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Data Size Converter

Convert MB to GB, TB, bytes, and binary units (MiB, GiB, TiB) instantly. Used by IT pros, cloud engineers & students. Free, no sign-up, displays up to 15 decimals.

Last revised 9 September 2026

By Team GlobalCalqulate · About our editorial standards

Data Size Conversion

Value

Enter the data size value to convert.

From Unit

Select the unit you want to convert from.

To Unit

Select the unit you want to convert to.

Toggle between decimal (KB, MB, GB) and binary (KiB, MiB, GiB) standards.

Decimal Places

Number of decimal places for the result.

Disclaimer: The single biggest source of confusion in data-size conversions is binary vs. decimal prefixes: storage manufacturers and network speeds use decimal (1 KB = 1000 bytes, per SI), while operating systems and RAM typically report binary (1 KiB = 1024 bytes, per IEC 80000-13). This converter lets you choose which standard to use — always check which one a size you're comparing against actually means before assuming they match. Full disclaimer.

Sources & methodology

Formula:: Two-step conversion through a base unit
Reference:: International Electrotechnical Commission (IEC)
Content last updated:: September 2026
Scheduled re-verification:: September 2027

Calculation type: Exact calculation. Figures are taken from International Electrotechnical Commission (IEC) and National Institute of Standards and Technology (NIST) — see sources below.

Formula & methodology

Formula used

Two-step conversion through a base unit

value_out = (value_in × factor_in→the byte) ÷ factor_out→the byte

Every data unit is defined as a multiple of the byte. A conversion goes in to the byte and back out again, so one factor per unit covers every possible pair rather than needing a factor for each combination.

Decimal and binary prefixes differ

1 kB = 1000 bytes;   1 KiB = 1024 bytes

SI prefixes (kB, MB, GB) are powers of 1000; IEC binary prefixes (KiB, MiB, GiB) are powers of 1024. The gap widens with scale — a "1 TB" drive holds about 0.909 TiB, which is why a new drive appears smaller than advertised.

Variable definitions

Symbol	Meaning	Unit
factor	Conversion factor. how many bytes one unit represents	B

Step-by-step calculation

1. Choose the unit you have
Note whether it is decimal (kB) or binary (KiB).
2. Choose the unit you want
The value is converted through bytes.

Limitations

Storage manufacturers use decimal units while many operating systems report binary units. Neither is wrong — they are different prefixes, and this converter distinguishes them.
Bits and bytes differ by a factor of 8. Network speeds are usually quoted in bits per second, file sizes in bytes.
The conversion factors are exact by definition, not measured, so the only error in a result is the rounding you choose for display.

This page is educational. It converts between units using the defined or standard factors shown above, so the arithmetic is exact to the precision displayed — but a converted value is only as good as the measurement behind it, and some units are defined only under stated conditions. Where a conversion is safety-critical or contractual, check it against the governing standard rather than relying on this page.

Sources & references

IEC 80000-13: Quantities and units — Information science and technology (binary prefixes: kibi, mebi, gibi, etc.) — International Electrotechnical Commission (IEC)
NIST Guide to SI Units — decimal metric prefixes (kilo, mega, giga) as applied to bytes and bits — National Institute of Standards and Technology (NIST)

Decimal prefixes (KB, MB, GB) follow the standard SI/metric definitions (powers of 1000); binary prefixes (KiB, MiB, GiB) follow the IEC 80000-13 standard (powers of 1024); see the sources above. Both conversions are exact by definition, so results are limited only by the display rounding you choose. Standards review: August 2026.

Help & FAQs

Frequently Asked Questions

Clear answers to common questions to help you use this calculator confidently.

How many MB in a GB?

Tap to view the answer

Decimal: 1 GB = 1,000 MB. Binary: 1 GiB = 1,024 MiB. Storage manufacturers use decimal (SI); operating systems typically display binary (IEC). Check which standard applies before comparing two numbers.

