How to use the MB to KB converter
- 1Type a Size and choose its Unit.
- 2If the unit is KB, MB, GB or TB, choose whether it's Decimal (1,000) or Binary (1,024). Use binary for sizes shown by Windows.
- 3Read the size in KB at the top and the full table in both conventions. Press Copy result to copy it.
2 MB both ways
2 MB (decimal) 2 MB (binary, as Windows shows)
2,000 KB · 1,953.125 KiB · 2,000,000 bytes 2,048 KiB · 2,097.152 KB · 2,097,152 bytes
1 MB = 1024 KB or 1000 KB?
Both, depending on who is counting:
- Decimal (SI): 1 KB = 1,000 bytes and 1 MB = 1,000 KB = 1,000,000 bytes. Used by storage makers, macOS, iOS, Android and most websites' upload limits.
- Binary: 1 KiB = 1,024 bytes and 1 MiB = 1,024 KiB = 1,048,576 bytes. Windows uses these values but labels them KB and MB.
To remove the ambiguity, the IEC defined the binary prefixes kibi (KiB), mebi (MiB) and gibi (GiB) in 1998. When a form says "max 2 MB", it usually means 2,000,000 bytes, but some systems check 2,097,152, so leave a little headroom.
KB, MB and GB conversions
| From | Decimal | Binary |
|---|---|---|
| 1 KB | 1,000 bytes | 1,024 bytes (1 KiB) |
| 1 MB | 1,000 KB | 1,024 KiB |
| 1 GB | 1,000 MB | 1,024 MiB |
| 1 TB | 1,000 GB | 1,024 GiB |
To convert, multiply or divide by 1,000 (or 1,024) once per step: MB → KB is × 1,000, KB → MB is ÷ 1,000. 500 KB = 0.5 MB in decimal units. The difference between the conventions grows with each step: 2.4% at KB, 4.9% at MB, 7.4% at GB and 10% at TB.
Why Windows and macOS show different sizes
A photo of exactly 2,000,000 bytes is "2 MB" in macOS Finder and "1.90 MB" in Windows Explorer, because Windows divides by 1,048,576. Nothing is lost; the same bytes are being counted with different units.
The same effect explains why a "1 TB" drive shows about 931 GB in Windows: 1,000,000,000,000 ÷ 1,073,741,824 = 931.3. Formatting and system files then take some more space, as Apple and drive makers explain in their capacity notes.
Reducing a file from MB to KB
Converting units doesn't change a file's size. If a form asks for a photo "under 100 KB" and yours is 2 MB, the file itself has to be made smaller by compressing it, reducing its pixel dimensions, or both.
- Reduce an image to an exact size in KB for application forms and ID photos.
- Compress an image to 1 MB for email and uploads.
- Compress a PDF for document uploads.
The image size tools count 1 KB as 1,000 bytes by default, matching most upload checks, and have a 1,024-byte option.
Is anything I enter stored?
This tool runs entirely in your browser. Your text is not uploaded to our servers.