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

Drive boxes advertise terabytes in decimal units, where 1 TB equals 1,000,000,000,000 bytes. Windows reports sizes in binary units, where 1 TiB equals 1,099,511,627,776 bytes. After formatting and the binary recount, 1 TB of decimal capacity shows up as roughly 931 GiB on screen.

What is the difference between MB and MiB?

MB (megabyte) is the decimal prefix and equals 1,000,000 bytes. MiB (mebibyte) is the binary prefix and equals 1,048,576 bytes. The two differ by about 4.9%, and the gap widens as you move up to GB versus GiB, TB versus TiB, and so on.

Do cloud storage plans use decimal or binary units?

Most consumer cloud plans, including Google Drive, Dropbox, and iCloud, advertise storage in decimal units so the numbers look round. A "2 TB" plan therefore contains 2,000 GB of decimal capacity, even though your operating system may report it using binary labels.

How many bytes are in a kilobyte?

There are 1,000 bytes in a decimal kilobyte and 1,024 bytes in a binary kilobyte (also called a kibibyte). The Data Storage Converter lets you pick which definition to use so every number downstream stays consistent with the standard you chose.

Can I convert bits to bytes and back?

Yes. One byte is always 8 bits regardless of standard, so any storage tool with a bits option can flip between bits and bytes directly. The Data Storage Converter includes bits as a unit so you can also scale up to kilobits, megabits, and gigabits for network-speed work.

Which standard should I pick for RAM?

RAM modules are usually labeled in decimal by the maker, but the operating system reports them in binary. If you want the figure your OS shows, pick binary; if you want the figure printed on the stick, pick decimal.

How to Change Cloud Storage Units Accurately

A data storage unit conversion is a calculation that translates one size of digital information into another — for example, turning 4,096 megabytes into 4 gigabytes, or expressing a 2-terabyte drive as 2,000 gigabytes. The conversion uses one of two prefix standards: decimal (SI), where every step up multiplies by 1,000, and binary (IEC), where every step up multiplies by 1,024. Picking the right standard matters because the same number written in MB can mean two different real-world byte counts depending on who is talking. The fastest way to get an exact answer is to load your value into the Data Storage Converter, choose the standard that matches your context, and read the converted result instantly in the unit you need.

Most people land on this page after seeing two numbers that don't agree. A new SSD box says 1,000 GB. The operating system says 931 GB. Neither is wrong — they're just speaking two different dialects of "giga." Once you understand the difference between decimal and binary prefixes, the math stops being mysterious and starts being a simple multiplication chain. The rest of this guide walks through what each standard means, why the gap exists, and exactly how to flip between units using the Data Storage Converter.

Decimal vs Binary Storage Prefixes

The decimal standard, formalized by the International System of Units, treats every prefix as a tidy power of 1,000. One kilobyte is 1,000 bytes, one megabyte is 1,000 kilobytes, and so on up to the petabyte. Hard drive makers, SSD spec sheets, and most cloud-storage marketing pages use this convention because the round numbers look bigger on the box. The binary standard, defined by the International Electrotechnical Commission, treats every prefix as a power of 1,024 because computers address memory in chunks that are naturally powers of two. Windows, macOS file explorers, and many Linux tools default to binary, which is why a "1 TB" drive appears as roughly 931 GB once it's formatted.

Prefix	Decimal (×1,000)	Binary (×1,024)
Kilobyte (KB / KiB)	1,000 bytes	1,024 bytes
Megabyte (MB / MiB)	1,000,000 bytes	1,048,576 bytes
Gigabyte (GB / GiB)	1,000,000,000 bytes	1,073,741,824 bytes
Terabyte (TB / TiB)	1,000,000,000,000 bytes	1,099,511,627,776 bytes
Petabyte (PB / PiB)	1,000,000,000,000,000 bytes	1,125,899,906,842,624 bytes

The table shows the official byte counts per the IEC 80000-13 and SI conventions. The percentage gap grows as you climb the scale: at the kilobyte level the two standards differ by only 2.4%, but by the terabyte level the binary number is roughly 10% larger than the decimal one. That compounding gap is the entire reason a "1 TB" drive seems to "lose" storage when you plug it in.

How to Convert Storage Units With the Data Storage Converter

The Data Storage Converter handles the multiplication chain for you, so you never have to memorize whether a gigabyte is 10⁹ or 2³⁰ bytes. Follow the steps below to switch between any two storage units in either standard.

