Data storage converter (KB, MB, GB, TB)
Convert bytes, KB, MB, GB, TB and PB with a switch between 1000-based and 1024-based counting, plus the IEC KiB, MiB and GiB units.
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Used by drive manufacturers, macOS, iOS, most network tools and the SI standard.
1 GB = 1,000 MB
Automatic formatting keeps up to 12 significant digits and switches to scientific notation only for numbers past 10¹⁸ or below 10⁻⁹. You can paste values with thousands separators, and fractions such as 3/4 or 1 1/2 are understood too.
MB = GB × 1,000
Same thing written another way: MB = GB ÷ 0.001
Your value: 1 × 1,000 = 1,000 MB
Gigabyte: The unit on most phone and drive labels. Counting decimally: GB = 1,000,000,000 bytes.
Megabyte: A minute of MP3 audio is roughly 1 MB. Counting decimally: MB = 1,000,000 bytes.
| GB | MB |
|---|---|
| 1 | 1,000 |
| 2 | 2,000 |
| 4 | 4,000 |
| 8 | 8,000 |
| 16 | 16,000 |
| 32 | 32,000 |
| 64 | 64,000 |
| 128 | 128,000 |
| 256 | 256,000 |
| 512 | 512,000 |
| 1,024 | 1,024,000 |
| 2,048 | 2,048,000 |
| MB | GB |
|---|---|
| 1 | 0.001 |
| 2 | 0.002 |
| 4 | 0.004 |
| 8 | 0.008 |
| 16 | 0.016 |
| 32 | 0.032 |
| 64 | 0.064 |
| 128 | 0.128 |
| 256 | 0.256 |
| 512 | 0.512 |
| 1,024 | 1.024 |
| 2,048 | 2.048 |
| Unit | Symbol | Value in bit | Notes |
|---|---|---|---|
| BitBase | bit | 1 bit = 1 bit | A single 0 or 1. |
| NibbleBase | nibble | 1 nibble = 4 bit | Four bits — one hexadecimal digit. |
| ByteBase | B | 1 B = 8 bit | Eight bits. One ASCII character. |
| KilobyteAmbiguous prefix | KB | 1 KB = 8,000 bit | The first ambiguous prefix. Counting decimally: KB = 1,000 bytes. |
| MegabyteAmbiguous prefix | MB | 1 MB = 8,000,000 bit | A minute of MP3 audio is roughly 1 MB. Counting decimally: MB = 1,000,000 bytes. |
| GigabyteAmbiguous prefix | GB | 1 GB = 8,000,000,000 bit | The unit on most phone and drive labels. Counting decimally: GB = 1,000,000,000 bytes. |
| TerabyteAmbiguous prefix | TB | 1 TB = 8,000,000,000,000 bit | A “1 TB” drive shows as 931 GiB in Windows. Counting decimally: TB = 1,000,000,000,000 bytes. |
| PetabyteAmbiguous prefix | PB | 1 PB = 8,000,000,000,000,000 bit | Data-centre scale. Counting decimally: PB = 1,000,000,000,000,000 bytes. |
| KibibyteBinary (IEC, always 1024) | KiB | 1 KiB = 8,192 bit | Exactly 1,024 bytes — never anything else. |
| MebibyteBinary (IEC, always 1024) | MiB | 1 MiB = 8,388,608 bit | Exactly 1,048,576 bytes. |
| GibibyteBinary (IEC, always 1024) | GiB | 1 GiB = 8,589,934,592 bit | Exactly 1,073,741,824 bytes. |
| TebibyteBinary (IEC, always 1024) | TiB | 1 TiB = 8,796,093,022,210 bit | Exactly 1,099,511,627,776 bytes. |
| PebibyteBinary (IEC, always 1024) | PiB | 1 PiB = 9,007,199,254,740,000 bit | — |
How to convert file sizes
- First choose how KB, MB, GB and TB should be counted — 1,000-based or 1,024-based. This is the setting that decides whether the answer is the one your operating system would give.
