How the Data Storage Converter Works
Files, photos, apps and drives are all measured in units of digital data. The smallest unit is the bit, and eight bits make one byte. Larger units, such as the kilobyte, megabyte and gigabyte, are used for everyday sizes. The Digital Data Storage Converter changes a size from one unit into another, and shows the same size in every unit at once.
What you enter
- The size: a number, which can have decimals.
- The unit you have (From): bits, bytes, KB, MB, GB, TB, PB, or the binary units KiB, MiB, GiB and TiB.
- The unit you want (To): any of the same units.
Two ways to count: 1000 or 1024
There are two systems, and this is the reason why sizes often do not match:
- Decimal (SI) units: every step is 1,000 times bigger. Drive makers, phone makers and internet providers use them. The names are KB, MB, GB, TB and PB.
- Binary (IEC) units: every step is 1,024 times bigger, because computers count in powers of 2. The names are KiB, MiB, GiB and TiB. Many operating systems use these sizes, but some of them still write "GB" when they mean GiB.
How the conversion works
Every unit has a fixed size in bytes. The converter turns your size into bytes, and then turns the bytes into the unit you chose:
bytes = size x bytes in the From unit result = bytes / bytes in the To unit
A bit is one eighth of a byte, so bits are changed with the number 8.
| Unit | Size in bytes |
|---|---|
| 1 bit | 0.125 |
| 1 byte (B) | 1 |
| 1 KB | 1,000 |
| 1 MB | 1,000,000 |
| 1 GB | 1,000,000,000 |
| 1 TB | 1,000,000,000,000 |
| 1 PB | 1,000,000,000,000,000 |
| Binary unit | Size in bytes |
|---|---|
| 1 KiB | 1,024 |
| 1 MiB | 1,048,576 |
| 1 GiB | 1,073,741,824 |
| 1 TiB | 1,099,511,627,776 |
A worked example
You buy a 256 GB drive, and you want to know the size that your computer will show (in GiB).
| Step | Value |
|---|---|
| GB to bytes (256 x 1,000,000,000) | 256,000,000,000 B |
| Bytes to GiB (divide by 1,073,741,824) | 238.42 GiB |
The same 256 GB in other units:
| Unit | Amount |
|---|---|
| Bits | 2,048,000,000,000 |
| Bytes | 256,000,000,000 |
| MB | 256,000 |
| GB | 256 |
| TB | 0.256 |
| GiB | 238.42 |
| TiB | 0.2328 |
No space is lost. The drive still holds the same 256 billion bytes. The two systems only use different units to count them.
Why the binary number looks smaller
A binary unit is a little bigger than the decimal unit with a similar name, and the gap grows with every step. So the same amount of data gives a smaller number in the binary unit. The first chart shows how much bigger the binary unit is.
KiB vs KB ████████ 2.4% bigger MiB vs MB ███████████████ 4.9% bigger GiB vs GB ███████████████████████ 7.4% bigger TiB vs TB ████████████████████████████████ 10.0% bigger PiB vs PB ████████████████████████████████████████ 12.6% bigger
How much looks "missing" on a drive
The orange bars show how much smaller the drive looks when your computer counts in binary units. The percentage is the share of the advertised size that does not show up.
KB level ████████ 2.3% MB level █████████████████ 4.6% GB level █████████████████████████ 6.9% TB level ████████████████████████████████ 9.0% PB level ████████████████████████████████████████ 11.2%
This is why a 1 TB drive shows as about 931 GiB, and a 128 GB drive shows as about 119 GiB. Operating systems also keep some space for the system and for formatting, which takes a little more.
Capacity shown on your computer
| Advertised | Shown (GiB) |
|---|---|
| 64 GB | 59.60 |
| 128 GB | 119.21 |
| 256 GB | 238.42 |
| 512 GB | 476.84 |
| 1 TB | 931.32 |
| 2 TB | 1,862.65 |
Doing it by hand
- Decimal units: move the decimal point three places for each step. 2,500 MB is 2.5 GB.
- Binary units: multiply or divide by 1,024 for each step. 3 GiB is 3 x 1,024 = 3,072 MiB.
- Bytes to bits: multiply by 8. 5 MB is 40 megabits.
- A quick estimate: a drive shows about 7% less in GiB than the GB on the box. For 500 GB, 7% is 35, so about 465 GiB. The exact answer is 465.66 GiB.
Bits, bytes and internet speed
Internet speed is given in bits per second (Mbps), and file sizes are given in bytes (MB). A capital B is a byte, and a small b is a bit. To change a speed in Mbps into MB per second, divide by 8.
| Speed | Megabytes per second |
|---|---|
| 8 Mbps | 1 MB/s |
| 50 Mbps | 6.25 MB/s |
| 100 Mbps | 12.5 MB/s |
| 1,000 Mbps (1 Gbps) | 125 MB/s |
For example, a 2 GB file is 16,000 megabits (2,000 MB x 8). At 100 Mbps it takes 16,000 / 100 = 160 seconds, which is 2 minutes 40 seconds. Real speeds are usually a little lower than the speed you pay for.
Where these conversions are used
- Buying drives, phones and memory cards: to know the size you will really see.
- Cloud storage and backups: to compare plans that use GB, TB or GiB.
- Downloads and streaming: to change a file size and a speed to the same unit.
- Web and software work: upload limits, memory use and database sizes.
Tips
- Check the letters. MB and MiB are not the same, and neither are B (byte) and b (bit).
- Check which system a program uses. Some systems write GB for 1,000 million bytes, and others write GB for 1,024 x 1,024 x 1,024 bytes.
- Use enough digits for small amounts. A few bytes in a petabyte is a very small number, so the converter shows many digits.
What this converter does not include
- Transfer speed over time. It changes sizes only, but the table above helps with speeds.
- The space that the file system and the operating system keep for themselves.
- Compression. A compressed file takes less space than its original size.
This tool gives an estimate for general information only. The real space on a device depends on its format and on the system files it holds.