It's estimated to be 1,708 times the radius of our Sun. To put that into perspective, if UY Scuti were placed at the center of our solar system, its surface would extend out past the orbit of Jupiter!

However, it's important to note that:

* Mass: While UY Scuti is massive, it's not the most massive star. Other stars like R136a1 are far more massive, though they are smaller in radius.

* Measurement Uncertainty: The size of UY Scuti is based on estimations and could be off by a significant margin. It's difficult to accurately measure the size of stars that are so far away.

Therefore, while UY Scuti is currently considered the biggest known star in terms of radius, there could be other stars even bigger that we haven't yet discovered or measured accurately.