Digital Unit Converter: Bits, Bytes, MB, MiB, GB and TB

Convert digital storage units quickly and accurately with our free online Digital Unit Converter.

A "1 TB" drive that shows up as 931 GB, a download that is "100 megabits" but saves at 12.5 megabytes, a 256 MiB file that another program calls 268 MB. None of these is a mistake: they come from two different ways of counting data, and from the difference between bits and bytes. This free converter handles both, so you can see exactly where the numbers come from.

Choose a value, pick the source and target units, and press Convert. It converts between bits, bytes, decimal units (KB, MB, GB, TB) and binary units (KiB, MiB, GiB, TiB), and lets you control the number of decimal places. Below the tool you will find the difference between MB and MiB explained, worked examples, and a note on how rounding works.

Digital Unit Converter

The converter is loading. If this message does not disappear, JavaScript did not start on this page. See the troubleshooting note below the tool.

Troubleshooting: if you still see the "loading" message above, JavaScript did not start. Reload the page, make sure JavaScript is enabled, and try another browser. If the tool says that BigInt is not supported, the converter has turned itself off, and you should update your browser.

How to use the converter

1. Enter the amount. Use a dot for decimals. Commas work as thousands separators (1,250), but a comma used as a decimal mark (12,5) is rejected, because it could mean two different numbers.
2. Choose the units. Each unit shows its size in bytes. Decimal units (KB, MB, GB, TB) are based on 1,000. Binary units (KiB, MiB, GiB, TiB) are based on 1,024. Use Swap to reverse the direction.
3. Set the precision. Pick 0 to 10 decimal places. Leave Remove trailing zeros on for a clean result (1.819), or turn it off to see the full width (1.8190).
4. Press Convert. You get the result plus the exact conversion factor, the same amount in bytes and in bits, and the definition of both units. Changing a unit or the precision updates the result automatically.
5. Copy or reset. Copy result copies the text. Reset restores the defaults (500 GB to GiB, 4 decimal places).

MB or MiB? Decimal and binary units explained

For most of computing history, people borrowed the metric prefixes (kilo, mega, giga) to mean powers of 1,024 instead of 1,000, because 1,024 (2¹⁰) is the closest power of two to 1,000. In 1998 the International Electrotechnical Commission approved separate names for the binary multiples: kibi, mebi, gibi and tebi, with the symbols Ki, Mi, Gi and Ti. NIST lists them on its page on prefixes for binary multiples.

Decimal unit	Size in bytes	Binary unit	Size in bytes	Binary is larger by
KB (kilobyte)	1,000	KiB (kibibyte)	1,024	2.4%
MB (megabyte)	1,000,000	MiB (mebibyte)	1,048,576	4.9%
GB (gigabyte)	1,000,000,000	GiB (gibibyte)	1,073,741,824	7.4%
TB (terabyte)	1,000,000,000,000	TiB (tebibyte)	1,099,511,627,776	10.0%

The gap grows with each step, which is why the difference is barely noticeable for kilobytes and obvious for terabytes. This converter never guesses what "KB" or "MB" means: KB, MB, GB and TB are always decimal, and KiB, MiB, GiB and TiB are always binary. If another program shows "MB" for a size, check whether it means 1,000,000 or 1,048,576 bytes, because some software still uses the decimal labels for binary sizes.

Worked examples

Example 1: why a 2 TB drive shows less

Input: 2 TB to TiB, 4 decimal places.
Result: 1.819 TiB (1.8190 with trailing zeros kept). A drive sold as 2 TB holds 2,000,000,000,000 bytes, and a tebibyte is 1,099,511,627,776 bytes. If a program counts in binary units but labels them TB, it shows about 1.82. File systems and reserved areas also use some space, so the free space you see can be lower still.

Example 2: binary to decimal

Input: 1 GiB to MB, 6 decimal places.
Result: 1,073.741824 MB. A gibibyte is 1,073,741,824 bytes, which is 1,073.741824 megabytes. With 4 decimal places the same result reads 1,073.7418 MB.

Example 3: staying inside the binary family

Input: 256 MiB to KiB.
Result: 262,144 KiB, because 256 × 1,024 = 262,144. Converting the same 256 MiB to MB gives 268.435456 MB (268.4355 at 4 decimal places).

