1 GB = 1000 MB, 1 GiB = 1024 MiB, and 1 B = 8 bits. For storage labels, attachment limits or homework, identify the unit and convention before doing arithmetic. Choosing 1024 does not automatically make a calculation more accurate.
Use this guide when you need to compare capacity labels. A photo count additionally needs the average size of your actual files; a transfer time needs an effective bit rate.
GB to MB conversion table: decimal or binary?
NIST defines binary prefixes; BIPM lists decimal SI prefixes. Lowercase k is the SI symbol for kilo. Uppercase B identifies bytes.
| Unit | Bytes per unit | Relationship |
|---|---|---|
| kB | 1,000 | 1000 B |
| MB | 1,000,000 | 1000 kB |
| GB | 1,000,000,000 | 1000 MB |
| TB | 1,000,000,000,000 | 1000 GB |
| KiB | 1,024 | 1024 B |
| MiB | 1,048,576 | 1024 KiB |
| GiB | 1,073,741,824 | 1024 MiB |
| TiB | 1,099,511,627,776 | 1024 GiB |
What if a document says KB but means 1024 bytes?
Older documents and applications can use KB, MB or GB for binary quantities. Read their definition rather than inferring it from the label. For a report, state the convention explicitly or use KiB, MiB and GiB for binary units. Follow an exam question’s stated definition.
Why 32 GB is about 29.80 GiB
32 × 1,000,000,000 ÷ 1,073,741,824 = 29.802322 GiB, rounded here to six decimal places. Both numbers describe 32,000,000,000 bytes.
Apple distinguishes advertised decimal capacity from formatted capacity. Filesystems, operating systems, reserved space and existing files also affect free space. A difference alone proves neither a defect nor the absence of one.
| Input quantity | Same bytes in another unit | Check before deciding |
|---|---|---|
| 32 GB | About 29.802322 GiB | Total capacity versus free space |
| 512 GB | About 476.837158 GiB | The application’s unit definition |
| 1 TB | About 931.322575 GiB | TB and TiB are different sizes |
| 25 MB limit | 25,000,000 B | The service’s definition and file bytes |
| 25 MiB limit | 26,214,400 B | 1,214,400 B more than 25 MB |
How to compare GB and GiB in the converter
The data size converter displays kB/MB/GB in decimal mode and KiB/MiB/GiB in binary mode. Changing the base also changes the meaning of the selected input unit. Leaving the value at 32 and changing GB to GiB calculates a different quantity.
To preserve the quantity, use decimal mode with 32 GB, read the B result (32,000,000,000), enter that value with input unit B, then select binary mode. The GiB result is about 29.802322. Keep the original byte count when comparing exact limits; displayed results are rounded.
Check the example with your own inputs
Convert 32 GB to bytes in decimal mode, then enter those bytes in binary mode. Check which value stays fixed when you change conventions.
Mbps versus MB/s: calculating transfer time
100 MB is 800,000,000 bits. At an effective 20 Mbit/s, the simple model gives 800 ÷20 = 40 seconds. If 20 Mbps is a nominal rate and the problem specifies 50% efficiency, the effective rate is 10 Mbps and the result is 80 seconds. There is no universal 50% network efficiency rule.
| Potential mistake | Correct operation | Example |
|---|---|---|
| Bits versus bytes | B to bits: ×8; bits to B: ÷8 | 8 bits = 1 B |
| Mbps versus MB/s | Divide decimal bit rate by 8 | 100 Mbps = 12.5 MB/s theoretically |
| GB versus GiB | Convert through B | 1 GB ≈0.931323 GiB |
| Photo count versus GB | Use a measured average file size | 100 photos totaling 480 MB average 4.8 MB |
| Characters versus B | Measure the encoded bytes | UTF-8 あ occupies 3 B |
For raw media and efficiency calculations, continue to the data size and transfer time guide. For text use character and byte counting. The measurement conversion guide explains how to cancel units in other calculations.
Check the example with your own inputs
Enter 8 with unit bit and check that the byte result is 1. Replace it with your own size; use the separate transfer calculator when time is the question.
Keep the convention for your next visit
Record the value, unit and base together. A tool favorite is a shortcut in the same browser, not input history or cross-device synchronization. The utility category offers other conversion tools.
Editorial verification and limits
Tools Hub editors checked the primary sources, arithmetic and input paths on 8 November 2026. Examples are editorial calculations. They do not diagnose hardware, establish a service’s current attachment limit or guarantee network throughput.
FAQ
Is 1 GB 1000 MB or 1024 MB?
A decimal GB is 1000 MB. A binary GiB is 1024 MiB. If an older document uses GB for a binary quantity, check and state that document’s definition.
Does a 32 GB device displaying 29.8 mean space is missing?
32,000,000,000 bytes is about 29.802322 GiB. Units alone can change the displayed number; the OS, filesystem, reserved space and existing files also affect available space.
Does changing the converter base preserve the quantity?
It also changes the input unit’s meaning. To preserve the quantity, first obtain its byte count, enter it with unit B, then switch the base.
Can 100 Mbps transfer 100 MB in one second?
No.100 Mbps is theoretically 12.5 MB/s, so 100 MB requires at least 8 seconds under ideal assumptions. Protocol overhead and network conditions affect real transfers.
