File Transfer Time Calculator: GB, GiB, Mbps and MB/s
Quick answer: Transfer time depends on the amount of data and the usable transfer rate. At an ideal 100 Mbps, 1 GB takes 80 seconds. At an assumed usable rate of 80%, the same calculation gives 100 seconds. These are mathematical examples, not measured internet speeds.
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File transfer time calculator
Set the amount of data, transfer rate and an explicit efficiency assumption. No files are uploaded.
Choose the right units before planning a transfer
A connection quoted in Mbps uses megabits per second. File sizes usually use bytes. One byte contains eight bits, so 100 Mbps is not 100 MB/s. Decimal GB and binary GiB also differ. The calculator keeps the choices separate: 1 GB is 1,000,000,000 bytes; 1 GiB is 1,073,741,824 bytes. See the NIST explanation of binary prefixes and our MB vs MiB guide.
Worked examples you can reproduce
| Data and rate | Ideal minimum | At an assumed 80% usable rate |
|---|---|---|
| 1 GB at 100 Mbps | 80 seconds | 100 seconds |
| 10 GB at 20 Mbps | 4,000 seconds (1h 6m 40s) | 5,000 seconds (1h 23m 20s) |
| 1 GiB at 100 Mbps | 85.899 seconds, approximately | 107.374 seconds, approximately |
| 1 GB at 100 MB/s | 10 seconds | 12.5 seconds |
Displayed durations round up to whole seconds. Decimal values in the table show the underlying calculation. No row is a product benchmark.
Why a real upload may take longer
This tool converts quantities; it does not test your network or storage device. Its ideal result assumes a continuous rate. Setup, retries, interruptions and other work are outside the calculation. If you know the usable rate from a representative transfer, enter that rate with 100% instead of applying a second efficiency reduction. Otherwise, use an explicit planning assumption and leave enough time to check the result.
For a cloud upload, start from the upload rate available to you, not an unrelated download figure. For a local copy, use an observed file-copy rate in the correct unit rather than treating a port’s advertised maximum as a guaranteed file-transfer rate.
The formula, without the tool
ideal seconds = file bytes × 8 / transfer bits per second adjusted seconds = ideal seconds / (usable rate percent / 100)
Example: 1,000,000,000 × 8 / 100,000,000 = 80. Divide 80 by 0.8 to get 100 seconds. The percentage does not predict overhead; it is a number you choose for the scenario.
A transfer is not complete until the result is checked
- Work out which files and total size are included.
- Keep the source while the transfer runs.
- Open the destination copy, not the original.
- Check a representative large file and the beginning and end of the expected set.
- For a backup, try restoring a separate sample before relying on it.
Use our backup restore checklist if this is your only recovery copy, or the unfinished-download guide if the destination is empty or will not open.
Frequently asked questions
Can this calculate several files?
Yes. Enter their combined size in one unit. It does not model pauses between individual files. Use a representative observed rate if that overhead matters to your task.
Is 80% the normal speed?
No. It is an editable example. Your usable rate may differ. The tool makes the assumption visible instead of hiding a fixed multiplier.
Does it upload files or measure my connection?
No. The calculator uses the numbers you enter in your browser. It has no file picker, network speed test or calculator-specific tracking request.
Calculator verified October 6, 2026 with decimal/binary units, bits/bytes, invalid values and long durations. Those checks validate the calculation, not the performance of a connection or storage product.