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About this tool
Convert astronomical units to light-years instantly. Free, bidirectional, and fully in-browser.
1 astronomical unit equals 1.581251e-5 light-years — enter any astronomical unit value to convert it to light-years instantly. This Astronomical unit to Light-year converter is a client-side tool: it applies a single multiplication (ly = AU × 1.581251e-5) in your browser, updates the moment you type, and works in both directions — edit either field, or press swap, to convert light-years back to astronomical units. A reference table lists common astronomical unit values already converted, and nothing you enter is sent to a server.
Open Astronomical unit to Light-year Converter on AltFTool — it loads instantly in your browser.
Type the value you want to convert into the Astronomical unit field.
Read the equivalent in light-years in the result field, and copy it if needed.
Use the decimal-places slider for more or less precision, or press swap to convert light-years to astronomical units.
The result updates as you type, and the swap button flips the conversion to light-year → astronomical unit without reloading.
The conversion uses the precise factor (ly = AU × 1.581251e-5), so the number matches a manual calculation to the decimal places you choose.
A slider sets 0–10 decimal places, and very small or very large results switch to scientific notation instead of rounding to zero.
Everything runs locally in your browser — no upload, no account, no limit on conversions.
One astronomical unit is 1.581251e-5 light-years. Multiply the astronomical unit value by 1.581251e-5 to convert. For example, 10 AU = 0.0001581250741 ly.
ly = AU × 1.581251e-5. This tool applies it automatically and shows a worked example: 10 AU = 0.0001581250741 ly.
Yes. Press the swap button, or type into the light-year field, and the tool converts light-years to astronomical units using the inverse of the same relationship.
It uses the standard distance and length definition (ly = AU × 1.581251e-5), not a rounded approximation, so results are exact to the number of decimal places you select.
Yes. The converter is a browser-side script with no network calls: your values are never uploaded, and once the page has loaded it keeps working without a connection.
Add the Astronomical unit to Light-year Converter widget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
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