Light-Year, Parsec & AU Converter
Convert any astronomical distance instantly between AU, light-years, parsecs, kilometers and meters.
Source unit
Same physical distance shown in every astronomical unit below
- 1
Conversion factor: 1 pc in light-years
3.0857e+16 m ÷ 9.4607e+15 m/ly = 3.261598All astronomical units are defined as fixed multiples of the metre. - 2
Light-years = value × conversion factor
1 × 3.261598 = 3.261598
How does this calculator work?
Pick a value and its unit (AU, ly, pc, km or m) and this converter expresses the same distance in every other unit. It uses fixed IAU factors in meters, giving relationships such as 1 parsec = 3.2616 light-years = 206,265 AU and 1 light-year = 63,241 AU.
Formula
How this is calculated
Enter a distance value and choose its source unit (AU, ly, pc, km or m). The calculator first converts your value into meters using a fixed factor for each unit, then divides that metre count by every other unit factor to produce all equivalents at once. Because all results describe the exact same physical distance, the headline figure is shown in light-years while the full table lists AU, ly, pc, km and m.
The factors are the standard IAU definitions: one astronomical unit (the average Earth–Sun distance) is 1.495978707×10¹¹ m, one light-year (the distance light travels in a Julian year) is 9.4607×10¹⁵ m, and one parsec is 3.0857×10¹⁶ m. These imply the familiar relationships 1 pc = 3.2616 ly = 206,265 AU and 1 ly = 63,241 AU.
Conversion is exact and linear, so no rounding occurs internally — only the displayed values are rounded for readability. Values can span dozens of orders of magnitude, so the meter scale indicator uses a base-10 logarithmic axis to place the distance from planetary (AU) through interstellar (ly) and galactic (pc–kpc) ranges.
Frequently asked questions
One parsec equals about 3.2616 light-years, derived from the IAU factors 1 pc = 3.0857×10¹⁶ m and 1 ly = 9.4607×10¹⁵ m.
One light-year contains roughly 63,241 astronomical units, since 1 ly = 9.4607×10¹⁵ m and 1 AU = 1.495978707×10¹¹ m.
An astronomical unit (AU) is the mean Earth–Sun distance, defined exactly as 1.495978707×10¹¹ meters, and is used for distances within the solar system.
Also known as
TG we-Calculate Editorial Team. (2026). Light-Year, Parsec & AU Converter [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/light-year-parsec-au-converter
TG we-Calculate Editorial Team. "Light-Year, Parsec & AU Converter." TG we-Calculate. 2026. https://we-calculate.com/calculator/light-year-parsec-au-converter.
TG we-Calculate Editorial Team, "Light-Year, Parsec & AU Converter," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/light-year-parsec-au-converter
@misc{wecalculate_light_year_parsec_au_converter, title = {Light-Year, Parsec & AU Converter}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/light-year-parsec-au-converter}}, year = {2026}, note = {TG we-Calculate} }
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