Star Sizes Compared to the Sun

Data

Source: Wikipedia — List of largest known stars.

Note: What You Should Know About Stars Compared to the Sun

When we talk about how big other stars are, the Sun is our natural ruler. Everything in the table above is measured in solar radii (R☉) — one solar radius equals the Sun's actual radius, roughly 695,700 kilometres (about 432,000 miles). So when a star has a radius of 887 R☉, like Betelgeuse, you're really looking at 887 Sun-like objects stacked end to end across its diameter. That's the kind of scale that makes the Sun feel almost small by comparison.

Where Our Sun Fits In

The Sun is a G-type main-sequence star — a fairly ordinary yellow dwarf. Astronomers call it main-sequence because it's in the long, stable middle phase of its life, steadily fusing hydrogen into helium in its core. Here's the honest truth: the Sun is pretty middling as stars go.

• The Sun's radius is the baseline — exactly 1 R☉, the very first row in the table.
• Sirius A (1.71 R☉) is only about 70% bigger than the Sun, yet it's one of the brightest stars in our sky because it sits relatively close.
• Giants like Pollux (8.8 R☉) and Arcturus (25.4 R☉) have puffed up enormously as they aged, even when their cores grew denser.
• Our Sun is actually smaller than many of the stars listed — the giant and supergiant stars in the table dwarf it completely.
• By comparing radius alone, the Sun looks unremarkable — exactly what you'd expect from an average star.

The Giants and Supergiants

The real monsters in the table are red supergiants and hypergiants. Aldebaran (45.1 R☉) is a red giant, while Rigel (78.9 R☉, actually a blue supergiant), Antares (680 R☉), Betelgeuse (887 R☉), VY Canis Majoris (1,420 R☉), and UY Scuti (1,708 R☉) are on an entirely different scale.

• The largest known stars in the Universe — including UY Scuti, Stephenson 2-18, and VY Canis Majoris — are red supergiants and hypergiants with radii thousands of times the Sun's.
• If UY Scuti (1,708 R☉) sat where our Sun is, its surface would reach far beyond the orbit of Jupiter.
• Stephenson 2-18 is often listed among the biggest of all known stars, with estimates up to about 2,150 R☉.
• Betelgeuse, at 887 R☉, is one of the most-studied supergiants — it's a young star that will one day explode as a supernova.
• Despite their huge sizes, many supergiants have surprisingly low surface temperatures — which is why they glow red rather than blue.

Radius vs. Mass vs. Volume

It's easy to assume a bigger radius means "more stuff," but that's not how stars work. Radius, mass, and volume are three very different descriptions of a star's size.

• UY Scuti may be thousands of times the Sun's volume, but its mass is only roughly 7–10 times the Sun's — its outer layers are almost a vacuum-thin envelope.
• Red supergiants are enormous in radius but surprisingly lightweight for their size — they're extremely puffy and diffuse.
• Mass matters more than radius for a star's fate: heavier stars burn hotter, faster, and die more violently than smaller ones.
• Volume scales with the cube of radius — a star at 10 R☉ isn't just ten times bigger, it has roughly a thousand times the Sun's volume. That's why supergiants can swallow whole planetary systems.
• So while the table ranks by radius, two stars with identical radius can still differ wildly in mass and density.

How Stellar Sizes Are Measured

Astronomers don't send tape measures into space — they measure star sizes from their light.

• A star's luminosity (total light output) plus its temperature lets astronomers estimate its radius, because hot, bright stars must have large surfaces.
• Interferometry combines light from multiple telescopes to resolve a star's apparent disk directly, even for distant stars.
• The distance to a star (measured by parallax) is crucial: knowing both apparent brightness and distance gives true luminosity.
• Measurements carry real uncertainty — especially for giant stars with fuzzy, extended atmospheres, which is why radius figures can vary between estimates.

Fun Facts

• You could fit about 1.3 million Earths inside the Sun — and roughly 1,000 Jupiters.
• If UY Scuti replaced the Sun, its outer edge would stretch far past Jupiter's orbit — and you'd barely notice it, because the star is so faint and diffuse.
• The Sun makes up about 99.86% of the entire mass of our Solar System — the planets are basically crumbs it left behind.
• Despite being small in the table, the Sun is still about 333,000 times more massive than Earth.
• Blue supergiants like Rigel are far hotter and denser than red supergiants, which is why often-smaller Rigel actually outmasses most red giants.
• Seeing stars like Betelgeuse or Antares "compared to the Sun" is a fast way to appreciate just how ordinary and small our home star really is.

So the next time you look up on a clear night, remember: even the faintest, twinkling star you can see is likely a giant compared to the Sun we call home. Size really is relative.