Billmonitor.com, the Ofcom-accredited mobile price comparison site, analysed 215,507 real mobile phone bills and found that almost half of smartphone users are consuming just 100MB of data per month, or less.
The company discovered that consumers are increasingly wasting hundreds of megabytes a month as they frequently overestimate their needs.
While 49% of all smartphone users were using just 100MB of mobile data a month, 88% were paying for a 500MB allowance.
Billmonitor said that consumers are overestimating their data needs over fear of 'bill shock', in which they incur excess charges when going over their data limits.
However, the research indicated that only 8% of smartphone users have recently experienced data charges, and so this fear is "usually unfounded".
Smartphone data usage is certainly on the rise, doubling over the past 18 months from 71MB to an average of 154MB per month.
But the report said that there is a much larger volume of data available than consumers are actually using, meaning most data allowances are "actually going to waste".
Billmonitor revealed that only 27% of mobile phone consumers are "power users", consuming more than 250MB per month.
Dr Stelios Koundouros, the Oxford mathematician who founded Billmonitor.com, said: "Virtually all smartphone users have one thing in common: they're all paying more for mobile data than they should.
"It is notoriously difficult for people to estimate their real data usage, and smartphone users who don't know how much data they are using cannot make an informed decision on which tariff is right for them.
"We urge people to take a good look at their consumption and make sure that they are not paying over the odds for their data."
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