Arcseconds to Radians Converter

About this calculator

An arcsecond is 1/3600 of a degree, the finest unit commonly used to describe tiny angles; converting to the radian — the SI angle unit where a full circle is 2π — gives 1 arcsecond = π/648,000 radians ≈ 4.8481×10⁻⁶ rad.

Astronomers use arcseconds to express stellar parallax, telescope angular resolution, and proper motion (since these angles are naturally tiny), but the underlying physics and optics equations — like the diffraction limit or small-angle approximations — are written in radians, so converting between the two is a routine step in astronomical and optical calculations.