Data Transfer Time Calculator
Calculate how long a file transfer will take at a given throughput, and the effective speed you actually achieve.
Your details
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This calculator runs entirely on your device. Nothing you enter is uploaded, stored, or sold. How this works
Transfer time
1 hr 25 min
512,000 MB at an effective 100.0 MB/s
Includes your inputs, the full breakdown, and every row of the table.
Effective throughput
800 Mbps
80% of 1,000 Mbps
In MB/s
100.00 MB/s
Total seconds
5,120
At full line rate
1 hr 8 min
Theoretical best case
- Size
- 512,000 MB
- Line rate
- 1,000 Mbps
- Efficiency (80%)
- 800 Mbps
- Effective bytes/sec
- 100.00 MB/s
- Transfer time
- 1 hr 25 min
| Link speed | Transfer time |
|---|---|
| 25 Mbps | 2 days 9 hr |
| 100 Mbps | 14 hr 13 min |
| 300 Mbps | 4 hr 44 min |
| 500 Mbps | 2 hr 51 min |
| 1 Gbps | 1 hr 25 min |
| 10 Gbps | 8 min 32 sec |
What this means
- Real throughput rarely exceeds eighty to ninety percent of line rate. TCP headers, acknowledgements, encryption, and disk I/O all take a cut.
- On long-distance links, latency limits throughput more than bandwidth does. A single TCP stream across a high-latency path may need window tuning or parallel streams to fill the pipe.
- Consider compressing the data first — text, logs, and databases often compress by 60-90%.
How the data transfer time calculation works
Transfer time is size divided by throughput, with the catch that size is normally quoted in bytes and throughput in bits. Convert one to match the other before dividing, or the answer will be off by a factor of eight.
Effective throughput is always lower than line rate. Between protocol overhead, TCP slow start, encryption, and storage bottlenecks at either end, eighty percent of the rated speed is a realistic planning assumption for a well-tuned link.
Frequently asked questions
How long to download 100 GB?
About 22 minutes on a 1 Gbps link at 80% efficiency, roughly 3.5 hours on 100 Mbps, and about 14 hours on 25 Mbps.
Why is my transfer slower than my connection speed?
Protocol overhead, disk speed on either end, the remote server's own limits, Wi-Fi, and TCP window sizing on high-latency paths all reduce real throughput below the rated line rate.
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Disclaimer. This calculator is provided for general information and educational purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Results are estimates based on the inputs you provide and the assumptions described above. Confirm any figure with a qualified professional before acting on it.