The basic rule
In most upload forms 1MB = 1024KB. So 2MB is 2048KB and 5MB is 5120KB. (Some systems use 1000, which is why a file can show slightly different sizes.)
Quick table
| MB | KB |
|---|---|
| 0.5 MB | 512 KB |
| 1 MB | 1024 KB |
| 2 MB | 2048 KB |
| 3 MB | 3072 KB |
| 5 MB | 5120 KB |
Staying under a limit
Aim a little below the limit. If a form allows 2MB, a 1.9MB file is safer than 2.0MB. Use the 2MB, 1MB or custom size compressor.
Where to see file size
On a phone, open the file details in your gallery or Files app. On Windows, right-click the file and choose Properties. On Mac, use Get Info.