File Size Converter
Convert between file size units: bytes, KB, MB, GB, TB. Supports decimal (SI) and binary (IEC) units.
About this calculator
File sizes can be written in decimal units (KB = 1,000 bytes) or binary units (KiB = 1,024 bytes). This converter shows both so you can see the gap. Enter a size, choose its unit, and every other unit appears.
The difference is about 7% at gigabytes, which explains why a 1 GB download is 953.7 MiB.
How to use it
- Type the Value.
- Choose the From Unit.
- Read bytes, KB, MB, GB, KiB, MiB and GiB.
Units
Decimal: 1 KB = 1,000 B, 1 MB = 1,000,000 B, 1 GB = 10⁹ B. Binary (IEC): 1 KiB = 1,024 B, 1 MiB = 1,048,576 B, 1 GiB = 1,073,741,824 B.
Worked example
1 GB (decimal)
| Bytes | 1,000,000,000 |
| KB | 1,000,000 |
| MB | 1,000 |
| MiB | 953.6743 |
| GiB | 0.9313 |
Tips and common mistakes
- Use MiB and GiB when you mean binary units.
- Email attachments often cap at 20 to 25 MB.
- Compressing images can cut file size by 70% or more.
- Check upload limits in decimal and binary before sending.
- A page of plain text is only a few KB.
Frequently asked questions
What is the difference between MB and MiB?
MB is 1,000,000 bytes, MiB is 1,048,576 bytes.
How many KB in 1 MB?
1,000 in decimal.
Why do file sizes differ between systems?
Some use decimal and some binary units.
How big is a GB?
About a thousand MB.
How many bytes in a KiB?
1,024.
Which is bigger, GB or GiB?
The GiB.