Parallax Distance Calculator
Stellar parallax is the gold standard for measuring distances to nearby stars: as Earth circles the Sun, a near star appears to shift slightly against the far background, and the size of that shift tells you the distance. This calculator applies the exact parallax relation, distance in parsecs equals one over the parallax angle in arcseconds, and also converts to light years. Enter a measured parallax angle to get the distance.
Parallax distance formula
distance (parsecs) = 1 / parallax angle (arcseconds)
distance (light years) = distance (parsecs) * 3.26156
The parsec is defined so that a parallax of 1 arcsecond corresponds to exactly 1 parsec. One parsec is about 3.26156 light years.
Worked example
Proxima Centauri has a parallax of about 0.7687 arcseconds. Distance is 1 / 0.7687 = 1.30 parsecs, which is about 4.24 light years, the closest star to the Sun.
Parallax distance: frequently asked questions
What is stellar parallax?
Parallax is the small apparent shift in a nearby star's position against distant background stars as Earth orbits the Sun. Measured as the angle from the Earth-Sun baseline, the parallax angle shrinks as the star gets farther away. It is the most direct method for measuring distances to nearby stars.
What is the parallax distance formula?
Distance in parsecs equals 1 divided by the parallax angle in arcseconds. By definition, a star with a parallax of exactly 1 arcsecond is 1 parsec away (about 3.26 light years). The relation is simple and exact because the parsec was defined precisely so this would hold.
Why are parallax angles so tiny?
Even the nearest stars are enormously far away compared to the size of Earth's orbit, so the angular shift is a fraction of an arcsecond. Proxima Centauri, the closest star to the Sun, has a parallax of only about 0.77 arcseconds. Measuring such small angles requires very precise instruments, such as space telescopes designed for astrometry.
Sources
- Parallax and the parsec: NASA NASA Science: Universe for background on the cosmic distance ladder. The parsec is defined so distance (pc) equals 1 over parallax (arcsec).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.