Data Transfer Time Calculator
Estimate how long a file will take to transfer at a given speed.
How long will it take
The time to transfer a file depends on its size and the connection speed. This estimates the transfer time from those, useful for judging how long a download, upload or copy will take before committing to it.
Enter the file size and speed to estimate the transfer time.
The bits-and-bytes confusion
There is a genuine trap in transfer calculations that trips almost everyone: connection speeds are quoted in bits per second, but file sizes are measured in bytes, and a byte is eight bits. This means a connection advertised at a certain number of megabits per second actually transfers roughly an eighth of that many megabytes per second — which is why downloads seem slower than the headline speed suggests, when really it is just the unit difference. The estimate accounts for this. Real transfers are also usually a bit slower than the theoretical maximum, because of overhead, congestion and the connection rarely running at full advertised speed. So the estimate is a reasonable guide rather than an exact promise, but understanding the bits-versus-bytes distinction alone clears up most of the confusion about why a transfer takes as long as it does.
Data Transfer Time Calculator FAQ
Why does a download seem slower than my connection speed?
Because speeds are quoted in bits per second but file sizes in bytes, and a byte is eight bits — so the real transfer rate is about an eighth of the headline megabits figure.
Will the transfer match the estimate exactly?
Usually it is a bit slower, due to overhead, congestion and connections rarely running at full advertised speed, so the estimate is a guide rather than an exact promise.
Is anything uploaded?
No. The calculation happens in your browser.