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

Tap to view the answer

Storage manufacturers advertise capacity in decimal units (1 TB = 1,000,000,000,000 bytes), but operating systems display it in binary units (1 TiB = 1,099,511,627,776 bytes). Converting: 1 TB ≈ 0.91 TiB (≈931 GiB) — the drive isn't defective, it's just a unit mismatch.

What is the difference between KB/MB/GB and KiB/MiB/GiB?

Tap to view the answer

KB/MB/GB are decimal units (base-10, per SI): 1 KB = 1,000 bytes. KiB/MiB/GiB are binary units (base-2, per IEC 80000-13): 1 KiB = 1,024 bytes. The gap compounds at larger sizes — about 2.4% at KB/KiB, over 10% at TB/TiB.

How many bytes are in a megabyte?

Tap to view the answer

Decimal: 1 MB = 1,000,000 bytes. Binary: 1 MiB = 1,048,576 bytes. Use decimal for cloud storage billing and network specs; use binary for RAM, file systems, and OS-reported sizes.

How accurate is this data size converter?

Tap to view the answer

It uses the standardized decimal (SI, base-1000) and binary (IEC 80000-13, base-1024) ratios exactly, so results are precise to the decimal places you choose. The only real source of error is picking the wrong standard for your comparison — toggle 'Use Binary Units' to match what you're converting against.

Need more help? Contact support or email globalcalqulate@gmail.com

We typically reply within 24–48 hours.

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From	To	Binary / Decimal
1 byte	8 bits	8
1 KB (kilobyte)	1,024 bytes	1,024
1 MB (megabyte)	1,024 KB	1,048,576
1 GB (gigabyte)	1,024 MB	1,073,741,824
1 TB (terabyte)	1,024 GB	1,099,511,627,776
1 PB (petabyte)	1,024 TB	1,125,899,906,842,624
1 KiB (kibibyte)	1,024 bytes	1,024
1 MiB (mebibyte)	1,024 KiB	1,048,576
1 GiB (gibibyte)	1,024 MiB	1,073,741,824
1 TB ≈	931.3 GiB	0.9313
1 GB in decimal	1,000 MB	1,000,000,000

From	To	Binary / Decimal
1 byte	8 bits	8
1 KB (kilobyte)	1,024 bytes	1,024
1 MB (megabyte)	1,024 KB	1,048,576
1 GB (gigabyte)	1,024 MB	1,073,741,824
1 TB (terabyte)	1,024 GB	1,099,511,627,776
1 PB (petabyte)	1,024 TB	1,125,899,906,842,624
1 KiB (kibibyte)	1,024 bytes	1,024
1 MiB (mebibyte)	1,024 KiB	1,048,576
1 GiB (gibibyte)	1,024 MiB	1,073,741,824
1 TB ≈	931.3 GiB	0.9313
1 GB in decimal	1,000 MB	1,000,000,000

Calculator inputs

Data Size Conversion

Your results

Sources & methodology

Formula & methodology

Formula used

Two-step conversion through a base unit

Decimal and binary prefixes differ

Variable definitions

Step-by-step calculation

Limitations

Sources & references

How many MB in a GB?

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

What is the difference between KB/MB/GB and KiB/MiB/GiB?

How many bytes are in a megabyte?

How accurate is this data size converter?

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Calculator inputs

Data Size Conversion

Your results

Sources & methodology

How to Use This Calculator

Example: Convert 1 TB to GB

Common Data Size Conversions

Understanding Your Results

Key Tips

Understanding Data Size Units

What Are Data Size Units?

Decimal vs Binary

Why the Confusion?

Real-World Examples

Formula & methodology

Formula used

Two-step conversion through a base unit

Decimal and binary prefixes differ

Variable definitions

Step-by-step calculation

Limitations

Sources & references

How to Use This Calculator

Example: Convert 1 TB to GB

Common Data Size Conversions

Understanding Your Results

Key Tips

Understanding Data Size Units

What Are Data Size Units?

Decimal vs Binary

Why the Confusion?

Real-World Examples