- Type a size into either field. Both convert live.
- The reference table at the bottom restates every unit in bits under whichever counting rule you picked, so you can see exactly what the tool did.
The 1000 versus 1024 problem, explained once
Computers address memory in powers of two, so 2¹⁰ = 1,024 was a convenient near-miss for "kilo" in the 1960s and the shorthand stuck. Metric prefixes, meanwhile, have always meant powers of a thousand. For a kilobyte the disagreement is 2.4 %; by the terabyte it is 10 %, which is large enough to look like a missing chunk of your drive.
| Prefix | Decimal (SI) | Binary | Gap |
|---|---|---|---|
| kilo | 1,000 | 1,024 | 2.4 % |
| mega | 1,000,000 | 1,048,576 | 4.9 % |
| giga | 1,000,000,000 | 1,073,741,824 | 7.4 % |
| tera | 10¹² | 1,099,511,627,776 | 10.0 % |
| peta | 10¹⁵ | 1,125,899,906,842,624 | 12.6 % |
Who uses which
| Counts in 1,000s | Counts in 1,024s |
|---|---|
| Hard drive and SSD manufacturers | Windows File Explorer and Task Manager |
| macOS and iOS since 2009 | RAM capacities, always |
| Ubuntu and most Linux desktops | Linux command-line tools by default |
| Network speeds and ISP plans | Most older software and BIOS screens |
| The SI and IEC standards | The JEDEC memory standard |
This is why a drive sold as 1 TB shows up as 931 GB in Windows. The manufacturer put 1,000,000,000,000 bytes in the box, which is exactly what it says on the label. Windows then divides by 1,024 three times, gets 931.32, and labels it "GB" when it means GiB. Nothing is missing; the two sides are simply using the same three letters for different numbers.
The unambiguous units: KiB, MiB, GiB
The IEC introduced binary prefixes in 1998 precisely to end this argument. A kibibyte (KiB) is always 1,024 bytes, a mebibyte (MiB) always 1,048,576, a gibibyte (GiB) always 1,073,741,824. They never change meaning, so they are always available in the list above regardless of which counting mode you have selected. If you are writing documentation or a spec, using them removes an entire class of misunderstanding.
Bits versus bytes, and internet speeds
A byte is eight bits. Storage is quoted in bytes with a capital B; network speed is quoted in bits with a lowercase b. That single letter is worth a factor of eight, and it is why a "100 Mbps" connection downloads at a maximum of 12.5 MB/s — and in practice a little less, because protocol overhead eats a few per cent.
| Line speed | Best case download | Time for a 5 GB file |
|---|---|---|
| 10 Mbps | 1.25 MB/s | 1 h 7 min |
| 50 Mbps | 6.25 MB/s | 13 min |
| 100 Mbps | 12.5 MB/s | 6 min 40 s |
| 500 Mbps | 62.5 MB/s | 1 min 20 s |
| 1 Gbps | 125 MB/s | 40 s |
Questions
Is a gigabyte 1,000 or 1,024 megabytes?
Both answers are in use. Drive makers, macOS and the SI standard say 1,000; Windows and RAM sizes say 1,024. The switch above changes every KB/MB/GB/TB row at once.
Why does my 1 TB drive show as 931 GB?
The manufacturer sold you 1,000,000,000,000 bytes, and Windows divides that by 1,024 three times, giving 931.32 — which it then labels GB even though it means GiB.
What are KiB, MiB and GiB?
The IEC binary units, always powers of 1,024 and never ambiguous. A kibibyte is 1,024 bytes, a mebibyte is 1,048,576 bytes, and so on up the scale.
Why are internet speeds in megabits, not megabytes?
Networking has always counted bits. A 100 Mbps line moves at most 12.5 MB per second, because there are 8 bits in a byte — convert bit to byte above to check.