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Parallax Calculator.

Estimate distance from annual stellar parallax in arcseconds.

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Distance: 10 pc

Distance

10.000000pc
Distance: 32.615638 ly

Distance

32.615638ly

Results update automatically as you type.

Use Cases

Astronomy Education

Helps students and enthusiasts understand how astronomers measure stellar distances using parallax.

Example: Input a parallax of 0.5 arcsec to see the distance is 2 parsecs.

Quick Distance Estimation

Provides a fast way to convert a measured parallax angle into a distance without manual calculation.

Example: For a parallax of 0.05 arcsec, the distance is 20 parsecs.

Frequently Asked Questions

What is the parallax formula used in this calculator?
The calculator uses the formula distance (in parsecs) = 1 / parallax angle (in arcseconds). For example, a parallax of 0.1 arcsec gives a distance of 10 parsecs.
Why is the distance in parsecs?
The parsec is defined as the distance at which one astronomical unit subtends an angle of one arcsecond. Using the inverse relationship, a parallax of 1 arcsec equals 1 parsec, making the calculation straightforward.
Can I use this for any star?
Yes, as long as you have the annual parallax angle in arcseconds. This method is most accurate for nearby stars; for distant stars, the parallax is very small and harder to measure precisely.

Tips & Common Mistakes

Tips

  • Ensure the parallax angle is in arcseconds, not degrees or radians.
  • Use precise measurements; small errors in parallax lead to large errors in distance.
  • For very small parallax values (e.g., <0.01 arcsec), the distance is large and may be less reliable.
  • Remember that 1 parsec ≈ 3.26 light-years if you need to convert to light-years.

Common Mistakes to Avoid

  • Using the parallax angle in degrees instead of arcseconds.
  • Forgetting that the formula is inverse: a larger parallax means a smaller distance.
  • Assuming the result is in light-years when it is in parsecs.

Last updated: August 13, 2026