Ever stood in a Tim Hortons lineup, desperate for coffee and haunted by the slight suspicion the large and extra-large cups might, in fact, be roughly the same size?

Sure, the extra large cup is taller, but it also appears to be narrower than the large, leading many Canadians to test for themselves the volume of both cups.

Strangely, videos appear online supporting both the prosecution:

and the defence:

So we decided it was up to the Canada's national broadcaster to put the nation's most popular coffee chain to the test.

A bit of background here: Tim Hortons super-sized its coffee cups in 2012. The 20-ounce cup previously known as "extra-large" was demoted to "large" and the chain introduced a 24-ounce extra-large cup in its place.

Tim Hortons introduces new cup sizes. Note L and XL

It's important to note the line a fraction of a centimetre beneath the rim of each cup. This is the level to which staff pour coffee, and proved to be crucial in myth-busting the Tim's truthers, who fill their cups to overflowing before comparing sizes.

We poured a large coffee into an extra-size cup within minutes of buying it at Tim Hortons, ensuring no tampering with the product.

The result? A gap which turned out to be exactly four ounces deep.

In other words, the difference between a 20 and 24 ounce cup is exactly spot on.

Myth busted!