# Astronomical Unit Converter (AU) URL: https://speedycalculator.com/calculators/conversion/astronomical-unit/ Last updated: 2026-10-25 > The astronomical unit converter converts distance between kilometres, metres, miles, light-years, parsecs, solar radii 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 (AU, m, km, cm, mm, dm, µm, nm, Å, in, ft, yd, mi, nmi, mil, furlong, chain, rod, fathom, hand, league, ly, pc, R☉, px (96 dpi), pt, gaj) ## Results - To - Metres - Miles - Light-years - Parsecs - Solar radii ## Formula ``` 1 AU = 149,597,870.6999999881 km 1 AU = 1.495979 × 10^11 m 1 AU = 92,955,807 mi 1 AU = 1.581251 × 10^-5 ly 1 AU = 4.848137 × 10^-6 pc ``` ## Explanation The astronomical unit was fixed by the International Astronomical Union in 2012 at exactly 149,597,870,700 m, roughly the average distance from Earth to the Sun. It is the natural ruler for the solar system: Mars orbits at about 1.52 AU and Neptune at about 30 AU. ### How to use the Astronomical Unit 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 “Astronomical Units 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 AU**. - Choose the unit you want in the **To** menu, for example kilometres. The page heading changes to “Astronomical Units to Kilometers Converter”. - The calculator multiplies by the metre factor of the “from” unit and divides by the factor of the “to” unit: 1 AU × 1.495979 × 1011 ÷ 1,000 = **149,597,870.6999999881 km**. ### 1 astronomical unit in common units UnitValueKilometres (km)149,597,870.6999999881Metres (m)1.495979 × 1011Miles (mi)92,955,807Light-years (ly)1.581251 × 10-5Parsecs (pc)4.848137 × 10-6Solar radii (R☉)215.03216 ### Astronomical units conversion table Astronomical unitskmmmily0.3958,343,1705.834317 × 101036,252,7656.166878 × 10-60.72107,710,466.90399999921.077105 × 101166,928,1811.138501 × 10-51149,597,870.69999998811.495979 × 101192,955,8071.581251 × 10-51.52227,388,763.46399998662.273888 × 1011141,292,827.05499881512.403501 × 10-55.2777,908,927.63999998577.779089 × 1011483,370,197.81973272568.222504 × 10-59.581.433148 × 1091.433148 × 1012890,516,633.67558455470.0001514838219.22.872279 × 1092.872279 × 10121.784751 × 1090.0003036001430.14.502896 × 1094.502896 × 10122.79797 × 1090.00047595647 ### What is an astronomical unit? The astronomical unit is exactly 149,597,870,700 m, roughly the mean Earth–Sun distance. Astronomers use it for distances within the solar system. ### 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 metre? The metre is the SI base unit of length. Since 1983 it has been defined as the distance light travels in a vacuum in 1/299,792,458 of a second, which ties it to a fundamental constant rather than a physical bar of metal. ### 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 AU. Results — **To = 149,597,870.7 km**; Metres = 149,597,870,700 m; Miles = 92,955,807.27302553 mi; Light-years = 0.00001581 ly; Parsecs = 0.00000485 pc; Solar radii = 215.03215567 R☉. ## Key terms - **Astronomical unit**: Exactly 149,597,870,700 m (IAU 2012). - **Parsec**: About 3.26 light-years; the distance at which 1 AU subtends one arcsecond. ## FAQ **How far is 1 AU in miles?** About 92.96 million miles. **How long does sunlight take to travel 1 AU?** About 8 minutes 19 seconds. **How many AU in a light-year?** About 63,241 AU. **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 “Astronomical Units 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 Astronomical Unit Converter use?** 1 AU = 149,597,870.6999999881 km. ## Sources - [IAU Resolution B2 (2012) – Re-definition of the astronomical unit of length](https://www.iau.org/static/resolutions/IAU2012_English.pdf) - [BIPM – The International System of Units (SI Brochure, 9th edition)](https://www.bipm.org/en/publications/si-brochure)