Australians are being urged to ensure they’re not overpaying for mobile data as big telcos pass on huge price increases to their post-paid mobile plans.

A series of price increases from Telstra recently will see over 40 per cent of Australian mobile users cop bill rises of up to 9 per cent in August, while other telcos are also hiking their prices.

That includes Optus, which earlier this year unveiled increases between 5 and 6 per cent.

Money saving expert Joel Gibson and telco comparison site WhistleOut say Australians should apply a simple rule of thumb to work out whether they’re overpaying for data after the hikes.

It’s called the “buck a gig rule” and it essentially means you shouldn’t pay more than about $1 per gigabyte of data you’re eligible for each month.

“Telstra’s cheapest post-paid plan, for example, includes 50GB of data for $62, soon to cost $65 a month,” he said.

“That’s $1.24 per gig, rising to $1.30 per gig in August. Not great value.”

Gibson isn’t the only one worried that Australians are paying too much for mobile plans, with the Australian Competition and Consumer Commission (ACCC) also holding concerns that many consumers are paying for data they don’t even use.

For example, ACCC analysis has found the average Australian uses just 7.5GB of mobile data each month.

But despite that, the median market plan carries a whopping 32GB of data, several orders of magnitude more than most people need.

So the first step is to work out how much data you actually need before signing up for a mobile deal. The best way to do this is to check your past usage through your smartphone settings.

If your usage varies month to month, then you’ll want to look for a deal that comes with data banking, a feature that allows you to carry over your allowance from one month to the next.

That means you won’t get caught out if your usage is very low in one month and then spikes in the next billing period, because all that data you didn’t use previously will still be available to you.

Gibson said his buck a gig rule of thumb works for medium sized plans, with smaller plans likely to cost more than $1 per gigabyte, though they will be less in absolute dollar terms.

“Right now you can get 50GB plans from providers with full Telstra network access for 78c-$1.40 per gig, or from Telstra-owned brands from 58c-87c per gig, or from other providers on the Telstra network starting from as little as 36c per gig,” he said.