Example 4: bits and bytes

Input: 100,000,000 bit to MB, 4 decimal places.
Result: 12.5 MB. A "100 megabit" amount is 12.5 megabytes, because a byte is 8 bits. Internet speeds are usually quoted in bits per second, and file sizes in bytes. This tool converts amounts, so for a speed in megabits per second, enter the number of bits and read the megabytes. The "per second" part carries over unchanged.

Example 5: how the precision setting changes the result

Input: 1 MB to GiB.
Result: with 4 decimal places it reads 0.0009 GiB. With 10 decimal places it reads 0.0009313226 GiB. Both come from the same exact value, and only the rounding differs. If the exact result is not zero but is too small for the chosen precision, the tool adds a note telling you to increase the decimal places.

How the conversion works and how results are rounded

• Bits as the common base. Every unit is stored as a number of bits (1 byte = 8 bits, 1 KB = 8,000 bits, 1 KiB = 8,192 bits, and so on). The result is value × (bits in the source unit) ÷ (bits in the target unit).
• Exact arithmetic. The tool calculates with whole numbers and fractions rather than ordinary floating-point numbers, so large values and long decimals do not pick up tiny errors.
• Rounding. The exact result is rounded once, at the end, to the number of decimal places you chose. A value exactly halfway is rounded up. If you ask for 0 decimals, you get a whole number.
• Trailing zeros. Removing trailing zeros only changes how the number is written, not its value.
• Conversion factor. The factor shown is the exact value of one source unit in the target unit, shown with up to 15 decimal places.

Limitations and common mistakes

• Bit versus byte. A lowercase b means bit and an uppercase B means byte. Mixing them up changes a result by a factor of 8.
• Mixing decimal and binary. GB and GiB are different sizes. The tool warns you when you convert between the two families.
• Labels in other software. Programs and devices do not always follow the same convention. Always check which one a given number uses.
• Amounts, not speeds. The converter changes the size of an amount of data. It does not calculate download time, and it does not include protocol overhead or file system overhead.
• Negative values. A data size cannot be negative, so the tool rejects negative numbers.
• Size limits. Up to 30 digits before the decimal point and 20 after it.
• Browser support. The exact arithmetic needs a browser that supports BigInt, which is the case for current versions of the major browsers.

When this converter is useful

• Checking why a new drive, memory card or USB stick shows a different capacity from the one on the box.
• Estimating whether a file will fit on a drive before you copy it. If space is tight, see our guide to freeing up storage on Windows 11.
• Comparing a cloud storage allowance with the size of your files.
• Turning an internet speed in megabits into megabytes for download planning.
• Writing documentation or a spreadsheet with the correct, unambiguous unit symbols.

Frequently asked questions

Why does my 1 TB drive show less than 1 TB?

A drive sold as 1 TB holds 1,000,000,000,000 bytes. A system that counts in binary units shows about 0.9095 TiB, or 931.3226 GiB, for the same drive. The numbers are consistent. They just use different units, and some programs print the binary figure with decimal labels.

What is the difference between MB and MiB?

A megabyte (MB) is 1,000,000 bytes. A mebibyte (MiB) is 1,048,576 bytes, which is about 4.9% larger.

Is 1 KB equal to 1,000 or 1,024 bytes?

In this converter, 1 KB is 1,000 bytes and 1 KiB is 1,024 bytes. Other software may use KB for either, so check the convention it follows.

How does the rounding work?

The exact result is rounded once, at the end, to the decimal places you choose. Values exactly halfway are rounded up. Turning off "Remove trailing zeros" shows every digit you asked for.

Can it convert megabits per second to megabytes per second?

Yes, for the size part. A megabit is 1,000,000 bits, and a byte is 8 bits, so 100 megabits is 12.5 megabytes. Enter the number of bits and convert to MB. The "per second" stays the same.

Does the tool store or send what I enter?

No. The conversion runs in your browser, and the tool does not send, save or log your numbers. As with any page on this site, the page itself may load ads or analytics described in our Privacy Policy.

Conclusion

Pick decimal or binary units on purpose, remember that a byte is 8 bits, and choose a precision that suits the job. For more free tools, try our Percentage and Discount Calculator to work out how much of a drive you have used, or the Age Calculator.