Bits, bytes and realistic transfer times
ToolMixo · Last reviewed:
One byte is eight bits. A 100 Mbps connection has a theoretical maximum of 12.5 MB per second, before protocol overhead, Wi-Fi conditions or the remote server slow it down. A 100 MB file therefore needs at least eight seconds at that rate. File size measures an amount; bandwidth measures an amount per unit of time.
Decimal storage units use powers of 1000: 1 MB is 1,000,000 bytes. Binary units use powers of 1024: 1 MiB is 1,048,576 bytes. Our file-size calculator uses binary steps, labelled KiB, MiB, GiB and TiB in the controls. Match the convention used by your upload destination before comparing limits.
Compare the choices
| Unit | Bytes |
|---|---|
| 1 KB | 1,000 |
| 1 KiB | 1,024 |
| 1 MB | 1,000,000 |
| 1 MiB | 1,048,576 |
| 100 KB | 100,000 |
| 100 KiB | 102,400 |
Worked example
An upload limit of 100 KB means 100,000 bytes when KB is decimal. A 100 KiB file contains 102,400 bytes and exceeds that limit. The compressor's Under 100 KB target uses decimal bytes. For a strict under-100-KB requirement, the output must be less than 100,000 bytes.
Before you publish or upload
- Check whether the destination means KB or KiB instead of relying on a rounded file-manager label.
- Ideal transfer seconds = bytes × 8 ÷ bits per second. A 10 MiB file on a 10 Mbps link needs at least 8.39 seconds, before overhead.
- Resize unnecessary pixels before lowering quality, then confirm the final file's exact size and appearance.