# Light Year Converter URL: https://speedycalculator.com/calculators/conversion/light-year-conversion/ Last updated: 2026-10-25 > The light year converter converts distance between kilometres, miles, astronomical units, parsecs, metres and more. Choose any “from” and “to” unit, type a number into any field and every other unit updates instantly; all conversion factors are exact definitions. ## Inputs - From (ly, m, km, cm, mm, dm, µm, nm, Å, in, ft, yd, mi, nmi, mil, furlong, chain, rod, fathom, hand, league, AU, pc, R☉, px (96 dpi), pt, gaj) ## Results - To - Miles - Astronomical units - Parsecs - Metres ## Formula ``` 1 ly = 9.46073 × 10^12 km 1 ly = 5.878625 × 10^12 mi 1 ly = 63,241.077 AU 1 ly = 0.30660139 pc 1 ly = 9.46073 × 10^15 m ``` ## Explanation A light-year is the distance light travels in one Julian year (365.25 days): exactly 9,460,730,472,580,800 m. Despite the name it measures distance, not time. The nearest star beyond the Sun, Proxima Centauri, is about 4.24 light-years away. ### How to use the Light Year Converter - Pick the unit you are starting from in the **From** menu and type your value. - Pick the unit you want in the **To** menu. The heading changes to match – for example “Light-years to Kilometers Converter”. - The most common distance units are shown below at the same time, so you can compare them at a glance. - Type into any result to convert backwards, then use **Copy results** – the copied text starts with the heading for your chosen units. Results update as you type. Everything is calculated in your browser. ### How it works Every distance unit is defined by an exact factor relative to the metre (the base unit). The calculator first turns the value you type into metres, then turns that into the unit you picked in the “To” menu and into each of the common units below it. This two-step method means any unit can be converted to any other – 27 units are available in each menu – and you can type into any field, including a result, to work in the other direction. Changing a unit menu keeps the quantity the same and just re-expresses it, and the page heading and copied results follow your choice. ### How to convert distance units - Choose the unit you have in the **From** menu and type the value, for example **1 ly**. - Choose the unit you want in the **To** menu, for example kilometres. The page heading changes to “Light-years to Kilometers Converter”. - The calculator multiplies by the metre factor of the “from” unit and divides by the factor of the “to” unit: 1 ly × 9.46073 × 1015 ÷ 1,000 = **9.46073 × 1012 km**. ### 1 light-year in common units UnitValueKilometres (km)9.46073 × 1012Miles (mi)5.878625 × 1012Astronomical units (AU)63,241.077Parsecs (pc)0.30660139Metres (m)9.46073 × 1015 ### Light-years conversion table Light-yearskmmiAUpc19.46073 × 10125.878625 × 101263,241.0770.306601394.244.01135 × 10132.492537 × 1013268,142.171.29998998.68.136228 × 10135.055618 × 1013543,873.262.6367721009.46073 × 10145.878625 × 10146,324,107.730.6601391,0009.46073 × 10155.878625 × 101563,241,077306.601392,500,0002.365183 × 10191.469656 × 10191.581027 × 1011766,503.48 ### What is a light-year? A light-year is the distance light travels in one Julian year, exactly 9,460,730,472,580,800 m. It is a unit of distance, used for distances to stars and galaxies. ### What is a kilometre? A kilometre is 1,000 metres. It is the standard unit for road distances, maps, running races and travel in almost every country except the U.S. and UK, where miles are still used on road signs. ### What is a mile? The statute mile is 5,280 feet, exactly 1,609.344 m. U.S. and UK road signs, speed limits and running races such as the mile and the marathon (26.2 mi) use it. ### Common mistakes to avoid Treating the light-year as a unit of time, and mixing parsecs with light-years (1 pc ≈ 3.26 ly). ## Worked example Inputs — From: 1 ly. Results — **To = 9,460,730,472,580.8 km**; Miles = 5,878,625,373,183.607 mi; Astronomical units = 63,241.07708427 AU; Parsecs = 0.30660139 pc; Metres = 9.4607e15 m. ## FAQ **Is a light-year a unit of time?** No, it is a distance: about 9.46 trillion km. **How far is the Andromeda galaxy?** About 2.5 million light-years. **What is a parsec in light-years?** About 3.2616 ly. **How do I change the units?** Pick any unit in the From and To menus. The value is converted in place, and the heading changes to show your conversion, for example “Light-years to Kilometers Converter”. **Can I type into any field?** Yes. Every field is editable, so you can start from whichever unit you have. **How many units can I convert between?** 27 distance units, from the everyday to the specialised. **Which units are exact?** All factors here are exact by definition except astronomical and similar reference values, which use internationally agreed constants. **What formula does the Light Year Converter use?** 1 ly = 9.46073 × 10^12 km. ## Sources - [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811) - [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)