The stars are big, no doubt about it. But even among the stars, there are stars so enormous that their size defies imagination (and extends our understanding of astrophysics in the process). To talk about how big the biggest stars are, let's talk about our own humble sun.
The Sun is formally a G-type main sequence star and, informally, a yellow dwarf. It is not very large by cosmic standards, but even then it is huge compared to Earth. You can pack 1.3 million soils into the space occupied by our modest sun.
The largest stars in the universe are known as "super giants" and the largest of such known stars is a red super giant called UY Scuti. First observed in 1860, further observations and calculations have shown that UY Scuti is astonishingly huge in volume and is currently the leading candidate for the largest observed star (as well as one of the most brilliant red super giants).
How big is UY Scuti? Its estimated volume is five billion times the sun and if we were to replicate the Earth-inside experiment with UY Scuti it would contain about 6.6 quadrillion Earths. It is such a big star that if you dropped it in the same place as our sun, its photo sphere would extend just beyond Jupiter's orbit.