Open the Data Storage Converter and locate the storage value field at the top of the tool.
Type the amount you want to convert into that field. Whole numbers like 512 or decimals like 1.75 both work.
Pick the prefix standard that matches your context. Choose Decimal (1000) for drive labels, spec sheets and cloud-plan marketing. Choose Binary (1024) for what your operating system shows in File Explorer or Finder.
Select the source unit from the first dropdown — for example, Gigabyte (GB) if that's how your number is currently labeled.
Select the target unit from the second dropdown — for example, Megabyte (MB) if you want the same value expressed in MB.
Read the converted result in the output box. It updates instantly as you change any input, so there's no submit button to press.
Tick the "Show all units at once" checkbox if you want to see bits, bytes, KB, MB, GB, TB and PB on the same screen for a side-by-side comparison.

If you need to flip standards mid-task — say, a cloud plan that advertises TB in decimal but your laptop reports GB in binary — leave the number alone, switch the standard toggle, and re-read the output. The tool recalculates from raw bytes, so the result stays internally consistent.

When to Use Decimal vs Binary

Use the decimal standard for anything that comes from a manufacturer, ISP or cloud vendor's pricing page. A 2 TB Google Drive plan, a 500 GB microSD card, and a 1 TB SSD on Amazon are all advertised in decimal units because the SI prefixes let the numbers look cleaner. Use the binary standard for anything you read on a formatted drive inside your operating system, including the Windows "This PC" pane, macOS storage settings, and most Linux df -h output.

For network speeds and download quotas, the decimal standard is also the convention — a 100 Mbps connection transfers 100 megabits per second in decimal terms. For RAM sizing, the binary standard is more accurate: a stick labeled "8 GB" by the maker holds 8,000,000,000,000 bytes, but the operating system shows it as 7.45 GiB because of the 1,024 multiplier. Knowing which side of the conversation you're on saves you from quoting the wrong number when capacity comes up.

Common Storage Conversion Tasks

The most common reason people search for a conversion is to check whether a file will fit on a drive, or to compare two cloud plans that quote different units. A 4.7 GB DVD image, for example, fits comfortably on a "5 GB" cloud allowance only if both numbers use the same standard. A 25 GB Blu-ray rip does not fit on a 25 GB OneDrive free tier if OneDrive is using decimal GB and your rip is measured in binary GiB.

Another common task is translating between bits and bytes when reading network speeds. A 1 Gbps fiber link delivers 1,000 megabits per second in decimal, which equals 125 megabytes per second in the same standard. Photographers and video editors often need to convert between GB and TB to plan backup storage, and developers routinely translate between bytes and bits when estimating upload sizes for APIs.

Tips for Accurate Storage Conversions

Always check which standard the source number uses before converting. If a cloud provider quotes "1 TB" on its pricing page, treat it as decimal unless the page explicitly says otherwise. If Windows reports your drive as 931 GB, treat that as binary even though the label says "GB" — Windows still uses binary units despite the SI-style prefix. The Data Storage Converter makes this easy because you can flip standards with one click and compare the two results directly.

When documenting capacity for a client or a ticket, write the standard next to the number. "500 GB (decimal)" and "465 GiB (binary)" remove all ambiguity and prevent the same confusion you ran into. For very large numbers in the petabyte range, prefer the decimal standard unless you have a specific reason to use binary, because the gap between the two grows past 10% and misquoting a petabyte by even a few percent is a real budget concern.

If you also work with screen resolutions or print sizing, the Pixels to CM Converter handles the pixels-to-physical-size side of digital media. For everyday length work alongside storage estimates, the Length Converter covers millimeters through miles in one place. And if your storage question is really about file sizes in code or scripting contexts, the Number Base Converter lets you flip between binary, decimal and hex representations of the same byte count.

Once you're comfortable with storage units, the same "decimal versus binary" idea shows up in time conversions — a year is about 365.25 days in the calendar sense but exactly 31,557,600 seconds in the SI sense, and tools like the Time Converter let you move between nanoseconds and years without losing precision.

Quick Reference: Bit and Byte Anchors

For any storage conversion, it helps to anchor the chain to bits and bytes. One byte is always 8 bits, regardless of standard. From there, every prefix multiplies by either 1,000 (decimal) or 1,024 (binary). The Data Storage Converter starts from this anchor and scales up, so even unusual conversions — say, terabytes to bits — give an exact answer with the standard chosen clearly labeled. Keeping that mental anchor turns storage math from a guessing game into a one-step lookup.

Whether you are sizing a backup, comparing cloud plans, or just trying to figure out why a brand-new drive shows less space than the box promised, the converter does the arithmetic and keeps the standard honest. Load your number, pick the side of the conversation you are on, and read the result.