How transfer time is calculated
File sizes are measured in bytes (MB) but connection speeds in bits per second (Mbps), and 1 byte = 8 bits. So the size is multiplied by 8 to turn megabytes into megabits, then divided by the speed.
- file size — megabytes (MB), decimal (1 MB = 1,000,000 bytes)
- speed — megabits per second (Mbps)
Common values
| File size (MB) | Transfer time |
|---|---|
| 100 MB | 8s |
| 250 MB | 20s |
| 500 MB | 40s |
| 1,000 MB | 1m 20s |
| 1,500 MB | 2m 0s |
| 2,000 MB | 2m 40s |
| 3,000 MB | 4m 0s |
| 5,000 MB | 6m 40s |
| 10,000 MB | 13m 20s |
More detail
Why megabytes and megabits differ by 8×
This is the single biggest source of confusion: a 100 Mbps connection is 100 megabits per second, not megabytes. Since 1 byte = 8 bits, that's only about 12.5 MB per second at best. A 1,000 MB file therefore takes roughly 80 seconds, not 10 — the factor of 8 is exactly why.
Practical tip. Real-world speeds run 10–30% below the advertised figure once protocol overhead, Wi-Fi loss, and server-side limits are counted. If a transfer matters, add a margin to whatever this calculator shows.
Frequently asked questions
How long to download 1,000 MB (1 GB) on 100 Mbps?
1,000 MB × 8 ÷ 100 = 80 seconds (1 minute 20 seconds) in the ideal case. Real downloads are usually 10–30% slower because of overhead.
Why is my download slower than my internet speed suggests?
Because speed is in megabits and file size in megabytes (8 bits per byte), and because real transfers lose 10–30% to protocol overhead, Wi-Fi, congestion, and server limits. This calculator shows the theoretical best case.
Is this using decimal (1000) or binary (1024) megabytes?
Decimal: 1 MB = 1,000,000 bytes and speeds are megabits per second, matching how ISPs advertise. If your file is in binary MiB (1,024 KiB), the real time is about 5% longer.
How do I convert MB/s to Mbps?
Multiply MB/s by 8: 12.5 MB/s = 100 Mbps. That 8× factor is why a 100 Mbps line downloads at only about 12.5 MB per second.