Stellar Parallax Distance Calculator

About this calculator

As Earth orbits the Sun, nearby stars appear to shift slightly against the distant background sky when viewed six months apart — this apparent shift is stellar parallax, and half the total angular shift (measured against a 1 AU baseline) gives the parallax angle p in arcseconds. Distance follows directly from d = 1/p, where d comes out in parsecs — the unit is literally defined this way, "parsec" meaning the distance at which 1 AU subtends 1 arcsecond of parallax.

One parsec equals about 3.26 light-years or roughly 206,265 astronomical units. This geometric method needs no assumptions about a star's brightness or type, which makes it the most direct distance measurement in astronomy; missions like Hipparcos and especially Gaia have measured parallaxes for over a billion stars, anchoring the entire cosmic distance ladder used for everything from stellar physics to galactic mapping.