Light-Year ConverterFree online science calculator — instant results, no sign-up
Convert light-years to kilometers, miles and astronomical units.
About the Light-Year Converter
The Light-Year Converter translates a distance in light-years into kilometers, miles, and astronomical units (AU). It helps you compare interstellar distances with familiar terrestrial units and the scale of the solar system. With the default input of 4.246 light-years, it displays 4.0170e+13 kilometers, 2.4961e+13 miles, and 268,522 AU.
- Light-years
- The distance to convert, measured in light-years, with a default value of 4.246.
Formula and method
K = L × 9.4607304725808 × 10^12; M = K ÷ 1.609344; A ≈ L × 63,241.6. Display K and M in scientific notation rounded to five significant figures, and A to the nearest whole astronomical unit.
- LInput distance in light-years.
- KEquivalent distance in kilometers.
- MEquivalent distance in international statute miles.
- AApproximate equivalent distance in astronomical units, using a rounded conversion factor consistent with the supplied example.
Multiply the light-year input by the kilometer conversion factor, then divide the kilometer result by 1.609344 to obtain miles. Multiply the light-year input by approximately 63,241.6 to reproduce the example's astronomical-unit output. Keep intermediate results unrounded and apply display rounding only at the end. For L = 4.246, the displayed results are Kilometers = 4.0170e+13; Miles = 2.4961e+13; Astronomical units = 268,522.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Light-years4.246
Results
- Kilometers4.0170e+13
- Miles2.4961e+13
- Astronomical units268,522
How to use the Light-Year Converter
- 1Enter the distance in the Light-years field, or leave the default value of 4.246.
- 2Run the conversion to calculate the equivalent distances.
- 3Read the Kilometers row; the default input displays 4.0170e+13.
- 4Read the Miles row; the default input displays 2.4961e+13.
- 5Read the Astronomical units row; the default input displays 268,522.
Reading your result
All three output rows describe the same input distance in different units. Kilometers and Miles use scientific notation: e+13 means multiply the preceding number by 10^13. Thus, 4.0170e+13 kilometers is about 40.170 trillion kilometers, and 2.4961e+13 miles is about 24.961 trillion miles. The Astronomical units result of 268,522 expresses the distance in units approximately equal to the Earth–Sun distance.
Limitations
The kilometer and mile conversions assume a light-year is the distance light travels in vacuum during one Julian year of 365.25 days. The supplied AU example uses an approximate factor: the standard defined AU of exactly 149,597,870,700 meters would give about 268,520 AU after whole-unit rounding, rather than 268,522. The AU formula here reproduces the supplied example and should not be treated as a precision conversion. Display rounding and uncertainty in the original distance also limit precision. This tool converts distance units; it does not calculate spacecraft travel times or cosmological distance corrections.
Common questions
Is a light-year a distance or a duration?+
A light-year is a distance: how far light travels in vacuum in one Julian year. The Light-years field therefore expects a distance, not a travel duration.
Why are the kilometer and mile results shown with e+13?+
Interstellar distances produce very large numbers in kilometers and miles. Scientific notation keeps them readable; for the default input, 4.0170e+13 means 4.0170 × 10^13 kilometers.
Why might another converter give a slightly different AU result for 4.246 light-years?+
The supplied result of 268,522 AU is consistent with an approximate factor of 63,241.6 AU per light-year. Using the standard Julian light-year and exact AU definition instead gives about 268,520 AU when rounded to a whole unit.
Does entering 4.246 light-years mean a spacecraft would take 4.246 years to arrive?+
No. It corresponds to 4.246 years of light travel in vacuum under the stated year convention. A spacecraft's travel time depends on its speed and trajectory, which this converter does not model.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.