Interactive tool
Light-year Distance Calculator
Convert light-years, parsecs, astronomical units and kilometers while keeping the scale and precision of the result visible.
Converted distance
Method and precision
The calculator uses the IAU-defined astronomical unit of exactly 149,597,870.7 km and a Julian year of exactly 365.25 days. From those definitions, one light-year is 9,460,730,472,580.8 km. The parsec conversion is shown to nine significant digits; displayed results are rounded and should not imply more precision than the input.
This is a unit converter, not a travel-time estimator. Distances reported for astronomical objects also carry measurement uncertainty that unit conversion does not remove.
Open the Andromeda Atlas page →Sources
- IAU 2012 Resolution B2: astronomical unit definition.
- International Astronomical Union: Measuring the Universe: distance-unit context.
Formula and input boundaries reviewed 9 October 2026.
Signal interpretation console · tools
Light-year Distance Calculator / observation pipeline
Photons
Identify wavelength, exposure, field of view and observing date before reading the image.
Detector
Separate object signal from point-spread function, noise, saturation and selection.
Calibration
Track background removal, alignment, scaling and color mapping as part of the measurement.
Physical claim
Connect “Method and precision” to “the fitted interpretation” through an explicit model.
Convert light-years, parsecs, astronomical units and kilometers while keeping the scale and precision of the result visible.
Brightness becomes distance only after assumptions about intrinsic luminosity, extinction, calibration and the distance indicator are made explicit. Projection, distance, extinction or adopted parameters may offer another explanation.
Query IAU 2012 Resolution B2 and International Astronomical Union: Measuring the Universe and seek an independent wavelength, spectrum, motion or catalogue measurement.