeds are traditionally advertised in bits per second (like Mbps) because data transmission over networks was historically measured bit-by-bit, whereas file and storage sizes use bytes. Divide Mbps by 8 to estimate megabytes per second.
Both are correct β they're simply different, officially standardized systems. Decimal (SI) units use multiples of 1,000 and are used by manufacturers and the International System of Units. Binary (IEC) units use multiples of 1,024 and are typically what operating systems calculate internally, sometimes mislabeled with decimal unit names.
This tool runs entirely in your browser β no data is sent to any server, and results update instantly as you type.
