What is the Star Distance Calculator?
Calculate how far away a star is using parallax or the distance modulus formula with this free star distance calculator. Convert results to parsecs, light-years, astronomical units, and kilometers. Includes Proxima Centauri, Sirius, and Polaris examples. Runs entirely in your browser with no signup.
How to use the Star Distance Calculator
- Choose Parallax, Magnitude, or Convert Units mode.
- Enter parallax in mas or arcseconds, or apparent and absolute magnitude, or a known distance.
- Click Calculate to get distance in parsecs, light-years, AU, and km.
- Review the step-by-step astronomy formulas used.
- Copy the full results for homework or research notes.
Common use cases
- Converting Gaia parallax in mas to light-years
- Finding Sirius distance from apparent and absolute magnitude
- Converting 10 parsecs to AU for an astronomy lab
Frequently asked questions
- How do you calculate distance from parallax?
- Distance in parsecs equals 1 divided by parallax in arcseconds, or 1000 divided by parallax in milliarcseconds (mas). Smaller parallax means a more distant star.
- What is the distance modulus formula?
- m − M = 5 log₁₀(d) − 5, where m is apparent magnitude, M is absolute magnitude, and d is distance in parsecs. Solving gives d = 10^((m − M + 5)/5).
- How many light-years are in a parsec?
- One parsec equals about 3.2616 light-years. This tool converts automatically between parsecs, light-years, AU, and kilometers.
- What parallax does Proxima Centauri have?
- Proxima Centauri has a parallax of about 768.5 mas, corresponding to roughly 1.30 parsecs or 4.24 light-years — the nearest known star to the Sun.
