How this calculator works
An upload pushes bytes from your device to a server, and the return path is usually the slower half of a home connection. The arithmetic is the same as for a download: file size in bytes times eight gives bits, and dividing by the upload speed gives seconds. Upload throughput is often more variable than download because of the provider plan, the server receiving the file and any per-connection limit. Video platforms also re-encode on arrival, so the upload may finish before the file is ready to watch.
Formula
upload time (s) = file size (bytes) x 8 / upload speed (bits per second). file size = upload speed x time / 8. upload speed = file size x 8 / time.
Worked example
A 1 GB video at 10 Mbit/s: 1,000,000,000 bytes x 8 = 8,000,000,000 bits. Dividing by 10,000,000 bits per second gives 800 seconds, which is 13 minutes 20 seconds. To upload the same file in 5 minutes you need 8,000,000,000 / 300 = about 26.7 Mbit/s.
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Frequently asked questions
Why is upload slower than download?
Many home plans are asymmetric because most households download far more than they upload. Cable and fibre-to-the-home plans commonly offer an upload speed a tenth of the download speed or less, so check the upload figure separately.
Does the browser slow uploads down?
It can. Browsers add protocol overhead, may limit concurrent requests and sometimes throttle background tabs. A dedicated upload tool can be faster for very large files, and a wired connection avoids Wi-Fi contention.
Why does a video upload show its own progress bar?
Video sites transcode after the upload finishes. The transfer may be complete while processing continues, and the reported progress can include processing time. Use the site's transfer indicator, not the processing indicator, when comparing with this estimate.
How do I find my upload speed?
Run a speed test and read the upload result, not the download result. Test over a wired connection with other devices idle for the most stable figure, and repeat at different times of day because shared neighbourhood links slow down in the evening.