How to use the data storage converter
- Enter an amount and choose its unit in From.
- Choose the unit you want in To. The table below lists the same size in every unit, in both the decimal (1,000) and binary (1,024) systems.
- Watch the label beside the result. When you start from a decimal unit such as GB, the tool also shows how Windows would display it, since that is the source of most confusion.
Units with bit in their name are for network speeds. Divide by 8 to go from bits to bytes.
1,000 or 1,024? Two systems, same names
Computers count in powers of two, so for decades a "kilobyte" meant 1,024 bytes (2¹⁰). But the prefix kilo means exactly 1,000 everywhere else in science, and storage makers use that meaning, because it gives a bigger-looking number. To end the confusion, the International Electrotechnical Commission introduced separate binary names in 1998: kibibyte (KiB), mebibyte (MiB), gibibyte (GiB) and so on.
| Prefix | Decimal (SI) | Binary (IEC) | Difference |
|---|---|---|---|
| Kilo / Kibi | 1 KB = 1,000 B | 1 KiB = 1,024 B | 2.4% |
| Mega / Mebi | 1 MB = 1,000,000 B | 1 MiB = 1,048,576 B | 4.9% |
| Giga / Gibi | 1 GB = 10⁹ B | 1 GiB = 1,073,741,824 B | 7.4% |
| Tera / Tebi | 1 TB = 10¹² B | 1 TiB = 1,099,511,627,776 B | 10.0% |
| Peta / Pebi | 1 PB = 10¹⁵ B | 1 PiB = 1,125,899,906,842,624 B | 12.6% |
The gap grows with each step, which is why a terabyte drive looks noticeably smaller than expected.
Why a 500 GB drive shows as 465 GB
A manufacturer sells a drive with 500,000,000,000 bytes and calls it 500 GB, using the decimal meaning. Windows divides by 1,073,741,824 (2³⁰) to display the size, but labels the result "GB" rather than "GiB":
500,000,000,000 ÷ 1,073,741,824 = 465.66 GiB (shown by Windows as "465 GB")
No storage is missing. The drive is exactly the size advertised. macOS has used the decimal system for storage since 2009, so the same drive shows as 500 GB there, and many Linux tools let you choose. A 1 TB drive appears as 931 GB on Windows (0.909 TiB), and a 4.7 GB DVD holds 4.38 GiB.
Formulas
bytes = bits ÷ 8 decimal: 1 KB = 1,000 B 1 MB = 1,000 KB 1 GB = 1,000 MB binary: 1 KiB = 1,024 B 1 MiB = 1,024 KiB 1 GiB = 1,024 MiB
The converter changes everything to bytes first, then to the target. The table of results on the page is therefore always consistent, and you can compare decimal and binary values side by side.
Worked examples and download times
- 1 GB in MB: decimal, 1,000 MB. If someone means GiB, then 1,024 MiB.
- 256 GB phone: 256 × 10⁹ ÷ 2³⁰ = 238.4 GiB reported by systems that use binary units.
- 100 Mbit/s broadband in MB/s: 100 ÷ 8 = 12.5 MB per second, the best case for a download.
- Time to download 1 GB at 100 Mbit/s: 1 GB is 8,000 Mbit, and 8,000 ÷ 100 = 80 seconds, or 1 minute 20 seconds. A 50 GB game takes about 67 minutes.
Real downloads are slower than these figures because of protocol overhead, shared connections and server limits. Subtract roughly 5 to 10% for a realistic estimate.
Common storage sizes
| Item | Approximate size | Notes |
|---|---|---|
| A plain-text page | 3 KB | About 500 words |
| A phone photo | 3 to 8 MB | Depends on the camera and format |
| A 3-minute MP3 song | 3 to 8 MB | 128 to 320 kbit/s |
| A 1-hour HD video | 1.5 to 4 GB | Depends on bitrate |
| A DVD | 4.7 GB | Single layer, decimal GB |
| A Blu-ray disc | 25 GB | Single layer |
| A modern big game | 50 to 150 GB | With updates |
Use the converter to turn these into the units your device reports. For example, a 128 GB phone has about 119 GiB of raw space, and the operating system itself takes several gigabytes of that before you install a single app. Always allow for this overhead when deciding how much storage to buy.
Accuracy and limits
All factors are exact definitions, so conversions are exact. The "shown by Windows" note is a general rule for how classic file explorers label sizes; some programs and operating systems display decimal units instead. File systems also set aside space for their own structures, so the usable space on a formatted drive is slightly less than its full size. Sizes of individual files may differ from their space on disk because of cluster size.
Frequently asked questions
How many MB are in a GB?
In the decimal system used by storage makers and network providers, 1 GB is 1,000 MB. In the binary system, 1 GiB is 1,024 MiB. Windows labels the binary version as GB, which causes the confusion.
What is the difference between GB and GiB?
GB means 1,000,000,000 bytes. GiB, the gibibyte, means 1,073,741,824 bytes (2³⁰). A GiB is about 7.4% bigger.
Why does my new hard drive show less space than advertised?
The maker counts 1 TB as 10¹² bytes, and Windows shows sizes in binary units, so 1 TB appears as about 931 GB. The drive has the full capacity; the units differ.
What is the difference between MB and Mb?
A capital B means bytes and a lowercase b means bits. A megabyte (MB) is eight megabits (Mb). Internet speeds are quoted in megabits per second, file sizes in megabytes.
How do I convert Mbps to MB/s?
Divide by 8. A 200 Mbps connection can download at most 25 MB per second.