It's tricky to give a single answer to "how big is a giant star" because "giant star" is a broad category, encompassing a wide range of sizes!

Here's a breakdown:

* Red Giants: These are the most common type of giant star. They are typically 10-100 times the size of our Sun. Imagine a sphere that could fit the entire orbit of Earth!

* Blue Giants: These stars are even larger, with diameters up to 1000 times that of our Sun. They are also much hotter and brighter than red giants.

* Supergiants: These are the absolute behemoths of the stellar world. Some supergiants can be hundreds of thousands of times larger than our Sun.

For example:

* Betelgeuse (in the constellation Orion) is a red supergiant with a diameter roughly 1,000 times that of our Sun. If it were in our solar system, it would engulf the orbits of Mercury, Venus, Earth, Mars, and even Jupiter!

* VY Canis Majoris, another red supergiant, is estimated to be 2,100 times the diameter of our Sun, making it one of the largest known stars.

So, to summarize, giant stars can range in size from 10 times the diameter of our Sun to hundreds of thousands of times larger.