How accurate is iPhone built in data counter?

The iPhone's data usage indicator has never been accurate & most likely never will be accurate. Fact is you cannot use this to estimate your data usage for billing purposes. Your actual data usage as calculated by your carrier's equipment on their end, and that's all that matters for billing purposes. Fact is, the usage counter on just about every phone is not accurate.

Download the AT&T myWireless app. It gives you up to date information on your data usage. I rely on that rather than the built in counter.

http://itunes.apple.com/us/app/at-t-mywireless-mobile/id309172177?mt=8

I was wondering the same thing so i did a test and reset it on the 1st of every month and checked with my bill at the end of the month.
Its been three months now and every time it is within 10% (both sent and recieved added together) of the amount that Vodafone has billed me for.
So for me its quite accuare.

Luckily Vodafone have got a data usage app anyway which shows the usage of the phone. Maybe O2 do something similar?

I'm afraid it is right - so be glad you don't live here. Check out these links to the UK Vodafone website. I have also checked O2 and Orange and they are the same or worse. with Vodafone if you exceed your monthly allowance you are charged £5 for the next 500mb. Personally, my monthly usage is around 700mb and I make sure that mobile data is turned off when I am at home so that all traffic has to use my WiFi connection.

http://shop.vodafone.co.uk/iphone/pay-monthly.html

http://shop.vodafone.co.uk/iphone/pay-as-you-go.html

http://shop.vodafone.co.uk/iphone/sim-only.html

yep us Brits have to suffer some really rubbish data limits and on top of that the BT backbone for the whole countries system of internet is just awful as well! LOL
i use iDateusage app to check my limits which you can set on a monthly rollover and will also supply an alarm if you half way and close to the limit of your usage. it seems farely good.
having said that ive used 10.3 meg of 1 gig limit in 17 days of my month!
i use my work wifi and my home wifi the most and as such ive really never found my 1 gig data limit to be even close to being used! LOL

my data reading in phone has never been reset and its reading 14.8 mb..which i guess will be about right; so i dont think its majorly innaccurate but there are apps out there that will provide you with better accuracy for sure!

I don't think the built in data counter is that accurate. For example. On my iphone, it reads that I have used 1.6 GB of data. While on my AT&T account, it is stated that I haved used 1.3 GB. So from what I'm seeing, I always go on my AT&T account and check my data usage from there. I never rely the usage readings on my device.

Based on my experience, the iPhone records all data sent and received, including data exchanges which you are NOT billed for. For example, if I reset my useage states at night, turn off wifi, have all email and such sent to manual data access only and nothing else running, there will still be cellular data exchanged during the overnight period - never more then a few hundred Kb, but still recored under useage stats nonetheless. To the best of my reckoning, that data never shows up on my billing statement. But, it does mean the iPhone will always be showing more data sent/received then I am actually billed for.

P.S. exactly what the non-billed data is, I don't know nor really care. Some sort of house-keeping or network timing data???

Just an F.Y.I, i do turn off cellular data during the night to prevent, the phantom usage and by doing so, nothing is sent, not even 1 KB or less. 0 KB is sent. And I do check my account daily, and look closely at the times of how much data I used at that time. Of course it can take up to 24-72 hours to record the latest usage but I still rely on my account data usage, but never on my device.

the problem is there is no real way to prove if its accurate or not... ive never reset mine...

If you do decide to try and prove you only used 164MB, make sure to point out the last reset date too(its on the bottom of the data counter page).

Good time to switch to an unlimited plan.

Then you never have to think about it.

Good time to switch to an unlimited plan.

Do UK carriers offer that option?

Don't think they do - with Vodafone it is either 1GB or 3GB

Don't think they do - with Vodafone it is either 1GB or 3GB

That CAN'T be right, no one would buy a phone with so little data. I use more than that in a week with NASA TV and Talk Radio Apps.