Originally from ticket #4470.
I'm supporting a group that is interested in using magpi for a study, and I
wondered if you have guidelines on budgeting for airtime. For instance, for
previous studies is there a formula that may have been used for previous
studies (ie. X minutes per data volume per day per cell phone)?
Thanks for writing, and for considering Magpi. The volume of data used depends on the number of questions in the form(s) that you are using, and of course the number of records collected. We used to calculate a formula such as you mention, but in the end stopped bothering because data transmission costs have dropped so low in most countries.
If you do want to calculate actual costs, you will need to find out the local cost of uploading per megabyte from the carrier you intend to use. As an example, for Safaricom in Kenya you can buy data at a cost of 1.25 Kenyan shillings per megabyte. That is 1.15 US cents per megabyte (not a misprint!). And if you buy a bigger bundle you can cut that in half.
Again, at that level of cost, I'm not sure it's worth calculating. And our users report that in most instances where they are uploading data via the local cellular internet (3G, etc) the costs are trivial: a few cents per uploaded data record.
Of course, one can minimize costs still further if all devices are going to return to a central location, in which case the data could be uploaded via office wifi.
I hope this is helpful.