The calculator can be used to determine one of three quantities:
To obtain any of them, user needs to input the remaining two and choose the units of measurement (for example, gigabytes, kilobytes/s, minutes).
For size, it should be listed in the download page (e.g. AppStore, webpage, Google Play Store), e.g. 24 MB, meaning 24 megabytes.
The speed is most confusing, with two variants used - one that is based on bytes (B) and one that is based on bits (b). One byte equals 8 bits. The speed of your internet connection, as declared in the contract with the ISP (Internet Service Provider) typically uses the notation with bits, e.g. 20Mb/s, 20Mbps (20 megabits per second). While downloading a file, however, the web browser or download client most often shows bytes per second, e.g. 2.5 MB/s (which corresponds to 20 Mb/s). Keep in mind, that commonly there is a difference between download speed (the speed with which you can get the data from a website or server) and the upload speed (the speed with which you are able to send the data from your computer, e.g. when uploading a picture to Facebook). ISPs often advertise the speeds in their offers as download/upload, e.g. a 20/1 Mbps offer would mean that you are able to download data with rate equal to 20 Mbps and upload the data 20x slower than that.
The unit of time should be chosen to be meaningful - e.g. if you have a 20 Mbps (download) connection and want to download a 2GB movie, it would take approximately 14 minutes. You can change the unit after filling the forms, and the utility will refresh the values.