Convert length and distance units — meters, feet, inches, kilometers, miles, light years and more.
| Unit | Name | Value |
|---|---|---|
| 0.001 ly | 63.242 au | |
| 0.01 ly | 632.42 au | |
| 0.1 ly | 6324.2 au | |
| 1 ly | 63242 au | |
| 5 ly | 316210 au | |
| 10 ly | 632420 au | |
| 50 ly | 3.1621e+06 au | |
| 100 ly | 6.3242e+06 au | |
| 1000 ly | 6.3242e+07 au |
Multiply the number of Light Years by 63242 to get Astronomical Units. Formula: au = ly × 63242. Example: 10 ly × 63242 = 632420 au. To reverse, divide Astronomical Units by 63242 to get Light Years.
| Light Year (ly) | Astronomical Unit (au) |
|---|---|
| 0.001 ly | 63.242 au |
| 0.01 ly | 632.42 au |
| 0.1 ly | 6324.2 au |
| 0.5 ly | 31621 au |
| 1 ly | 63242 au |
| 2 ly | 126484 au |
| 5 ly | 316210 au |
| 10 ly | 632420 au |
| 20 ly | 1264840 au |
| 50 ly | 3162100 au |
| 100 ly | 6324200 au |
| 250 ly | 15810500 au |
| 500 ly | 31621000 au |
| 1000 ly | 63242000 au |
| 10000 ly | 632420000 au |
To convert Light Year to Astronomical Unit, multiply by 63242. Example: 10 ly = 632420 au
To convert Astronomical Unit back to Light Year, divide by 63242 (multiply by 1.58123e-05). Use the swap button above.
Start with 100 Light Years = 6324200 au as your reference point. Scale up or down from there.
Astronomers describing nearby stars in light-years convert to AU to compare with solar system scales — Proxima Centauri (4.24 ly = 268,332 AU) is dramatically far even in AU terms, contextualising planetary orbit scales.
The Oort Cloud extends to ~100,000 AU or about 1.6 light-years. Astronomers studying the boundary between the solar system and interstellar space convert between AU and light-years constantly in this transitional region.
Engineers designing hypothetical probes like Breakthrough Starshot to Proxima Centauri express target distance in light-years for public context, then convert to AU for comparison with existing solar system mission precedents.
Exoplanet orbital parameters are expressed in AU while the distance to the host star system uses light-years — both units appear in every exoplanet discovery paper, requiring readers to convert between AU and light-years fluidly.
Long-period comets originating from the Oort Cloud travel from distances of ~0.5–2 light-years (31,600–126,000 AU) down to perihelion. Cometary scientists convert between light-years and AU for orbital energy calculations.
Teaching stellar distances requires converting between light-years (for intuition) and AU (for solar system comparison) — "the nearest star is 63,241 times further than the Sun" contextualises stellar distance in familiar terms.
The Light Year is a unit of Length measurement (symbol: ly). 1 ly = 63242 au. Used in scientific and practical Length measurement applications.
The Astronomical Unit is a unit of Length measurement (symbol: au). It is part of an internationally recognised measurement system used alongside the Light Year.
The light-year first appeared in a German publication in 1851 written by Otto Ule as a way to make stellar distances comprehensible to general audiences — it was not coined by professional astronomers. It equals the distance light travels in one Julian year: exactly 9,460,730,472,580.8 kilometres. Professional astronomers often prefer parsecs (which relate directly to parallax measurements), but the light-year became the public's unit of choice for cosmic distance because it connects the familiar concept of speed with cosmic scale. One light-year equals about 63,241 astronomical units.
The astronomical unit has ancient roots — Aristarchus of Samos attempted to measure the Earth-Sun distance around 270 BC. For centuries the AU was estimated using Venus transit observations. Edmond Halley organised the first coordinated international transit-of-Venus expedition in 1716. The modern value was determined by radar ranging to Venus in 1961. The IAU formally defined the AU as exactly 149,597,870,700 metres in 2012 — a fixed constant of physics.
Common use: Light Year to Astronomical Unit conversion is needed when working with international standards, scientific publications, or reference materials that use different unit systems for Length measurement.