When O2 said it was scrapping unlimited iPhone data in favour of a 500MB cap there was plenty of disquiet. But just how unreasonable is a 500MB a month limit to deter bandwidth hogs?

MacFormat set out to investigate by asking nearly 1,000 iPhone owners just how much data they'd used since they last reset the count on their iPhones - and over how long a period of time that usage was.

It turns out, that a cap of 500MB is not that unreasonable at all - based on people's current levels of iPhone usage, of course. Excluding the top one per cent of users, the average monthly data burn is 221MB.

You can see the full iPhone data usage survey results over at MacFormat.co.uk including plenty of trendy pie charts and graphs.

"Four in five people use less than 500MB a month, and only one in ten use more data than O2's standard plans allow for," says MacFormat's Chris Phin.

Some chew through 10GB

One per cent of users used 10GB of data a month or more - presumably jailbreaking their iPhones and tethering them. This skews the average amount of data used across all users to nearly 720MB.

"If you want more, pay more," adds Chris. "As it happens, however, most people were surprised to see how little data they'd actually used."

This survey obviously doesn't take into account future data usage - if FaceTime became available over cellular, for example, or data tethering becomes more common, then iPhone data usage will go up significantly.

For the record, Chris uses less than 170MB, while this writer uses around 150MB – and neither of us are lightweight users.

If you want to work out your monthly average, head over to MacFormat to see how - and check out the survey results.

iPhone data usage