Star Distance via Parallax

Summary

Enter a star's annual parallax in arcseconds and instantly get its distance in parsecs, light-years, and astronomical units.

How it works

1. Enter the star's annual parallax angle in arcseconds (milliarcseconds and microarcseconds are also accepted).
2. Select the input unit: arcseconds, milliarcseconds (mas), or microarcseconds (µas).
3. Click Calculate to apply d = 1/p and convert the result into parsecs, light-years, and AU.
4. The result panel shows the distance in all three units along with an uncertainty estimate if you supply a parallax error.
5. Use the preset famous-star buttons to explore well-known examples instantly.

Use cases

• Convert Hipparcos or Gaia catalog parallaxes to intuitive distance units.
• Check the distance to a named star quickly without manual unit conversions.
• Teach students the parsec definition and the parallax-distance relationship.
• Verify hand-computed stellar distances against this tool.
• Explore how measurement precision (mas vs. arcsec) affects distance accuracy.
• Compare distances of nearby vs. distant stars on the same scale.
• Estimate distance uncertainty from a parallax measurement error.
• Convert between parsecs, light-years, and astronomical units in one step.

Frequently Asked Questions