Parsecs To Light Years
Calculator
Results
- Distance (light years)
- 4.243946
- Distance (AU)
- 268,391.765888
- Distance (trillion km)
- 40.150836
Astronomy results
| Distance (light years) | 4.243946 |
| Distance (AU) | 268,391.765888 |
| Distance (trillion km) | 40.150836 |
formula-map diagram
- Distance (light years)
- 4.243946
- Distance (AU)
- 268,391.765888
- Distance (trillion km)
- 40.150836
Astronomical relationship
Formula
d_ly = d_pc × (1 pc / 1 ly) = d_pc × 3.261563…= 4.2439467868503
Note
This result is a simplified model: it applies the displayed textbook formula to the values you entered, assuming ideal spherical bodies, circular orbits, blackbody radiation and perfect optics, and ignoring atmospheric seeing, relativistic corrections beyond those stated, cosmological models and measurement uncertainty. Use published ephemerides and catalogue data for real observations.
More in Astronomy and space
See all →Frequently asked questions
What is a parsec, and why does astronomy use it?+
A parsec is the distance at which one astronomical unit subtends an angle of one arcsecond, derived directly from parallax measurements astronomers use to gauge stellar distances. It equals about 3.2616 light-years, and it's preferred in professional astronomy because it ties distance directly to an observable angle.
How does the calculator convert parsecs to light-years?+
It multiplies the number of parsecs by the fixed factor of about 3.26156 light-years per parsec. This factor comes from the definition of the astronomical unit and the geometry of parallax at one arcsecond.
Why does 1 parsec not equal a round number of light-years?+
Because the parsec is defined geometrically, from parallax angle and the astronomical unit, rather than being defined in terms of light travel time at all. The conversion factor to light-years is simply where those two independently-defined units happen to align.
What do units like kiloparsec or megaparsec mean?+
A kiloparsec (kpc) is 1,000 parsecs, used for distances across our galaxy, and a megaparsec (Mpc) is a million parsecs, used for distances between galaxies. Multiplying by 3.26156 still converts these to light-years, just scaled by the same 1,000 or 1,000,000 factor.
Is parallax the same method used to measure all parsec distances?+
Parallax directly measures the closer distances, typically up to a few thousand light-years using space telescopes like Gaia, but more distant objects use other methods calibrated against parallax. The parsec unit is still used for those larger distances even though parallax itself isn't directly observable at that range.