Plan the upload you actually need to finish
You have finished exporting a video, but the upload still needs to finish before the deadline. Start with the exported file’s size and your upload speed. The download number advertised with a broadband plan can be very different, so it may be the wrong input for sending a file.
The other common trap is the capital letter. Mbps means megabits per second; MB/s means megabytes per second. One byte is eight bits. A continuous 100 Mbps data rate corresponds to 12.5 MB/s before allowances for reduced throughput. The selector handles that conversion, and keeps a binary MiB/s rate distinct from MB/s.
At 100% efficiency, the result is the ideal duration for continuous delivery at the entered rate. A lower percentage models less usable speed. It is a planning assumption, not a speed test or a prediction trained on your connection. Wi-Fi contention, server throttling, retries and disk speed can change actual completion time. If your input is already a measured payload rate, reducing efficiency again may count the same loss twice.
Choose the processed output to compare its actual bytes against the source size above. The tool uses the same rate for both files and shows extra transfer time if the output grew. It does not compare their content or certify successful conversion.
The size-reduction comparison helps you decide whether compression is worth trying. At the same throughput, reducing the bytes by 40% reduces the transfer portion by 40%. It does not include the time needed to compress or encode the file. An already compressed ZIP, JPEG or video may offer little extra saving without a quality tradeoff.
For several files, the calculation uses their combined bytes. It does not model one setup delay per file, parallel connections or a cloud service’s processing queue. Use the estimate to compare scenarios, and allow extra time for a deadline rather than treating the displayed second as a promise.
Formula and worked example
Seconds = file bytes × 8 ÷ (speed in bits per second × efficiency ÷ 100).
A 25 MB PDF is 200,000,000 bits. At 10 Mbps and 100% efficiency, its transfer takes 20 seconds. At 80% efficiency it takes 25 seconds. A hypothetical 40% smaller PDF takes 15 seconds at that same 80% efficiency, saving 10 seconds of transfer time.
Unit definitions: NIST: binary prefixes and SI comparisons. Calculations use JavaScript numbers; displayed conversions are rounded to six decimal places, with scientific notation for very small values. Inputs above the safe byte-count range are rejected.