This $66 Aussie escape has been named the nation's most affordable day trip

Think a weekend getaway is out of your budget? Think again. A new index has revealed Australia's top budget-friendly road trips - including a day out for two for under $70.

From sipping world-class Shiraz in South Australia's McLaren Vale for around $120 a couple, to exploring the coastal lookouts of Geelong or the cliffside walking trails of Katoomba, the options cover both wine country and wilderness.

So before you head out on your next road trip, check this list.

When money gets tight, weekend trips are usually the first thing to be crossed off the priority list, but taking a good break doesn't require a massive budget.

A national study from car insurance provider ROLLiN' assessed 73 of regional Australia's most popular weekend escape destinations based on value for money across fuel, food, entry fees and attraction costs for two adults.

While the calculations don't include accommodation costs, budget-conscious road-trippers can stay overnight at low-cost options such as national park unpowered sites.

The research found McLaren Vale, in the popular South Australian wine region, claimed the top spot with a bang-for-buck score of 73.96 out of 100.

For an estimated $127.76, couples can enjoy an affordable escape to McLaren Vale, an area boasting 39 free activities and 38 natural attractions.

Geelong in Victoria took the second position, with a 70.98 rating out of 100, and a trip cost of $104.83.

The city, near Victoria's Great Ocean Road, has seven beaches, seven lookouts and nine walking trails.

Wollongong, an hour and a half south of Sydney, ranked third at 70.76 out of 100, with an average cost of $102.29.

The city has 44 attractions, 30 free activities, reliable weather and well-reviewed eateries.

Katoomba in NSW's Blue Mountains placed fourth, with 68 natural attractions, stunning natural scenery and a high rating on Google for the area's major highlights.

Rounding out the top five, Perth Hills (Kalamunda) in Western Australia delivers 29 natural attractions and nearly nine hours of fun at the destination for just $72.15.

At the top of the national affordability index sits South Australia's Williamstown, where a complete day out for two people costs about $66.04.

With a perfect 100/100 affordability score, the destination is a cheap, easy escape from Adelaide, the research found.

Just on the edge of the Barossa Valley, the area is flush with scenic drives and free landmarks such as the Whispering Wall at Barossa Reservoir Reserve.

ROLLiN' executive manager Brendan Griffiths said the research showed that you don't need to travel far or spend big to have a great day out.

"There are plenty of destinations around Australia where a drive, a change of scenery and a day exploring still offers so much value," he said.

But what makes a destination good value? It depends on the visitor and the budget, so the study evaluated destinations through two lenses: overall value and pure affordability.

Overall value measures what your money buys, by balancing cost against quality, weighing up free sights, reliable weather as well as time spent exploring (not behind the wheel).

Pure affordability looks at the bottom line, tallying expenses to find the cheapest possible escape.