Astronomical Unit to Parsec Converter

astronomical unit to parsec – How to convert AU to pc

When you start measuring distances beyond our solar system, everyday units like kilometers or miles quickly lose their usefulness. That’s why astronomers rely on specialized units like the astronomical unit (AU) and the parsec (pc). Both help us describe space — but on very different scales. Converting astronomical units to parsecs bridges the gap between our solar system and the stars beyond.

Let’s explore how this conversion works, what makes these units different, and how both continue to shape how we understand the universe.

What is an astronomical unit (AU)?

An astronomical unit is defined as the average distance from the Earth to the Sun. Numerically:

1 AU ≈ 149,597,870.7 kilometers
Or about 93 million miles

The AU is perfect for expressing distances within the solar system:

• Earth to Sun: 1 AU

• Mars to Sun: ~1.5 AU

• Neptune to Sun: ~30 AU

It's a convenient way to measure the relative spacing of planets, moons, and spacecraft trajectories without dealing with long strings of zeros.

What is a parsec (pc)?

A parsec (short for “parallax-second”) is a much larger unit, used to express interstellar distances. It’s defined based on the Earth’s orbit and the method of stellar parallax — the tiny shift in a star’s apparent position when viewed from opposite sides of Earth’s orbit.

1 parsec ≈ 3.26156 light years
Or:
1 parsec ≈ 206,264.806 AU

That means a parsec equals over 206,000 times the Earth–Sun distance, making it ideal for measuring the space between stars and galaxies.

How to convert astronomical units to parsecs

To convert AU to pc, just divide by the conversion factor:

1 parsec = 206,264.806 AU

So the formula is:

parsecs = AU ÷ 206,264.806

Example conversion

Let’s convert 500,000 AU to parsecs:

pc = 500,000 ÷ 206,264.806
pc ≈ 2.423

So, 500,000 astronomical units equals approximately 2.423 parsecs.

Need to convert different values? Try the Length Converter or explore additional tools in the full Conversion tools collection.

Did you know?

• Proxima Centauri, the closest star to the Sun, is about 1.3 parsecs away — or roughly 268,000 AU.

• The Oort Cloud, a distant shell of icy bodies around our solar system, may extend up to 100,000 AU, or nearly 0.5 parsecs.

• Parsecs are often used in Hubble’s Law, which describes the rate at which galaxies are receding based on their distance from Earth.

• Galactic maps are often scaled in kiloparsecs (kpc), with 1 kpc = 1,000 parsecs, or over 206 million AU.

• The unit “parsec” became widely known in pop culture after a misused reference in Star Wars, though in science, it remains the gold standard.

From planets to stars: scaling the universe with AU and pc

Imagine using inches to measure a continent. That’s the challenge astronomers face if they try to use AU beyond the solar system. The unit works beautifully within planetary distances, but when you're looking at other stars, galaxies, or the large-scale structure of the universe, it becomes too small to manage effectively.

This is where the parsec comes in — built on geometric principles that relate directly to how we observe the sky. When astronomers calculate the distance to a star using parallax, they’re working in parsecs by default.

In contrast, AU remains a trusted tool for space missions, solar studies, and planetary science. The Voyager probes, for example, are now well beyond 150 AU from Earth — still a speck compared to even a single parsec.

Together, AU and pc offer a way to zoom from planetary scales to stellar neighborhoods, keeping our understanding of space consistent, clear, and scalable.

A cosmic conversion worth knowing

To convert astronomical units to parsecs:

parsecs = AU ÷ 206,264.806

This simple formula helps you navigate some of the biggest distances we know — from deep within our solar system to the edge of nearby star systems. Whether you're charting spacecraft paths or mapping the Milky Way, switching between AU and parsecs is essential to speaking the language of space.

For instant calculations, try the Length Converter, or check out our full range of Conversion tools to work across any distance, large or small.