What this calculator does
Switch any amount of digital storage between bits, bytes, MB, GB and the look-alike units MiB and GiB. There are two sets of size names, and they look almost the same. The decimal (SI) names count in steps of 1,000, so a gigabyte is 1,000,000,000 bytes. The binary (IEC) names count in steps of 1,024, so a gibibyte is 1,073,741,824 bytes. Drive makers and network speeds use the decimal units. Many operating systems and memory specs use the binary ones, sometimes still labeled with the decimal names.
This converter keeps the two systems apart. Enter an amount and pick the units. You get the result and the working, which goes through bytes. You also get a table showing the same amount in bits, decimal units and binary units.
Where it's used
Why this math matters outside the classroom:
- Drive capacity. Computer buyers see why a 1 TB drive shows about 931 GiB in the operating system, since 10¹² ÷ 2³⁰ ≈ 931.
- Bits and bytes. Students convert 100 Mbit of data to 12.5 MB by dividing by 8 bits per byte.
- Cloud plans. Office managers compare cloud storage plans by converting everyone's usage into the same unit.
- Photo libraries. A photographer storing 5,000 photos of 25 MB each needs 125,000 MB, which is 125 GB.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 5.NBT.A.2, 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the amount of data. Zero and decimals are allowed, but negative amounts aren't.
- Choose the unit you're converting from and the unit you want. Units with an “i” (KiB, MiB, GiB) are the binary ones.
- Read the result, or compare the decimal and binary columns in the table.
What the inputs mean
- Amount of data
- The amount of data to convert, in the “From” unit.
- From
- The unit your number is in. A lowercase b or “bit” means bits. An uppercase B means bytes.
- To
- The unit you want the answer in.
Formula and method
result = value × (from-unit in bytes) ÷ (to-unit in bytes) 1 byte = 8 bits Decimal: 1 kB = 1,000 B; 1 MB = 1,000² B; 1 GB = 1,000³ B; 1 TB = 1,000⁴ B Binary: 1 KiB = 1,024 B; 1 MiB = 1,024² B; 1 GiB = 1,024³ B; 1 TiB = 1,024⁴ B
B stands for bytes, and value is the amount you enter. Each unit is stored as its size in bytes. To convert, the calculator multiplies by the size of the unit you start with to get bytes. Then it divides by the size of the unit you want.
The gap between the two systems grows with each step up. A KiB is 2.4% larger than a kB. A GiB is about 7.4% larger than a GB, and a TiB is almost 10% larger than a TB. That gap is why a drive sold as 1 TB shows up as about 931 GB on some computers. They measure in binary units but label them GB.
Worked example
A drive is sold as 500 GB. How many GiB will an operating system that counts in binary units report?
- 500 GB × 1,000,000,000 = 500,000,000,000 bytes.
- 500,000,000,000 ÷ 1,073,741,824 = 465.661287 GiB.
Result: 500 GB is about 465.66 GiB. No space is missing. The two numbers measure the same bytes with different units.
Understanding the result
If a file manager shows less space than the box promised, it's almost always this unit difference. A little space is also used for formatting.
Network and internet speeds are given in bits per second. So a 100 Mbit/s connection moves at most 12.5 MB of data each second, before overhead (the extra data that keeps the connection running).
Assumptions and limitations
- A byte is 8 bits.
- Decimal prefixes are powers of 1,000 and binary prefixes are powers of 1,024. That follows the SI and IEC standards.
- It doesn't estimate formatted capacity, file-system overhead or compression.
- Transfer rates aren't converted directly. Convert the amount, then divide by the time yourself.
- Units above the petabyte and pebibyte aren't included.
Frequently asked questions
Why does my 1 TB drive show about 931 GB?
The drive holds 1,000,000,000,000 bytes. Dividing by 1,024³ gives about 931.32. Some operating systems show that figure with the label GB, even though it's really GiB.
What is the difference between Mb and MB?
Mb (megabit) is a million bits. MB (megabyte) is a million bytes, eight times as much. Internet plans are sold in megabits per second, while file sizes are shown in megabytes.
Is a kilobyte 1,000 or 1,024 bytes?
Under the SI standard, a kilobyte (kB) is 1,000 bytes, and 1,024 bytes is a kibibyte (KiB). Older software and manuals often used kilobyte for 1,024 bytes. So check the context of older figures.
Is there a page for a single pair, such as MB to GB?
Yes. Megabytes to gigabytes and kilobytes to megabytes have their own pages. Each has a reference table of typical file and storage sizes. Both use decimal prefixes. This converter is the place for the binary units such as MiB and GiB.
How this calculator is checked
Method: 1 byte = 8 bits; SI decimal prefixes (powers of 10³) and IEC 80000-13 binary prefixes (powers of 2¹⁰). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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