Time and Data CalculatorsHow long does a download take? A table of sizes and speeds
Time equals size divided by speed, after you convert bytes to bits. This table has the answers for common cases.
The table
Best-case times, calculated with Python when this page was built, using decimal units (1 GB = 10^9 bytes) and the full line speed.
| File | 10 Mbit/s | 50 Mbit/s | 100 Mbit/s | 300 Mbit/s | 1,000 Mbit/s |
|---|---|---|---|---|---|
| 100 MB | 1 min 20 s | 16 s | 8 s | 3 s | 1 s |
| 1 GB | 13 min 20 s | 2 min 40 s | 1 min 20 s | 27 s | 8 s |
| 4.7 GB | 1 h 2 min | 12 min 32 s | 6 min 16 s | 2 min 5 s | 38 s |
| 10 GB | 2 h 13 min | 26 min 40 s | 13 min 20 s | 4 min 27 s | 1 min 20 s |
| 50 GB | 11 h 6 min | 2 h 13 min | 1 h 6 min | 22 min 13 s | 6 min 40 s |
| 100 GB | 22 h 13 min | 4 h 26 min | 2 h 13 min | 44 min 27 s | 13 min 20 s |
How to adjust it
Real downloads reach perhaps 80 to 90 percent of the line speed on a good cable, and less over Wi-Fi. Divide the best-case time by 0.85 for a realistic estimate on a cable: 10 minutes becomes about 12 minutes.
The formula
Time in seconds = size in bytes x 8 divided by speed in bits per second. For 4.7 GB at 100 Mbit/s: 4.7 x 10^9 x 8 / 100 x 10^6 = 376 seconds.
Planning big transfers
- Overnight. If the time is hours, start the transfer in the evening.
- A cable, not Wi-Fi. It makes the biggest difference.
- Check data limits. Some plans slow down after a monthly quota.
- Use a program that resumes interrupted downloads.
- Check your upload speed if you are sending, because it is often slower.
Common mistakes
- Using Mbit/s as if it were MB/s.
- Ignoring the allowance for real-world overhead.
- Not checking whether your plan's data limit allows the download.
How long does 50 GB take on 100 Mbit/s?
The table gives the best case. Add 15 to 20 percent for a realistic time.
What speed should I buy for large files?
Choose the plan by how long you are willing to wait for your typical files, using the table.
This is an independent guide. It is not connected with the IERS, BIPM, IANA, NIST or any company named here. Facts were read on 14 November 2026 from the sources named on each page; calculated values come from Python.